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diff --git a/39263-h/39263-h.htm b/39263-h/39263-h.htm new file mode 100644 index 0000000..3207cad --- /dev/null +++ b/39263-h/39263-h.htm @@ -0,0 +1,11620 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + Astronomical Curiosities: Facts and Fallacies, by J. Ellard Gore—A Project Gutenberg eBook + </title> + + <style type="text/css"> + + p {margin-top: .75em; text-align: justify; margin-bottom: .75em;} + + body {margin-left: 12%; margin-right: 12%;} + + .pagenum {position: absolute; left: 92%; font-size: smaller; text-align: right; font-style: normal;} + + h1,h2,h3,h4,h5,h6 {text-align: center; clear: both;} + + hr {width: 33%; margin-top: 2em; margin-bottom: 2em; margin-left: auto; margin-right: auto; clear: both;} + + table {margin-left: auto; margin-right: auto;} + .botbor {border-bottom: solid 1px;} + + .giant {font-size: 200%} + .huge {font-size: 150%} + .large {font-size: 125%} + + .blockquot {margin-left: 5%; margin-right: 10%;} + .poem {margin-left: 15%;} + .note {margin-left: 20%; margin-right: 20%;} + .index {margin-left: 10%;} + .caption {text-align: center; font-size: small;} + .title {text-align: center; font-size: 150%;} + + .right {text-align: right;} + .center {text-align: center;} + + .smcap {font-variant: small-caps;} + .smcaplc {text-transform: lowercase; font-variant: small-caps;} + + .figcenter {margin: auto; text-align: center;} + + p.dropcap:first-letter{float: left; padding-right: 3px; font-size: 250%; line-height: 83%; width:auto;} + .caps {text-transform:uppercase;} + + a:link {color:#0000ff; text-decoration:none} + a:visited {color:#6633cc; text-decoration:none} + + .spacer {padding-left: 1em; padding-right: 1em;} + + </style> + </head> +<body> + + +<pre> + +The Project Gutenberg EBook of Astronomical Curiosities, by J. Ellard Gore + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org/license + + +Title: Astronomical Curiosities + Facts and Fallacies + +Author: J. Ellard Gore + +Release Date: March 25, 2012 [EBook #39263] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK ASTRONOMICAL CURIOSITIES *** + + + + +Produced by The Online Distributed Proofreading Team at +http://www.pgdp.net (This file was produced from images +generously made available by The Internet Archive.) + + + + + + +</pre> + + + +<div class="figcenter"><img src="images/cover.jpg" alt="" /></div> +<p> </p><p> </p> + +<h1>ASTRONOMICAL CURIOSITIES</h1> +<p class="center"><span class="huge">FACTS AND FALLACIES</span></p> + + +<p> </p><p> </p> +<p class="center"><span class="huge">ASTRONOMICAL<br /> +CURIOSITIES</span></p> +<p class="center"><span class="large">FACTS AND FALLACIES</span></p> +<p> </p> +<p class="center"><small>BY</small><br /> +<span class="large">J. ELLARD GORE</span><br /> +<small>MEMBER OF THE ROYAL IRISH ACADEMY<br /> +FELLOW OF THE ROYAL ASTRONOMICAL SOCIETY<br /> +CORRESPONDING MEMBER OF THE ROYAL ASTRONOMICAL SOCIETY OF CANADA<br /> +ETC.<br /> +AUTHOR OF “ASTRONOMICAL ESSAYS,” “STUDIES IN ASTRONOMY,”<br /> +“THE VISIBLE UNIVERSE,” ETC.</small></p> +<p> </p> +<p class="center">LONDON<br /> +CHATTO & WINDUS<br /> +1909</p> + + +<p> </p><p> </p> +<p class="center">PRINTED BY<br /> +WILLIAM CLOWES AND SONS, LIMITED<br /> +LONDON AND BECCLES</p> + +<p class="center"><i>All rights reserved</i></p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<h2>PREFACE</h2> + +<div class="note"> +<p>The curious facts, fallacies, and paradoxes contained in the following +pages have been collected from various sources. Most of the information +given will not, I think, be found in popular works on astronomy, and will, +it is hoped, prove of interest to the general reader.</p> + +<p class="right">J. E. G.</p> + +<p><i>September, 1909.</i></p></div> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p class="title">CONTENTS</p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td><small>CHAPTER</small></td> + <td> </td> + <td align="right"><small>PAGE</small></td></tr> +<tr><td align="right"><a href="#CHAPTER_I">I.</a></td> + <td>THE SUN</td> + <td align="right"><a href="#Page_1">1</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_II">II.</a></td> + <td>MERCURY</td> + <td align="right"><a href="#Page_10">10</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_III">III.</a></td> + <td>VENUS</td> + <td align="right"><a href="#Page_17">17</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_IV">IV.</a></td> + <td>THE EARTH</td> + <td align="right"><a href="#Page_32">32</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_V">V.</a></td> + <td>THE MOON</td> + <td align="right"><a href="#Page_48">48</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VI">VI.</a></td> + <td>MARS</td> + <td align="right"><a href="#Page_59">59</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VII">VII.</a></td> + <td>THE MINOR PLANETS</td> + <td align="right"><a href="#Page_68">68</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VIII">VIII.</a></td> + <td>JUPITER</td> + <td align="right"><a href="#Page_74">74</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_IX">IX.</a></td> + <td>SATURN</td> + <td align="right"><a href="#Page_84">84</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_X">X.</a></td> + <td>URANUS AND NEPTUNE</td> + <td align="right"><a href="#Page_91">91</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XI">XI.</a></td> + <td>COMETS</td> + <td align="right"><a href="#Page_97">97</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XII">XII.</a></td> + <td>METEORS</td> + <td align="right"><a href="#Page_117">117</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XIII">XIII.</a></td> + <td>THE ZODIACAL LIGHT AND GEGENSCHEIN</td> + <td align="right"><a href="#Page_127">127</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XIV">XIV.</a></td> + <td>THE STARS</td> + <td align="right"><a href="#Page_135">135</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XV">XV.</a></td> + <td>DOUBLE AND BINARY STARS</td> + <td align="right"><a href="#Page_160">160</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XVI">XVI.</a></td> + <td>VARIABLE STARS</td> + <td align="right"><a href="#Page_170">170</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XVII">XVII.</a></td> + <td>NEBULÆ AND CLUSTERS</td> + <td align="right"><a href="#Page_191">191</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XVIII">XVIII.</a></td> + <td>HISTORICAL</td> + <td align="right"><a href="#Page_217">217</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XIX">XIX.</a></td> + <td>THE CONSTELLATIONS</td> + <td align="right"><a href="#Page_239">239</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XX">XX.</a></td> + <td>THE VISIBLE UNIVERSE</td> + <td align="right"><a href="#Page_313">313</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XXI">XXI.</a></td> + <td>GENERAL</td> + <td align="right"><a href="#Page_329">329</a></td></tr> +<tr><td> </td> + <td>INDEX</td> + <td align="right"><a href="#Page_359">359</a></td></tr></table> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p class="title">ILLUSTRATIONS</p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td colspan="2"> </td> + <td align="right"><small>PAGE</small></td></tr> +<tr><td>AL-SUFI’S “EARTHEN JAR”</td> + <td><span class="spacer"> </span></td> + <td align="right"><a href="#Page_248">247</a></td></tr> +<tr><td>AL-SUFI’S “FISHES” IN ANDROMEDA</td> + <td> </td> + <td align="right"><a href="#Page_250">249</a></td></tr></table> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> +<p class="center"><span class="giant">ASTRONOMICAL CURIOSITIES</span></p> +<p> </p> +<h2><a name="CHAPTER_I" id="CHAPTER_I"></a>CHAPTER I</h2> +<p class="title">The Sun</p> + +<p> </p> +<p class="dropcap"><span class="caps">Some</span> observations recently made by Prof. W. H. Pickering in Jamaica, make +the value of sunlight 540,000 times that of moonlight. This makes the +sun’s “stellar magnitude” minus 26·83, and that of moonlight minus 12·5. +Prof. Pickering finds that the light of the full moon is equal to 100,000 +stars of zero magnitude. He finds that the moon’s “albedo” is about +0·0909; or in other words, the moon reflects about one-tenth of the light +which falls on it from the sun. He also finds that the light of the full +moon is about twelve times the light of the half moon: a curious and +rather unexpected result.</p> + +<p>M. C. Fabry found that during the total eclipse of the sun on August 30, +1905, the light of the corona at a distance of five minutes of arc from +the sun’s limit, and in the vicinity of the sun’s equator, was about 720 +candle-power. Comparing this<span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> with the intrinsic light of the full moon +(2600 candle-power) we have the ratio of 0·28 to 1. He finds that the +light of the sun in the zenith, and at its mean distance from the earth, +is 100,000 times greater than the light of a “decimal candle” placed at a +distance of one metre from the eye.<a name='fna_1' id='fna_1' href='#f_1'><small>[1]</small></a> He also finds that sunlight is +equal to 60,000 million times the light of Vega. This would make the sun’s +“stellar magnitude” minus 26·7, which does not differ much from Prof. +Pickering’s result, given above, and is probably not far from the truth.</p> + +<p>From experiments made in 1906 at Moscow, Prof. Ceraski found that the +light of the sun’s limb is only 31·4 to 38·4 times brighter than the +illumination of the earth’s atmosphere very near the limb. This is a very +unexpected result; and considering the comparative faintness of the sun’s +corona during a total eclipse, it is not surprising that all attempts to +photograph it without an eclipse have hitherto failed.<a name='fna_2' id='fna_2' href='#f_2'><small>[2]</small></a></p> + +<p>From Paschen’s investigations on the heat of the sun’s surface, he finds a +result of 5961° (absolute), “assuming that the sun is a perfectly black +body.”<a name='fna_3' id='fna_3' href='#f_3'><small>[3]</small></a> Schuster finds that “There is a stratum near the sun’s surface +having an average temperature of approximately 5500° C., to which about +0·3 of the sun’s radiation is due. The<span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span> remaining portion of the radiation +has an intensity equal to that due to a black body having a temperature of +about 6700° C.” The above results agree fairly well with those found by +the late Dr. W. E. Wilson.<a name='fna_4' id='fna_4' href='#f_4'><small>[4]</small></a> The assumption of the sun being “a black +body” seems a curious paradox; but the simple meaning of the statement is +that the sun is assumed to act as a radiator as <i>if it were a perfectly +black body heated to the high temperature given above</i>.</p> + +<p>According to Prof. Langley, the sun’s photosphere is 5000 times brighter +than the molten metal in a “Bessemer convertor.”<a name='fna_5' id='fna_5' href='#f_5'><small>[5]</small></a></p> + +<p>Observations of the sun even with small telescopes and protected by dark +glasses are very dangerous to the eyesight. Galileo blinded himself in +this way; Sir William Herschel lost one of his eyes; and some modern +observers have also suffered. The present writer had a narrow escape from +permanent injury while observing the transit of Venus, in 1874, in India, +the dark screen before the eyepiece of a 3-inch telescope having +blistered—that is, partially fused during the observation. Mr. Cooper, +Markree Castle, Ireland, in observing the sun, used a “drum” of alum water +and dark spectacles, and found this sufficient protection against the +glare in using his large refracting telescope of 13·3-inches aperture.</p> + +<p><span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span>Prof. Mitchell, of Columbia University (U.S.A.), finds that lines due to +the recently discovered atmospherical gases argon and neon are present in +the spectrum of the sun’s chromosphere. The evidence for the existence of +krypton and xenon is, however, inconclusive. Prof. Mitchell suggests that +these gases may possibly have reached the earth’s atmosphere from the sun. +This would agree with the theory advanced by Arrhenius that “ionised +particles are constantly being repulsed by the pressure of light, and thus +journey from one sun to another.”<a name='fna_6' id='fna_6' href='#f_6'><small>[6]</small></a></p> + +<p>Prof. Young in 1870, and Dr. Kreusler in June, 1904, observed the helium +line D<sub>3</sub> as a <i>dark</i> line “in the spectrum of the region about a +sun-spot.”<a name='fna_7' id='fna_7' href='#f_7'><small>[7]</small></a> This famous line, from which helium was originally +discovered in the sun, and by which it was long afterwards detected in +terrestrial minerals, usually appears as a <i>bright</i> line in the spectrum +of the solar chromosphere and “prominences.” It has also been seen <i>dark</i> +by Mr. Buss in sun-spot regions.<a name='fna_8' id='fna_8' href='#f_8'><small>[8]</small></a></p> + +<p>The discovery of sun-spots was claimed by Hariotte, in 1610, and by +Galileo, Fabricius, and Scheiner, in 1611. The latter wrote 800 pages on +them, and thought they were small planets revolving round the sun! This +idea was also held by Tardè, who called them <i>Astra Borbonia</i>, and by<span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span> C. +Malapert, who termed them <i>Sydera Austricea</i>. But they seem to have been +noticed by the ancients.</p> + +<p>Although in modern times there has been no extraordinary development of +sun-spots at the epoch of maximum, it is not altogether impossible that in +former times these spots may have occasionally increased to such an +extent, both in number and size, as to have perceptibly darkened the sun’s +light. A more probable explanation of recorded sun-darkenings seems, +however, to be the passing of a meteoric or nebulous cloud between the sun +and the earth. A remarkable instance of sun-darkening recorded in Europe +occurred on May 22, 1870, when the sun’s light was observed to be +considerably reduced in a cloudless sky in the west of Ireland, by the +late John Birmingham; at Greenwich on the 23rd; and on the same date, but +at a later hour, in North-Eastern France—“a progressive manifestation,” +Mr. Birmingham says, “that seems to accord well with the hypothesis of +moving nebulous matter.” A similar phenomenon was observed in New England +(U.S.A.), on September 6, 1881.</p> + +<p>One of the largest spots ever seen on the sun was observed in June, 1843. +It remained visible for seven or eight days. According to Schwabe—the +discoverer of the sun-spot period—its diameter was 74,000 miles, so that +its area was many times<span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span> that of the earth’s surface. The most curious +thing about this spot was that it appeared near a <i>minimum</i> of the +sun-spot cycle! and was therefore rather an anomalous phenomenon. It was +suggested by the late Daniel Kirkwood that this great spot was caused by +the fall of meteoric matter into the sun; and that it had possibly some +connection with the great comet of 1843, which approached the sun nearer +than any other recorded comet, its distance from the sun at perihelion +being about 65,000 miles, or less than one-third of the moon’s distance +from the earth. This near approach of the comet to the sun occurred about +three months before the appearance of the great sun-spot; and it seems +probable that the spot was caused by the downfall of a large meteorite +travelling in the wake of the comet.<a name='fna_9' id='fna_9' href='#f_9'><small>[9]</small></a> The connection between comets and +meteors is well known.</p> + +<p>The so-called blackness of sun-spots is merely relative. They are really +very bright. The most brilliant light which can be produced artificially +looks like a black spot when projected on the sun’s disc.</p> + +<p>According to Sir Robert Ball a pound of coal striking a body with a +velocity of five miles a second would develop as much heat as it would +produce by its combustion. A body falling into the sun from infinity would +have a velocity of<span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span> 450 miles a second when it reached the sun’s surface. +Now as the momentum varies as the square of the velocity we have a pound +of coal developing 90<sup>2</sup> (= <span style="font-size: 0.8em;"><sup>450</sup></span>⁄<span style="font-size: 0.6em;">5</span>)<sup>2</sup>, +or 8,100 times as much heat as would be produced by its combustion. If the sun were formed of coal it would be +consumed in about 3000 years. Hence it follows that the contraction of the +sun’s substance from infinity would produce a supply of heat for 3000 × +8100, or 24,300,000 years.</p> + +<p>The late Mr. Proctor and Prof. Young believed “that the contraction theory +of the sun’s heat is the true and only available theory.” The theory is, +of course, a sound one; but it may now be supplemented by supposing the +sun to contain a certain small amount of radium. This would bring physics +and geology into harmony. Proctor thought the “sun’s real globe is very +much smaller than the globe we see. In other words the process of +contraction has gone on further than, judging from the sun’s apparent +size, we should suppose it to have done, and therefore represents more sun +work” done in past ages.</p> + +<p>With reference to the suggestion, recently made, that a portion, at least, +of the sun’s heat may be due to radium, and the experiments which have +been made with negative results, Mr. R. T. Strutt—the eminent +physicist—has made some calculations on the subject and says, “even if +all<span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span> the sun’s heat were due to radium, there does not appear to be the +smallest possibility that the Becquerel radiation from it could ever be +detected at the earth’s surface.”