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  <section id="cover">
    <h1>Auroræ : their characters and spectra</h1>




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    <p>Project Gutenberg's Auroræ: Their Characters and Spectra, by J. Rand Capron</p>


    <p>This eBook is for the use of anyone anywhere in the United States and most
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    <p>Title: Auroræ: Their Characters and Spectra<br/>

    Release Date: December 10, 2017 [EBook #56159]<br/>

    Language: English<br/>
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  </section>



  <!-- page half title _________________________________________________________ -->
  <section class="frontmatter" data-type="half-title">
    <h1>Auroræ<br />
    <span class="smaller">Their characters and spectra</span></h1>
  </section>

  <!-- page half title _________________________________________________________ -->
  <section class="frontmatter" data-type="titlepage">

    <h1>Auroræ<span class="smaller">Their characters and spectra</span></h1>

    <p id="author"><span>By</span> J. Rand Capron, F.R.A.S</p>


    <div id="editor">
    <p class="editor">London<br/>E. &amp; F. N. Spon, 46 Charing cross</p>

    <p class="editor">New York<br/>446 Broom Street</p>

    <p class="editor">1879</p>
  </div>


  </section>

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      <p>
        Printed by Taylor and Francis<br/>
        Red Lion Court, Fleet Street</p>
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  <!-- page dedication_________________________________________________________ -->
  <section class="frontmatter" data-type="dedication">
    <p>To Prof. Charles Piazzi Smyth, F.R.S.E.,<br/>
      astronomer royal for Scotland,<br/>
      one of the earliest spectroscopic observers<br/>
      of the aurora and zodiacal light,<br/>
      this volume is respectfully dedicated <br/>by the author.
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  </section>


  <section class="frontmatter" data-type="epigraph">
    <blockquote>
      <p>
        And now the Northern Lights begin to burn, faintly at first, like sunbeams playing in the waters of the blue sea. Then a soft crimson glow tinges the heavens. There is a blush on the cheek of night. The colours come and go; and change from crimson to gold, from gold to crimson. The snow is stained with rosy light. Twofold from the zenith, east and west, flames a fiery sword; and a broad band passes athwart the heavens, like a summer sunset. Soft purple clouds come sailing over the sky, and through their vapoury folds the winking stars shine white as silver. With such pomp as this is Merry Christmas ushered in, though only a single star heralded the first Christmas.
      </p>

      <p class="caption">Longfellow</p>

    </blockquote>
  </section>








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  </section>





  <!-- page preface_________________________________________________________ -->
  <section class="frontmatter preface">
    <h2>Preface</h2>
    <p class="shorter">Preface</p>

     <p>
       Probably few of the phenomena of Nature so entirely charm and interest scientific and non-scientific observers alike as the Aurora Borealis, or “Northern Lights” as it is popularly called. Whether contemplated as the long low quiescent arc of silver light illuminating the landscape with a tender radiance, as broken clouds and columns of glowing ruddy light, or as sheaves of golden rays, aptly compared by old writers to aerial spears, such a spectacle cannot fail at all times to be a subject of admiration, in some cases even of awe.
     </p>
     <div id="test-bleed"></div>
     <p>
       Hence it is no wonder that the Aurora has always received a considerable amount of attention at the hands of scientific men. Early explorers of the Arctic Regions made constant and important observations of it and its character; and the list of references to works given in the Appendix will show how often it formed the subject of monographs and communications to learned Societies. The early contributions seem relatively more numerous than those of a later date; and the substance of them will be found well summed up in Dr. Brewster’s ‘Edinburgh Encyclopædia’ (1830), article “Aurora.” A most complete and able epitome of our more recent experience and knowledge of the Aurora and its spectrum has been contributed by my friend Mr. Henry R. Procter to the present (9th) edition of the ‘Encyclopædia Britannica,’ article “Aurora Polaris.” It is, however, a drawback to Encyclopædic articles that their matter is of necessity condensed, and that they rarely have the very desirable aid of drawings and engravings to illustrate their subjects. In spite, therefore, of the exhaustive way, both as to fact and theory, in which the contributor to the ‘Encyclopædia Britannica’ has realized his task, it seemed to me there was still room left for a popular treatise, having for its object the description of Auroræ, their characters and spectra. The question of the Aurora spectrum seems the more worthy of extended discussion in that it still remains an unsolved problem. In spite of the observations and researches of Ångström, Lemström, and Vogel abroad, and of Piazzi Smyth, Herschel, Procter, Backhouse, and others at home, the goal is not yet reached; for while the faint and more refrangible lines are but doubtfully referred to air, the bright and sharp red and green lines, which mainly characterize the spectrum, are as yet unassociated with any known analogue.
    </p>
    <p>
      With these views, and to incite to further and closer observations, I have been induced to publish the present volume as a sort of Auroral Guide. For much of the history of the Aurora I am indebted to, and quote from former articles and records, including the two excellent Encyclopædic ones before referred to. Mr. Procter, Mr. Backhouse, and my friend Mr. W. H. Olley have each kindly furnished me with much in the way of information and suggestion. Dr. Schuster has lent me tubes showing the true oxygen spectrum; while Herr Carl Bock, the Norwegian naturalist, has enabled me to reproduce a veritable curiosity, viz. a picture in oil painted by the light of a Lapland Aurora. The experiments detailed in Part III. were suggested by the earlier ones of De la Rive, Varley, and others, and demonstrate the effect of the magnet on electric discharges. For assistance in these I am indebted to my friend Mr. E. Dowlen.
    </p>
    <p>
      The illustrations are mainly from original drawings of my own. Those from other sources are acknowledged. Messrs. Mintern have well reproduced in chromo-lithography the coloured drawings illustrating the Auroræ, moon-patches, &amp;c.
    </p>
  </section>

  <!-- page introduction _________________________________________________________ -->
  <section class="frontmatter introduction">

    <h2>Introduction</h2>
    <p class="shorter">Introduction</p>
     <p>
       Probably few of the phenomena of Nature so entirely charm and interest scientific and non-scientific observers alike as the Aurora Borealis, or “Northern Lights” as it is popularly called. Whether contemplated as the long low quiescent arc of silver light illuminating the landscape with a tender radiance, as broken clouds and columns of glowing ruddy light, or as sheaves of golden rays, aptly compared by old writers to aerial spears, such a spectacle cannot fail at all times to be a subject of admiration, in some cases even of awe.
     </p>
     <p>
       Hence it is no wonder that the Aurora has always received a considerable amount of attention at the hands of scientific men. Early explorers of the Arctic Regions made constant and important observations of it and its character; and the list of references to works given in the Appendix will show how often it formed the subject of monographs and communications to learned Societies. The early contributions seem relatively more numerous than those of a later date; and the substance of them will be found well summed up in Dr. Brewster’s ‘Edinburgh Encyclopædia’ (1830), article “Aurora.” A most complete and able epitome of our more recent experience and knowledge of the Aurora and its spectrum has been contributed by my friend Mr. Henry R. Procter to the present (9th) edition of the ‘Encyclopædia Britannica,’ article “Aurora Polaris.” It is, however, a drawback to Encyclopædic articles that their matter is of necessity condensed, and that they rarely have the very desirable aid of drawings and engravings to illustrate their subjects. In spite, therefore, of the exhaustive way, both as to fact and theory, in which the contributor to the ‘Encyclopædia Britannica’ has realized his task, it seemed to me there was still room left for a popular treatise, having for its object the description of Auroræ, their characters and spectra. The question of the Aurora spectrum seems the more worthy of extended discussion in that it still remains an unsolved problem. In spite of the observations and researches of Ångström, Lemström, and Vogel abroad, and of Piazzi Smyth, Herschel, Procter, Backhouse, and others at home, the goal is not yet reached; for while the faint and more refrangible lines are but doubtfully referred to air, the bright and sharp red and green lines, which mainly characterize the spectrum, are as yet unassociated with any known analogue.
    </p>
    <p>
      With these views, and to incite to further and closer observations, I have been induced to publish the present volume as a sort of Auroral Guide. For much of the history of the Aurora I am indebted to, and quote from former articles and records, including the two excellent Encyclopædic ones before referred to. Mr. Procter, Mr. Backhouse, and my friend Mr. W. H. Olley have each kindly furnished me with much in the way of information and suggestion. Dr. Schuster has lent me tubes showing the true oxygen spectrum; while Herr Carl Bock, the Norwegian naturalist, has enabled me to reproduce a veritable curiosity, viz. a picture in oil painted by the light of a Lapland Aurora. The experiments detailed in Part III. were suggested by the earlier ones of De la Rive, Varley, and others, and demonstrate the effect of the magnet on electric discharges. For assistance in these I am indebted to my friend Mr. E. Dowlen.
    </p>
    <p>
      The illustrations are mainly from original drawings of my own. Those from other sources are acknowledged. Messrs. Mintern have well reproduced in chromo-lithography the coloured drawings illustrating the Auroræ, moon-patches, &amp;c.
    </p>
  </section>

  <!-- List of plates_________________________________________________________
  <section class="frontmatter list-plates">
    <h2>List of plates</h2>

    <table summary="List of plates" id="plates">
      <tr>
        <th class="tdr smaller">Plate.</th>
        <th></th>
        <th></th>
        <th></th>
      </tr>
      <tr>
        <td class="tdr">I.</td>
        <td>The Aurora during the Ice-pressure</td>
        <td class="nw vb"><i>To face page</i></td>
        <td class="tdr vb"><a href="#plate1">14</a></td>
      </tr>
      <tr>
        <td class="tdr">II.</td>
        <td>Aurora seen by Dr. Hayes, 6th January, 1861</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate2">16</a></td>
      </tr>
      <tr>
        <td class="tdr">III.</td>
        <td>Aurora, Guildford, Oct. 24, 1870</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate3">18</a></td>
      </tr>
      <tr>
        <td class="tdr">IV.</td>
        <td>Aurora, Guildford, Feb. 4, 1872; Eclipsed Moon, Aug. 23, 24, 1877</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate4">20</a></td>
      </tr>
      <tr>
        <td class="tdr">V.</td>
        <td>Corona, Graphical Auroræ, Zodiacal Light, &amp;c.</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate5">21</a></td>
      </tr>
      <tr>
        <td class="tdr">VI.</td>
        <td>Aurora, Guildford, Feb. 4, 1874; Spectrum des Nordlichts (Vogel)</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate6">22</a></td>
      </tr>
      <tr>
        <td class="tdr">VII.</td>
        <td>Aurora, Kyle Akin, Isle of Skye, Sept. 11, 1874</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate7">24</a></td>
      </tr>
      <tr>
        <td class="tdr">VIII.</td>
        <td>Herr Carl Bock’s Lapland Aurora, Oct. 3, 1877</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate8">25</a></td>
      </tr>
      <tr>
        <td class="tdr">IX.</td>
        <td>Compared Aurora and other Spectra. Loomis’s curves of Auroras, Magnetic Declination, and Solar Spots</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate9">59</a></td>
      </tr>
      <tr>
        <td class="tdr">X.</td>
        <td>Spectroscope, Micrometer, Tubes</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate10">91</a></td>
      </tr>
      <tr>
        <td class="tdr">XI.</td>
        <td>Aurora-spectra, Candle-spectrum</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate11">102</a></td>
      </tr>
      <tr>
        <td class="tdr">XII.</td>
        <td>Aurora-spectrum, Solar spectrum, and Candle-spectrum</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate12">104</a></td>
      </tr>
      <tr>
        <td class="tdr">XIII.</td>
        <td>Vogel’s Aurora-lines, Aurora-lines near G, and in the red and green</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate13">108</a></td>
      </tr>
      <tr>
        <td class="tdr">XIV.</td>
        <td>Aurora, Hydrocarbons, Oxygen</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate14">110</a></td>
      </tr>
      <tr>
        <td class="tdr">XV.</td>
        <td>Aurora and Air-tubes, &amp;c.</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate15">115</a></td>
      </tr>
      <tr>
        <td class="tdr">XVI.</td>
        <td>Aurora, Phosphoretted Hydrogen, Iron, &amp;c.</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate16">117</a></td>
      </tr>
      <tr>
        <td class="tdr">XVII.</td>
        <td>Effect of Magnet on Tubes and Spark</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate17">134</a></td>
      </tr>
      <tr>
        <td class="tdr">XVIII.</td>
        <td>Same, and Oxygen-spectrum</td>
        <td class="nw vb"><span class="ditto1">”</span> <span class="ditto1">”</span></td>
        <td class="tdr vb"><a href="#plate18">154</a></td>
      </tr>
    </table>
  </section>
-->


  <!-- PART I_________________________________________________________ -->
  <section class="part">
    <h2 class="title-part" id="part-1">The Aurora and its characters</h2>
  </section>


  <!-- Chapitre 1_________________________________________________________-->
  <section class="chapter" id="chapter-1">

    <h3 class="titlechapter" id="chap-1">The aurora as known <br/>to the ancients </h3>
    <p class="shorter">The aurora as known to the ancients</p>


    <p>In Seneca’s ‘Quæstiones Naturales,’ Lib. I. c. xiv., we find the following:<span class="sidenote">Seneca’s ‘Quæstiones Naturales,’ Lib. I. c. xiv. Description of Auroræ.</span>—“Tempus est, alios quoque ignes percurrere,
      quorum diversæ figuræ sunt. Aliquando emicat stella, aliquando ardores sunt, aliquando fixi et hærentes,
      nonnunquam volubiles. Horum plura genera conspiciantur. Sunt <i>Bothynoë</i>&nbsp;<span class="footnote"><span class="greek">βόθυνος</span>, a hollow.</span> Seneca’s ‘Quæstiones Naturales,’ Lib. I. c. xiv. Description of Auroræ.</span>, quum velut corona cingente
      introrsus igneus cœli recessus est similis effossæ in orbem speluncæ. Sunt <i>Pithitæ</i>&nbsp;<span class="footnote"><span class="greek">πίθος</span>, a cask.</span>, quum magnitudo
      vasti rotundique ignis dolio similis, vel fertur vel in uno loco flagrat. Sunt <i>Chasmata</i>&nbsp;<span class="footnote"><span class="greek">χάσμς</span>, a chasm.</span>, quum aliquod
      cœli spatium desedit, et flammam dehiscens, velut in abdito, ostentat. Colores quoque omnium horum plurimi sunt. Quidam ruboris acerrimi, quidam evanidæ ac levis flammæ, quidam candidæ lucis, quidam micantes, quidam æqualiter et sine eruptionibus aut radiis fulvi.
    </p>