<a name='fna_10' id='fna_10' href='#f_10'><small>[10]</small></a></p> + +<p>The eminent Swedish physicist Arrhenius, while admitting that a large +proportion of the sun’s heat is due to contraction, considers that it is +probably the chemical processes going on in the sun, and not the +contraction which constitute the <i>chief</i> source of the solar heat.<a name='fna_11' id='fna_11' href='#f_11'><small>[11]</small></a></p> + +<p>As the centre of gravity of the sun and Jupiter lies at a distance of +about 460,000 miles from the sun’s centre, and the sun’s radius is only +433,000 miles, it follows that the centre of gravity of the sun and planet +is about 27,000 miles <i>outside</i> the sun’s surface. The attractions of the +other planets perpetually change the position of the centre of gravity of +the solar system; but in some books on astronomy it is erroneously stated +that the centre of gravity of the system is <i>always</i> within the sun’s +surface. If <i>all</i> the planets lay on the same side of the sun at the same +time (as might possibly happen), then the centre of gravity of the whole +system would lie considerably more than 27,000 miles outside the sun’s +surface.</p> + +<p>With reference to the sun’s great size, Carl Snyder has well said, “It was +as if in Vulcan’s<span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span> smithy the gods had moulded one giant ball, and the +planets were but bits and small shot which had spattered off as the +glowing ingot was cast and set in space. Little man on a little part of a +little earth—a minor planet, a million of which might be tumbled into the +shell of the central sun—was growing very small; his wars, the +convulsions of a state, were losing consequence. Human endeavour, human +ambitions could now scarce possess the significance they had when men +could regard the earth as the central fact of the universe.”<a name='fna_12' id='fna_12' href='#f_12'><small>[12]</small></a></p> + +<p>With reference to the late Prof. C. A. Young (U.S.A.)—a great authority +on the sun—an American writer has written the following lines:—</p> + +<p class="poem">“The destined course of whirling worlds to trace,<br /> +To plot the highways of the universe,<br /> +And hear the morning stars their song rehearse,<br /> +And find the wandering comet in his place;<br /> +This is the triumph written in his face,<br /> +And in the gleaming eye that read the sun<br /> +Like open book, and from the spectrum won<br /> +The secrets of immeasurable space.”<a name='fna_13' id='fna_13' href='#f_13'><small>[13]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span></p> +<h2><a name="CHAPTER_II" id="CHAPTER_II"></a>CHAPTER II</h2> +<p class="title">Mercury</p> + +<p> </p> +<p class="dropcap"><span class="caps">As</span> the elongation of Mercury from the sun seldom exceeds 18°, it is a +difficult object, at least in this country, to see without a telescope. As +the poet says, the planet—</p> + +<p class="poem">“Can scarce be caught by philosophic eye<br /> +Lost in the near effulgence of its blaze.”</p> + +<p>Tycho Brahé, however, records several observations of Mercury with the +unaided vision in Denmark.</p> + +<p>It can be occasionally caught with the naked eye in this country after +sunset, when it is favourably placed for observation, and I have so seen +it several times in Ireland. On February 19, 1888, I found it very visible +in strong twilight near the western horizon, and apparently brighter than +an average star of the first magnitude would be in the same position. In +the clear air of the Punjab sky I observed Mercury on November 24-29, +1872, near the western horizon after sunset. Its appearance was that of a +reddish star of the first magnitude. On November 29 I compared its +brilliancy<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> with that of Saturn, which was some distance above it, and +making allowance for the glare near the horizon in which Mercury was +immersed, its brightness appeared to me to be quite equal to that of +Saturn. In June, 1874, I found it equal to Aldebaran, and of very much the +same colour. Mr. W. F. Denning, the famous observer of meteors, states +that he observed Mercury with the naked eye about 150 times during the +years 1868 to 1905.<a name='fna_14' id='fna_14' href='#f_14'><small>[14]</small></a></p> + +<p>He found that the duration of visibility after sunset is about 1<sup>h</sup> 40<sup>m</sup> +when seen in March, 1<sup>h</sup> 30<sup>m</sup> in April, and 1<sup>h</sup> 20<sup>m</sup> in May. He thinks +that the planet is, at its brightest, “certainly much brighter than a +first magnitude star.”<a name='fna_15' id='fna_15' href='#f_15'><small>[15]</small></a> In February, 1868, he found that its brightness +rivalled that of Jupiter, then only 2° or 3° distant. In November, 1882, +it seemed brighter than Sirius. In 1876 it was more striking than Mars, +but the latter was then “faint and at a considerable distance from the +earth.”</p> + +<p>In 1878, when Mercury and Venus were in the same field of view of a +telescope, Nasmyth found that the surface brightness (or “intrinsic +brightness,” as it is called) of Venus was at least twice as great as that +of Mercury; and Zöllner found that from a photometric point of view the +surface of Mercury is comparable with that of the moon.</p> + +<p><span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span>With reference to the difficulty of seeing Mercury, owing to its proximity +to the sun, Admiral Smyth says, “Although Mercury is never in <i>opposition</i> +to the earth, he was, when in the house of Mars, always viewed by +astrologers as a most malignant planet, and one full of evil influences. +The sages stigmatized him as a false deceitful star (<i>sidus dolosum</i>), the +eternal torment of astronomers, eluding them as much as terrestrial +mercury did the alchemists; and Goad, who in 1686 published a whole folio +volume full of astro-meteorological aphorisms, unveiling the choicest +secrets of nature, contemptuously calls Mercury a ‘squinting lacquey of +the sun, who seldom shows his head in these parts, as if he was in debt.’ +His extreme mobility is so striking that chemists adopted his symbol to +denote quicksilver.”<a name='fna_16' id='fna_16' href='#f_16'><small>[16]</small></a></p> + +<p>Prof. W. H. Pickering thinks that the shortness of the cusps (or “horns”) +of Mercury’s disc indicates that the planet’s atmosphere is of small +density—even rarer than that of Mars.</p> + +<p>The diameter of Mercury is usually stated at about 3000 miles; but a long +series of measures made by Prof. See in the year 1901 make the real +diameter about 2702 miles. This would make the planet smaller than some of +the satellites of the large planets, probably smaller than satellites III. +and IV. of Jupiter, less than Saturn’s satellite<span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span> Titan, and possibly +inferior in size to the satellite of Neptune. Prof. Pickering thinks that +the density of Mercury is about 3 (water = 1). Dr. See’s observations show +“no noticeable falling off in the brightness of Mercury near the limb.” +There is therefore no evidence of any kind of atmospheric absorption in +Mercury, and the observer “gets the impression that the physical condition +of the planet is very similar to that of our moon.”<a name='fna_17' id='fna_17' href='#f_17'><small>[17]</small></a></p> + +<p>Schröter (1780-1815) observed markings on Mercury, from which he inferred +that the planet’s surface was mountainous, and one of these mountains he +estimated at about 11 miles in height!<a name='fna_18' id='fna_18' href='#f_18'><small>[18]</small></a> But this seems very doubtful.</p> + +<p>To account for the observed irregularities in the motion of Mercury in its +orbit, Prof. Newcomb thinks it possible that there may exist a ring or +zone of “asteroids” a little “outside the orbit of Mercury” and having a +combined mass of “one-fiftieth to one-three-hundredth of the mass of +Venus, according to its distance from Mercury.” Prof. Newcomb, however, +considers that the existence of such a ring is extremely improbable, and +regards it “more as a curiosity than a reality.”<a name='fna_19' id='fna_19' href='#f_19'><small>[19]</small></a></p> + +<p>M. Léo Brenner thinks that he has seen the<span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span> dark side of Mercury, in the +same way that the dark side of Venus has been seen by many observers. In +the case of Mercury the dark side appeared <i>darker</i> than the background of +the sky. Perhaps this may be due to its being projected on the zodiacal +light, or outer envelope of the sun.<a name='fna_20' id='fna_20' href='#f_20'><small>[20]</small></a></p> + +<p>Mercury is said to have been occulted by Venus in the year 1737.<a name='fna_21' id='fna_21' href='#f_21'><small>[21]</small></a> But +whether this was an actual occultation, or merely a near approach does not +seem to be certain.</p> + +<p>The first transit of Mercury across the sun’s disc was observed by +Gassendi on November 6, 1631, and Halley observed one on November 7, 1677, +when in the island of St. Helena.</p> + +<p>Seen from Mercury, Venus would appear brighter than even we see it, and as +it would be at its brightest when in opposition to the sun, and seen on a +dark sky with a full face, it must present a magnificent appearance in the +midnight sky of Mercury. The earth will also form a brilliant object, and +the moon would be distinctly visible. The other planets would appear very +much as they do to us, but with somewhat less brilliancy owing to their +greater distance.</p> + +<p>As the existence of an intra-Mercurial planet (that is a planet revolving +round the sun within the orbit of Mercury) seems now to be very<span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a></span> +improbable, Prof. Perrine suggests that possibly “the finely divided +matter which produces the zodiacal light when considered in the aggregate +may be sufficient to cause the perturbations in the orbit of Mercury.”<a name='fna_22' id='fna_22' href='#f_22'><small>[22]</small></a> +Prof. Newcomb, however, questions the exact accuracy of Newton’s law, and +seems to adopt Hall’s hypothesis that gravity does not act <i>exactly</i> as +the inverse square of the distance, and that the exponent of the distance +is not 2, but 2·0000001574.<a name='fna_23' id='fna_23' href='#f_23'><small>[23]</small></a></p> + +<p>Voltaire said, “If Newton had been in Portugal, and any Dominican had +discovered a heresy in his inverse ratio of the squares of the distances, +he would without hesitation have been clothed in a <i>san benito</i>, and burnt +as a sacrifice to God at an <i>auto da fé</i>.”<a name='fna_24' id='fna_24' href='#f_24'><small>[24]</small></a></p> + +<p>An occultation of Mercury by Venus was observed with a telescope on May +17, 1737.<a name='fna_25' id='fna_25' href='#f_25'><small>[25]</small></a></p> + +<p>May transits of Mercury across the sun’s disc will occur in the years +1924, 1957, and 1970; and November transits in the years 1914, 1927, and +1940.<a name='fna_26' id='fna_26' href='#f_26'><small>[26]</small></a></p> + +<p>From measurements of the disc of Mercury during the last transit, M. R. +Jonckheere concludes that the <i>polar</i> diameter of the planet is greater<span class="pagenum"><a name="Page_16" id="Page_16">[Pg 16]</a></span> +than the <i>equatorial</i>! His result, which is very curious, if true, seems +to be supported by the observations of other observers.<a name='fna_27' id='fna_27' href='#f_27'><small>[27]</small></a></p> + +<p>The rotation period of Mercury, or the length of its day, seems to be +still in doubt. From a series of observations made in the years 1896 to +1909, Mr. John McHarg finds a period of 1·0121162 day, or 1<sup>d</sup> 0<sup>h</sup> 17<sup>m</sup> +26<sup>s</sup>·8. He thinks that “the planet possesses a considerable atmosphere +not so clear as that of Mars”; that “its axis is very considerably +tilted”; and that it “has fairly large sheets of water.”<a name='fna_28' id='fna_28' href='#f_28'><small>[28]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span></p> +<h2><a name="CHAPTER_III" id="CHAPTER_III"></a>CHAPTER III</h2> +<p class="title">Venus</p> + +<p> </p> +<p class="dropcap"><span class="caps">Venus</span> was naturally—owing to its brightness—the first of the planets +known to the ancients. It is mentioned by Hesiod, Homer, Virgil, Martial, +and Pliny; and Isaiah’s remark about “Lucifer, son of the morning” (Isaiah +xiv. 12) probably refers to Venus as a “morning star.” An observation of +Venus is found on the Nineveh tablets of date <span class="smcaplc">B.C.</span> 684. It was observed in +daylight by Halley in July, 1716.</p> + +<p>In <i>very</i> ancient times Venus, when a morning star, was called Phosphorus +or Lucifer, and when an evening star Hesperus; but, according to Sir G. C. +Lewis, the identity of the two objects was known so far back as 540 <span class="smcaplc">B.C.</span></p> + +<p>When Venus is at its greatest brilliancy, and appears as a morning star +about Christmas time (which occurred in 1887, and again in 1889), it has +been mistaken by the public for a return of the “Star of Bethlehem.”<a name='fna_29' id='fna_29' href='#f_29'><small>[29]</small></a> +But whatever “the star<span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span> of the Magi” was it certainly was <i>not</i> Venus. It, +seems, indeed absurd to suppose that “the wise men” of the East should +have mistaken a familiar object like Venus for a strange apparition. There +seems to be nothing whatever in the Bible to lead us to expect that the +star of Bethlehem will reappear.</p> + +<p>Mr. J. H. Stockwell has suggested that the “Star of Bethlehem” may perhaps +be explained by a conjunction of the planets Venus and Jupiter which +occurred on May 8, <span class="smcaplc">B.C.</span> 6, which was two years before the death of Herod. +From this it would follow that the Crucifixion took place on April 3, <span class="smcaplc">A.D.</span> +33. But it seems very doubtful that the phenomenon recorded in the Bible +refers to any conjunction of planets.</p> + +<p>Chacornac found the intrinsic brightness of Venus to be ten times greater +than the most luminous parts of the moon.<a name='fna_30' id='fna_30' href='#f_30'><small>[30]</small></a> But this estimate is +probably too high.</p> + +<p>When at its brightest, the planet is visible in broad daylight to good +eyesight, if its exact position in the sky is known. In the clear air of +Cambridge (U.S.A.) it is said to be possible to see it in this way in all +parts of its orbit, except when the planet is within 10° of the sun.<a name='fna_31' id='fna_31' href='#f_31'><small>[31]</small></a> +Mr. A. Cameron, of Yarmouth, Nova Scotia, has, however, seen Venus with +the naked eye three<span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span> days before conjunction when the planet was only +6¼° from the sun.<a name='fna_32' id='fna_32' href='#f_32'><small>[32]</small></a> This seems a remarkable observation, and shows +that the observer’s eyesight must have been very keen. In a private letter +dated October 22, 1888, the late Rev. S. J. Johnson informed the present +writer that he saw Venus with the naked eye only four days before +conjunction with the sun in February, 1878, and February, 1886.</p> + +<p>The crescent shape of Venus is said to have been seen with the naked eye +by Theodore Parker in America when he was only 12 years old. Other +observers have stated the same thing; but the possibility of such an +observation has been much disputed in recent years.</p> + +<p>In the Chinese Annals some records are given of Venus having been seen in +the Pleiades. On March 16, <span class="smcaplc">A.D.</span> 845, it is said that “Venus eclipsed the +Pleiades.” This means, of course, that the cluster was apparently effaced +by the brilliant light of the planet. Computing backwards for the above +date, Hind found that on the evening of March 16, 845, Venus was situated +near the star Electra; and on the following evening the planet passed +close to Maia; thus showing the accuracy of the Chinese record. Another +“eclipse” of the Pleiades by Venus is recorded in the same annals as +having occurred on March 10, <span class="smcaplc">A.D.</span> 1002.<a name='fna_33' id='fna_33' href='#f_33'><small>[33]</small></a></p> + +<p><span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span>When Venus is in the crescent phase, that is near “Inferior conjunction” +with the sun, it will be noticed, even by a casual observer, that the +crescent is not of the same shape as that of the crescent moon. The horns +or “cusps” of the planetary crescent are more prolonged than in the case +of the moon, and extend beyond the hemisphere. This appearance is caused +by refraction of the sun’s light through the planetary atmosphere, and is, +in fact, a certain proof that Venus has an atmosphere similar to that of +the earth. Observations further show that this atmosphere is denser than +ours.</p> + +<p>Seen from Venus, the earth and moon, when in opposition, must present a +splendid spectacle. I find that the earth would shine as a star about half +as bright again as Venus at her brightest appears to us, and the moon +about equal in brightness to Sirius! the two forming a superb “naked eye +double star”—perhaps the finest sight of its kind in the solar +system.