    <p class="separator"></p>

    <p><span class="sidenote">Seneca,c. xv.</span>C. xv. “Inter hæc ponas licet et quod frequenter in historiis legimus,
    cœlum ardere visum: cujus nonnunquam tam sublimis ardor est ut inter
    ipsa sidera videatur, nonnunquam tam humilis ut speciem longinqui incendii
    præbeat.</p>

    <p>“Sub Tiberio Cæsare cohortes in auxilium Ostiensis coloniæ cucurrerunt,
    tanquam conflagrantis, quum cœli ardor fuisset per magnam partem noctis,
    parum lucidus crassi fumidique ignis.”</p>

    <p>We may translate this:<span class="sidenote">Seneca,c. xv.</span>—“It is time other fires also to describe, of which
    there are diverse forms.</p>

    <p>“Sometimes a star shines forth; at times there are fire-glows, sometimes
    fixed and persistent, sometimes flitting. Of these many sorts may be distinguished.
    There are Bothynoë, when, as within a surrounding corona, the
    fiery recess of the sky is like to a cave dug out of space. There are Pithitæ,
    when the expanse of a vast and rounded fire similar to a tub (dolium) is either
    carried about or glows in one spot.</p>

    <p>“There are Chasmata, when a certain portion of the sky opens, and gaping
    displays the flame as in a porch. The colours also of all these are many.
    Certain are of the brightest red, some of a flitting and light flame-colour,
    some of a white light, others shining, some steadily and yellow without
    eruptions or rays.</p>

    <p class="separator"></p>


    <p>“Amongst these we may notice, what we frequently read of in history, the
    sky is seen to burn, the glow of which is occasionally so high that it may be
    seen amongst the stars themselves, sometimes so near the Earth (humilis) that
    it assumes the form of a distant fire. Under Tiberius Cæsar the cohorts ran
    together in aid of the colony of Ostia as if it were in flames, when the
    glowing of the sky lasted through a great part of the night, shining dimly
    like a vast and smoking fire.”</p>


    <p>From the above passages many striking particulars of the Aurora may be
    gathered; and by the division of the forms of Aurora into classes it is
    evident they were, at that period, the subject of frequent observation.
    The expression <span class="sidenote"> Auroræ frequently read of in history.</span>“et quod frequenter in historiis legimus” shows, too, that the
    phenomena of Auroral displays were a matter of record and discussion with
    the writers of the day.</p>

    <p>Various forms of Aurora may be recognized in the passages from Chap. xiv.;
    while in those from Chap. xv. a careful distinction is drawn between the
    Auroræ seen in the zenith or the upper regions of the sky, and those seen on
    the horizon or apparently (and no doubt in some cases actually) near the
    Earth’s surface.</p>


    <p>The description of the cohorts running to the fire only to find it an Aurora,
    calls to mind the many similar events happening in our own days. Not,
    however, but that a mistake may sometimes occur in an opposite direction.
    <span class="sidenote">A spurious Aurora.</span>“In the memoirs of Baron Stockmar an amusing anecdote is related of one
    Herr von Radowitz, who was given to making the most of easily picked up
    information. A friend of the Baron’s went to an evening party near Frankfort,
    where he expected to meet Herr von Radowitz. On his way he saw a
    barn burning, stopped his carriage, assisted the people, and waited till the
    flames were nearly extinguished. When he arrived at his friend’s house he
    found Herr von Radowitz, who had previously taken the party to the top of
    the building to see an Aurora, dilating on terrestrial magnetism, electricity,
    and so forth. Radowitz asked Stockmar’s friend, “Have you seen the beautiful
    Aurora Borealis?” He replied, “Certainly; I was there myself; it will soon
    be over.” An explanation followed as to the barn on fire: Radowitz was
    silent some ten minutes, then took up his hat and quietly disappeared.</p>



    <p>It is probable that many of the phantom combats which are recorded to
    have appeared in forms of fire in the air on the evenings preceding great
    battles might be traced to Auroræ, invested with distinct characteristics by
    the imagination of the beholders. <span class="sidenote">Auroræ as portents.</span>Auroræ are said to have appeared in the
    shape of armies of horse and foot engaged in battle in the sky before the
    death of Julius Cæsar, which they were supposed to foretell. For more than
    a year before the siege and destruction of Jerusalem by Titus Vespasian, the
    Aurora was said to have been frequently visible in Palestine.</p>

    <p>Josephus, in his ‘Wars of the Jews’ (Whiston’s Translation, Book VI.
    chap. v. sect. 3), in referring to the signs and wonders preceding the destruction
    of Jerusalem, speaks of a star or comet, and that a great light shone
    round about the altar and the holy house, which light lasted for half an hour,
    and that a few days after the feast of unleavened bread a certain prodigious
    and incredible phenomenon appeared—“for before sunsetting chariots and
    troops of soldiers in their armour were seen running about among the clouds,
    and surrounding of cities.” (This, if an Aurora, must have been an instance
    of a daylight one.)</p>

    <p>We find in Book II. of Maccabees, chap. v. verses 1, 2, 3, 4 (<span class="smcapuc">B.C.</span> about
    176 years):</p>


      <p>“1. About this same time Antiochus prepared his second voyage into Egypt:</p>

      <p>“2. And then it happened that through all the city, for the space almost of
      forty days, there were seen horsemen running in the air, in cloth of gold, and
      armed with lances like a band of soldiers.</p>

      <p>“3. And troops of horsemen in array, encountering and running one against
      another, with shaking of shields and multitude of pikes, and drawing of
      swords and casting of darts, and glittering of golden ornaments and harness
      of all sorts.</p>

      <p>“4. Wherefore every man prayed that that apparition might turn to
      good.”</p>



    <p><span class="sidenote">Early descriptions of Auroræ.</span>In Aristotle’s ‘De Meteoris,’ Lib. I. c. iv. and v., the Aurora is described
    as an appearance resembling flame mingled with smoke, and of a purple red
    or blue colour. Pliny (Lib. II. c. xxvii.) speaks of a bloody appearance of
    the heavens which seemed like a fire descending on the earth, seen in the
    third year of the 107th Olympiad, and of a light seen in the nighttime
    equal to the brightness of the day, in the Consulship of Cæcilius and Papirius
    (Lib. II. c. xxxiii.), both of which may be referred to Auroræ.</p>

    <p>In the ‘Annals of Philosophy,’ vol. ix. p. 250, it is stated that the Aurora
    among English writers is first described by Matthew of Westminster, who
    relates that in <span class="smcapuc">A.D.</span> 555 lances were seen in the air (“quasi species lancearum
    in aëre visæ sunt a septentrionali usque ad occidentem”).</p>

    <p>In the article in the ‘Edinb. Encyc.’ vol. iii. (1830), the Aurora (known to the
    vulgar as “streamers” or “merry dancers”) is distinguished in two kinds—the
    “tranquil” and the “varying.” Musschenbroek enumerates as forms:—<i>trabs</i>,
    “the beam,” an oblong tract parallel to the horizon; <i>sagitta</i>, “the
    arrow;” <i>faces</i>, “the torch;” <i>capra saltans</i>, “the dancing goat;” <i>bothynoë</i>,
    “the cave,” a luminous cloud having the appearance of a recess or hollow in
    the heavens, surrounded by a corona; <i>pithiæ</i>, “the tun,” an Aurora resembling
    a large luminous <i>cask</i>. The two sorts of Auroræ distinguished as
    the “bothynoë” and “pithiæ” are evidently taken from the passage in Seneca’s
    ‘Quæstiones’ before quoted. In ‘Liberti Fromondi Meteorologicorum’
    (London, 1656), Lib. II. cap. v. “De Meteoris supremæ regionis aëris,”
    art. 1. De Capra, Trabe, Pyramide, &amp;c., these and other fantastic forms
    attributable to Auroræ are more fully described.</p>

    <p>In the article “Aurora Polaris,” Encyc. Brit. edit. ix., we find noted that
    from a curious passage in Sirr’s ‘Ceylon and the Cingalese,’ vol. ii. p. 117, it
    would seem that the Aurora, or something like it, is visible occasionally in
    Ceylon, where the natives call it “Buddha Lights,” and that in many parts
    of Ireland a scarlet Aurora is supposed to be a shower of blood. The earliest
    mentioned Aurora (in Ireland) was in 688, in the ‘Annals of Cloon-mac-noise,’
    after a battle between Leinster and Munster, in which Foylcher O’Moyloyer
    was slain.</p>

    <p>In the article in the Edinb. Encyc. before referred to it is stated that it was
    not much more than a century ago that the phenomenon had been noticed to
    occur with frequency in our latitudes.</p>

    <p>Dr. Halley had begun to despair of seeing one till the fine display of
    1716.</p>

    <p><span class="sidenote">Early notices of Auroræ not frequent in our latitudes.</span> The first account on record in an English work is said to be in a book
    entitled ‘A Description of Meteors by W. F. D. D.’ (reprinted, London, 1654),
    which speaks of “burning spears” being seen January 30, 1560. The next
    is recorded by Stow as occurring on October 7, 1564; and, according to Stow
    and Camden, an Aurora was seen on two nights, 14th and 15th November,
    1574.</p>

    <p>Twice, again, an Aurora was seen in Brabant, 13th February and 28th
    September, 1575. Cornelius Gemma compared these to spears, fortified
    cities, and armies fighting in the air. Auroræ were seen in 1580 and 1581
    in Wirtemberg, Germany.</p>

    <p>Then we have no record till 1621, when an Aurora, described by Gassendi
    in his ‘Physics,’ was seen all over France, September 2nd of that year.</p>

    <p>In November 1623 another, described by Kepler, was seen all over
    Germany.</p>

    <p>From 1666 to 1716 no appearance is recorded in the ‘Transactions of the
    French Academy of Sciences;’ but in 1707 one was seen in Ireland and at
    Copenhagen; while in 1707 and 1708 the Aurora was seen five times.</p>

    <p>The Aurora of 1716, occurring after an interval of eighty years, which
    Dr. Halley describes, was very brilliant and extended over much country,
    being seen from the west of Ireland to the confines of Russia and the east of
    Poland, extending nearly 30° of longitude, and from about the 50th degree of
    latitude, over almost all the north of Europe, and in all places exhibiting at
    the same time appearances similar to those observed in London. An Aurora
    observed in Bologna in 1723 was stated to be the first that had ever been
    seen there; and one recorded in the ‘Berlin Miscellany’ for 1797 is called a
    very unusual phenomenon. Nor did Auroræ appear more frequent in the
    Polar Regions at that time, for Cælius states that the oldest inhabitants of
    Upsala considered the phenomenon as quite rare before 1716. Anderson, of
    Hamburg, writing about the same time, says that in Iceland the inhabitants
    themselves were astonished at the frequent Auroræ then beginning to take
    place; while Torfæus, the Icelander, who wrote in 1706, was old enough
    to remember the time when the Aurora was an object of terror in his native
    country.</p>

    <p>According to M. Mairan, 1441 Auroræ were observed between <span class="smcapuc">A.D.</span> 583
    and 1751, of which 972 were observed in the winter half-years and 469
    during the summer half-years. In our next Chapter we propose to give some
    general descriptions of Auroræ from comparatively early sources.</p>

  </section>

  <!-- Chapitre 2_________________________________________________________-->
  <section class="chapter" id="chapter-2">

    <h3 class="titlechapter" id="chap-2">Some general descriptions of auroræ</h3>
    <p class="shorter">Some general descriptions of auroræ</p>


    <p><span class="sidenote">Sir John Franklin’s description.</span>Sir John Franklin (‘Narrative of a Journey to the Shores of the Polar Sea
    in the years 1819, 1820, 1821, 1822’) describes an Aurora in these terms:—</p>

    <p><span class="sidenote">Parts of the Aurora: beams, flashes, and arches.</span>“For the sake of perspicuity I shall describe the several parts of the
    Aurora, which I term beams, flashes, and arches.</p>

    <p>“The beams are little conical pencils of light, ranged in parallel lines,
    with their pointed extremities towards the earth, generally in the direction
    of the dipping-needle.</p>

    <p><span class="sidenote">Formation of the Aurora.</span>“The flashes seem to be scattered beams approaching nearer to the earth,
    because they are similarly shaped and infinitely larger. I have called them
    flashes, because their appearance is sudden and seldom continues long.
    When the Aurora first becomes visible it is formed like a rainbow, the light
    of which is faint, and the motion of the beams undistinguishable. It is
    then in the horizon. As it approaches the zenith it resolves itself into
    beams which, by a quick undulating motion, project themselves into wreaths,
    afterwards fading away, and again and again brightening without any visible
    expansion or contraction of matter. Numerous flashes attend in different
    parts of the sky.”</p>

    <p><span class="sidenote">Arches of the Aurora.</span>Sir John Franklin then points out that this mass would appear like an arch
    to a person situated at the horizon by the rules of perspective, assuming its
    parts to be equidistant from the earth; and mentions a case when an Aurora,
    which filled the sky at Cumberland House from the northern horizon to the
    zenith with wreaths and flashes, assumed the shape of arches at some distance
    to the southward. He then continues:—“But the Aurora does not always
    make its first appearance as an arch. It sometimes rises from a confused mass
    of light in the east or west, and crosses the sky towards the opposite point,
    exhibiting wreaths of beams or coronæ boreales on its way. An arch also,
    which is pale and uniform at the horizon, passes the zenith without displaying
    any irregularity or additional brilliancy.” Sir John Franklin then mentions
    seeing three arches together, very near the northern horizon, one of which
    exhibited beams and even colours, but the other two were faint and uniform.
    (See example of a doubled arc Aurora observed at Kyle Akin, Skye, Plate
    VII.)</p>


    <p>He also mentions an arch visible to the southward exactly similar to one in
    the north. It appeared in fifteen minutes, and he suggests it probably had
    passed the zenith before sunset. The motion of the whole body of the
    Aurora from the northward to the southward was at angles not more than
    20° from the magnetic meridian. The centres of the arches were as often in
    the magnetic as in the true meridian. A delicate electrometer, suspended
    50 feet from the ground, was never perceptibly affected by the Aurora.</p>


    <p><span class="sidenote">Aurora does not often appear until some hours after sunset.</span>Sir John Franklin further remarks that the Aurora did not often appear
    immediately after sunset, and that the absence of that luminary for some
    hours was in general required for the production of a state of atmosphere
    favourable to the generation of the Aurora.</p>


    <p><span class="sidenote">Aurora seen in daylight.</span>On one occasion, however (March 8th, 1821), he observed it distinctly
    previous to the disappearance of daylight; and he subsequently states that
    on four occasions the coruscations of the Aurora were seen very distinctly
    before daylight had disappeared.</p>

    <p>[In the article “Aurora Polaris,” Encyc. Brit. edit. ix., the Transactions of
    the Royal Irish Academy, 1788, are referred to, where Dr. Usher notices that
    the Aurora makes the stars flutter in the telescope; and that, having remarked
    this effect strongly one day at 11 <span class="smcapuc">A.M.</span>, he examined the sky, and saw
    an Auroral corona with rays to the horizon.</p>

    <p>Instances are by no means rare of the principal Aurora-line having been
    seen in waning sunlight, and in anticipation of an Aurora which afterwards
    appeared.]</p>

    <span class="sidenote"> Auroral arch. Passage across the zenith.</span>

    <p><span class="sidenote">The Rev. James Farquharson’s observations.</span>The Rev. James Farquharson, from the observation of a number of Auroræ
    in Aberdeenshire in 1823 (‘Philosophical Transactions,’ 1829), concluded:—that
    the Aurora follows an invariable order in its appearance and progress;
    that the streamers appear first in the north, forming an arch from east to
    west, having its vertex at the line of the magnetic meridian <span class="sidenote">Auroral arch.</span>(when this
    arch is of low elevation it is of considerable breadth from north to south,
    having the streamers placed crosswise in relation to its own line, and all
    directed towards a point a little south of the zenith); that the arch moves
    forward towards the south, contracting laterally as it approaches the zenith,
    and increasing its intensity of light by the shortening of the streamers and the
    gradual shifting of the angles which the streamers near the east and west
    extremities of the arch make with its own line, till at length these streamers
    become parallel to that line, and then the arch is seen in a narrow belt 3° or
    4° only in breadth, stretching across the zenith at right angles to the magnetic
    meridian; that it still makes progress southwards, and after it has reached
    several degrees south of the zenith again enlarges its breadth by exhibiting
    an order of appearances the reverse of that which attended its progress
    towards the zenith from the north; <span class="sidenote">Passage across the zenith.</span>that the only conditions that can explain
    and reconcile these appearances are that the streamers of the Aurora are
    vertical, or nearly so, and form a deep fringe which stretches a great way from
    east to west at right angles to the magnetic meridian, but which is of no great
    thickness from north to south, and that the fringe moves southward, preserving
    its direction at right angles to the magnetic meridian.</p>


    <p><span class="sidenote">M. Lottin’s observations.</span>Dr. Lardner, in his ‘Museum of Science and Art,’ vol. x. p. 189 <i>et seq.</i>,
    alludes to a description of “this meteor” (<i>sic</i>) supplied by M. Lottin, an officer
    of the French Navy, and a Member of the Scientific Commission to the North
    Seas. Between September 1838 and April 1839, being the interval when
    the sun was constantly below the horizon, this savant observed nearly 150
    Auroræ. During this period sixty-four were visible, besides many concealed
    by a clouded sky, but the presence of which was indicated by the disturbances
    they produced upon the magnetic needle.</p>

    <p>The succession of appearances and changes presented by these “meteors”
    is thus graphically described by M. Lottin:—</p>

    <p><span class="sidenote">Formation of the auroral bow.</span>“Between four and eight o’clock <span class="smcapuc">P.M.</span> a light fog, rising to the altitude of
    six degrees, became coloured on its upper edge, being fringed with the light
    of the meteor rising behind it. This border, becoming gradually more
    regular, took the form of an arch, of a pale yellow colour, the edges of which
    were diffuse, the extremities resting on the horizon. This bow swelled slowly
    upwards, its vertex being constantly on the magnetic meridian. Blackish
    streaks divided regularly the luminous arc, and resolved it into a system of
    rays. These rays were alternately extended and contracted, sometimes slowly,
    sometimes instantaneously, sometimes they would dart out, increasing and
    diminishing suddenly in splendour. The inferior parts, or the feet of the
    rays, presented always the most vivid light, and formed an arc more or less
    regular. The length of these rays was very various, but they all converged
    to that point of the heavens indicated by the direction of the southern pole
    of the dipping-needle. Sometimes they were prolonged to the point where
    their directions intersected, and formed the summit of an enormous dome of
    light.</p>


    <p><span class="sidenote">It ascends to the zenith.</span>“The bow then would continue to ascend toward the zenith. It would
    suffer an undulatory motion in its light—that is to say, that from one extremity
    to the other the brightness of the rays would increase successively in
    intensity. This luminous current would appear several times in quick succession,
    and it would pass much more frequently from west to east than in
    the opposite direction. Sometimes, but rarely, a retrograde motion would
    take place immediately afterward; and as soon as this wave of light had run
    successively over all the rays of the Aurora from west to east, it would return
    in the contrary direction to the point of its departure, producing such an
    effect that it was impossible to say whether the rays themselves were actually
    affected by a motion of translation in a direction nearly horizontal, or if this
    more vivid light was transferred from ray to ray, the system of rays themselves
    suffering no change of position. The bow, thus presenting the appearance
    of an alternate motion in a direction nearly horizontal, had usually
    the appearance of the undulations or folds of a ribbon or flag agitated by the
    wind. Sometimes one, and sometimes both of its extremities would desert
    the horizon, and then its folds would become more numerous and marked,
    the bow would change its character and assume the form of a long sheet of
    rays returning into itself, and consisting of several parts forming graceful
    curves. The brightness of the rays would vary suddenly, sometimes surpassing
    in splendour stars of the first magnitude; these rays would rapidly
    dart out, and curves would be formed and developed like the folds of a
    serpent; then the rays would affect various colours, the base would be red,
    the middle green, and the remainder would preserve its clear yellow hue.
    Such was the arrangement which the colours always preserved. They were
    of admirable transparency, the base exhibiting blood-red, and the green of
    the middle being that of the pale emerald; the brightness would diminish,
    the colours disappear and all be extinguished, sometimes suddenly and sometimes
    by slow degrees. After this disappearance fragments of the bow
    would be reproduced, would continue their upward movement and approach
    the zenith; the rays, by the effect of perspective, would be gradually
    shortened; the thickness of the arc, which presented then the appearance of
    a large zone of parallel rays, would be extended; then the vertex of the
    bow would reach the magnetic zenith, or the point to which the south pole
    of the dipping-needle is directed. <span class="sidenote">Reaches the zenith.</span>At that moment the rays would be seen
    in the direction of their feet. If they were coloured they would appear as
    a large red band, through which the green tints of their superior parts could
    be distinguished, and if the wave of light above mentioned passed along
    them their feet would form a long sinuous undulating zone; while throughout
    all these changes the rays would never suffer any oscillation in the direction
    of their axis, and would constantly preserve their mutual parallelisms.</p>

    <p>“While these appearances are manifested new bows are formed, either
    commencing in the same diffuse manner or with vivid and ready formed rays;
    they succeed each other, passing through nearly the same phases, and arrange
    themselves at certain distances from each other. <span class="sidenote">Multiple bows.</span>As many as nine have been
    counted having their ends supported on the earth, and in their arrangement
    resembling the short curtains suspended one behind the other over the scene
    of a theatre, and intended to represent the sky. Sometimes the intervals
    between these bows diminish, and two or more of them close upon each
    other, forming one large zone traversing the heavens and disappearing towards
    the south, becoming rapidly feeble after passing the zenith. But sometimes
    also, when this zone extends over the summit of the firmament from east to
    west, <span class="sidenote">Corona formed.</span>the mass of rays appear suddenly to come from the south, and to form,
    with those from the north, the real boreal corona, all the rays of which
    converge to the zenith. This appearance of a crown, therefore, is doubtless
    the mere effect of perspective; and an observer placed at the same instant at
    a certain distance to the north or to the south would perceive only an arc.</p>

    <p>“The total zone, measuring less in the direction north and south than in
    the direction east and west, since it often leans upon the corona, would be
    expected to have an elliptical form; but that does not always happen: it has
    been seen circular, the unequal rays not extending to a greater distance than
    from eight to twelve degrees from the zenith, while at other times they reach
    the horizon.</p>

    <p>“Let it then be imagined that all these vivid rays of light issue forth
    with splendour, subject to continual and sudden variations in their length
    and brightness; that these beautiful red and green tints colour them at intervals;
    that waves of light undulate over them; that currents of light
    succeed each other; and in fine, that the vast firmament presents one immense
    and magnificent dome of light, reposing on the snow-covered base supplied
    by the ground, which itself serves as a dazzling frame for a sea calm and
    black as a pitchy lake. And some idea, though an imperfect one, may be
    obtained of the splendid spectacle which presents itself to him who witnesses
    the Aurora from the Bay of Alten.</p>


    <p><span class="sidenote">Duration of corona.</span>“The corona when it is formed only lasts for some minutes; it sometimes
    forms suddenly, without any previous bow. There are rarely more than two
    on the same night, and many of the Auroras are attended with no crown
    at all.</p>



    <p>“The corona becomes gradually faint, the whole phenomenon being to the
    south of the zenith, forming bows gradually paler and generally disappearing
    before they reach the southern horizon. All this most commonly takes place
    in the first half of the night, after which the Aurora appears to have lost its
    intensity; the pencils of rays, the bands, and the fragments of bows appear
    and disappear at intervals. Then the rays become more and more diffused,
    and ultimately merge into the vague and feeble light which is spread over
    the heavens, grouped like little clouds, and designated by the name of
    auroral plates (plaques aurorales). Their milky light frequently undergoes
    striking changes in the brightness, like motions of dilatation and contraction,
    which are propagated reciprocally between the centre and the circumference,
    like those which are observed in marine animals called Medusæ. <span class="sidenote">Disappearance of Aurora.</span>The phenomena
    become gradually more faint, and generally disappear altogether on
    the appearance of twilight. Sometimes, however, the Aurora continues
    after the commencement of daybreak, when the light is so strong that a
    printed book may be read. It then disappears, sometimes suddenly; but it
    often happens that, as the daylight augments, the Aurora becomes gradually
    vague and undefined, takes a whitish colour, and is ultimately so mingled
    with the cirro-stratus clouds that it is impossible to distinguish it from them.”</p>

    <p>Lieutenant Weyprecht has grandly described forms of Aurora in Payer’s
    ‘New Lands within the Arctic Circle’ (vol. i. p. 328 <i>et seq.</i>) as follows:—</p>


    <p><span class="sidenote">Lieut. Weyprecht’s description.</span>“There in the south, low on the horizon, stands a faint arch of light. It
    looks as it were the upper limit of a dark segment of a circle; but the stars,
    which shine through it in undiminished brilliancy, convince us that the
    darkness of the segment is a delusion produced by contrast. Gradually the
    arch of light grows in intensity and rises to the zenith. It is perfectly
    regular; its two ends almost touch the horizon, and advance to the east and
    west in proportion as the arch rises. No beams are to be discovered in it,
    but the whole consists of an almost uniform light of a delicious tender colour.
    It is transparent white with a shade of light green, not unlike the pale green
    of a young plant which germinates in the dark. The light of the moon
    appears yellow contrasted with this tender colour, so pleasing to the eye and
    so indescribable in words, a colour which nature appears to have given only
    to the Polar Regions by way of compensation. The arch is broad, thrice the
    breadth, perhaps, of the rainbow, and its distinctly marked edges are strongly
    defined on the profound darkness of the Arctic heavens. The stars shine
    through it with undiminished brilliancy. The arch mounts higher and
    higher. An air of repose seems spread over the whole phenomenon; here
    and there only a wave of light rolls slowly from one side to the other. It
    begins to grow clear over the ice; some of its groups are discernible. The
    arch is still distant from the zenith, a second detaches itself from the dark
    segment, and this is gradually succeeded by others. All now rise towards
    the zenith; the first passes beyond it, then sinks slowly towards the northern
    horizon, and as it sinks loses its intensity. <span class="sidenote">Formation of arches.</span>Arches of light are now stretched
    over the whole heavens; seven are apparent at the same time on the sky,
    though of inferior intensity. The lower they sink towards the north the
    paler they grow, till at last they utterly fade away. Often they all return
    over the zenith, and become extinct just as they came.</p>


    <p>“It is seldom, however, that an Aurora runs a course so calm and so
    regular. The typical dark segment, which we see in treatises on the subject,
    in most cases does not exist. A thin bank of clouds lies on the horizon.
    <span class="sidenote">Band of light appears.</span>The upper edge is illuminated; out of it is developed a band of light, which
    expands, increases in intensity of colour, and rises to the zenith. The colour
    is the same as in the arch, but the intensity of the colour is stronger. The
    colours of the band change in a never-ceasing play, but place and form
    remain unaltered. The band is broad, and its intense pale green stands out
    with wonderful beauty on the dark background. Now the band is twisted
    into many convolutions, but the innermost folds are still to be seen distinctly
    through the others. Waves of light continually undulate rapidly through
    its whole extent, sometimes from right to left, sometimes from left to right.
    Then, again, it rolls itself up in graceful folds. It seems almost as if breezes
    high in the air played and sported with the broad flaming streamers, the
    ends of which are lost far off on the horizon. The light grows in intensity,
    the waves of light follow each other more rapidly, prismatic colours appear
    on the upper and lower edge of the band, the brilliant white of the centre
    is enclosed between narrow stripes of red and green. Out of one band have
    now grown two. <span class="sidenote"> Second band and rays.</span>The upper continually approaches the zenith, rays begin
    to shoot forth from it towards a point near the zenith to which the south
    pole of the magnetic needle, freely suspended, points.</p>

    <p>“The band has nearly reached it, and now begins a brilliant play of rays
    lasting for a short time, the central point of which is the magnetic pole—a
    sign of the intimate connexion of the whole phenomenon with the magnetic
    forces of the earth. Round the magnetic pole short rays flash and flare
    on all sides, prismatic colours are discernible on all their edges, longer and
    shorter rays alternate with each other, waves of light roll round it as a centre.
    <span class="sidenote">Corona formed.</span>What we see is the auroral corona, and it is almost always seen when a band
    passes over the magnetic pole. This peculiar phenomenon lasts but a short
    time. The band now lies on the northern side of the firmament, gradually
    it sinks, and pales as it sinks; it returns again to the south to change and
    play as before. So it goes on for hours, the Aurora incessantly changes
    place, form, and intensity. It often entirely disappears for a short time,
    only to appear again suddenly, without the observers clearly perceiving how
    it came and where it went; simply, it is there.</p>