<a name='fna_34' id='fna_34' href='#f_34'><small>[34]</small></a></p> + +<p>Some of the earlier observers, such as La Hire, Fontana, Cassini, and +Schröter, thought they saw evidence of mountains on Venus. Schröter +estimated some of these to be 27 or 28 miles in height! but this seems +very doubtful. Sir William Herschel severely attacked these supposed +discoveries. Schröter defended himself, and was supported by Beer and +Mädler, the famous<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> lunar observers. Several modern observers seem to +confirm Schröter’s conclusions; but very little is really known about the +topography of Venus.</p> + +<p>The well-known French astronomer Trouvelot—a most excellent observer—saw +white spots on Venus similar to those on Mars. These were well seen and +quite brilliant in July and August, 1876, and in February and November, +1877. The observations seem to show that these spots do not (unlike Mars) +increase and decrease with the planet’s seasons. These white spots had +been previously noticed by former observers, including Bianchini, Derham, +Gruithuisen, and La Hire; but these early observers do not seem to have +considered them as snow caps, like those of Mars. Trouvelot was led by his +own observations to conclude that the period of rotation of Venus is +short, and the best result he obtained was 23<sup>h</sup> 49<sup>m</sup> 28<sup>s</sup>. This does +not differ much from the results previously found by De Vico, Fritsch, and +Schröter.<a name='fna_35' id='fna_35' href='#f_35'><small>[35]</small></a></p> + +<p>A white spot near the planet’s south pole was seen on several occasions by +H. C. Russell in May and June, 1876.<a name='fna_36' id='fna_36' href='#f_36'><small>[36]</small></a></p> + +<p>Photographs of Venus taken on March 18 and April 29, 1908, by M. Quénisset +at the Observatory of Juvissy, France, show a white polar spot. The<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> spot +was also seen at the same observatory by M. A. Benoit on May 20, 1903.</p> + +<p>The controversy on the period of rotation of Venus, or the length of its +day, is a very curious one and has not yet been decided. Many good +observers assert confidently that it is short (about 24 hours); while +others affirm with equal confidence that it is long (about 225 days, the +period of the planet’s revolution round the sun). Among the observers who +favour the short period of rotation are: D. Cassini (1667), J. Cassini +(1730), Schröter (1788-93), Mädler (1836), De Vico (1840?) Trouvelot +(1871-79), Flammarion, Léo Brenner, Stanley Williams, and J. McHarg; and +among those who support the long period are: Bianchini (1727), +Schiaparelli, Cerulli, Tacchini, Mascari, and Lowell. Some recent +spectroscopic observations seem to favour the short period.</p> + +<p>Flammarion thinks that “nothing certain can be descried upon the surface +of Venus, and that whatever has hitherto been written regarding its period +of rotation must be considered null and void”; and again he says, “Nothing +can be affirmed regarding the rotation of Venus, inasmuch as the +absorption of its immense atmosphere certainly prevents any detail on its +surface from being perceived.”<a name='fna_37' id='fna_37' href='#f_37'><small>[37]</small></a></p> + +<p>The eminent Swedish physicist Arrhenius thinks, however, that the dense +atmosphere and clouds<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> of Venus are in favour of a rapid rotation on its +axis.<a name='fna_38' id='fna_38' href='#f_38'><small>[38]</small></a> He thinks that the mean temperature of Venus may “not differ +much from the calculated temperature 104° F.” “Under these circumstances +the assumption would appear plausible that a very considerable portion of +the surface of Venus, and particularly the districts about the poles, +would be favourable to organic life.”<a name='fna_39' id='fna_39' href='#f_39'><small>[39]</small></a></p> + +<p>The “secondary light of Venus,” or the visibility of the dark side, seems +to have been first mentioned by Derham in his <i>Astro Theology</i> published +in 1715. He speaks of the visibility of the dark part of the planet’s disc +“by the aid of a light of a somewhat dull and ruddy colour.” The date of +Derham’s observation is not given, but it seems to have been previous to +the year 1714. The light seems to have been also seen by a friend of +Derham. We next find observations by Christfried Kirch, assistant +astronomer to the Berlin Academy of Sciences, on June 7, 1721, and March +8, 1726. These observations are found in his original papers, and were +printed in the <i>Astronomische Nachrichten</i>, No. 1586. On the first date +the telescopic image of the planet was “rather tremulous,” but in 1726 he +noticed that the dark part of the circle seemed to belong to a smaller +circle than the illuminated portion of the disc.<a name='fna_40' id='fna_40' href='#f_40'><small>[40]</small></a> The same effect was +also noted by<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> Webb.<a name='fna_41' id='fna_41' href='#f_41'><small>[41]</small></a> A similar illusion is seen in the case of the +crescent moon, and this has given rise to the saying, “the old moon in the +new moon’s arms.”</p> + +<p>We next come, in order of date, to an observation made by Andreas Mayer, +Professor of Mathematics at Griefswald in Prussia. The observation was +made on October 20, 1759, and the dark part of Venus was seen distinctly +by Mayer. As the planet’s altitude at the time was not more than 14° above +the horizon, and its apparent distance from the sun only 10°, the +phenomenon—as Professor Safarik has pointed out—“must have had a most +unusual intensity.”</p> + +<p>Sir William Herschel makes no mention of having ever seen the “secondary +light” of Venus, although he noticed the extension of the horns beyond a +semicircle.</p> + +<p>In the spring and summer of the year 1793, Von Hahn of Remplin in +Mecklenburg, using excellent telescopes made by Dollond and Herschel, saw +the dark part of Venus on several occasions, and describes the light as +“grey verging upon brown.”</p> + +<p>Schröter of Lilienthal—the famous observer of the moon—saw the horns of +the crescent of Venus extended many degrees beyond the semicircle on +several occasions in 1784 and 1795, and the border of the dark part +faintly lit up by a dusky grey light. On February 14, 1806, at<span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a></span> +7 <span class="smcaplc">P.M.</span> he saw the whole of the dark part visible with an ash-coloured light, and he +was satisfied that there was no illusion. On January 24 of the same year, +1806, Harding at Göttingen, using a reflector of 9 inches aperture and +power 84, saw the dark side of Venus “shining with a pale ash-coloured +light,” and very visible against the dark background of the sky. The +appearance was seen with various magnifying powers, and he thought that +there could be no illusion. In fact the phenomenon was as evident as in +the case of the moon. Harding again saw it on February 28 of the same +year, the illumination being of a reddish grey colour, “like that of the +moon in a total eclipse.”</p> + +<p>The “secondary light” was also seen by Pastorff in 1822, and by +Gruithuisen in 1825. Since 1824 observations of the “light” were made by +Berry, Browning, Guthrie, Langdon, Noble, Prince, Webb, and others. Webb +saw it with powers of 90 and 212 on a 9·38-inch mirror, and found it +“equally visible when the bright crescent was hidden by a field bar.”<a name='fna_42' id='fna_42' href='#f_42'><small>[42]</small></a></p> + +<p>Captain Noble’s observation was rather unique. He found that the dark side +was “always distinctly and positively <i>darker</i> than the background upon +which it is projected.”</p> + +<p>The “light” was also seen by Lyman in America in 1867, and by Safarik at +Prague. In<span class="pagenum"><a name="Page_26" id="Page_26">[Pg 26]</a></span> 1871 the whole disc of Venus was seen by Professor +Winnecke.<a name='fna_43' id='fna_43' href='#f_43'><small>[43]</small></a> On the other hand, Winnecke stated that he only saw it twice +in 24 years; and the great observers Dawes and Mädler never saw it at +all!<a name='fna_44' id='fna_44' href='#f_44'><small>[44]</small></a></p> + +<p>Various attempts have been made to explain the visibility—at times—of +the “dark side” of Venus. The following may be mentioned<a name='fna_45' id='fna_45' href='#f_45'><small>[45]</small></a>:—(1) +Reflected earth-light, analogous to the dark side of the crescent moon. +This explanation was advocated by Harding, Schröter, and others. But, +although the earth is undoubtedly a bright object in the sky of Venus, the +explanation is evidently quite inadequate. (2) Phosphorescence of the +planet’s atmosphere. This has been suggested by some observers. (3) +Visibility by contrast, a theory advanced by the great French astronomer +Arago. (4) Illumination of the planet’s surface by an aurora borealis. +This also seems rather inadequate, but would account for the light being +sometimes visible and sometimes not. (5) Luminosity of the oceans—if +there be any—on Venus. But this also seems inadequate. (6) A planetary +surface glowing with intense heat. But this seems improbable. (7) The +Kunstliche Feuer (artificial fire) of Gruithuisen, a very fanciful theory. +Flammarion thinks that the visibility of the dark side may perhaps be +explained by its<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span> projection on a somewhat lighter background, such as the +zodiacal light, or an extended solar envelope.<a name='fna_46' id='fna_46' href='#f_46'><small>[46]</small></a></p> + +<p>It will be seen that none of these explanations are entirely satisfactory, +and the phenomenon, if real, remains a sort of astronomical enigma. The +fact that the “light” is visible on some occasions and not on others would +render some of the explanations improbable or even inadmissible. But the +condition of the earth’s atmosphere at times might account for its +invisibility on many occasions.</p> + +<p>A curious suggestion was made by Zöllner, namely, that if the secondary +light of Venus could be observed with the spectroscope it would show +bright lines! But such an observation would be one of extreme difficulty.</p> + +<p>M. Hansky finds that the visibility of the “light” is greater during +periods of maximum solar activity—that is, at the maxima of sun spots. +This he explains by the theory of Arrhenius, in which electrified “ions +emitted by the sun cause the phenomena of terrestrial magnetic storms and +auroras.” “In the same way the dense atmosphere of Venus is rendered more +phosphorescent, and therefore more easily visible by the increased solar +activity.”<a name='fna_47' id='fna_47' href='#f_47'><small>[47]</small></a> This seems a very plausible hypothesis.</p> + +<p>On the whole the occasional illumination of the<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> night side of Venus by a +very brilliant aurora (explanation (4) above) seems to the present writer +to be the most probable explanation. Gruithuisen’s hypothesis (7) seems +utterly improbable.</p> + +<p>There is a curious apparent anomaly about the motion of Venus in the sky. +Although the planet’s period of revolution round the sun is 224·7 days, it +remains on the same side of the sun, as seen from the earth, for 290 days. +The reason of this is that the earth is going at the same time round the +sun in the same direction, though at a slower pace; and Venus must +continue to appear on the same side of the sun until the excess of her +daily motion above that of the earth amounts to 179°, and this at the +daily rate of 37′ will be about 290 days.</p> + +<p>Several observations have been recorded of a supposed satellite of Venus. +But the existence of such a body has never been verified. In the year +1887, M. Stroobant investigated the various accounts, and came to the +conclusion that in several at least of the recorded observations the +object seen was certainly a star. Thus, in the observation made by +Rœdickœr and Boserup on August 4, 1761, a satellite and star are +recorded as having been seen near the planet. M. Stroobant finds that the +supposed “satellite” was the star χ<sub>4</sub> Orionis, and the “star” +<span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span>χ<sub>3</sub> Orionis. A supposed observation of a satellite made by +Horrebow on January 3, 1768, was undoubtedly θ Libræ. M. +Stroobant found that the supposed motion of the “satellite” as seen by +Horrebow is accurately represented by the motion of Venus itself during +the time of observation. In most of the other supposed observations of a +satellite a satisfactory identification has also been found. M. Stroobant +finds that with a telescope of 6 inches aperture, a star of the 8th or +even the 9th magnitude can be well seen when close to Venus.<a name='fna_49' id='fna_49' href='#f_49'><small>[49]</small></a></p> + +<p>On the night of August 13, 1892, Professor Barnard, while examining Venus +with the great 36-inch telescope of the Lick Observatory, saw a star of +the 7th magnitude in the same field with the planet. He carefully +determined the exact position of this star, and found that it is not in +Argelander’s great catalogue, the <i>Durchmusterung</i>. Prof. Barnard finds +that owing to elongation of Venus from the sun at the time of observation +the star could not possibly be an intra-Mercurial planet (that is, a +planet revolving round the sun inside the orbit of Mercury); but that +possibly it might be a planet revolving between the orbits of Venus and +Mercury. As the brightest of the minor planets—Ceres, Pallas, Juno, and +Vesta—were not at the time near the position of the observed object, the +observation<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span> remains unexplained. It might possibly have been a <i>nova</i>, or +temporary star.<a name='fna_50' id='fna_50' href='#f_50'><small>[50]</small></a></p> + +<p>Scheuten is said to have seen a supposed satellite of Venus following the +planet across the sun at the end of the transit of June 6, 1761.<a name='fna_51' id='fna_51' href='#f_51'><small>[51]</small></a></p> + +<p>Humboldt speaks of the supposed satellite of Venus as among “the +astronomical myths of an uncritical age.”<a name='fna_52' id='fna_52' href='#f_52'><small>[52]</small></a></p> + +<p>An occultation of Venus by the moon is mentioned in the Chinese Annals as +having occurred on March 19, 361 <span class="smcaplc">A.D.</span>, and Tycho Brahé observed another on +May 23, 1587.<a name='fna_53' id='fna_53' href='#f_53'><small>[53]</small></a></p> + +<p>A close conjunction of Venus and Regulus (α Leonis) is recorded +by the Arabian astronomer, Ibn Yunis, as having occurred on September 9, +885 <span class="smcaplc">A.D.</span> Calculations by Hind show that the planet and star were within 2′ +of arc on that night, and consequently would have appeared as a single +star to the naked eye. The telescope had not then been invented.<a name='fna_54' id='fna_54' href='#f_54'><small>[54]</small></a></p> + +<p>Seen from Venus, the maximum apparent distance between the earth and moon +would vary from about 5′ to 31′.<a name='fna_55' id='fna_55' href='#f_55'><small>[55]</small></a></p> + +<p>It is related by Arago that Buonaparte, when going to the Luxembourg in +Paris, where the<span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span> Directory were giving a fête in his honour, was very +much surprised to find the crowd assembled in the Rue de Touracour “pay +more attention to a region of the heavens situated above the palace than +to his person or the brilliant staff that accompanied him. He inquired the +cause and learned that these curious persons were observing with +astonishment, although it was noon, a star, which they supposed to be that +of the conqueror of Italy—an allusion to which the illustrious general +did not seem indifferent, when he himself, with his piercing eyes, +remarked the radiant body.” The “star” in question was Venus.<a name='fna_56' id='fna_56' href='#f_56'><small>[56]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span></p> +<h2><a name="CHAPTER_IV" id="CHAPTER_IV"></a>CHAPTER IV</h2> +<p class="title">The Earth</p> + +<p> </p> +<p class="dropcap"><span class="caps">The</span> earth being our place of abode is, of course, to us the most important +planet in the solar system. It is a curious paradox that the moon’s +surface (at least the visible portion) is better known to us than the +surface of the earth. Every spot on the moon’s visible surface equal in +size to say Liverpool or Glasgow is well known to lunar observers, whereas +there are thousands of square miles on the earth’s surface—for example, +near the poles and in the centre of Australia—which are wholly unknown to +the earth’s inhabitants; and are perhaps likely to remain so.</p> + +<p>Many attempts have been made by “paradoxers” to show that the earth is a +flat plane and not a sphere. But M. Ricco has found by actual experiment +that the reflected image of the setting sun from a smooth sea is an +elongated ellipse. This proves mathematically beyond all doubt that the +surface of the sea is spherical; for the reflection from a plane surface +would be<span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span> necessarily <i>circular</i>. The theory of a “flat earth” is +therefore proved to be quite untenable, and all the arguments (?) of the +“earth flatteners” have now been—like the French Revolution—“blown into +space.”</p> + +<p>The pole of minimum temperature in the northern hemisphere, or “the pole +of cold,” as it has been termed, is supposed to lie near Werchojansk in +Siberia, where a temperature of nearly -70° has been observed.</p> + +<p>From a series of observations made at Annapolis (U.S.A.) on the gradual +disappearance of the blue of the sky after sunset, Dr. See finds that the +extreme height of the earth’s atmosphere is about 130 miles. Prof. Newcomb +finds that meteors first appear at a mean height of about 74 miles.<a name='fna_57' id='fna_57' href='#f_57'><small>[57]</small></a></p> + +<p>An aurora seen in Canada on July 15, 1893, was observed from stations 110 +miles apart, and from these observations the aurora was found to lie at a +height of 166 miles above the earth’s surface. It was computed that if the +auroral “arch maintained an equal height above the earth its ends were +1150 miles away, so that the magnificent sight was presented of an auroral +belt in the sky with 2300 miles between its two extremities.”<a name='fna_58' id='fna_58' href='#f_58'><small>[58]</small></a></p> + +<p>“Luminous clouds” are bright clouds sometimes seen at night near the end +of June and beginning<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span> of July. They appear above the northern horizon +over the sun’s place about midnight, and evidently lie at a great height +above the earth’s surface. Observations made in Germany by Dr. Jesse, and +in England by Mr. Backhouse, in the years 1885-91, show that the height of +these clouds is nearly constant at about 51 miles.<a name='fna_59' id='fna_59' href='#f_59'><small>[59]</small></a> The present writer +has seen these remarkable clouds on one or two occasions in County Sligo, +Ireland, during the period above mentioned.</p> + +<p>M. Montigny has shown that “the approach of violent cyclones or other +storms is heralded by an increase of scintillation” (or twinkling of the +stars). The effect is also very evident when such storms pass at a +considerable distance. He has also made some interesting observations +(especially on the star Capella), which show that, not only does +scintillation increase in rainy weather, but that “it is very evident, at +such times, in stars situated at an altitude at which on other occasions +it would not be perceptible at all; thus confirming the remark of +Humboldt’s with regard to the advent of the wet season in tropical +countries.”<a name='fna_60' id='fna_60' href='#f_60'><small>[60]</small></a></p> + +<p>In a paper on the subject of “Optical Illusions” in <i>Popular Astronomy</i>, +February, 1906, Mr.<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span> Arthur K. Bartlett, of Batter Creek, Michigan +(U.S.A.), makes the following interesting remarks:—</p> + +<div class="blockquot"><p>“The lunar halo which by many persons is regarded as a remarkable and +unexplained luminosity associated with the moon, is to meteorological +students neither a mysterious nor an anomalous occurrence. It has been +frequently observed and for many years thoroughly understood, and at +the present time admits of an easy scientific explanation. It is an +atmospheric exhibition due to the refraction and dispersion of the +moon’s light through very minute ice crystals floating at great +elevations above the earth, and it is explained by the science of +meteorology, to which it properly belongs; for it is not of cosmical +origin, and in no way pertains to astronomy, as most persons suppose, +except as it depends on the moon, whose light passing through the +atmosphere, produces the luminous halo, which as will be seen, is +simply an optical illusion, originating, not in the vicinity of the +moon—two hundred and forty thousand miles away—but just above the +earth’s surface, and within the aqueous envelope that surrounds it on +all sides.... A halo may form round the sun as well as the moon ... +but a halo is more frequently noticed round the moon for the reason +that we are too much dazzled by the sun’s light to distinguish faint +colours surrounding its disc, and to see them it is necessary to look +through smoked glass, or view the sun by reflection from the surface +of still water, by which its brilliancy is very much reduced.”...</p></div> + +<p>“A ‘corona’ is an appearance of faintly coloured rings often seen around +the sun and moon when<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> a light fleecy cloud passes over them, and should +not be mistaken for a halo, which is much larger and more complicated in +its structure. These two phenomena are frequently confounded by +inexperienced observers.” With these remarks the present writer fully +concurs.</p> + +<p>Mr. Bartlett adds—</p> + +<div class="blockquot"><p>“As a halo is never seen except when the sky is hazy, it indicates +that moisture is accumulating in the atmosphere which will form +clouds, and usually result in a storm. But the popular notion that the +number of bright stars visible within the circle indicates the number +of days before the storm will occur, is without any foundation +whatever, and the belief is almost too absurd to be refuted. In +whatever part of the sky a lunar halo is seen, one or more bright +stars are always sure to be noticed inside the luminous ring, and the +number visible depends entirely upon the position of the moon. +Moreover, when the sky within the circle is examined with even a small +telescope, hundreds of stars are visible where only one, or perhaps +two or three, are perceived with the naked eye.”</p></div> + +<p>It is possible to have five Sundays in February (the year must of course +be a “leap year”). This occurred in the year 1880, Sunday falling on +February 1, 8, 15, 22, and 29. But this will not happen again till the +year 1920. No century year (such as 1900, 2000, etc.) could possibly have +five Sundays in February, and the Rev. Richard Campbell, who investigated +this matter, finds<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> the following sequence of years in which five Sundays +occur in February: 1604, 1632, 1660, 1688, 1728, 1756, 1784, 1824, 1852, +1880, 1920, 1948, 1976.<a name='fna_61' id='fna_61' href='#f_61'><small>[61]</small></a></p> + +<p>In an article on “The Last Day and Year of the Century: Remarks on Time +Reckoning,” in <i>Nature</i>, September 10, 1896, Mr. W. T. Lynn, the eminent +astronomer, says, “The late Astronomer Royal, Sir George Airy, once +received a letter requesting him to settle a dispute which had arisen in +some local debating society, as to which would be the first day of the +next century. His reply was, ‘A very little consideration will suffice to +show that the first day of the twentieth century will be January 1, 1901.’ +Simple as the matter seems, the fact that it is occasionally brought into +question shows that there is some little difficulty connected with it. +Probably, however, this is in a great measure due to the circumstance that +the actual figures are changed on January 1, 1900, the day preceding being +December 31, 1899. A century is a very definite word for an interval +respecting which there is no possible room for mistake or difference of +opinion. But the date of its ending depends upon that of its beginning. +Our double system of backward and forward reckoning leads to a good deal +of inconvenience. Our reckoning supposes (what we know was not the case, +but as an era the date<span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span> does equally well) that Christ was born at the end +of <span class="smcaplc">B.C.</span> 1. At the end of <span class="smcaplc">A.D.</span> 1, therefore, one year had elapsed from the +event, at the end of <span class="smcaplc">A.D.</span> 100, one century, and at the end of 1900, +nineteen centuries.... It is clear, then, that the year, as we call it, is +an ordinal number, and that 1900 years from the birth of Christ (reckoning +as we do from <span class="smcaplc">B.C.</span> 1) will not be completed until the end of December 31 +in that year, the twentieth century beginning with January 1, 1901, that +is (to be exact) at the previous midnight, when the day commences by civil +reckoning.” With these remarks of Mr. Lynn I fully concur, and, so far as +I know, all astronomers agree with him. As the discussion will probably +again arise at the end of the twentieth century, I would like to put on +record here what the scientific opinion was at the close of the nineteenth +century.</p> + +<p>Prof. E. Rutherford, the well-known authority on radium, suggests that +possibly radium is a source of heat from within the earth. Traces of +radium have been detected in many rocks and soils, and even in sea water. +Calculation shows that the total amount distributed through the earth’s +crust is enormously large, although relatively small “compared with the +annual output of coal for the world.” The amount of radium necessary to +compensate for the present loss of heat from the earth “corresponds to +only five parts in one hundred million<span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span> millions per unit mass,” and the +“observations of Elster and Gertel show that the radio-activity observed +in soils corresponds to the presence of about this proportion of +radium.”<a name='fna_62' id='fna_62' href='#f_62'><small>[62]</small></a></p> + +<p>The earth has 12 different motions. These are as follows:—</p> + +<p>1. Rotation on its axis, having a period of 24 hours.</p> + +<p>2. Revolution round the sun; period 365¼ days.</p> + +<p>3. Precession; period of about 25,765 years.</p> + +<p>4. Semi-lunar gravitation; period 28 days.</p> + +<p>5. Nutation; period 18½ years.</p> + +<p>6. Variation in obliquity of the ecliptic; about 47″ in 100 years.</p> + +<p>7. Variation of eccentricity of orbit.</p> + +<p>8. Change of line of apsides; period about 21,000 years.</p> + +<p>9. Planetary perturbations.</p> + +<p>10. Change of centre of gravity of whole solar system.</p> + +<p>11. General motion of solar system in space.</p> + +<p>12. Variation of latitude with several degrees of periodicity.<a name='fna_63' id='fna_63' href='#f_63'><small>[63]</small></a></p> + +<div class="blockquot"><p>“An amusing story has been told which affords a good illustration of +the ignorance and popular notions regarding the tides prevailing even +among persons of average intelligence. ‘Tell me,’ said a man to an +eminent living English<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> astronomer not long ago, ‘is it still +considered probable that the tides are caused by the moon?’ The man of +science replied that to the best of his belief it was, and then asked +in turn whether the inquirer had any serious reason for questioning +the relationship. ‘Well, I don’t know,’ was the answer; ‘sometimes +when there is no moon there seems to be a tide all the same.’”!<a name='fna_64' id='fna_64' href='#f_64'><small>[64]</small></a></p></div> + +<p>With reference to the force of gravitation, on the earth and other bodies +in the universe, Mr. William B. Taylor has well said, “With each revolving +year new demonstrations of its absolute precision and of its universal +domination serves only to fill the mind with added wonder and with added +confidence in the stability and the supremacy of the power in which has +been found no variableness neither shadow of turning, but which—the same +yesterday, to-day and for ever—</p> + +<p class="poem">“Lives through all life, extends through all extent,<br /> +Spreads undivided, operates unspent.”<a name='fna_65' id='fna_65' href='#f_65'><small>[65]</small></a></p> + +<p>With reference to the habitability of other planets, Tennyson has +beautifully said—</p> + +<p class="poem">“Venus near her! smiling downwards at this earthlier earth of ours,<br /> +Closer on the sun, perhaps a world of never fading flowers.<br /> +Hesper, whom the poets call’d the Bringer home of all good things;<br /> +<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span>All good things may move in Hesper; perfect people, perfect kings.<br /> +Hesper—Venus—were we native to that splendour, or in Mars,<br /> +We should see the globe we groan in fairest of their evening stars.<br /> +Could we dream of war and carnage, craft and madness, lust and spite,<br /> +Roaring London, raving Paris, in that spot of peaceful light?<br /> +Might we not in glancing heavenward on a star so silver fair,<br /> +Yearn and clasp the hands, and murmur, ‘Would to God that we were there!’”</p> + +<p>The ancient Greek writer, Diogenes Laertius, states that Anaximander +(610-547 <span class="smcaplc">B.C.</span>) believed that the earth was a sphere. The Greek words are: +μίσην τε τὴν γήν κεῖσθαι, +κέντρυ τάξιν ἐπεχοῦσαν +οὐσαν σφαιροειδῆ.<a name='fna_66' id='fna_66' href='#f_66'><small>[66]</small></a></p> + +<p>With reference to the Aurora Borealis, the exact nature of which is not +accurately known, “a good story used to be told some years ago of a +candidate who, undergoing the torture of a <i>vivâ voce</i> examination, was +unable to reply satisfactorily to any of the questions asked. ‘Come, sir,’ +said the examiner, with the air of a man asking the simplest question, +‘explain to me the cause of the aurora borealis.’ ‘Sir,’ said the unhappy +aspirant for physical honours, ‘I could have explained it perfectly +yesterday, but nervousness has, I think, made me lose my memory.’ ‘This is +very unfortunate,’ said the examiner; ‘you are the only man who could have +explained this mystery, and you have forgotten it.’”<a name='fna_67' id='fna_67' href='#f_67'><small>[67]</small></a> This was written +in the year 1899, and probably the<span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span> phenomenon of the aurora remains +nearly as great a mystery to-day. In 1839, MM. Bravais and Lottin made +observations on the aurora in Norway in about N. latitude 70°. Bravais +found the height to be between 62 and 93 miles above the earth’s surface.</p> + +<p>The cause of the so-called Glacial Epoch in the earth’s history has been +much discussed. The Russian physicist, Rogovsky, has advanced the +following theory—</p> + +<div class="blockquot"><p>“If we suppose that the temperature of the sun at the present time is +still increasing, or at least has been increasing until now, the +glacial epoch can be easily accounted for. Formerly the earth had a +high temperature of its own, but received a lesser quantity of heat +from the sun than now; on cooling gradually, the earth’s surface +attained such a temperature as caused a great part of the surface of +the northern and southern hemispheres to be covered with ice; but the +sun’s radiation increasing, the glaciers melted, and the climatic +conditions became as they are now. In a word, the temperature of the +earth’s surface is a function of two quantities: one decreasing (the +earth’s own heat), and the other increasing (the sun’s radiation), and +consequently there may be a minimum, and this minimum was the glacial +epoch, which, as shown by recent investigations, those of Luigi de +Marchi (Report of <i>G. Schiaparelli, Meteorolog. Zeitschr.</i>, 30, +130-136, 1895), are not local, but general for the whole earth” (see +also M. Neumahr, <i>Erdegeschicht</i>).<a name='fna_68' id='fna_68' href='#f_68'><small>[68]</small></a></p></div> + +<p><span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span>Prof. Percival Lowell thinks that the life of geological palæozoic times +was supported by the earth’s internal heat, which maintained the ocean at +a comparatively warm temperature.<a name='fna_69' id='fna_69' href='#f_69'><small>[69]</small></a></p> + +<p>The following passage in the Book of the Maccabees may possibly refer to +an aurora—</p> + +<div class="blockquot"><p>“Now about this time Antiochus made his second inroad into Egypt. And +it <i>so</i> befell that throughout all the city, for the space of almost +forty days, there appeared in the midst of the sky horsemen in swift +motion, wearing robes inwrought with gold and <i>carrying</i> spears, +equipped in troops for battle; and drawing of swords; and <i>on the +other side</i> squadrons of horse in array; and encounters and pursuits +of both armies; and shaking of shields, and multitudes of lances, and +casting of darts, and flashing of golden trappings, and girding on of +all sorts of armour. Wherefore all men besought that the vision might +have been given for food.”<a name='fna_70' id='fna_70' href='#f_70'><small>[70]</small></a></p></div> + +<p>According to Laplace “the decrease of the mean heat of the earth during a +period of 2000 years has not, taking the extremist limits, diminished as +much as <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">300</span>th of a degree Fahrenheit.”<a name='fna_71' id='fna_71' href='#f_71'><small>[71]</small></a></p> + +<p>From his researches on the cause of the Precession of the Equinoxes, +Laplace concluded that “the motion of the earth’s axis is the same as if +the<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> whole sea formed a solid +mass adhering to its surface.”<a name='fna_72' id='fna_72' href='#f_72'><small>[72]</small></a></p> + +<p>Laplace found that the major (or longer) axis of the earth’s orbit +coincided with the line of Equinoxes in the year 4107 <span class="smcaplc">B.C.</span> The earth’s +perigee then coincided with the autumnal equinox. The epoch at which the +major axis was perpendicular to the line of equinoxes fell in the year +1250 <span class="smcaplc">A.D.</span><a name='fna_73' id='fna_73' href='#f_73'><small>[73]</small></a></p> + +<p>Leverrier has found the minimum eccentricity of the earth’s orbit round +the sun to be 0·0047; so that the orbit will never become absolutely +circular, as some have imagined.