    <p><span class="sidenote">Single-rayed band.</span>“But the band is often seen in a perfectly different form. Frequently it
    consists of single rays, which, standing close together, point in an almost
    parallel direction towards the magnetic pole. These become more intensely
    bright with each successive wave of light; hence each ray appears to flash
    and dart continually, and their green and red edges dance up and down as
    the waves of light run through them. Often, again, the rays extend through
    the whole length of the band, and reach almost up to the magnetic pole.
    These are sharply marked, but lighter in colour than the band itself, and in
    this particular form they are at some distance from each other. Their colour
    is yellow, and it seems as if thousands of slender threads of gold were
    stretched across the firmament. A glorious veil of transparent light is spread
    over the starry heavens; the threads of light with which this veil is woven
    are distinctly marked on the dark background; its lower border is a broad
    intensely white band, edged with green and red, which twists and turns in
    constant motion. A violet-coloured auroral vapour is often seen simultaneously
    on different parts of the sky.</p>



    <p><span class="sidenote">Aurora in stormy weather.</span>“Or, again, there has been tempestuous weather, and it is now, let us
    suppose, passing away. Below, on the ice, the wind has fallen; but the
    clouds are still driving rapidly across the sky, so that in the upper regions its
    force is not yet laid. Over the ice it becomes somewhat clear; behind the
    clouds appears an Aurora amid the darkness of the night. Stars twinkle
    here and there; through the opening of the clouds we see the dark firmament,
    and the rays of the Aurora chasing one another towards the zenith. The
    heavy clouds disperse, mist-like masses drive on before the wind. <span class="sidenote">Fragments.</span>Fragments
    of the northern lights are strewn on every side: it seems as if the storm had
    torn the Aurora bands to tatters, and was driving them hither and thither
    across the sky. These threads change form and place with incredible
    rapidity. Here is one! lo, it is gone! Scarcely has it vanished before it
    appears again in another place. Through these fragments drive the waves of
    light: one moment they are scarcely visible, in the next they shine with
    intense brilliancy. But their light is no longer that glorious pale green; it
    is a dull yellow. It is often difficult to distinguish what is Aurora and what
    is vapour; the illuminated mists as they fly past are scarcely distinguishable
    from the auroral vapour which comes and goes on every side.</p>




    <p><span class="sidenote">Bands.</span>“But, again, another form. Bands of every possible form and intensity
    have been driving over the heavens. It is now eight o’clock at night, the
    hour of the greatest intensity of the northern lights. For a moment some
    bundles of rays only are to be seen in the sky. In the south a faint, scarcely
    visible band lies close to the horizon. All at once it rises rapidly, and spreads
    east and west. The waves of light begin to dart and shoot, some rays mount
    towards the zenith. For a short time it remains stationary, then suddenly
    springs to life. The waves of light drive violently from east to west, the
    edges assume a deep red and green colour, and dance up and down. The
    rays shoot up more rapidly, they become shorter; all rise together and
    approach nearer and nearer to the magnetic pole. <span class="sidenote">Rays reach the pole.</span>It looks as if there were
    a race among the rays, and that each aspired to reach the pole first. And
    now the point is reached, and they shoot out on every side, to the north and
    the south, to the east and the west. Do the rays shoot from above downwards,
    or from below upwards? Who can distinguish? From the centre
    issues a sea of flames: is that sea red, white, or green? Who can say? It is
    all three colours at the same moment! The rays reach almost to the horizon:
    the whole sky is in flames. Nature displays before us such an exhibition of
    fireworks as transcends the powers of imagination to conceive. Involuntarily
    we listen; such a spectacle must, we think, be accompanied with sound.
    <span class="sidenote">No noise.</span>But unbroken stillness prevails; not the least sound strikes on the ear.
    Once more it becomes clear over the ice, and the whole phenomenon has
    disappeared with the same inconceivable rapidity with which it came, and
    gloomy night has again stretched her dark veil over everything. This was the
    Aurora of the coming storm—the Aurora in its fullest splendour. No pencil
    can draw it, no colours can paint it, and no words can describe it in all its
    magnificence.”</p>

    <p>A reproduction of the woodcut in Payer’s ‘Austrian Arctic Voyages,’
    illustrating some of the features of the above description, will be found on
    <span class="cross-ref">Plate I</span>.</p>

    <figure class="plate" id="plate1">
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      <figcaption>The aurora during the ice-pressure.</figcaption>
      <p class="figsource"><i>[Payer's Austrian Artics Voyages.]</i></p>
    </figure>

    <p>In the ‘Edinburgh Encyclopædia,’ article “Aurora,” we find:—</p>



    <p><span class="sidenote">Descriptions of Auroræ in high Northern latitudes.</span>“In high Northern latitudes the Auroræ Boreales are singularly resplendent,
    and even terrific.</p>

    <p>“They frequently occupy the whole heavens, and, according to the testimony
    of some, eclipse the splendour of stars, planets, and moon, and even of the
    sun itself.</p>

    <p><span class="sidenote">In Siberia.</span>“In the south-eastern districts of Siberia, according to the description of
    Gmelin, cited and translated by Dr. Blagden (Phil. Trans. vol. lxxiv. p. 228),
    the Aurora is described to begin with single bright pillars, rising in the
    north, and almost at the same time in the north-east, which, gradually
    increasing, comprehend a large space of the heavens, rush about from place
    to place with incredible velocity, and finally almost cover the whole sky up
    to the zenith, and produce an appearance as if a vast tent were expanded in
    the heavens, glittering with gold, rubies, and sapphires. A more beautiful
    spectacle cannot be painted; but whoever should see such a northern light
    for the first time could not behold it without terror.”</p>


    <p><span class="sidenote">Maupertius’s description at Oswer-Zornea.</span>Maupertius describes a remarkable Aurora he saw at Oswer-Zornea on the
    18th December, 1876. An extensive region of the heavens towards the
    south appeared tinged of so lively a red that the whole constellation of Orion
    seemed as if dyed in blood. The light was for some time fixed, but soon
    became movable, and, after having successively assumed all the tints of violet
    and blue, it formed a dome of which the summit nearly approached the
    zenith in the south-west.</p>

    <p><span class="sidenote">Red Auroræ rare in Lapland.</span>Maupertius adds that he observed only two of the red northern lights in
    Lapland, and that they are of very rare occurrence in that country.</p>

    <p>The observations of Carl Bock, the Norwegian naturalist, kindly communicated
    by him to me, and detailed in Chapter III., quite confirm this
    observation of Maupertius as to the rare occurrence of red Auroræ in
    Lapland, he having only seen one.</p>

  </section>

  <!-- Chapitre 3_________________________________________________________-->
  <section class="chapter" id="chapter-3">
    <h3 class="titlechapter" id="chap-3">Some specific descriptions of auroræ, including results of the english arctic expedition, 1875-76</h3>
    <p class="shorter">Some specific descriptions of auroræ</p>

    <h4 id="chap-3-1">Captain Sabine’s Auroræ.</h4>

    <p>Captain Sabine describes Auroræ seen at Melville Island<span class="sidenote">Captain Sabine’s Auroræ.</span>(Parry’s first
    voyage, January 15). Towards the southern horizon an ordinary Aurora
    appeared. The luminous arch broke into masses streaming in different
    directions, always to the east of the zenith.</p>


    <p>The various masses seemed to arrange themselves in two arches, one
    passing near the zenith and a second midway between the zenith and the
    horizon<span class="sidenote">Curvature of arches towards each other.</span>, both north and south, but curving towards each other. At one
    time a part of the arch near the zenith was bent into convolutions like a
    snake in motion and undulating rapidly.</p>

    <h4 id="chap-3-2">Aurora seen at Sunderland, February 8th, 1817.</h4>

    <p>(‘Annals of Philosophy,’ vol. ix. p. 250.)</p>

    <p>It began about 7 <span class="smcapuc">P.M.</span> during a strong gale from the N.W., with single
    bright streamers in the N. and N.W., which covered a large space and rushed
    about from place to place with amazing velocity, and had a fine tremulous
    motion, illuminating the hemisphere as much as the moon does eight or nine
    days from change. About 11 o’clock part of the streamers appeared as if
    projected south of the zenith and looked like the pillars of an immense
    amphitheatre<span class="sidenote">Aurora seen at Sunderland, Feb. 8, 1817. Formation of corona.</span>, presenting a most brilliant spectacle and seeming to be in a
    lower region of the atmosphere, and to descend and ascend in the air for
    several minutes. (This appears to have been the formation of a corona.)
    One streamer passed over Orion, but neither increased nor diminished its
    splendour.</p>

    <h4 id="chap-3-3">Description of Aurora by Dr. Hayes, 6th January, 1861.</i></h4>



    <p><span class="sidenote">Dr. Hayes’s Aurora, 6th January, 1861.</span>‘Recent Polar Voyages’ contains a narrative of the voyage of Dr. Hayes,
    who sailed from Boston on the 6th of July, 1860, and wintered at Port
    Foulbe. He witnessed a remarkable display of the Aurora Borealis on the
    morning of the 6th January, 1861.<span class="sidenote">Development of Aurora.</span></p>




    <p>The darkness was so profound as to be oppressive. Suddenly, from the
    rear of the black cloud which obscured the horizon, flashed a bright ray.
    Presently an arch of many colours fixed itself across the sky, and the Aurora
    gradually developed.</p>


    <p>The space within the arch was filled by the black cloud; but its borders
    brightened steadily, though the rays discharged from it were exceeding
    capricious, now glaring like a vast conflagration, now beaming like the glow
    of a summer morn. More and more intense grew the light, until, from
    irregular bursts, it matured into an almost uniform sheet of radiance.
    Towards the end of the display its character changed. Lurid fires flung
    their awful portents across the sky, before which the stars seemed to recede
    and grow pale.</p>


    <p>The colour of the light was chiefly red; but every tint had its turn, and
    sometimes two or three were mingled; blue and yellow streamers shot across
    the terrible glare, or, starting side by side from the wide expanse of the
    radiant arch, melted into each other, and flung a strange shade of emerald
    over the illuminated landscape. Again this green subdues and overcomes
    the red; then azure and orange blend in rapid flight, subtle rays of violet
    pierce through a broad flash of yellow, and the combined streams issue in
    innumerable tongues of white flame, which mount towards the zenith. <span class="sidenote">Mixed colours. Colours change. Tongues of white flame formed.</span>
    </p>

    <p>The illustration which accompanies this description in the work is reproduced
    on Plate II., and forcibly reminds one of the “curtains” of the
    Aurora described in the preceding Chapter by Mons. Lottin.</p>



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      <figcaption></figcaption>
    </figure>

    <h4 id="chap-3-4">Prof. Lemström’s Aurora of 1st September, 1868.</h4>



    <p><span class="sidenote">Prof. Lemström’s Aurora, 1st September, 1868.</span>In the first Swedish Expedition, 1868, some remarkable observations were
    made on the appearance of luminous beams around the tops of mountains,
    which M. Lemström showed by the spectroscope to be of the same nature as
    Auroræ.</p>



    <p>On the 1st September, 1868, on the Isle of Amsterdam in the Bay of
    Sweerenberg, there was a light fall of snow, and the snowflakes were observed
    falling obliquely. <span class="sidenote">Aurora from earth’s surface.</span>All at once there appeared a luminous phenomenon
    which, starting from the earth’s surface, shot up vertically, cutting the
    direction of the falling snowflakes, and this appearance lasted for some
    seconds.  <span class="sidenote">Yellow-green line seen.</span>On examination with a spectroscope the yellow-green line was
    found by Lemström (but of feeble intensity) when the slit of the instrument
    was directed towards a roof or other object covered with snow, and even in
    the snow all round the observer.</p>




    <p><span class="sidenote">Lemström’s conclusions.</span>M. Lemström concluded that an electric discharge of an auroral nature,
    which could only be detected by means of the spectroscope, was taking place
    on the surface of the ground all around him, and that, from a distance, it
    would appear as a faint display of Aurora.</p>

    <p>[It should, however, here be noted that the reflection of an Aurora from a
    white or bright surface would give, in a fainter degree, the spectrum of the
    Aurora itself; and, apart from the phenomena seen by the eye, the case
    fails to be conclusive that an Aurora on the surface of the ground was
    examined.]</p>

    <h4 id="chap-3-5">Mr. J. R. Capron’s Aurora of October 24th, 1870.</h4>






    <p><span class="sidenote">Mr. J. R. Capron’s Aurora, Oct. 24, 1870.</span>The description, from my notes made at the time of this fine display, is as
    follows:—“Last evening (October 24) the Aurora Borealis was again most
    beautifully seen here (Guildford). At 6 <span class="smcapuc">P.M.</span> indications of the coming
    display were visible in the shape of <span class="sidenote">Silver glow in north.</span>a bright silver glow in the north, which
    contrasted strongly with the opposite dark horizon. For two hours this
    continued, with the addition from time to time of a crimson glow in the
    north-east, <span class="sidenote">Phosphorescent cloud-streamers.</span>and of streamers of opaque-white phosphorescent cloud, shaped
    like horse-tails (very different from the more common transparent auroral
    diverging streams of light), which floated upwards and across the sky from
    east and west to the zenith. At about 8 o’clock the display culminated; and
    few observers, I should think, ever saw a more lovely sky-picture.
    <span class="sidenote">Crimson masses on horizon.</span>Two
    patches of intense crimson light about this time massed themselves on the
    north-east and north-west horizon, the sky between having a bright silver
    glow. The crimson masses became more attenuated as they mounted upwards;
    and from them there suddenly ran up bars or streamers of crimson
    and gold light,<span class="sidenote">Coloured streamers.</span> which, as they rose, curved towards each other in the north,
    and, ultimately meeting, formed a glorious arch of coloured light, having at
    its apex an oval white luminous corona or cloud of similar character to the
    phosphorescent clouds previously described, but brighter. <span class="sidenote">Corona formed.</span>At this time the
    spectator appeared to be looking at the one side of a cage composed of
    glowing red and gold bars, which extended from the distant parts of the
    horizon to a point over his head. Shortly after this the Auroral display
    gradually faded away, and at 9 o’clock the sky was of its usual appearance,
    <span class="sidenote">Aurora fades away.</span>except that the ordinary tint seemed to have more of indigo, probably by
    contrast with the marvellous colours which had so lately shone upon it.”</p>




    <span class="sidenote">T. F.’s description of same at Torquay.</span><p>T. F., describing the same Aurora from Torquay, says it showed itself at
    sundown, attained its maximum at 8, and lasted until 11. At 8 o’clock more
    than half the visible heavens was one sea of colour; the general ground
    greenish yellow and pale rose, with extensive shoals of deep rose in the east
    and west; while from the north, streaming upwards to and beyond the
    zenith, were tongues and brushes of rosy red, so deep that the sky between
    looked black. Mr. Gibbs reported that in London, at about 8 o’clock, <span class="sidenote">TMr. Gibbs’s report in London.</span>brilliant
    crimson rays shot up to the zenith, and the sky seemed one mass of fire.</p>

    <p>A facsimile of my water-colour sketch of this fine discharge is given on
    Plate III.</p>



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    <h4 id="chap-3-6">Mr. Barker’s (superposed) red and white Auroræ, 9th November (1870?).</h4>





    <p><span class="sidenote">Mr. Barker’s Auroræ, 9th November (1870?).</span>On the 9th November (1870?) Mr. Barker saw at New Haven (U. S.) a most
    magnificent crimson Aurora. At about a quarter to 6 <span class="smcapuc">P.M.</span> it consisted of a
    brilliant streamer shooting up from the north-western horizon. This was
    continued in a brilliant red<span class="sidenote">Red Aurora.</span>, but rather nebulous, mass of light passing
    upwards and to the north. Its highest points were from 30° to 40° in
    altitude. <span class="sidenote">White Aurora.</span>A white Aurora, consisting of bright streamers, appeared simultaneously
    and extended round to the north-east. Prof. Newton informed
    Mr. Barker that he had observed an equally brilliant red patch of auroral
    light in the north-east five or ten minutes earlier.</p>



    <p><span class="sidenote">Red seen through white.</span>Since the lower end of the red streamers was much lower than that of the
    white, it would seem as if the red were seen through the white, the red being
    most remote.</p>



    <p><span class="sidenote">Crimson line not seen in white Aurora.</span>Spectroscopic observations of this Aurora were made. The crimson Aurora
    lasted less than half an hour, and then disappeared. In the white Aurora,
    which remained, the crimson line could not be seen.</p>



    <span class="sidenote">Carl Bock’s vibrating rays.</span><p>It may be here noted that during the Aurora seen by Carl Bock in Lapland,
    and painted by him by its own light (described, p. 25), he had the impression
    of sets of vibrating rays behind each other, and in the drawing it looks as if
    streamers were seen behind an arc.</p>

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    <h4 id="chap-3-7">Mr. J. R. Capron’s Aurora of February 4th, 1872.</h4>


    <p><span class="sidenote">Mr. J. R. Capron’s Aurora, Feb. 4, 1872. Masses of phosphorescent vapour. Rose tints appeared. Aurora from behind clouds. Formation of corona. Duration of corona. Streamers from corona. Rain during Aurora. Wind during night. Phosphorescent clouds preceded the Aurora in daylight.</span>
My description of this Aurora as seen at Guildford, and as given at the time,
    is as follows:—“Last evening, returning from church a little before 8 <span class="smcapuc">P.M.</span>,
    the sky presented a weird and unusual aspect, which at once struck the eye.
    A lurid tinge upon the clouds which hung around suggested the reflection of
    a distant fire; while scattered among these, torn and broken masses of vapour,
    having a white and phosphorescent appearance, and quickly changing their
    forms, reminded me of a similar appearance preceding the great Aurora of
    24th October, 1870. Shortly some of these shining white clouds or vapours
    partly arranged themselves in columns from east to west, and at the same
    time appeared the characteristic patches of rose-coloured light which are
    often seen in an auroral display. About 8 o’clock the clouds had to a certain
    extent broken away, and the Aurora shone out from behind heavy banks of
    vapour, which still rested on the eastern horizon, the north-west horizon
    being free from cloud and glowing brightly with red light. And now, at
    about 8.15, was presented a most beautiful phenomenon. While looking
    upwards, I saw a corona or stellar-shaped mass of white light form in the
    clear blue sky immediately above my head&nbsp;<span class="footnote">M. Lemström (Swedish Expedition, 1868) concludes that the corona of the Aurora Borealis
is not entirely a phenomenon of perspective, but that the rays have a true curvature, that they
    are currents flowing in the same direction and attract each other. There is also an account
    [<i>antè</i>, p. 16] of an Aurora at Melville Island (Parry’s first voyage), in which two arches were
    seen curving towards each other.</span>, not by small clouds or rays
    collecting, but more in the way that a cloud suddenly forms by condensation
    in the clear sky on a mountain top, or a crystal shoots in a transparent
    liquid, having too, as I thought, an almost traceable nucleus or centre, from
    which spear-like rays projected. From this corona in a few seconds shot
    forth diverging streamers of golden light, which descended to and mingled
    with the rosy patches of the Aurora hanging about the horizon. The spaces
    of sky between the streamers were of a deep purple (probably an effect of
    contrast). The display of the corona, though lasting a few minutes only,
    was equal to, if not excelling in beauty, the grand display of October 1870,
    before described, in which case, however, a ring or disk of white light of considerable
    size took the place of the stellar-shaped corona. What struck me
    particularly was the corona developing itself as from a centre in the clear
    sky, and the diverging streamers apparently shooting downwards, whereas in
    general the streamers are seen to shoot up from the horizon and converge
    overhead. The effect may have been an illusion; but, if so, it was a remarkable
    one. The general Aurora lasted for some time, till it was lost in a
    clouded sky; and, in fact, rain was descending at one time while the Aurora
    was quite bright. Strong wind prevailed during the night&nbsp;<span class="footnote">A brilliant display in December 1870, on the east coast of Sicily, was followed by very
    violent storms, with the overflow of the Tiber and the flooding of Rome.</span>. The Aurora
    was probably very extensive, as the evening, notwithstanding the clouds, was
    nearly as bright as moonlight. The peculiar clouds referred to must have
    preceded the Aurora in daylight, as I recollect seeing them at 6.30 as we
    went to church.”</p>

    <span class="sidenote">Aurora
    predicted.</span>

    <p>They had even then a peculiarly wild, ragged, and phosphorescent appearance,
    and so much resembled some I had seen to accompany the Aurora
    of October 1870, that I predicted (as came to pass) a display later in the
    evening. A <i>facsimile</i> of my water-colour sketch of this Aurora is given on
    Plate IV. fig. 1, while the corona and rays are represented (with rather too
    hard an outline) on Plate V. fig. 2.</p>

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    <h4 id="chap-3-8"><i>Description of an Aurora seen at Cardiff.</i></h4>

    <span class="sidenote">Aurora seen
    at Cardiff. Formation
    of corona.</span>

    <p>An Aurora was seen at Cardiff. A dusky red aspect of the sky towards the
    north, and extending itself across the zenith westward, made its appearance
    about half-past 5 <span class="smcapuc">P.M.</span> The lights reached their greatest intensity at 6 o’clock,
    when the sky was suffused with a rich crimson glow, a broad band of colour
    reaching from N.E. to W. A corona of deep hue, having rugged sharply
    defined edges, stood out prominently in the zenith, apparently on a parallel
    plane to the earth, and having its centre almost immediately over the head of
    the spectator.</p>

    <span class="sidenote">Radii
    thrown out
    from corona.</span>

    <p>From this corona, elliptic in form, and in its broadest diameter about four
    times the size of the moon, there were thrown out brilliant silvery blue radii,
    extending to the N.E. and W. horizon, and presenting the appearance of a
    vast cupola of fire.</p>

    <span class="sidenote">Rain fell
    when Aurora
    died out.</span>

    <p>At half-past 6 the lights died completely out, leaving masses of cloud
    drifting up from the south, and a shower of rain fell. The corona was
    remarked upon as unusual. At Edinburgh the sky was brilliant for several
    hours. (The date of this Aurora is uncertain, as the account is from an
    undated newspaper cutting. It is supposed to be in February 1872, but
    could hardly have been on the 4th, as the Aurora of that date did not reach
    its maximum development at Edinburgh till 8 <span class="smcapuc">P.M.</span>)</p>

    <h4 id="chap-3-9"><i>Mr. J. R. Capron’s Aurora, seen at Guildown, Guildford,
    February 4th, 1874.</i></h4>

    <span class="sidenote">Silvery
    brightness
    in N.E. Light-cloud,
    which moved
    from E. to
    W. Formation
    of arc in N. Streamers. Horizontal
    clouds of
    misty light.</span>

    <p>About 7 <span class="smcapuc">P.M.</span> my attention was drawn to a silvery brightness in the north-east.
    Above, and still more to the east, was a bright cloud of light, which
    looked dense and misty, and gave one the impression of an illuminated fog-cloud.
    The edges were so bright that the adjacent sky, but for the stars
    shining in it, might, by contrast, have been taken for a dark storm-cloud.
    The light-cloud expanded upwards until its apex became conical, and then
    moved rapidly from east, along the northern horizon, until it reached the
    due west, where it rested, and formed for some time a luminous spot in
    the sky. About the same time a long low arch of light formed along the
    northern horizon, having a brighter patch at each extremity; and these being
    higher in the sky, the arch and turned-up ends were in shape like a Tartar
    bow. This bow was permanent; and later on a cloud of rose-coloured light
    formed in the east, looking like the reflection of a distant fire. From the
    bow also shot up curved streamers of silver light towards the zenith, which
    at one time threatened to form a corona. This, however, did not happen,
    and the Aurora gradually faded away, until, when the moon rose about 8,
    a silver tinge in the east alone remained. I should also mention that fleecy
    horizontal clouds of misty light floated in the north above the bow across the
    streamers.</p>

    <p>Mr. H. Taylor informed me he saw a similar Aurora some three weeks
    before, in which the bright horizontal light and short white streamers were
    the main characters. I am not sure that the horizontal light-clouds were not
    actual mist-clouds illuminated by reflection of the Aurora; not so, however,
    I think, the first-mentioned cloud, which had more the appearance of the
    <i>aura</i> in the large end of an illuminated Geissler tube.</p>

    <span class="sidenote">Spectrum of
    the Aurora
    described.</span>

    <p>I examined the Aurora with a Browning direct-vision spectroscope, and
    found Ångström’s line quite bright, and by the side of it three faint and misty
    bands towards the blue end of the spectrum upon a faintly illuminated
    ground. I could also see at times a bright line beyond the bands towards the
    violet. There was not light enough to take any measurements of position of
    the lines.</p>

    <p>I made a pencil sketch of this Aurora, at the time when the light-cloud
    had moved W. and the arc formed, and of the spectrum. These drawings are
    reproduced on Plate VI. figs. 1 and 1<i>a</i>.</p>

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    <h4 id="chap-3-10"><i>Mr. Herbert Ingall’s Aurora, July 18th, 1874.</i></h4>

    <span class="sidenote">Mr. Herbert
    Ingall’s
    Aurora, July
    18, 1874. Haze canopy
    formed. Bright
    bluish flames
    appeared. Beams and
    streamers
    appeared. Oscillatory
    motion of
    rays.</span>

    <p>An Aurora of July 18th, 1874, seen by Mr. Herbert Ingall at Champion
    Hill, S.E., was described by him as an extraordinary one. About 11 the
    sky was clear; at midnight the sky was covered by a sort of haze canopy,
    sometimes quite obscuring the stars, and then suddenly fading away. Mr.
    Ingall was shortly after remarking the sky in the S.E. and S. horizon as being
    more luminous than usual, when his attention was drawn to a growing
    brightness in the S.W., and a moment afterwards bright bluish flames
    “swept over the S.W. and W. horizon, as if before a high wind. They were
    not streamers, but bright blue flames.” They lasted about a minute and
    faded; but about two minutes afterwards a glowing luminosity appeared in
    the W.S.W., and broke into brilliant beams and streamers. The extreme
    rays made an angle of 90° with each other, the central ray reaching an
    altitude of 50°. The extreme divergence of the streamers (indicating their
    height above the earth’s surface), and their direction (from W.S.W. to E.N.E.)
    at right angles to the magnetic meridian, suggested to Mr. Ingall a disturbance
    of an abnormal character. The rays had an oscillatory motion for about
    fifteen seconds, and then disappeared, “as if a shutter had suddenly obscured
    the source of light.”</p>


    <span class="sidenote">Mr. Ingall’s
    remarks corroborated.</span>

    <p>Mr. Ingall’s remarks were corroborated by an observer in lat. 54° 46´ 6″·2 N.,
    long. 6h 12m 19s·75 W. The display, however, was more brilliant, and the
    intensity of light at midnight illuminated the whole district as with an electric
    light. The rays, too, bore tints differing from one another; the largest
    seemed to partake of the nature of the blue sky, while the smaller ones,
    running parallel with the horizon, were ever changing from blue to orange-red.</p>

    <span class="sidenote">Rev. C.
    Gape saw
    flashes or
    streaks of a
    pale blue
    colour.</span>

    <p>On June 25 (same year?), between 9 and 10 o’clock, the Rev. Chas. Gape
    saw at Rushall Vicarage, Scole, Norfolk, in the E.S.E., very frequent flashes
    or streaks of a pale blue colour darting from the earth towards the heavens
    like an Aurora. The day had been dull and close, with distant thunder.
    In the E.S.E. it was dark, but overhead and everywhere else it was clear
    and starry.</p>

    <h4 id="chap-3-11"><i>Mr. J. R. Capron’s White Aurora of September 11th, 1874.</i></h4>

    <span class="sidenote">Mr. J. R.
    Capron’s
    white
    Aurora of
    Sept. 11,
    1874.</span>

    <p>On September 11, 1874, we were at Kyle Akin, in the Isle of Skye. The
    day had been wet and stormy, but towards evening the wind fell and the
    sky became clear. About 10 <span class="smcapuc">P.M.</span> my attention was called to a beautiful
    Auroral display.</p>

    <span class="sidenote">Double arc
    of pure
    white light
    in the N.</span>

    <p>No crimson or rose tint was to be seen, but a long low-lying arc of the
    purest white light was formed in the north, and continued to shine with more
    or less brilliancy for some time. The arc appeared to be a double one, by the
    presence of a dark band running longitudinally through it.</p>