</p> + +<p>Laplace says—</p> + +<div class="blockquot"><p>“Astronomy considered in its entirety is the finest monument of the +human mind, the noblest essay of its intelligence. Seduced by the +illusions of the senses and of self-pride, for a long time man +considered himself as the centre of the movement of the stars; his +vain-glory has been punished by the terrors which his own ideas have +inspired. At last the efforts of several centuries brushed aside the +veil which concealed the system of the world. We discover ourselves +upon a planet, itself almost imperceptible in the vast extent of the +solar system, which in its turn is only an insensible point in the +immensity of space. The sublime results to which this discovery has +led should suffice to console us for our extreme littleness, and the +rank which it assigns to the earth. Let us treasure with<span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span> solicitude, +let us add to as we may, this store of higher knowledge, the most +exquisite treasure of thinking beings.”<a name='fna_74' id='fna_74' href='#f_74'><small>[74]</small></a></p></div> + +<p>With reference to probable future changes in climate, the great physicist, +Arrhenius, says—</p> + +<div class="blockquot"><p>“We often hear lamentation that the coal stored up in the earth is +wasted by the present generation without any thought of the future, +and we are terrified by the awful destruction of life and property +which has followed the volcanic eruptions of our days. We may find a +kind of consolation in the consideration that here, as in every other +case, there is good mixed with evil. By the influence of the +increasing percentage of carbonic acid in the atmosphere, we may hope +to enjoy ages with more equable and better climates, especially as +regards the colder regions of the earth, ages when the earth will +bring forth much more abundant crops than at present, for the benefit +of rapidly propagating mankind.”<a name='fna_75' id='fna_75' href='#f_75'><small>[75]</small></a></p></div> + +<p>The night of July 1, 1908, was unusually bright. This was noticed in +various parts of England and Ireland, and by the present writer in Dublin. +Humboldt states that “at the time of the new moon at midnight in 1743, the +phosphorescence was so intense that objects could be distinctly recognized +at a distance of more than 600 feet.”<a name='fna_76' id='fna_76' href='#f_76'><small>[76]</small></a></p> + +<p>An interesting proof of the earth’s rotation on its axis has recently been +found.</p> + +<div class="blockquot"><p><span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span>“In a paper in the +<i>Proceedings</i> of the Vienna Academy (June, 1908) by Herr Tumlirz, it is shown mathematically that if a liquid is flowing +outwards between two horizontal discs, the lines of flow will be +strictly straight only if the discs and vessel be at rest, and will +assume certain curves if that vessel and the discs are in rotation, +as, for example, due to the earth’s rotation. An experimental +arrangement was set up with all precautions, and the stream lines were +marked with coloured liquids and photographed. These were in general +accord with the predictions of theory and the supposition that the +earth is rotating about an axis.”<a name='fna_77' id='fna_77' href='#f_77'><small>[77]</small></a></p></div> + +<p>In a book published in 1905 entitled <i>The Rational Almanac</i>, by Moses B. +Cotsworth, of York, the author states that (p. 397), “The explanation is +apparent from the Great Pyramid’s Slope, which conclusively proves that +when it was built the latitude of that region was 7°·1 more than at +present. Egyptian Memphis now near Cairo was then in latitude 37°·1, where +Asia Minor now ranges, whilst Syria would then be where the Caucasus +regions now experience those rigorous winters formerly experienced in +Syria.” But the reality of this comparatively great change of latitude in +the position of the Great Pyramid can be easily disproved. Pytheas of +Marseilles—who lived in the time of Alexander the Great, about 330 +<span class="smcaplc">B.C.</span>—measured the latitude of Marseilles by means of a gnomon, and found +it to be about 42° 56′½. As the present latitude of Marseilles is<span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span> 43° +17′ 50″, no great change in the latitude could have taken place in over +2000 years.<a name='fna_78' id='fna_78' href='#f_78'><small>[78]</small></a> From this we may conclude that the latitude of the Great +Pyramid has <i>not</i> changed by 7°·1 since its construction. There is, it is +true, a slow diminution going on in the obliquity of the ecliptic (or +inclination of the earth’s axis), but modern observations show that this +would not amount to as much as one degree in 6000 years. Eudemus of +Rhodes—a disciple of Aristotle (who died in 322 <span class="smcaplc">B.C.</span>)—found the +obliquity of the ecliptic to be 24°, which differs but little from its +present value, 23° 27′. Al-Sufi in the tenth century measured the latitude +of Schiraz in Persia, and found it 29° 36′. Its present latitude is 29° +36′ 30″,<a name='fna_79' id='fna_79' href='#f_79'><small>[79]</small></a> so that evidently there has been no change in the latitude in +900 years.</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span></p> +<h2><a name="CHAPTER_V" id="CHAPTER_V"></a>CHAPTER V</h2> +<p class="title">The Moon</p> + +<p> </p> +<p class="dropcap"><span class="caps">The</span> total area of the moon’s surface is about equal to that of North and +South America. The actual surface visible at any one time is about equal +to North America.</p> + +<p>The famous lunar observer, Schröter, thought that the moon had an +atmosphere, but estimated its height at only a little over a mile. Its +density he supposed to be less than that of the vacuum in an air-pump. +Recent investigations, however, seem to show that owing to its small mass +and attractive force the moon could not retain an atmosphere like that of +the earth.</p> + +<p>Prof. N. S. Shaler, of Harvard (U.S.A.), finds from a study of the moon +(from a geological point of view) with the 15-inch refractor of the +Harvard Observatory, that our satellite has no atmosphere nor any form of +organic life, and he believes that its surface “was brought to its present +condition before the earth had even a solid crust.”<a name='fna_80' id='fna_80' href='#f_80'><small>[80]</small></a></p> + +<p>There is a curious illusion with reference to the<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> moon’s apparent +diameter referred to by Proctor.<a name='fna_81' id='fna_81' href='#f_81'><small>[81]</small></a> If, when the moon is absent in the +winter months, we ask a person whether the moon’s diameter is greater or +less than the distance between the stars δ and ε, and +ε and ζ Orionis, the three well-known stars in the “belt +of Orion,” the answer will probably be that the moon’s apparent diameter +is about equal to each of these distances. But in reality the apparent +distance between δ and ε Orionis (or between ε +and ζ, which is about the same) is more than double the moon’s +apparent diameter. This seems at first sight a startling statement; but +its truth is, of course, beyond all doubt and is not open to argument. +Proctor points out that if a person estimates the moon as a foot in +diameter, as its apparent diameter is about half a degree, this would +imply that the observer estimates the circumference of the star sphere as +about 720 feet (360° × 2), and hence the radius (or the moon’s distance +from the earth) about 115 feet. But in reality all such estimates have no +scientific (that is, accurate) meaning. Some of the ancients, such as +Aristotle, Cicero, and Heraclitus, seem to have estimated the moon’s +apparent diameter at about a foot.<a name='fna_82' id='fna_82' href='#f_82'><small>[82]</small></a> This shows that even great minds +may make serious mistakes.</p> + +<p>It has been stated by some writer that the moon as seen with the highest +powers of the great<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> Yerkes telescope (40 inches aperture) appears “just +as it would be seen with the naked eye if it were suspended 60 miles over +our heads.” But this statement is quite erroneous. The moon as seen with +the naked eye or with a telescope shows us nearly a whole hemisphere of +its surface. But if the eye were placed only 60 miles from the moon’s +surface, we should see only a small portion of its surface. In fact, it is +a curious paradox that the nearer the eye is to a sphere the less we see +of its surface! The truth of this will be evident from the fact that on a +level plain an eye placed at a height, say 5 feet, sees a very small +portion indeed of the earth’s surface, and the higher we ascend the more +of the surface we see. I find that at a distance of 60 miles from the +moon’s surface we should only see a small portion of its visible +hemisphere (about <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">90</span>th). The lunar features would also appear under a +different aspect. The view would be more of a landscape than that seen in +any telescope. This view of the matter is not new. It has been previously +pointed out, especially by M. Flammarion and Mr. Whitmell, but its truth +is not, I think, generally recognized. Prof. Newcomb doubts whether with +any telescope the moon has ever been seen so well as it would be if +brought within 500 miles of the earth.</p> + +<p>A relief map of the moon 19 feet in diameter was added, in 1898, to the +Field Columbian<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> Museum (U.S.A.). It was prepared with great care from the +lunar charts of Beer and Mädler, and Dr. Schmidt of the Athens +Observatory, and it shows the lunar features very accurately. Its +construction took five years.</p> + +<p>On a photograph of a part of the moon’s surface near the crater +Eratosthenes, Prof. William H. Pickering finds markings which very much +resemble the so-called “canals” of Mars. The photograph was taken in +Jamaica, and a copy of it is given in Prof. Pickering’s book on the Moon, +and in <i>Popular Astronomy</i>, February, 1904.</p> + +<p>Experiments made in America by Messrs. Stebbins and F. C. Brown, by means +of selenium cells, show that the light of the full moon is about nine +times that of the half moon;<a name='fna_83' id='fna_83' href='#f_83'><small>[83]</small></a> and that “the moon is brighter between +the first quarter and full than in the corresponding phase after full +moon.” They also find that the light of the full moon is equal to “0·23 +candle power,”<a href='#f_83'><small>[83]</small></a> that is, according to the method of measurement used in +America, its light is equal to 0·23 of a standard candle placed at a +distance of one metre (39·37 inches) from the eye.<a name='fna_84' id='fna_84' href='#f_84'><small>[84]</small></a></p> + +<p>Mr. H. H. Kimball finds that no less than 52 per cent. of the observed +changes in intensity of the “earth-shine” visible on the moon when at or +near the crescent phase is due to the eccentricity<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> of the lunar orbit, +and “this is probably much greater than could be expected from any +increase or diminution in the average cloudiness over the hemisphere of +the earth reflecting light to the moon.”<a name='fna_85' id='fna_85' href='#f_85'><small>[85]</small></a></p> + +<p>The “moon maiden” is a term applied to a fancied resemblance of a portion +of the Sinus Iridum to a female head. It forms the “promontory” known as +Cape Heraclides, and may be looked for when the moon’s “age” is about 11 +days. Mr. C. J. Caswell, who observed it on September 29, 1895, describes +it as resembling “a beautiful silver statuette of a graceful female figure +with flowing hair.”</p> + +<p>M. Landerer finds that the angle of polarization of the moon’s +surface—about 33°—agrees well with the polarizing angle for many +specimens of igneous rocks (30° 51′ to 33° 46′). The polarizing angle for +ice is more than 37°, and this fact is opposed to the theories of lunar +glaciation advanced by some observers.<a name='fna_86' id='fna_86' href='#f_86'><small>[86]</small></a></p> + +<p>Kepler states in his <i>Somnium</i> that he saw the moon in the crescent phase +on the morning and evening of the <i>same</i> day (that is, before and after +conjunction with the sun). Kepler could see 14 stars in the Pleiades with +the naked eye, so his eyesight must have been exceptionally keen.</p> + +<p>Investigations on ancient eclipses of the moon show that the eclipse +mentioned by Josephus as<span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span> having occurred before the death of Herod is +probably that which took place on September 15, <span class="smcaplc">B.C.</span> 5. This occurred +about 9.45 p.m.; and probably about six months before the death of Herod +(St. Matthew ii. 15).</p> + +<p>The total lunar eclipse which occurred on October 4, 1884, was remarkable +for the almost total disappearance of the moon during totality. One +observer says that “in the open air, if one had not known exactly where to +look for it, one might have searched for some time without discovering it. +I speak of course of the naked eye appearance.”<a name='fna_87' id='fna_87' href='#f_87'><small>[87]</small></a> On the other hand the +same observer, speaking of the total eclipse of the moon on August 23, +1877, which was a bright one, says—</p> + +<div class="blockquot"><p>“The moon even in the middle of the total phase was a conspicuous +object in the sky, and the ruddy colour was well marked. In the very +middle of the eclipse the degree of illumination was as nearly as +possible equal all round the edge of the moon, the central parts being +darker than those near the edge.”</p></div> + +<p>In Roger de Hovedin’s <i>Chronicle</i> (<span class="smcaplc">A.D.</span> 756) an account is given of the +occultation of “a bright star,” by the moon during a total eclipse. This +is confirmed by Simeon of Durham, who also dates the eclipse <span class="smcaplc">A.D.</span> 756. +This is, however, a mistake, the eclipse having occurred on the evening of +November 23, <span class="smcaplc">A.D.</span> 755. Calvisius supposed that +<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> the occulted “star” might +have been Aldebaran. Pingré, however, showed that this was impossible, and +Struyck, in 1740, showed that the planet Jupiter was the “star” referred +to by the early observer. Further calculations by Hind (1885) show +conclusively that Struyck was quite correct, and that the phenomenon +described in the old chronicles was the occultation of Jupiter by a +totally eclipsed moon—a rather unique phenomenon.<a name='fna_88' id='fna_88' href='#f_88'><small>[88]</small></a></p> + +<p>An occultation of Mars by the moon is recorded by the Chinese, on February +14, <span class="smcaplc">B.C.</span> 69, and one of Venus, on March 30, <span class="smcaplc">A.D.</span> 361. These have also been +verified by Hind, and his calculations show the accuracy of these old +Chinese records.</p> + +<p>It has been suggested that the moon may possibly have a satellite +revolving round it, as the moon itself revolves round the earth. This +would, of course, form an object of great interest. During the total lunar +eclipses of March 10 and September 3, 1895, a careful photographic search +was made by Prof. Barnard for a possible lunar satellite. The eclipse of +March 10 was not very suitable for the purpose owing to a hazy sky, but +that of September 3 was “entirely satisfactory,” as the sky was very +clear, and the duration of totality was very long. On the latter occasion +“six splendid” photographs were obtained of the total phase with a 6-inch +Willard lens. The result<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> was that none of these photographs “show +anything which might be taken for a lunar satellite,” at least any +satellite as bright as the 10th or 12th magnitude. It is, of course, just +possible that the supposed satellite might have been behind the moon +during the totality.</p> + +<p>With reference to the attraction between the earth and moon, Sir Oliver +Lodge says—</p> + +<div class="blockquot"><p>“The force with which the moon is held in its orbit would be great +enough to tear asunder a steel rod 400 miles thick, with a tenacity of +30 tons to the square inch, so that if the moon and earth were +connected by steel instead of gravity, a forest of pillars would be +necessary to whirl the system once a month round their common centre +of gravity. Such a force necessarily implies enormous tensure or +pressure in the medium. Maxwell calculates that the gravitational +stress near the earth, which we must suppose to exist in the invisible +medium, is 3000 times greater than what the strongest steel can stand, +and near the sun it should be 2500 times as great as that.”