    <span class="sidenote">White
    streamers. Auroral bow
    believed to
    be near the
    earth.</span>

    <p>Occasional streamers of equally pure white light ran upwards from either
    end of the bow. The moon was only a day old, but the landscape was lighted
    up as if by the full moon; and the effect of Kyle Akin lighthouse, the
    numerous surrounding islands, and the still sea between was a true thing of
    beauty. The display itself formed a great contrast to the more brilliant
    but restless forms of Auroræ generally seen. I particularly noticed a somewhat
    misty and foggy look about the brilliant arc, giving it almost a solid
    appearance. The space of sky between the horizon and the lower edge of
    the arc was of a deep indigo colour, probably the effect of contrast. I had a
    strong impression that the bow was near to the earth, and was almost convinced
    that the eastern end and some fleecy clouds in which it was involved
    were between myself and the peaks of some distant mountains.</p>

    <p>I have not seen any other account of this Aurora, of which I was able at
    the time to obtain a sketch. This is reproduced on Plate VII. It was a
    lovely sight, and wonderfully unlike the cloud-accompanied and crimson
    Auroræ which I had seen in the South.</p>

    <p>It is noticed in Parry’s ‘Third Voyage’ that the lower edge of the auroral
    arch is generally well defined and unbroken, and the sky beneath it so exactly
    like a dark cloud (to him often of a brownish colour), that nothing could
    convince to the contrary, if the stars, shining through with undiminished
    lustre, did not discover the deception.</p>

    <span class="sidenote">No trace of
    brown colour
    in segment
    of sky below
    the arc.</span>

    <p>I saw no trace of brown colour. The segment below the arch resting on
    the horizon was of a deep indigo colour.</p>

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    <h4 id="chap-3-12"><i>Dr. Allnatt’s Aurora, June 9th, 1876.</i></h4>

    <span class="sidenote">Dr. Allnatt’s
    Aurora,
    June 9, 1876. Band of
    auroral light
    appeared. Streaks of
    cirro-stratus
    divided the
    Aurora. Want of
    electric
    manifestations
    attributed
    to
    absence of
    sun-spots.</span>

    <p>Dr. Allnatt, writing to the ‘Times’ from Abergele, North Wales, near the
    coast of the Irish Channel, reported an Aurora on the night of the 9th
    June, 1876. After a cool and gusty day, with a strong N.E. wind and a
    disturbed sea, there appeared at 11 <span class="smcapuc">P.M.</span> in the N. horizon a broad band of
    vivid auroral light, homogeneous, motionless, and without streamers. About
    midnight a long attenuated streak of black cirro-stratus stretched parallel
    with the horizon, and divided the Aurora into nearly symmetrical sections.
    On the preceding day the sky was covered with dark masses of electric cloud
    of weird and fantastic forms. The season had been singularly unproductive
    of high electric manifestations, which Dr. Allnatt thought might be attributable
    to the comparative absence of spots on the solar disk. [It may here
    be noted how conspicuous the years 1877 and 1878 have been for absence of
    Sun-spots and of Auroræ.]</p>

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    <h4 id="chap-3-13"><i>Herr Carl Bock’s Lapland Aurora, 3rd October, 1877.</i></h4>

    <span class="sidenote">Herr Carl
    Bock’s Lapland
    Aurora,
    3rd Oct.
    1877. Lapland
    Auroræ
    generally of
    the yellow
    type.</span>

    <p>In January 1878 I had the pleasure to meet, at the Westminster Aquarium,
    Herr Carl Bock, the Norwegian naturalist, who accompanied four Laplanders,
    two men and two women, with sledges, tents, &amp;c., on their visit to this
    country. The Laplanders (as mentioned elsewhere) did not confirm the
    accounts of noises said to have been observed by Greenlanders and others
    during the Aurora. Carl Bock mentioned to me that the displays he saw in
    Lapland were most brilliant, but generally of the yellow type (the Laplanders
    called the Aurora “yellow lights”). He saw only one red Aurora.
    He kindly lent me a picture (probably in its way unique), an oil-painting of
    an Aurora Borealis, entirely sketched by the light of the Aurora itself.</p>

    <span class="sidenote">A picture
    painted by
    light of the
    Aurora. Movement
    of the rays. Inner edge
    of arc
    fringed with
    rays.</span>

    <p>The painting is remarkable for the tender green of the sky, an effect
    probably due to a mixture of the ordinary sky colour with the yellow light of
    the Aurora. This picture was taken at Porsanger Fjord, in lat. 71° 50´, on
    3rd October, 1877. It lasted from 9 <span class="smcapuc">P.M.</span> till about 11 <span class="smcapuc">P.M.</span> The rays kept
    continually moving, and certain of them seemed in perspective and behind
    the others. It will be noticed that the <i>inner</i> edge of the arc is fringed with
    rays, contrary to the sharp and definite margin which is usually presented.
    Probably two Auroræ or auroral forms were seen—a quiescent arc in front,
    and a set of moving streamers beyond. Two larger and brighter patches of
    light are seen at each extremity of the arc, as in the case of the Aurora seen
    by me at Guildown, February 4th, 1874, which, indeed, the display much
    resembles. A reduced facsimile of Herr Bock’s excellent picture is given on
    Plate VIII.</p>

    <span class="sidenote">Aurora of
    longitudinal
    rays.</span>

    <p>Herr Bock also acquainted me that on the following day he saw an Aurora
    in which the lines of light, instead of being vertical, were longitudinal, and
    were continually swept along in several currents. They were not so strong
    as in the former case.</p>

    <h4 id="chap-3-14"><i>Rev. T. W. Webb’s Aurora.</i></h4>

    <span class="sidenote">Rev. T. W.
    Webb’s
    Aurora. Arc resolved
    into sets of
    streamers
    moving in
    opposite
    directions.</span>

    <p>The Rev. T. W. Webb has described to me in a letter an Aurora very like
    that seen by Carl Bock in Lapland, and apparently the prevailing type in
    those regions. An arc similar to that figured by Carl Bock appeared in the
    N.W., and seemed to resolve itself into two sets of streamers moving in
    opposite directions (or the one set might be fixed and the other moving), like
    the edges of two great revolving toothed wheels. This lasted but for a few
    seconds; but during that interval the tints were varied and brilliant, including
    blue and green.</p>

    <h4 id="chap-3-15"><i>The English Arctic Expedition 1875-76, under Capt. Sir George Nares.</i></h4>

    <span class="sidenote">English
    Arctic
    Expedition,
    1875-76. Instructions
    for use of
    officers. Appendix B. Capt. Sir
    G. Nares’s
    report. True Auroræ
    seldom observed,
    and
    displays
    faint. Citron-line
    observed on
    only two
    displays. Appendix C.</span>

    <p>In anticipation of the starting of this Expedition, some instructions for the
    use of the officers in connexion with the hoped for display of brilliant Auroræ
    were prepared:—as to general features of the Auroræ, by Professor Stokes; as
    to Polarization, by Dr. William Spottiswoode; and as to Spectrum work, by
    Mr. Norman Lockyer and myself. As these instructions were somewhat
    elaborate, and will apply to all Auroral displays, I have supplied a copy
    of them in Appendix B. They were unfortunately not brought into
    requisition, for want of the Auroræ themselves. Capt. Sir George Nares
    has reported to the Admiralty, under date 5th December, 1877, as follows:—“Although
    the auroral glow was observed on several occasions between
    25 October, 1875, and 26 February, 1876, true Auroræ were seldom observed;
    and the displays were so faint, and lasted so short a time, and the spectrum
    observations led to such poor results, that no special report has been considered
    necessary. Although the citron-line was observed occasionally, on
    only two displays of the Aurora was it well defined, and then for so short a
    time that no measure could be obtained.” (For Sir George Nares’s further
    Report see Appendix C, containing extracts from blue-book, ‘Results derived
    from the Arctic Expedition, 1875-6.’)</p>

    <h4 id="chap-3-16"><i>Aurora Australis.</i></h4>

    <span class="sidenote">Aurora
    Australis. Mr. Forster’s
    description. Long
    columns of
    white light
    spreading
    over the
    whole sky.</span>

    <p>In an article on Auroræ in high Southern latitudes (Phil. Trans. No. 461,
    and vol. liv. No. 53), we find that Mr. Forster, who as naturalist accompanied
    Capt. Cook on his second voyage round the world, says:—“On
    February 17th, 1773, in south latitude 58°, a beautiful phenomenon was
    observed during the preceding night, which appeared again this, and several
    following nights. It consisted of long columns of a clear white light
    shooting up from the horizon to the eastward almost to the zenith, and
    gradually spreading over the whole southern part of the sky. These columns
    were sometimes bent sideways at their upper extremities; and though in most
    respects similar to the northern lights of our hemisphere, yet differed from
    them in being always of a whitish colour, whereas ours assume various tints,
    especially those of a fiery and purple hue. The sky was generally clear when
    they appeared, and the air sharp and cold, the thermometer standing at the
    freezing point.” This account agrees very closely in particulars with Capt.
    Maclear’s notice of Aurora Australis [after referred to], and especially in the
    marked absence of red Auroræ.</p>

    <p>The height of the barometer does not appear to be mentioned, the temperature
    being apparently much the same as in the more recent cases.</p>

    <span class="sidenote">Capt.
    Maclear’s
    Aurora
    Australis,
    3rd March,
    1874. Light of
    pale yellow
    tint only.</span>

    <p>In a letter dated from H.M.S. ‘Challenger,’ North Atlantic, April 10th,
    1876, Capt. Maclear was good enough to communicate to me some particulars
    of an Aurora Australis seen 3rd March 1874, in lat. 54° S., long. 108° E.
    The letter is mainly descriptive of the spectrum (which will be described in
    connexion with the general question of the spectrum of the Aurora). It
    states that the red line was looked for in vain, and that the light appeared
    of a <i>pale yellow</i>, and had none of the rosy tint seen in the northern
    displays.</p>

    <span class="sidenote">Capt.
    Maclear’s
    Auroræ
    described in
    ‘Nature.’</span>

    <p>Capt. Maclear has since contributed to ‘Nature,’ of 1st November 1877, a
    description of four Auroræ seen from the ‘Challenger’ in high southern
    latitudes (including the one communicated to me). He speaks of the opportunity
    of observing as not frequent, either from the rarity of the phenomena,
    or because the dense masses of cloud prevalent in those regions prevented
    their being seen except when exceptionally bright. There were four appearances
    described:—</p>

    <span class="sidenote">Feb. 9, 1874.</span>

    <p>(1.) At 1.30 on the morning of February 9th, 1874, preceded by a watery
    sunset, lat. 57° S. and long. 75° E., bar. 29·0 in., ther. 35°; brilliant streaks
    to the westward. Day broke afterwards with high cirrus clouds and clear
    horizon.</p>

    <span class="sidenote">Feb. 21,
    1874.</span>

    <p>(2.) At 9.30 <span class="smcapuc">P.M.</span>, February 21, 1874, lat. 64° S., long. 89° E., bar. 28·8 in.,
    ther. 31°; one bright curved streamer. The Aurora preceded a fine morning
    with cumulo-stratus clouds, extending from Jupiter (which appeared to be
    near the focus) through Orion and almost as far beyond. Under this a black
    cloud, with stars visible through it. Real cumuli hid great part of the
    remainder of the sky, but there were two vertical flashing rays which moved
    slowly to the right (west). Generally the Aurora was still bright.</p>

    <span class="sidenote">March 3,
    1874. Auroral line
    found in
    light to
    southward.</span>

    <p>(3.) At midnight, March 3rd, 1874, lat. 53° 30´ S., long. 109° E., bar. 29·1,
    ther. 36°, after some days’ stormy weather, a brilliant sunset, followed by a
    fine morning. Soon after 8 <span class="smcapuc">P.M.</span> the sky began to clear and the moon shone
    out. Noticing the light to the southward to be particularly bright, Capt.
    Maclear applied the spectroscope, and found the distinguishing auroral line.</p>

    <span class="sidenote">Brilliant
    white clouds
    seen.</span>

    <p>About midnight the sky was almost clear, but south were two or three
    brilliant light clouds, colour very white-yellow, shape cumulo-stratus. From
    about west to near south extended a long feathery light of the same colour,
    parallel with the horizon, and between south and west there appeared occasionally
    brilliant small clouds. The upper edges seemed hairy, and gave one
    the idea of a bright light behind a cloud. The forms changed, but no particular
    order was noticed.</p>

    <p>(Here follows a description of the spectrum, and the mode in which a
    delineation by the lines was obtained.)</p>

    <span class="sidenote">March 6,
    1874. Capt.
    Maclear
    suggests
    whether a
    low barometer
    has
    to do with
    the absence
    of red.</span>

    <p>(4.) At 8 <span class="smcapuc">P.M.</span>, March 6th, 1874. This was a slight Aurora, seen to the
    southward; after this the clouds changed to high cirrus. Capt. Maclear
    suggests whether a low barometer has any thing to do with the absence of red
    in the spectrum, the normal state of the barometer being an inch lower in
    those regions than in more temperate latitudes.</p>

    <span class="sidenote">Barometer
    falls after
    the Aurora,
    and strong
    gale from
    the S. or S.W.
    follows.</span>

    <p>Edin. Encyc. vol. iii. article “Aurora.” Dr. Kirwan observed that the
    barometer commonly falls after the Aurora. Mr. Winn, in the seventy-third
    volume of the Phil. Trans., makes the same remark, and says that in twenty-three
    instances, without fail, a strong gale from the south or south-west
    followed the appearance of an Aurora. If the Aurora were bright, the gale
    came on within twenty-four hours, but was of no long continuance; if the
    light was faint and dull, the gale was less violent, longer in coming, and longer
    in duration.</p>

    <span class="sidenote">Pale yellow
    glow rare in
    the Aurora
    Borealis.</span>

    <p>The pale yellow-coloured glow referred to by Capt. Maclear is, in my experience,
    rare in the Aurora Borealis. It is probably the “æqualiter et sine
    eruptionibus aut radiis <i>fulvi</i>,” described by Seneca (<i>antè</i>, p. 1), and may probably
    belong to more southern climes.</p>

    <span class="sidenote">Spectrum
    of Auroræ
    Australes
    extends
    more into
    the violet.</span>