<a name='fna_89' id='fna_89' href='#f_89'><small>[89]</small></a></p></div> + +<p>With reference to the names given to “craters” on the moon, Prof. W. H. +Pickering says,<a name='fna_90' id='fna_90' href='#f_90'><small>[90]</small></a> “The system of nomenclature is, I think, unfortunate. +The names of the chief craters are generally those of men who have done +little or nothing for selenography, or even for astronomy, while the men +who should be really commemorated are<span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span> represented in general by small and +unimportant craters,” and again—</p> + +<div class="blockquot"><p>“A serious objection to the whole system of nomenclature lies in the +fact that it has apparently been used by some selenographers, from the +earliest times up to the present, as a means of satisfying their spite +against some of their contemporaries. Under the guise of pretending to +honour them by placing their names in perpetuity upon the moon, they +have used their names merely to designate the smallest objects that +their telescopes were capable of showing. An interesting illustration +of this point is found in the craters of Galileo and Riccioli, which +lie close together on the moon. It will be remembered that Galileo was +the discoverer of the craters on the moon. Both names were given by +Riccioli, and the relative size and importance of the craters +[Riccioli large, and Galileo very small] probably indicates to us the +relative importance that he assigned to the two men themselves. Other +examples might be quoted of craters named in the same spirit after men +still living.... With the exception of Maedler, one might almost say, +the more prominent the selenographer the more insignificant the +crater.”</p></div> + +<p>The mathematical treatment of the lunar theory is a problem of great +difficulty. The famous mathematician, Euler, described it as <i>incredibile +stadium atque indefessus labor</i>.<a name='fna_91' id='fna_91' href='#f_91'><small>[91]</small></a></p> + +<p>With reference to the “earth-shine” on the moon when in the crescent +phase, Humboldt says, “Lambert made the remarkable observation<span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span> (14th of +February, 1774) of a change of the ash-coloured moonlight into an +olive-green colour, bordering upon yellow. The moon, which then stood +vertically over the Atlantic Ocean, received upon its night side the green +terrestrial light, which is reflected towards her when the sky is clear by +the forest districts of South America.”<a name='fna_92' id='fna_92' href='#f_92'><small>[92]</small></a> Arago said, “Il n’est donc pas +impossible, malgré tout ce qu’un pareil résultat exciterait de surprise au +premier coup d’œil qu’un jour les météorologistes aillent puiser dans +l’aspect de la Lune des notions précieuses sur <i>l’etat moyen</i> de +diaphanité de l’atmosphère terrestre, dans les hemisphères qui +successivement concurrent à la production de la lumière cendrée.”<a name='fna_93' id='fna_93' href='#f_93'><small>[93]</small></a></p> + +<p>The “earth-shine” on the new moon was successfully photographed in +February, 1895, by Prof. Barnard at the Lick Observatory, with a 6-inch +Willard portrait lens. He says—</p> + +<div class="blockquot"><p>“The earth-lit globe stands out beautifully round, encircled by the +slender crescent. All the ‘seas’ are conspicuously visible, as are +also the other prominent features, especially the region about +<i>Tycho</i>. <i>Aristarchus</i> and <i>Copernicus</i> appear as bright specks, and +the light streams from <i>Tycho</i> are very distinct.”<a name='fna_94' id='fna_94' href='#f_94'><small>[94]</small></a></p></div> + +<p>Kepler found that the moon completely disappeared during the total eclipse +of December 9,<span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span> 1601, and Hevelius observed the same phenomenon during the +eclipse of April 25, 1642, when “not a vestige of the moon could be +seen.”<a name='fna_95' id='fna_95' href='#f_95'><small>[95]</small></a> In the total lunar eclipse of June 10, 1816, the moon during +totality was not visible in London, even with a telescope!<a href='#f_95'><small>[95]</small></a></p> + +<p>The lunar mountains are <i>relatively</i> much higher than those on the earth. +Beer and Mädler found the following heights: Dörfel, 23,174 feet; Newton, +22,141; Casatus, 21,102; Curtius, 20,632; Callippus, 18,946; and Tycho, +18,748 feet.<a name='fna_96' id='fna_96' href='#f_96'><small>[96]</small></a></p> + +<p>Taking the earth’s diameter at 7912 miles, the moon’s diameter, 2163 +miles, and the height of Mount Everest as 29,000 feet, I find that</p> + +<table border="0" cellpadding="0" cellspacing="0" summary="table"> +<tr><td align="center" class="botbor">Everest</td> + <td rowspan="2" align="center"> = </td> + <td align="center" class="botbor">1</td> + <td rowspan="2" align="center"> , and </td> + <td align="center" class="botbor">Dörfel</td> + <td rowspan="2" align="center"> = </td> + <td align="center" class="botbor">1</td></tr> +<tr><td align="center">Earth’s diameter</td> + <td align="center">1440</td> + <td align="center">moon’s diameter</td> + <td align="center">492</td></tr></table> + +<p>From which it follows that the lunar mountains are <i>proportionately</i> about +three times higher than those on the earth.</p> + +<p>According to an hypothesis recently advanced by Dr. See, all the +satellites of the solar system, including our moon, were “captured” by +their primaries. He thinks, therefore, that the “moon came to earth from +heavenly space.”<a name='fna_97' id='fna_97' href='#f_97'><small>[97]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span></p> +<h2><a name="CHAPTER_VI" id="CHAPTER_VI"></a>CHAPTER VI</h2> +<p class="title">Mars</p> + +<p> </p> +<p class="dropcap"><span class="caps">Mars</span> was called by the ancients “the vanishing star,” owing to the long +periods during which it is practically invisible from the earth.<a name='fna_98' id='fna_98' href='#f_98'><small>[98]</small></a> It +was also called πυρόεις and Hercules.</p> + +<p>I have seen it stated in a book on the “Solar System” by a well-known +astronomer that the <i>axis</i> of Mars “is inclined to the plane of the orbit” +at an angle of 24° 50′! But this is quite erroneous. The angle given is +the angle between <i>the plane of the planet’s equator</i> and the plane of its +orbit, which is quite a different thing. This angle, which may be called +the obliquity of Mars’ ecliptic, does not differ much from that of the +earth. Lowell finds it 23° 13′ from observations in 1907.<a name='fna_99' id='fna_99' href='#f_99'><small>[99]</small></a></p> + +<p>The late Mr. Proctor thought that Mars is “far the reddest star in the +heavens; Aldebaran and Antares are pale beside him.”<a name='fna_100' id='fna_100' href='#f_100'><small>[100]</small></a> But this does +not<span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span> agree with my experience. Antares is to my eye quite as red as Mars. +Its name is derived from two Greek words implying “redder than Mars.” The +colour of Aldebaran is, I think, quite comparable with that of the “ruddy +planet.” In the telescope the colour of Mars is, I believe, more yellow +than red, but I have not seen the planet very often in a telescope. Sir +John Herschel suggested that the reddish colour of Mars may possibly be +due to red rocks, like those of the Old Red Sandstone, and the red soil +often associated with such rocks, as I have myself noticed near Torquay +and other places in Devonshire.</p> + +<p>The ruddy colour of Mars was formerly thought to be due to the great +density of its atmosphere. But modern observations seem to show that the +planet’s atmosphere is, on the contrary, much rarer than that of the +earth. The persistent visibility of the markings on its surface shows that +its atmosphere cannot be cloud-laden like ours; and the spectroscope shows +that the water vapour present is—although perceptible—less than that of +our terrestrial envelope.</p> + +<p>The existence of water vapour is clearly shown by photographs of the +planet’s spectrum taken by Mr. Slipher at the Lowell Observatory in 1908. +These show that the water vapour bands <i>a</i> and near D are stronger in the +spectrum of Mars than in that of the moon at the same altitude.<a name='fna_101' id='fna_101' href='#f_101'><small>[101]</small></a></p> + +<p><span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span>The dark markings on Mars were formerly supposed to represent water and +the light parts land. But this idea has now been abandoned. Light +reflected from a water surface is polarized at certain angles. Prof. W. H. +Pickering, in his observations on Mars, finds no trace of polarization in +the light reflected from the dark parts of the planet. But under the same +conditions he finds that the bluish-black ring surrounding the white polar +cap shows a well-marked polarization of light, thus indicating that this +dark ring is probably water.<a name='fna_102' id='fna_102' href='#f_102'><small>[102]</small></a></p> + +<p>Projections on the limb of the planet have frequently been observed in +America. These are known <i>not</i> to be mountains, as they do not reappear +under similar conditions. They are supposed to be clouds, and one seen in +December, 1900, has been explained as a cloud lying at a height of some 13 +miles above the planet’s surface and drifting at the rate of about 27 +miles an hour. If there are any mountains on Mars they have not yet been +discovered.</p> + +<p>The existence of the so-called “canals” of Mars is supposed to be +confirmed by Lowell’s photographs of the planet. But what these “canals” +really represent, that is the question. They have certainly an artificial +look about them, and they form one of the most curious and interesting +problems in the heavens. Prof. Lowell says—</p> + +<div class="blockquot"><p><span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span>“Most suggestive of all Martian phenomena are the canals. Were they +more generally observable the world would have been spared much +scepticism and more theory. They may of course not be artificial, but +observations here [Flagstaff] indicate that they are; as will, I +think, appear from the drawings. For it is one thing to see two or +three canals and quite another to have the planet’s disc mapped with +them on a most elaborate system of triangulation. In the first place +they are this season (August, 1894) bluish-green, of the same colour +as the seas into which the longer ones all eventually debouch. In the +next place they are almost without exception geodetically straight, +supernaturally so, and this in spite of their leading in every +possible direction. Then they are of apparently nearly uniform width +throughout their length. What they are is another matter. Their mere +aspect, however, is enough to cause all theories about glaciation +fissures or surface cracks to die an instant and natural death.”<a name='fna_103' id='fna_103' href='#f_103'><small>[103]</small></a></p></div> + +<p>Some of the observed colour-changes on Mars are very curious. In April, +1905, Mr. Lowell observed that the marking known as Mare Erythræum, just +above Syrtis, had “changed from a blue-green to a chocolate-brown colour.” +The season on Mars corresponded with our February.</p> + +<p>Signor V. Cerulli says that, having observed Mars regularly for ten years, +he has come to the conclusion that the actual existence of the “canals” is +as much a subject for physiological<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> as for astronomical investigation. He +states that “the phenomena observed are so near the limit of the range of +the human eye that in observing them one really experiences an effect +accompanying the ‘birth of vision.’ That is to say, the eye sees more and +more as it becomes accustomed, or strained, to the delicate markings, and +thus the joining up of spots to form ‘canals’ and the gemination of the +latter follow as a physiological effect, and need not necessarily be +subjective phenomena seen by the unaccustomed eye.”<a name='fna_104' id='fna_104' href='#f_104'><small>[104]</small></a></p> + +<p>The possibility of life on Mars has been recently much discussed; some +denying, others asserting. M. E. Rogovsky says—</p> + +<div class="blockquot"><p>“As free oxygen and carbonic dioxide may exist in the atmosphere of +<i>Mars</i>, vegetable and animal life is quite possible. If the +temperature which prevails upon <i>Mars</i> is nearer to -36° C. than to +-73° C., the existence of living beings like ourselves is possible. In +fact, the ice of some Greenland and Alpine glaciers is covered by red +algæ (<i>Sphærella nivalis</i>); we find there also different species of +rotaloria, variegated spiders, and other animals on the snow fields +illuminated by the sun; at the edges of glacier snows in the Tyrol we +see violet bells of <i>Soldanella pusilla</i>, the stalks of which make +their way through the snow by producing heat which melts it round +about them. Finally the Siberian town Verkhociansk, near Yakutsk, +exists, though the temperature there falls to -69°·8 C. and the mean +temperature of January to -51°·2, and the mean pressure of the vapour +of water is<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span> less than 0·05mm. It is possible, therefore, that living +beings have become adapted to the conditions now prevailing upon +<i>Mars</i> after the lapse of many ages, and live at an even lower +temperature than upon the earth, developing the necessary heat +themselves.”</p></div> + +<p>M. Rogovsky adds, “Water in organisms is mainly a liquid or solvent, and +many other liquids may be the same. We have no reason to believe that life +is possible only under the same conditions and with the same chemical +composition of organisms as upon the earth, although indeed we cannot +affirm that they actually exist on Mars.”<a name='fna_105' id='fna_105' href='#f_105'><small>[105]</small></a> With the above views the +present writer fully concurs.</p> + +<p>Prof. Lowell thinks that the polar regions of Mars, both north and south, +are actually warmer than the corresponding regions of the earth, although +the mean temperature of the planet is probably twelve degrees lower than +the earth’s mean temperature.<a name='fna_106' id='fna_106' href='#f_106'><small>[106]</small></a></p> + +<p>A writer in <i>Astronomy and Astrophysics</i> (1892, p. 748) says—</p> + +<div class="blockquot"><p>“Whether the planet Mars is inhabited or not seems to be the +all-absorbing question with the ordinary reader. With the astronomer +this query is almost the last thing about the planet that he would +think of when he has an opportunity to study its surface markings ... +no<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> astronomer claims to know whether the planet is inhabited or not.”</p></div> + +<p>Several suggestions have been made with reference to the possibility of +signalling to Mars. But, as Mr. Larkin of Mount Lowe (U.S.A.) points out, +all writers on this subject seem to forget the fact that the night side of +two planets are never turned towards each other. “When the sun is between +them it is day on the side of Mars which is towards us, and also day on +the side of the earth which is towards Mars. When they are on the same +side of the sun, it is day on Mars when night on the earth, and for this +reason they could never see our signals. This should make it apparent that +the task of signalling to Mars is a more difficult one than the most +hopeful theorist has probably considered. All this is under the +supposition that the Martians (if there are such) are beings like +ourselves. If they are not like us, we cannot guess what they are +like.”<a name='fna_107' id='fna_107' href='#f_107'><small>[107]</small></a> These views seem to me to be undoubtedly correct, and show the +futility of visual signals. Electricity might, however, be conceivably +used for the purpose; but even this seems highly improbable.</p> + +<p>Prof. Newcomb, in his work <i>Astronomy for Everybody</i>, says with reference +to this question, “The reader will excuse me from saying nothing in this +chapter about the possible inhabitants of<span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span> Mars. He knows just as much +about the subject as I do, and that is nothing at all.”</p> + +<p>It is, however, quite possible that life <i>in some form</i> may exist on Mars. +As Lowell well says, “Life but waits in the wings of existence for its cue +to enter the scene the moment the stage is set.”<a name='fna_108' id='fna_108' href='#f_108'><small>[108]</small></a> With reference to +the “canals” he says—</p> + +<div class="blockquot"><p>“It is certainly no exaggeration to say that they are the most +astonishing objects to be viewed in the heavens. There are celestial +sights more dazzling, spectacles that inspire more awe, but to the +thoughtful observer who is privileged to see them well, there is +nothing in the sky so profoundly impressive as these canals of +Mars.”<a name='fna_109' id='fna_109' href='#f_109'><small>[109]</small></a></p></div> + +<p>The eminent Swedish physicist Arrhenius thinks that the mean annual +temperature on Mars may possibly be as high as 50° F. He says, “Sometimes +the snow-caps on the poles of Mars disappear entirely during the Mars +summer; this never happens on our terrestrial poles. The mean temperature +of Mars must therefore be above zero, probably about +10° [Centigrade = +50° Fahrenheit]. Organic life may very probably thrive, therefore, on +Mars.”<a name='fna_110' id='fna_110' href='#f_110'><small>[110]</small></a> He thinks that this excess of mean temperature above the +calculated temperature may be due to an increased amount of carbonic acid +in the planet’s atmosphere, and says “any doubling of the percentage of +carbon<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> dioxide in the air would raise the temperature of the earth’s +surface by 4°; and if the carbon dioxide were increased fourfold, the +temperature would rise by 8°.”<a name='fna_111' id='fna_111' href='#f_111'><small>[111]</small></a></p> + +<p>Denning says,—<a name='fna_112' id='fna_112' href='#f_112'><small>[112]</small></a></p> + +<div class="blockquot"><p>“A few years ago, when christening celestial formations was more in +fashion than it is now, a man simply had to use a telescope for an +evening or two on Mars or the moon, and spice the relation of his +seeings with something in the way of novelty, when his name would be +pretty certainly attached to an object and hung in the heavens for all +time! A writer in the <i>Astronomical Register</i> for January, 1879, +humorously suggested that ‘the matter should be put into the hands of +an advertising agent,’ and ‘made the means of raising a revenue for +astronomical purposes.’ Some men would not object to pay handsomely +for the distinction of having their names applied to the seas and +continents of Mars or the craters of the moon.”</p></div> + +<p>An occultation of Mars by the moon is recorded by Aristotle as having +occurred on April 4, 357 <span class="smcaplc">B.C.</span><a name='fna_113' id='fna_113' href='#f_113'><small>[113]</small></a></p> + +<p>Seen from Mars the maximum apparent distance between the earth and moon +would vary from 3½′ to nearly 17′.<a name='fna_114' id='fna_114' href='#f_114'><small>[114]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span></p> +<h2><a name="CHAPTER_VII" id="CHAPTER_VII"></a>CHAPTER VII</h2> +<p class="title">The Minor Planets</p> + +<p> </p> +<p class="dropcap"><span class="caps">Up</span> to 1908 the number of minor planets (or asteroids) certainly known +amounted to over 650.</p> + +<p>From an examination of the distribution of the first 512 of these small +bodies, Dr. P. Stroobant finds that a decided maximum in number occurs +between the limits of distance of 2·55 and 2·85 (earth’s mean distance +from sun = 1), “199 of the asteroids considered revolving in this +annulus.” He finds that nearly all the asteroidal matter is concentrated +near to the middle of the ring in the neighbourhood of the mean distance +of 2·7, and the smallest asteroids are relatively less numerous in the +richest zones.<a name='fna_115' id='fna_115' href='#f_115'><small>[115]</small></a></p> + +<p>There are some “striking similarities” in the orbits of some of the +asteroids. Thus, in the small planets Sophia (No. 251 in order of +discovery) and Magdalena (No. 318) we have the mean distance of Sophia +3·10, and that of Magdalena 3·19 (earth’s mean distance = 1).<span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span> The +eccentricities of the orbits are 0·09 and 0·07; and the inclinations of +the orbits to the plane of the ecliptic 10° 29′ and 10° 33′ +respectively.<a name='fna_116' id='fna_116' href='#f_116'><small>[116]</small></a> This similarity may be—and probably is—merely +accidental, but it is none the less curious and interesting.</p> + +<p>Some very interesting discoveries have recently been made among the minor +planets. The orbit of Eros intersects the orbit of Mars; and the following +have nearly the same mean distance from the sun as Jupiter:—</p> + +<p class="poem">Achilles (1906 TG), No. 588,<br /> +Patrocles (1906 XY), No. 617,<br /> +Hector (1907 XM), No. 624,</p> + +<p>and another (No. 659) has been recently found. Each of these small planets +“moves approximately in a vertex of an equilateral triangle that it forms +with Jupiter and the sun.”<a name='fna_117' id='fna_117' href='#f_117'><small>[117]</small></a> The minor planet known provisionally as HN +is remarkable for the large eccentricity of its orbit (0·38), and its +small perihelion distance (1·6). When discovered it had a very high South +Declination (61½°), showing that the inclination of the plane of its +orbit to the plane of the ecliptic is considerable.<a name='fna_118' id='fna_118' href='#f_118'><small>[118]</small></a></p> + +<p>Dr. Bauschinger has made a study of the minor planets discovered up to the +end of 1900.<span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span> He finds that the ascending nodes of the orbits show a +marked tendency to cluster near the ascending node of Jupiter’s orbit, a +fact which agrees well with Prof. Newcomb’s theoretical results. There +seems to be a slight tendency for large inclinations and great +eccentricities to go together; but there appears to be no connection +between the eccentricity and the mean distance from the sun. The +longitudes of the perihelia of these small planets “show a well-marked +maximum near the longitude of <i>Jupiter’s</i> perihelion, and equally +well-marked minimum near the longitude of his aphelion,” which is again in +good agreement with Newcomb’s calculations.<a name='fna_119' id='fna_119' href='#f_119'><small>[119]</small></a> Dr. Bauschinger’s +diameter for Eros is 20 miles. He finds that the whole group, including +those remaining to be discovered, would probably form a sphere of about +830 miles in diameter.</p> + +<p>The total mass of the minor planets has been frequently estimated, but +generally much too high. Mr. B. M. Roszel of the John Hopkins University +(U.S.A.) has made a calculation of the probable mass from the known +diameter of Vesta (319 miles, Pickering), and finds the volume of the +first 216 asteroids discovered. From this calculation it appears that it +would take 310 asteroids of the 6th magnitude, or 1200 of the 7th to equal +the moon in volume. Mr. Roszel concludes that the probable mass of the +whole<span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span> asteroidal belt is between +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">50</span>th +and <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">100</span>th of that of the +moon.<a name='fna_120' id='fna_120' href='#f_120'><small>[120]</small></a> Subsequently Mr. Roszel extended his study to the mass of 311 +asteroids,<a name='fna_121' id='fna_121' href='#f_121'><small>[121]</small></a> and found a combined mass of about +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">40</span>th of the moon’s mass.</p> + +<p>Dr. Palisa finds that the recently discovered minor planet (1905 QY) +varies in light to a considerable extent.<a name='fna_122' id='fna_122' href='#f_122'><small>[122]</small></a> This planet was discovered +by Dr. Max Wolf on August 23, 1905; but it was subsequently found that it +is identical with one previously known, (167) Urda.<a name='fna_123' id='fna_123' href='#f_123'><small>[123]</small></a> The light +variation is said to be from the 11th to the 13th magnitude.<a name='fna_124' id='fna_124' href='#f_124'><small>[124]</small></a> +Variation in some of the other minor planets has also been suspected. +Prof. Wendell found a variation of about half a magnitude in the planet +Eunomia (No. 15). He also found that Iris (No. 7) varies about a quarter +of a magnitude in a period of about 6<sup>h</sup> 12<sup>m</sup>.<a name='fna_125' id='fna_125' href='#f_125'><small>[125]</small></a> But these variations +are small, and perhaps doubtful. The variability of Eros is well known.</p> + +<p>The planet Eros is a very interesting one. The perihelion portion of its +orbit lies between the orbits of Mars and the earth, and the aphelion part +is outside the orbit of Mars. Owing to the great variation in its distance +from the earth the brightness of Eros varies from the 6th to the 12th +magnitude. That is, when brightest, it is 250<span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72]</a></span> times brighter than when it +is faintest.<a name='fna_126' id='fna_126' href='#f_126'><small>[126]</small></a> This variation of light, is of course, merely due to the +variation of distance; but some actual variation in the brightness of the +planet has been observed.</p> + +<p>It has been shown by Oeltzen and Valz that Cacciatore’s supposed distant +comet, mentioned by Admiral Smyth in his <i>Bedford Catalogue</i>, must have +been a minor planet.<a name='fna_127' id='fna_127' href='#f_127'><small>[127]</small></a></p> + +<p>Dr. Max Wolf discovered 36 new minor planets by photography in the years +1892-95. Up to the latter year he had never seen one of these through a +telescope! His words are, “Ich selsbt habe noch nie einen meinen kleinen +Planeten am Himmel gesehen.”<a name='fna_128' id='fna_128' href='#f_128'><small>[128]</small></a></p> + +<p>These small bodies have now become so numerous that it is a matter of much +difficulty to follow them. At the meeting of the Royal Astronomical +Society on January 8, 1909, Mr. G. F. Chambers made the following +facetious remarks—</p> + +<div class="blockquot"><p>“I would like to make a suggestion that has been in my mind for +several years past—that it should be made an offence punishable by +fine or imprisonment to discover any more minor planets. They seem to +be an intolerable nuisance, and are a great burden upon the literary +gentlemen who have to keep pace with them and record them. I have +never seen, during the last few<span class="pagenum"><a name="Page_73" id="Page_73">[Pg 73]</a></span> years at any rate, any good come from +them, or likely to come, and I should like to see the supply stopped, +and the energies of the German gentlemen who find so many turned into +more promising channels.”</p></div> + +<p>Among the minor planets numbered 1 to 500, about 40 “have not been seen +since the year of their discovery, and must be regarded as lost.”<a name='fna_129' id='fna_129' href='#f_129'><small>[129]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_74" id="Page_74">[Pg 74]</a></span></p> +<h2><a name="CHAPTER_VIII" id="CHAPTER_VIII"></a>CHAPTER VIII</h2> +<p class="title">Jupiter</p> + +<p> </p> +<p class="dropcap"><span class="caps">This</span> brilliant planet—only inferior to Venus in brightness—was often +seen by Bond (Jun.) with the naked eye in “high and clear sunshine”; also +by Denning, who has very keen eyesight. Its brightness on such occasions +is so great, that—like Venus—it casts a distinct shadow in a dark +room.<a name='fna_130' id='fna_130' href='#f_130'><small>[130]</small></a></p> + +<p>The great “red spot” on Jupiter seems to have been originally discovered +by Robert Hooke on May 9, 1664, with a telescope of 2 inches aperture and +12 feet focus. It seems to have existed ever since; at least the evidence +is, according to Denning, in favour of the identity of Hooke’s spot with +the red spot visible in recent years. The spot was also observed by +Cassini in the years 1665-72, and is sometimes called “Cassini’s spot.” +But the real discoverer was Hooke.<a name='fna_131' id='fna_131' href='#f_131'><small>[131]</small></a></p> + +<p>The orbit of Jupiter is so far outside the earth’s<span class="pagenum"><a name="Page_75" id="Page_75">[Pg 75]</a></span> orbit that there can +be little visible in the way of “phase”—as in the case of Mars, where the +“gibbous” phase is sometimes very perceptible. Some books on astronomy +state that Jupiter shows no phase. But this is incorrect. A distinct, +although very slight, gibbous appearance is visible when the planet is +near quadrature. Webb thought it more conspicuous in twilight than in a +dark sky. With large telescopes, Jupiter’s satellites II. and III. have +been seen—in consequence of Jupiter’s phase—to emerge from occultation +“at a sensible distance from the limb.”<a name='fna_132' id='fna_132' href='#f_132'><small>[132]</small></a></p> + +<p>According to M. E. Rogovsky, the high “albedo of Jupiter, the appearance +of the clear (red) and dark spots on its surface and their continual +variation, the different velocity of rotation of the equatorial and other +zones of its surface, and particularly its small density (1·33, water as +unity), all these facts afford irrefragable proofs of the high temperature +of this planet. The dense and opaque atmosphere hides its glowing surface +from our view, and we see therefore only the external surface of its +clouds. The objective existence of this atmosphere is proved by the bands +and lines of absorption in its spectrum. The interesting photograph +obtained by Draper, September 27, 1879, in which the blue and green parts +are more brilliant for the equatorial zone than for the<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span> adjacent parts of +the surface, appears to show that <i>Jupiter</i> emits its proper light. It is +possible that the constant red spot noticed on its surface by several +observers, as Gledhill, Lord Rosse, and Copeland (1873), Russel and +Bredikhin (1876), is the summit of a high glowing mountain. G. W. Hough +considers Jupiter to be gaseous, and A. Ritter inferred from his formulæ +that in this case the temperature at the centre would be 600,000° C.”<a name='fna_133' id='fna_133' href='#f_133'><small>[133]</small></a></p> + +<p>The four brighter satellites of Jupiter are usually known by numbers I., +II., III., and IV.; I. being the nearest to the planet, and IV. the +farthest. III. is usually the brightest, and IV. the faintest, but +exceptions to this rule have been noticed.</p> + +<p>With reference to the recently discovered sixth and seventh satellites of +Jupiter, Prof. Perrine has suggested that the large inclination of their +orbits to the plane of the planet’s equator seems to indicate that neither +of these bodies was originally a member of Jupiter’s family, but has been +“captured by the planet.” This seems possible as the orbits of some of the +minor planets lie near the orbit of Jupiter (see “Minor Planets”). A +similar suggestion has been made by Prof. del Marmol.<a name='fna_134' id='fna_134' href='#f_134'><small>[134]</small></a></p> + +<p>Many curious observations have been recorded<span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span> with reference to Jupiter’s +satellites; some very difficult of explanation. In 1711 Bianchini saw +satellite IV. so faint for more than an hour that it was hardly visible! A +similar observation was made by Lassell with a more powerful telescope on +June 13, 1849. Key, T. T. Smyth, and Denning have also recorded unusual +faintness.<a name='fna_135' id='fna_135' href='#f_135'><small>[135]</small></a> A very remarkable phenomenon was seen by Admiral Smyth, +Maclear, and Pearson on June 26, 1828. Satellite II., “having fairly +entered on Jupiter, was found 12 or 13 minutes afterwards <i>outside the +limb</i>, where it remained visible for at least 4 minutes, and then suddenly +vanished.” As Webb says, “Explanation is here set at defiance; +demonstrably neither in the atmosphere of the earth, nor Jupiter, where +and what could have been the cause? At present we can get no answer.”<a name='fna_136' id='fna_136' href='#f_136'><small>[136]</small></a> +When Jupiter is in opposition to the sun—that is, on the meridian at +midnight—satellite I. has been seen projected on its own shadow, the +shadow appearing as a dark ring round the satellite.</p> + +<p>On January 28, 1848, at Cambridge (U.S.A.) satellite III. was seen in +transit lying between the shadows of I. and II. and so black that it could +not be distinguished from the shadows, “except by the place it occupied.” +This seems to suggest inherent light in the planet’s surface, as the +satellite was at the time illuminated by full<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> sunshine; its apparent +blackness being due to the effect of contrast. Cassini on one occasion +failed to find the shadow of satellite I. when it should have been on the +planet’s disc,<a name='fna_137' id='fna_137' href='#f_137'><small>[137]</small></a> an observation which again points to the glowing light +of Jupiter’s surface. Sadler and Trouvelot saw the shadow of satellite I. +double! an observation difficult to explain—but the same phenomenon was +again seen on the evening of September 19, 1891, by Mr. H. S. Halbert of +Detroit, Michigan (U.S.A.). He says that the satellite “was in transit +nearing egress, and it appeared as a white disc against the dark southern +equatorial belt; following it was the usual shadow, and at an equal +distance from this was a second shadow, smaller and not so dark as the +true one, and surrounded by a faint penumbra.”<a name='fna_138' id='fna_138' href='#f_138'><small>[138]</small></a></p> + +<p>A dark transit of satellite III. was again seen on the evening of December +19, 1891, by two observers in America. One observer noted that the +satellite, when on the disc of the planet, was intensely black. To the +other observer (Willis L. Barnes) it appeared as an ill-defined <i>dark</i> +image.<a name='fna_139' id='fna_139' href='#f_139'><small>[139]</small></a> A similar observation was made on October 9 of the same year +by Messrs. Gale and Innes.<a name='fna_140' id='fna_140' href='#f_140'><small>[140]</small></a></p> + +<p><span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span>A “black transit” of satellite IV. was seen by several observers in 1873, +and by Prof. Barnard on May 4, 1886. The same phenomenon was observed on +October 30, 1903, in America, by Miss Anne S. Young and Willis S. Barnes. +Miss Young says—</p> + +<div class="blockquot"><p>“The ingress of the satellite took place at 8<sup>h</sup> 50<sup>m</sup> (E. standard +time) when it became invisible upon the background of the planet. An +hour later it was plainly visible as a dark round spot upon the +planet. It was decidedly darker than the equatorial belt.”<a name='fna_141' id='fna_141' href='#f_141'><small>[141]</small></a></p></div> + +<p>The rather rare phenomenon of an occultation of one of Jupiter’s +satellites by another was observed by Mr. Apple, director of the Daniel +Scholl Observatory, Franklin and Marshall College, Lancaster, Pa. +(U.S.A.), on the evening of March 16, 1908. The satellites in question +were I. and II., and they were so close that they could not be separated +with the 11·5-inch telescope of the Observatory.