    <p>We shall see too, by-and-by, that these Auroræ Australes as to spectrum
    extend more into the violet than the Aurora Borealis. The yellow, as complementary
    to violet, is likely thus to make (in the absence of the red) its
    appearance.</p>

    <p>It is, however, somewhat singular that Carl Bock found almost exclusively
    yellow Auroræ in Lapland.</p>

    <p>In Proctor’s ‘Borderland of Science,’ article “The Antarctic Regions,” we
    find quoted a passage from a letter by Capt. Howes, of the ‘Southern Cross,’
    in which a graphic description is given of a Southern Aurora:—</p>

    <span class="sidenote">Capt.
    Howes’s description
    of
    a Southern
    Aurora.</span>

    <p>“At about half-past one on the 2nd of last September the rare phenomenon
    of the Aurora Australis manifested itself in a most magnificent manner.
    Our ship was off Cape Horn, in a violent gale, plunging furiously into a
    heavy sea, flooding her decks, and sometimes burying her whole bows beneath
    the waves. The heavens were as black as death, not a star was to be seen,
    when the brilliant spectacle first appeared.</p>


    <span class="sidenote">Balls of
    electric fire
    resting on
    mast-heads
    &amp;c.</span>

    <p>“I cannot describe the awful grandeur of the scene; the heavens gradually
    changed from murky blackness till they became like vivid fire, reflecting a
    lurid glowing brilliancy over every thing. The ocean appeared like a sea of
    vermilion lashed into fury by the storm, the waves dashing furiously over our
    side, ever and anon rushed to leeward in crimson torrents. Our whole ship—sails,
    spars, and all—seemed to partake of the same ruddy hues. They were
    as if lighted up by some terrible conflagration. Taking all together—the
    howling, shrieking storm, the noble ship plunging fearlessly beneath the
    crimson-crested ways, the furious squalls of hail, snow, and sleet, drifting
    over the vessel, and falling to leeward in ruddy showers, the mysterious
    balls of electric fire resting on our mast-heads, yard-arms, &amp;c., and, above all,
    the awful sublimity of the heavens, through which coruscations of auroral
    light would shoot in spiral streaks, and with meteoric brilliancy,—there was
    presented a scene of grandeur surpassing the wildest dreams of fancy.”</p>

    <p>The foregoing picture presents a singular contrast to the yellow-white
    Auroræ described as seen in high southern latitudes by Capt. Maclear, and is
    interesting as a southern Aurora of a red or ruddy tint. Looking, however,
    at the extreme rarity of red Auroræ in those latitudes, and the description of
    “mysterious balls of electric fire resting on our mast-heads, yard-arms, &amp;c.” (a
    phenomenon not often noticed in connexion with the Aurora), it suggests
    itself that the case in question may have been an instance not of a true
    Aurora, but of an electric display, with conditions approaching those experienced
    by travellers who have found themselves in mountainous districts
    surrounded by storm-clouds charged with electricity&nbsp;<span class="footnote">Some curious instances have been recently (January 1879) given in the ‘Times’ of such electric phenomena, comprising, amongst others, gas lighted by the finger in Canada, points of flame seen on the ironwork of Teignmouth Bridge, and similar points seen on the alpenstocks and axes of a party making a mountain ascent in Switzerland.</span>.</p>

    <h4 id="chap-3-17"><i>Prof. Piazzi Smyth’s Typical Auroræ.</i></h4>

    <span class="sidenote">Prof. Piazzi
    Smyth’s
    typical
    Auroræ.</span>

    <p>Prof. Piazzi Smyth was kind enough lately to send me the fourteenth
    volume of the ‘Astronomical Observations made at the Royal Observatory,
    Edinburgh, during the years 1870-1877.’ This volume, amongst its other
    interesting matter, affords some valuable information on the subject of the
    Aurora Borealis. The Aurora plates are five in number, three comprising
    some well-executed chromo-lithographs of typical Auroræ, from sketches
    made by Prof. Smyth, the other two plates being of the Aurora spectrum.
    The Auroræ delineated are thus described:—</p>


    <span class="sidenote">Aug. 6, 1871,
    quiescent
    arc. August 21,
    1871,
    active arc.</span>

    <p>Plate 5. (August 6, 1871.) An example of a mild quiescent kind of
    auroral arc, with dark cavernous substratum. (August 21, 1871.) An example
    of a bright large active arc darting out rays.</p>

    <span class="sidenote">Sept. 7, 1871,
    arc streamers
    and
    clouds. May 8, 1871,
    double arc
    (longitudinal).</span>

    <p>Plate 6. (September 7, 1871.) An auroral arc, with streamers and dark
    clouds, and maintaining a bright appearance though in proximity to the
    moon. (May 8, 1871.) A double-arched auroral arc (the arches are longitudinally
    arranged).</p>

    <span class="sidenote">April 28,
    1871, multiple
    arc. Oct. 25,
    1870,
    coloured
    Aurora.</span>

    <p>Plate 7. (April 28, 1871.) A multiple-arched arc of Aurora with moonlight.
    (October 25, 1870.) A case of grandest coloured Auroræ, or Aurora
    superb and almost universal.</p>

    <p>All the foregoing drawings are very vivid and striking, and form a most
    interesting set of typical forms of Auroræ.</p>

    <p>According to my own experience, the Aurora with arches arranged longitudinally,
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    thus, <img src="assets/aurorae/images/i_030.jpg" width="60" height="18" alt="Symbols" />, is the rarest of all the forms. I have not met
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4006 4007 4008 4009 4010 4011 4012 4013 4014 4015 4016 4017 4018 4019 4020 4021 4022 4023 4024 4025 4026 4027 4028 4029 4030 4031 4032 4033 4034 4035 4036 4037 4038 4039 4040 4041 4042 4043 4044 4045 4046 4047 4048 4049 4050 4051 4052 4053 4054 4055 4056 4057 4058 4059 4060 4061 4062 4063 4064 4065 4066 4067 4068 4069 4070 4071 4072 4073 4074 4075 4076 4077 4078 4079 4080 4081 4082 4083 4084 4085 4086 4087 4088 4089 4090 4091 4092 4093 4094 4095 4096 4097 4098 4099 4100 4101 4102 4103 4104 4105 4106 4107 4108 4109 4110 4111 4112 4113 4114 4115 4116 4117 4118 4119 4120 4121 4122 4123 4124 4125 4126 4127 4128 4129 4130 4131 4132 4133 4134 4135 4136 4137 4138 4139 4140 4141 4142 4143 4144 4145 4146 4147 4148 4149 4150 4151 4152 4153 4154 4155 4156 4157 4158 4159 4160 4161 4162 4163 4164 4165 4166 4167 4168 4169 4170 4171 4172 4173 4174 4175 4176 4177 4178 4179 4180 4181 4182 4183 4184 4185 4186 4187 4188 4189 4190 4191 4192 4193 4194 4195 4196 4197 4198 4199 4200 4201 4202 4203 4204 4205 4206 4207 4208 4209 4210 4211 4212 4213 4214 4215 4216 4217 4218 4219 4220 4221 4222 4223 4224 4225 4226
    with it myself, nor do I recollect an illustration of one other than Prof.
    Smyth’s.</p>

  </section>

  <!-- Chapitre 4_________________________________________________________-->
  <section class="chapter" id="chapter-4">
    <h3 class="titlechapter" id="chap-4">Phenomena simuling auroræ</h3>
    <p class="shorter">Phenomena simuling auroræ</p>

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    <div id="chap-4-flow-fr">
      <h4 id="chap-4-1"><i>Auroric Lights (Kinahan).</i></h4>


      <p>Mr. G. Henry Kinahan writes to ‘Nature,’ from Ovoca, under date
      January 27th, 1877, and speaks of two distinct kinds of light so classed—one
      brilliant and transparent, of a white yellowish-blue or yellowish-red colour,
      while the other is semi-opaque and of a bloody red colour, the latter being
      considered in Ireland a forerunner of bad weather. The first kind generally
      appears as intermittent pencils of light that suddenly appear and disappear.</p>

      <div class="sidenote">Frequently
      not stationary,
      but
      jumping
      about.</div>

      <p>Usually they proceed or radiate from some point near the north of the
      horizon; but Mr. Kinahan has frequently seen them break from a point in
      the heavens, not stationary, but jumping about within certain limits. Sometimes
      these lights occur as suddenly flashing clouds of light of a white colour,
      but at other times of blue and reddish yellow.</p>

      <div class="sidenote">In daylight
      like sun-rays. Red light
      appears in
      clouds floating
      upwards
      or diffused.</div>


            <div class="sidenote">Frequently
            not stationary,
            but
            jumping
            about.</div>

            <p>Usually they proceed or radiate from some point near the north of the
            horizon; but Mr. Kinahan has frequently seen them break from a point in
            the heavens, not stationary, but jumping about within certain limits. Sometimes
            these lights occur as suddenly flashing clouds of light of a white colour,
            but at other times of blue and reddish yellow.</p>

            <div class="sidenote">In daylight
            like sun-rays. Red light
            appears in
            clouds floating
            upwards
            or diffused.</div>

            <p>If this class of lights is watched into daylight, they appear somewhat like
            faint rays of a rising sun. One morning, while travelling in West Galway in
            the twilight, they were very brilliant, and quite frightened Mr. Kinahan’s
            car-driver, who thought the sun was going to rise in the north instead of the
            east. The second, or bloody red light, usually occurs in clouds floating in
            one direction up into the heavens, but often diffused over a portion of the sky.
            Mr. Kinahan has never seen them coming from the east, and on only a few
            occasions from the south, but generally from the west, north-west, or north.</p>

            <div class="sidenote">Red light
            appears as
            dirty misty
            clouds in
            daylight,
            or as a mist
            or misty
            rays.</div>

            <p>If both kinds of light appear at the same time, the second while passing
            over the first dims it. If the second class is watched into daylight, they
            appear as dirty misty clouds that suddenly form and disappear without the
            spectator being able to say where they come from or where they go to, or as
            a hazy mist over a portion of the sky, that suddenly appears and disappears, or
            as misty rays proceeding from a point in the horizon. Generally, when
            these clouds occur, there is a bank of black clouds to the westward.</p>

            <div class="sidenote">Season since
            October
            1876 prolific
            in auroric
            light.</div>

            <p>Mr. Kinahan then speaks of the season as having been prolific in auroric
            light, as there had been few nights since the 1st October then last (1876) in
            which they did not appear. On many occasions they were late in the night,
            being very common and brilliant during the dark days of December, a few
            hours before dawn (about 5 o’clock). Each time there was a fine day they
            appeared also, and the weather broke again.</p>

            <div class="sidenote">Mr. J. Allan
            Broun questions
            nature
            of these
            lights, as
            Aurora is
            seldom seen
            at 5 <span class="smcapuc">A.M.</span> in
            this country. On 77 occasions
            seen
            only twice
            so early. Season was
            of marked
            infrequency
            elsewhere.</div>

            <p>Mr. Jno. Allan Broun refers to this graphic account of Mr. Kinahan’s,
            and concludes there must have been some mistake as to the nature of these
            “auroric lights,” as the Aurora Borealis is very rarely seen at 5 <span class="smcapuc">A.M.</span> in this
            country. In the years 1844 and 1845, during which the Aurora was sought for
            at Makerstown every hour of the night, it was observed in 77 nights on an
            average of nearly three hours each night; but it was seen only twice so early,
            and that with a bright or brilliant Aurora, which remained during five hours
            on the first occasion, and from 6 <span class="smcapuc">P.M.</span> to 6 <span class="smcapuc">A.M.</span> on the second. Parts of the
            phenomenon seen by Mr. Kinahan, Mr. Broun also could not say he had ever
            seen; and if Mr. Kinahan’s observations could have been confirmed it would
            have been most important, especially as made so frequently at the epoch of
            minimum. The description is in many respects a sufficiently recognizable
            one of auroral discharges; but the frequent appearance in early morning is
            certainly unusual, and few if any Auroræ seem to have been recorded as
            appearing elsewhere in Great Britain during the time which Mr. Kinahan refers
            to as so prolific (see, however, Dr. Allnatt’s, <i>antè</i>, p. 24). In fact, the season
            in question was one of marked infrequency (see English Arctic Expedition
            Report, <i>antè</i>, p. 26). Mr. Buchan furnished Mr. Broun with a note of Auroræ
            seen in the stations of the Scottish Meteorological Society during the year
            1876, and they were 42 in number, 26 in the first half, and 16 in the second
            half of the year. The greater part were seen in the most northerly stations,
            including the Orkney, Shetland, and Faroe Islands, and only 9 south of
            the Forth.</p>

            <h4 id="chap-4-2"><i>Luminous Arch.</i></h4>

            <div class="sidenote">Luminous
            arch, Sept.
            11, 1814. Height
            above horizon
            6 to 9
            miles.</div>

            <p>In the ‘Annals of Philosophy,’ vol. iv. p. 362, there is a minute description
            of a luminous arch which appeared in the sky on the night of Sunday,
            September 11th, 1814, and was seen in the west of England opposite the
            Irish Sea, the west part of the south of Scotland, and part of the west of
            Ireland. It was described as a part of either a body of dense greyish-white
            light, or a mass of luminous matter in the shape of an arch. Its height above
            the horizontal line was estimated at not more than 9 nor less than 6 miles.</p>

            <div class="sidenote">It moved
            southward,
            and was
            assumed to
            differ from
            the Aurora.</div>

            <p>Its direction when first seen was N. 80° E., and S. 80° W. It moved to the
            southward. It was assumed to differ from the Aurora Borealis in wanting
            coruscations, and in its having a much paler light.</p>

    </div>






    <div id="chap-4-flow-eng">


          <p>Mr. G. Henry Kinahan writes to ‘Nature,’ from Ovoca, under date
          January 27th, 1877, and speaks of two distinct kinds of light so classed—one
          brilliant and transparent, of a white yellowish-blue or yellowish-red colour,
          while the other is semi-opaque and of a bloody red colour, the latter being
          considered in Ireland a forerunner of bad weather. The first kind generally
          appears as intermittent pencils of light that suddenly appear and disappear.</p>

          <div class="sidenote">Frequently
          not stationary,
          but
          jumping
          about.</div>

          <p>Usually they proceed or radiate from some point near the north of the
          horizon; but Mr. Kinahan has frequently seen them break from a point in
          the heavens, not stationary, but jumping about within certain limits. Sometimes
          these lights occur as suddenly flashing clouds of light of a white colour,
          but at other times of blue and reddish yellow.</p>

          <div class="sidenote">In daylight
          like sun-rays. Red light
          appears in
          clouds floating
          upwards
          or diffused.</div>

          <p>If this class of lights is watched into daylight, they appear somewhat like
          faint rays of a rising sun. One morning, while travelling in West Galway in
          the twilight, they were very brilliant, and quite frightened Mr. Kinahan’s
          car-driver, who thought the sun was going to rise in the north instead of the
          east. The second, or bloody red light, usually occurs in clouds floating in
          one direction up into the heavens, but often diffused over a portion of the sky.
          Mr. Kinahan has never seen them coming from the east, and on only a few
          occasions from the south, but generally from the west, north-west, or north.</p>

          <div class="sidenote">Red light
          appears as
          dirty misty
          clouds in
          daylight,
          or as a mist
          or misty
          rays.</div>

          <p>If both kinds of light appear at the same time, the second while passing
          over the first dims it. If the second class is watched into daylight, they
          appear as dirty misty clouds that suddenly form and disappear without the
          spectator being able to say where they come from or where they go to, or as
          a hazy mist over a portion of the sky, that suddenly appears and disappears, or
          as misty rays proceeding from a point in the horizon. Generally, when
          these clouds occur, there is a bank of black clouds to the westward.</p>

          <div class="sidenote">Season since
          October
          1876 prolific
          in auroric
          light.</div>

          <p>Mr. Kinahan then speaks of the season as having been prolific in auroric
          light, as there had been few nights since the 1st October then last (1876) in
          which they did not appear. On many occasions they were late in the night,
          being very common and brilliant during the dark days of December, a few
          hours before dawn (about 5 o’clock). Each time there was a fine day they
          appeared also, and the weather broke again.</p>

          <div class="sidenote">Mr. J. Allan
          Broun questions
          nature
          of these
          lights, as
          Aurora is
          seldom seen
          at 5 <span class="smcapuc">A.M.</span> in
          this country. On 77 occasions
          seen
          only twice
          so early. Season was
          of marked
          infrequency
          elsewhere.</div>

          <p>Mr. Jno. Allan Broun refers to this graphic account of Mr. Kinahan’s,
          and concludes there must have been some mistake as to the nature of these
          “auroric lights,” as the Aurora Borealis is very rarely seen at 5 <span class="smcapuc">A.M.</span> in this
          country. In the years 1844 and 1845, during which the Aurora was sought for
          at Makerstown every hour of the night, it was observed in 77 nights on an
          average of nearly three hours each night; but it was seen only twice so early,
          and that with a bright or brilliant Aurora, which remained during five hours
          on the first occasion, and from 6 <span class="smcapuc">P.M.</span> to 6 <span class="smcapuc">A.M.</span> on the second. Parts of the
          phenomenon seen by Mr. Kinahan, Mr. Broun also could not say he had ever
          seen; and if Mr. Kinahan’s observations could have been confirmed it would
          have been most important, especially as made so frequently at the epoch of
          minimum. The description is in many respects a sufficiently recognizable
          one of auroral discharges; but the frequent appearance in early morning is
          certainly unusual, and few if any Auroræ seem to have been recorded as
          appearing elsewhere in Great Britain during the time which Mr. Kinahan refers
          to as so prolific (see, however, Dr. Allnatt’s, <i>antè</i>, p. 24). In fact, the season
          in question was one of marked infrequency (see English Arctic Expedition
          Report, <i>antè</i>, p. 26). Mr. Buchan furnished Mr. Broun with a note of Auroræ
          seen in the stations of the Scottish Meteorological Society during the year
          1876, and they were 42 in number, 26 in the first half, and 16 in the second
          half of the year. The greater part were seen in the most northerly stations,
          including the Orkney, Shetland, and Faroe Islands, and only 9 south of
          the Forth.</p>


          <div class="sidenote">Luminous
          arch, Sept.
          11, 1814. Height
          above horizon
          6 to 9
          miles.</div>

          <p>In the ‘Annals of Philosophy,’ vol. iv. p. 362, there is a minute description
          of a luminous arch which appeared in the sky on the night of Sunday,
          September 11th, 1814, and was seen in the west of England opposite the
          Irish Sea, the west part of the south of Scotland, and part of the west of
          Ireland. It was described as a part of either a body of dense greyish-white
          light, or a mass of luminous matter in the shape of an arch. Its height above
          the horizontal line was estimated at not more than 9 nor less than 6 miles.</p>

          <div class="sidenote">It moved
          southward,
          and was
          assumed to
          differ from
          the Aurora.</div>

          <p>Its direction when first seen was N. 80° E., and S. 80° W. It moved to the
          southward. It was assumed to differ from the Aurora Borealis in wanting
          coruscations, and in its having a much paler light.</p>
    </div>

  </section>

  <!-- Chapitre 5_________________________________________________________-->
  <section class="chapter" id="chapter-5">
    <h3 class="titlechapter" id="chap-5">Some qualities of the aurora</h3>
    <p class="shorter">Some qualities of the aurora</p>



    <h4 id="chap-5-1"><i>Noises attending Auroræ.</i></h4>

    <span class="sidenote">Sir John Franklin negatives them.</span>



    <p>In the Edinb. Encyc., Gmelin is stated, in continuation of his description of
    an Arctic Aurora, to add:—“For however fine the illumination may be, it is
    attended, as I have heard from the relation of many persons, with such a
    hissing, cracking, and rushing noise through the air, as if the largest fireworks
    were playing off.” To describe what they then heard, the natives are
    said to use the expression, “Spolochi chodjat”—that is, The raging host is passing.
    The hunter’s dogs, too, are also described as so much frightened when
    the Auroræ overtake the hunters, that they will not move, but lie obstinately
    on the ground till the noise has passed. This account of noises seems to be
    confirmed by other testimony. They are stated to have been heard at Hudson’s
    Bay and in Sweden; and Musschenbroek mentions that the Greenland
    whale-fishers assured him they had frequently heard the noise of the Aurora
    Borealis, but adds that “no person in Holland had ever experienced this
    phenomenon.” Mr. Cavallo declares he “has repeatedly heard a crackling
    sound proceeding from the Aurora Borealis” (Elements of Nat. or Exper.
    Phil. vol. iii. p. 449). Mr. Nairne mentions that in Northampton, when the
    northern lights were very bright, he is confident he perceived a hissing or
    whizzing sound. Mr. Belknap of Dover, New Hampshire, North America,
    testifies to a similar fact (American Trans. vol. ii. p. 196).</p>

    <div class="sidenote">Noises attending
    Auroræ. Gmelin affirms
    them. Other testimony
    to
    them. Musschenbroek. Cavallo. Nairne. Belknap.</div>


    <p>Sir John Franklin mentions, in his ‘Journey to the Shores of the Polar
    Sea’:—“Nor could we distinguish its (the Aurora’s) rustling noise, of which,
    however, such strong testimony has been given to us that no doubt can remain
    of the fact.”</p>

    <div class="sidenote">March 11th.
    Hissing
    noise heard
    during Aurora’s
    passage. Explained
    to arise from
    the snow.</div>

    <p>In detail, he mentions he never heard any sound that could be unequivocally
    considered as originating in the Aurora, although he had had an opportunity
    of observing that phenomenon for upwards of 200 nights (the Aurora
    was registered at Bear Lake 343 times without any sound being heard to
    attend its motions); but the uniform testimony of the natives and all the
    older residents in the country induced him to believe that its motions were
    sometimes audible. On the 11th March, at 10 <span class="smcapuc">P.M.</span>, a body of Aurora rose
    N.N.W.; and after a mass had passed E. by S., the remainder broke away
    in portions, which crossed about 40° of the sky with great rapidity. A hissing
    noise, like that of a bullet passing through the air, was heard, which seemed
    to proceed from the Aurora; but Mr. Wentzel assured the party the noise
    was occasioned by severe cold succeeding mild weather, and acting upon the
    surface of the snow previously melted in the sun’s rays. A similar noise was
    heard the next morning.</p>

    <div class="sidenote">Capt. Sabine
    also negatives
    noise.</div>

    <p>In Parry’s first voyage, Captain Sabine describes an Aurora seen at Melville
    Island, and adds that the Aurora had the appearance of being <i>very near</i> the
    party, but <i>no sound could be heard</i>.</p>

    <div class="sidenote">Article
    “Aurora
    Polaris,”
    Encyc. Brit.,
    suggests
    noises as
    not improbable.</div>

    <p>In the article “Aurora Polaris,” Encyc. Brit, edition ix., the writer admits
    the evidence of scientific Arctic voyagers having listened in vain for such
    noises; but, referring to the statements of Greenlanders and others on the
    subject, concludes there is no <i>à priori</i> improbability of such sounds being
    occasionally heard, since a somewhat similar sound accompanies the brush-discharge
    of the electric machine.</p>

    <div class="sidenote">Payer negatives
    and
    discredits
    noises.</div>

    <p>Payer, of the Austrian Polar Expedition (1872-1874), states that the
    Aurora was never accompanied by noise, and discredits the alleged accounts
    of noises in the Shetlands and Siberia.</p>

    <span class="sidenote">As also Weyprecht.</span>

    <p>Lieut. Weyprecht, of the same expedition, says (<i>antè</i>, p. 14):—“Involuntarily
    we listen; such a spectacle must, we think, be accompanied with sound, but
    unbroken silence prevails, not the least sound strikes on the ear.”</p>

    <div class="sidenote">Herr Carl
    Bock negatives
    noises
    in the case
    of Lapland
    Auroræ.</div>

    <p>Herr Carl Bock, who accompanied the Laplanders visiting this country (at the
    Westminster Aquarium) in 1877-78, and who witnessed many brilliant auroral
    displays in Lapland, assured me he could trace no noise, except on one occasion,
    when he heard a sort of rustling, which he attributed to the wind. The
    Laplanders themselves did not associate any special noise with the Aurora.</p>

    <div class="sidenote">Auroral
    noises in
    telephone. Ringing
    sound in
    vacuum-tube
    under influence
    of
    magnet.</div>

    <p>It has been recently stated, in an article on the Telephone in ‘Nature,’ that
    Professor Peirce “has observed the most curious sounds produced from a
    telephone in connexion with a telegraph wire during the Aurora Borealis;”
    but no further details are given. In experimenting with a silicic fluoride
    vacuum-tube between the poles of an electro-magnet, I found, on the magnet
    being excited, that the capillary stream of blue light was decreased in volume
    and brightness, and at the same time from within the tube a peculiar whistling
    or slightly metallic ringing sound was heard.</p>

    <div class="sidenote">Adverse
    conclusion
    as to noises
    accompanying
    Aurora.</div>

    <p>I certainly have never met with an instance of noise accompanying an
    Aurora and traced to it. On the whole the balance of evidence seems quite
    adverse to any proof of noises proper ordinarily accompanying an Aurora.</p>

    <p></p>

    <h4 id="chap-5-2"><i>Colours of the Aurora.</i></h4>

    <div class="sidenote">Colours of
    the Aurora. Sir John
    Franklin’s
    views. Other observers
    have
    described all
    colours of
    spectrum. Violet rare.
    Crimson
    indicates
    coming
    Aurora.</div>

    <p>Sir John Franklin considered the colours in the Polar Aurora did not
    depend on the presence of any luminary, but were generated by the motion
    of the beams, and then only when that motion was rapid and the light brilliant.
    The lower extremities, he says, quivered with a fiery red colour, and
    the upper with orange. He also saw violet in the former. Other observers
    have, in their various descriptions of Auroræ, mentioned the colours of the
    rays or beams as red, crimson, green, yellow, &amp;c.; in fact, comprising the
    range of the spectrum. Violet seems less frequently mentioned. The red
    or crimson colour is frequently the first indication of the coming Aurora, and
    is usually seen on or near the horizon. The colours have frequently been
    observed to shift or change.</p>

    <div class="sidenote">Prof. Piazzi
    Smyth describes
    colours
    of Aurora
    of Feb.
    4, 1872, as
    seen at
    Edinburgh.</div>

    <p>Prof. Piazzi Smyth, in a letter to ‘Nature,’ describing the Aurora of
    February 4th, 1872, as seen at Edinburgh, says that when the maximum development
    was reached all the heavens were more or less covered with pink
    ascending streamers, except towards the N., which was dark and grey—first by
    means of a long low arch of blackness, transparent to large stars, and then by
    the streamers which shot up from this arch, which were green and grey only
    for several degrees of their height, and only became pink as they neared the
    zenith. The red streamers varied from orange to rose-pink, red rose, and
    damask rose.</p>

    <p>The Professor pointed out that the spectroscope knew no variety of reds
    giving one red line only, and attributed this to the mixing up of rays and
    streamers of blackness out of the long low arch. When the Aurora faded
    away a true starlight-night sky appeared; so that evidently the dark arch and
    streamers were as much part of the Aurora as the green and red lights.</p>

    <div class="sidenote">Dr. Allnatt
    at Frant
    describes
    vivid colours
    of same
    Aurora.</div>

    <p>Dr. Allnatt, at Frant, found in the case of the same Aurora the south-western
    part of the heavens tinged by a bright crimson band. A dark elliptical cloud
    extending from S. to S.E. was illuminated at its upper edge with a pale yellow
    light, and sent up volumes of carmine radii interspersed with green and the
    black alternating matter characteristic of elemental electricity. Almost due
    E., and of about 25 degrees elevation, was a bright insulated spot of vivid
    emerald-green, which appeared almost sufficiently intense to cast a faint
    shadow from intercepting objects. At 7 o’clock the Aurora had passed the
    zenith, and the sky presented a weird and wonderful appearance. A dark
    rugged cloud, some 8 degrees E. of the zenith, was surrounded by electric
    light of all hues—carmine, green, yellow, blood-red, white, and black; and
    the bright spot still existed in the south.</p>

    <div class="sidenote">Descriptions
    at Blackburn
    and
    Cambridge. Lapland
    Auroræ
    yellow.</div>

    <p>At Blackburn, in Lancashire, the rays were described as glowing in the
    N.E. from silvery white to deepest crimson; and at Cambridge the same
    Aurora was described as of a brilliant carmine tint. The Auroræ seen in
    Lapland by Herr Carl Bock, were, he informed me, almost invariably yellow;
    he saw only one red one.</p>

    <div class="sidenote">Hydrogen
    vacuum-tube
    su