<a name='fna_142' id='fna_142' href='#f_142'><small>[142]</small></a> One of the present +writer’s first observations with a telescope is dated May 17, 1873, and is +as follows: “Observed one of Jupiter’s satellites occulted (or very nearly +so) by another. Appeared as one with power 133” (on 3-inch refractor in +the Punjab). These satellites were probably I. and II.</p> + +<p>Jupiter has been seen on several occasions apparently without his +satellites; some being<span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span> behind the disc, some eclipsed in his shadow, and +some in transit across the disc. This phenomenon was seen by Galileo, +March 15, 1611; by Molyneux, on November 12, 1681; by Sir William +Herschel, May 23, 1802; by Wallis, April 15, 1826; by Greisbach, September +27, 1843; and by several observers on four occasions in the years +1867-1895.<a name='fna_143' id='fna_143' href='#f_143'><small>[143]</small></a> The phenomenon again occurred on October 3, 1907, No. 1 +being eclipsed and occulted, No. 2 in transit, No. 3 eclipsed, and No. 4 +occulted.<a name='fna_144' id='fna_144' href='#f_144'><small>[144]</small></a> It was not, however, visible in Europe, but could have been +seen in Asia and Oceania.<a href='#f_144'><small>[144]</small></a> The phenomenon will occur again on October +22, 1913.<a name='fna_145' id='fna_145' href='#f_145'><small>[145]</small></a></p> + +<p>On the night of September 19, 1903, a star of magnitude 6½ was occulted +by the disc of Jupiter. This curious and rare phenomenon was photographed +by M. Lucien Rudaux at the Observatory of Donville, France.<a name='fna_146' id='fna_146' href='#f_146'><small>[146]</small></a> The star +was Lalande 45698 (= BAC 8129).<a name='fna_147' id='fna_147' href='#f_147'><small>[147]</small></a></p> + +<p>Prof. Barnard, using telescopes with apertures from 5 inches up to 36 +inches (Lick), has failed to see a satellite through the planet’s limb (an +observation which has been claimed by other astronomers). He says, “To my +mind this has<span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span> been due to either poor seeing, a poor telescope, or an +excited observer.”<a name='fna_148' id='fna_148' href='#f_148'><small>[148]</small></a> He adds—</p> + +<div class="blockquot"><p>“I think it is high time that the astronomers reject the idea that the +satellites of Jupiter can be seen through his limb at occultation. +When the seeing is bad there is a spurious limb to Jupiter that well +might give the appearance of transparency at the occultation of a +satellite. But under first-class conditions the limb of Jupiter is +perfectly opaque. It is quibbling and begging the question altogether +to say the phenomenon of transparency may be a rare one and so have +escaped my observations. Has any one said that the moon was +transparent when a star has been seen projected on it when it ought to +have been behind it?”</p></div> + +<p>Prof. Barnard and Mr. Douglass have seen white polar caps on the third and +fourth satellites of Jupiter. The former says they are “exactly like those +on Mars.” “Both caps of the fourth satellite have been clearly +distinguished, that at the north being sometimes exceptionally large, +covering a surface equal to one-quarter or one-third of the diameter of +the satellite.”<a name='fna_149' id='fna_149' href='#f_149'><small>[149]</small></a> This was confirmed on November 23, 1906, when Signor +J. Comas Sola observed a brilliant white spot surrounded by a dark marking +in the north polar region of the third satellite. There were other dark +markings visible, and the satellite presented the appearance of a +miniature of Mars.<a name='fna_150' id='fna_150' href='#f_150'><small>[150]</small></a></p> + +<p><span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span>An eighth satellite of Jupiter has recently been discovered by Mr. Melotte +at the Greenwich Observatory by means of photography. It moves in a +retrograde direction round Jupiter in an orbit inclined about 30° to that +of the planet. The period of revolution is about two years. The orbit is +very eccentric, the eccentricity being about one-third, or greater than +that of any other satellite of the solar system. When nearest to Jupiter +it is about 9 millions of miles from the planet, and when farthest about +20 millions.<a name='fna_151' id='fna_151' href='#f_151'><small>[151]</small></a> It has been suggested by Mr. George Forbes that this +satellite may possibly be identical with the lost comet of Lexell which at +its return in the year 1779 became entangled in Jupiter’s system, and has +not been seen since. If this be the case, we should have the curious +phenomenon of a comet revolving round a planet!</p> + +<p>According to Humboldt the four bright satellites of Jupiter were seen +almost simultaneously and quite independently by Simon Marius at Ausbach +on December 29, 1609, and by Galileo at Padua on January 7, 1610.<a name='fna_152' id='fna_152' href='#f_152'><small>[152]</small></a> The +actual priority, therefore, seems to rest with Simon Marius, but the +publication of the discovery was first made by Galileo in his <i>Nuncius +Siderius</i> (1610).<a name='fna_153' id='fna_153' href='#f_153'><small>[153]</small></a> Grant, however, in his <i>History of Physical +Astronomy</i>,<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> calls Simon Marius an “impudent pretender”! (p. 79).</p> + +<p>M. Dupret at Algiers saw Jupiter with the naked eye on September 26, 1890, +twenty minutes before sunset.<a name='fna_154' id='fna_154' href='#f_154'><small>[154]</small></a></p> + +<p>Humboldt states that he saw Jupiter with the naked eye when the sun was +from 18° to 20° above the horizon.<a name='fna_155' id='fna_155' href='#f_155'><small>[155]</small></a> This was in the plains of South +America near the sea-level.</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span></p> +<h2><a name="CHAPTER_IX" id="CHAPTER_IX"></a>CHAPTER IX</h2> +<p class="title">Saturn</p> + +<p> </p> +<p class="dropcap"><span class="caps">To</span> show the advantages of large telescopes over small ones, Mr. C. Roberts +says that “with the 25-inch refractor of the Cambridge Observatory the +view of the planet Saturn is indescribably glorious; everything I had ever +seen before was visible at a glance, and an enormous amount of detail that +I had never even glimpsed before, after a few minutes’ observation.”<a name='fna_156' id='fna_156' href='#f_156'><small>[156]</small></a></p> + +<p>Chacornac found that the illumination of Saturn’s disc is the reverse of +that of Jupiter, the edges of Saturn being brighter than the centre of the +disc, while in the case of Jupiter—as in that of the sun—the edges are +fainter than the centre.<a name='fna_157' id='fna_157' href='#f_157'><small>[157]</small></a> According to Mr. Denning, Saturn bears +satisfactorily “greater magnifying power than either Mars or +Jupiter.”<a name='fna_158' id='fna_158' href='#f_158'><small>[158]</small></a></p> + +<p>At an occultation of Saturn by the moon, which occurred on June 13, 1900, +M. M. Honorat<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> noticed the great contrast between the slightly yellowish +colour of the moon and the greenish tint of the planet.<a name='fna_159' id='fna_159' href='#f_159'><small>[159]</small></a></p> + +<p>In the year 1892, when the rings of Saturn had nearly disappeared, Prof. +L. W. Underwood, of the Underwood Observatory, Appleton, Wisconsin +(U.S.A.), saw one of Saturn’s satellites (Titan) apparently moving along +the needlelike appendage to the planet presented by the rings. “The +apparent diameter of the satellite so far exceeded the apparent thickness +of the ring that it gave the appearance of a beautiful golden bead moving +very slowly along a fine golden thread.”<a name='fna_160' id='fna_160' href='#f_160'><small>[160]</small></a></p> + +<p>In 1907, when the rings of Saturn became invisible in ordinary telescopes, +Professor Campbell, observing with the great Lick telescope, noticed +“prominent bright knots, visible ... in Saturn’s rings. The knots were +symmetrically placed, two being to the east and two to the west.” This was +confirmed by Mr. Lowell, who says, “Condensations in Saturn’s rings +confirmed here and measured repeatedly. Symmetric and permanent.” This +phenomenon was previously seen by Bond in the years 1847-56. Measures of +these light spots made by Prof. Barnard with the 40-inch Yerkes telescope +show that the outer one corresponded in position with the outer edge<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span> of +the middle ring close to the Cassini division, and the inner condensation, +curious to say, seemed to coincide in position with the “crape ring.” +Prof. Barnard thinks that the thickness of the rings “must be greatly +under 100 miles, and probably less than 50 miles,” and he says—</p> + +<div class="blockquot"><p>“The important fact clearly brought out at this apparition of <i>Saturn</i> +is that the bright rings are not opaque to the light of the sun—and +this is really what we should expect from the nature of their +constitution as shown by the theory of Clerk Maxwell, and the +spectroscopic results of Keeler.”<a name='fna_161' id='fna_161' href='#f_161'><small>[161]</small></a></p></div> + +<p>Under certain conditions it would be theoretically possible, according to +Mr. Whitmell, to see the globe of Saturn through the Cassini division in +the ring. But the observation would be one of great difficulty and +delicacy. The effect would be that, of the arc of the division which +crosses the planet’s disc, “a small portion will appear bright instead of +dark, and may almost disappear.”<a name='fna_162' id='fna_162' href='#f_162'><small>[162]</small></a></p> + +<p>A remarkable white spot was seen on Saturn on June 23, 1903, by Prof. +Barnard, and afterwards by Mr. Denning.<a name='fna_163' id='fna_163' href='#f_163'><small>[163]</small></a> Another white spot was seen +by Denning on July 9 of the same year.<a name='fna_164' id='fna_164' href='#f_164'><small>[164]</small></a> From numerous observations of +these spots, Denning found a rotation period for the planet of about<span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span> +10<sup>h</sup> 39<sup>m</sup> 21<sup>s</sup>.<a name='fna_165' id='fna_165' href='#f_165'><small>[165]</small></a> From observations of the same spots Signor Comas +Sola found a period 10<sup>h</sup> 38<sup>m</sup>·4, a close agreement with Denning’s +result. For Saturn’s equator, Prof. Hill found a rotation period of 10<sup>h</sup> +14<sup>m</sup> 23<sup>s</sup>·8, so that—as in the case of Jupiter—the rotation is faster +at the equator than in the northern latitudes of the planet. A similar +phenomenon is observed in the sun. Mr. Denning’s results were fully +confirmed by Herr Leo Brenner, and other German astronomers.<a name='fna_166' id='fna_166' href='#f_166'><small>[166]</small></a></p> + +<p>Photographs taken by Prof. V. M. Slipher in America show that the spectrum +of Saturn is similar to that of Jupiter. None of the bands observed in the +planet’s spectrum are visible in the spectrum of the rings. This shows +that if the rings possess an atmosphere at all, it must be much rarer than +that surrounding the ball of the planet. Prof. Slipher says that “none of +the absorption bands in the spectrum of <i>Saturn</i> can be identified with +those bands due to absorption in the earth’s atmosphere,” and there is no +trace of aqueous vapour.<a name='fna_167' id='fna_167' href='#f_167'><small>[167]</small></a></p> + +<p>In September, 1907, M. G. Fournier suspected the existence of a “faint +transparent and luminous ring” outside the principal rings of Saturn. He +thinks that it may possibly be subject to periodical fluctuations of +brightness, sometimes being visible<span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span> and sometimes not.<a name='fna_168' id='fna_168' href='#f_168'><small>[168]</small></a> This dusky +ring was again suspected at the Geneva Observatory in October, 1908.<a name='fna_169' id='fna_169' href='#f_169'><small>[169]</small></a> +M. Schaer found it a difficult object with a 16-inch Cassegrain reflector. +Prof. Stromgen at Copenhagen, and Prof. Hartwig at Bamberg, however, +failed to see any trace of the supposed ring.<a name='fna_170' id='fna_170' href='#f_170'><small>[170]</small></a> It was seen at +Greenwich in October, 1908.</p> + +<p>A “dark transit” of Saturn’s satellite Titan across the disc of the planet +has been observed on several occasions. It was seen by Mr. Isaac W. Ward, +of Belfast, on March 27, 1892, with a 4·3-inch Wray refractor. The +satellite appeared smaller than its shadow. The phenomenon was also seen +on March 12 of the same year by the Rev. A. Freeman, Mr. Mee, and M. F. +Terby; and again on November 6, 1907, by Mr. Paul Chauleur and Mr. A. B. +Cobham.<a name='fna_171' id='fna_171' href='#f_171'><small>[171]</small></a></p> + +<p>The recently discovered tenth satellite of Saturn, Themis, was discovered +by photography, and has never been seen by the eye even with the largest +telescopes! But its existence is beyond all doubt, and its orbit round the +planet has been calculated.</p> + +<p>Prof. Hussey of the Lick Observatory finds that Saturn’s satellite Mimas +is probably larger than Hyperion. He also finds from careful measurements +that the diameter of Titan is certainly<span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span> overestimated, and that its +probable diameter is about 2500 miles.<a name='fna_172' id='fna_172' href='#f_172'><small>[172]</small></a></p> + +<p>The French astronomer, M. Lucien Rudaux, finds the following variation in +the light of the satellites of Saturn:—</p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td>Japetus</td> + <td>from</td> + <td>9th</td> + <td>magnitude to</td> + <td>12th</td></tr> +<tr><td>Rhea</td> + <td align="center">"</td> + <td>9</td> + <td align="center">"</td> + <td>10·6</td></tr> +<tr><td>Dione</td> + <td align="center">"</td> + <td>9·5</td> + <td align="center">"</td> + <td>10·5</td></tr> +<tr><td>Tethys</td> + <td align="center">"</td> + <td>9·8</td> + <td align="center">"</td> + <td>10·5</td></tr> +<tr><td>Titan</td> + <td align="center">"</td> + <td>8</td> + <td align="center">"</td> + <td><span style="margin-left: .5em;">8·6</span></td></tr></table> + +<p>The variation of light is, he thinks, due to the fact that the period of +rotation of each satellite is equal to that of their revolution round the +planet; as in the case of our moon.<a name='fna_173' id='fna_173' href='#f_173'><small>[173]</small></a></p> + +<p>The names of the satellites of Saturn are derived from the ancient heathen +mythology. They are given in order of distance from the planet, the +nearest being Mimas and the farthest Themis.</p> + +<p>1. Mimas was a Trojan born at the same time as Paris.</p> + +<p>2. Enceladus was son of Tartarus and Ge.</p> + +<p>3. Tethys was wife of Oceanus, god of ocean currents. She became mother of +all the chief rivers in the universe, as also the Oceanides or sea nymphs.</p> + +<p>4. Dione was one of the wives of Zeus.</p> + +<p>5. Rhea was a daughter of Uranus. She married Saturn, and became the +mother of Vesta, Ceres, Juno, and Pluto.</p> + +<p><span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span>6. Titan was the eldest son of Uranus.</p> + +<p>7. Hyperion was the god of day, and the father of sun and moon.</p> + +<p>8. Japetus was the fifth son of Uranus, and father of Atlas and +Prometheus.<a name='fna_174' id='fna_174' href='#f_174'><small>[174]</small></a></p> + +<p>9. Phœbe was daughter of Uranus and Ge.</p> + +<p>10. Themis was daughter of Uranus and Ge, and, therefore, sister of +Phœbe.</p> + +<p>In a review of Prof. Comstock’s <i>Text Book of Astronomy</i> in <i>The +Observatory</i>, November, 1901, the remark occurs, “We are astonished to see +that Mr. Comstock alludes with apparent seriousness to the <i>nine</i> +satellites of Saturn. As regards the ninth satellite, we thought that all +astronomers held with Mrs. Betsy Prig on the subject of this astronomical +Mrs. Harris.” This reads curiously now (1909) when the existence of the +ninth satellite (Phœbe) has been fully confirmed, and a tenth satellite +discovered.</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span></p> +<h2><a name="CHAPTER_X" id="CHAPTER_X"></a>CHAPTER X</h2> +<p class="title">Uranus and Neptune</p> + +<p> </p> +<p class="dropcap"><span class="caps">From</span> observations of Uranus made in 1896, M. Leo Brenner concluded that +the planet rotates on its axis in about 8½ hours (probably 8<sup>h</sup> 27<sup>m</sup>). +This is a short period, but considering the short periods of Jupiter and +Saturn there seems to be nothing improbable about it.</p> + +<p>Prof. Barnard finds that the two inner satellites of Uranus are difficult +objects even with the great 36-inch telescope of the Lick Observatory! +They have, however, been photographed at Cambridge (U.S.A.) with a 13-inch +lens, although they are “among the most difficult objects known.”<a name='fna_175' id='fna_175' href='#f_175'><small>[175]</small></a></p> + +<p>Sir William Huggins in 1871 found strong absorption lines (six strong +lines) in the spectrum of Uranus. One of these lines indicated the +presence of hydrogen, a gas which does not exist in our atmosphere. Three +of the other lines seen were situated near lines in the spectrum of +atmospheric air. Neither carbonic acid nor sodium<span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span> showed any indications +of their presence in the planet’s spectrum. A photograph by Prof. Slipher +of Neptune’s spectrum “shows the spectrum of this planet to contain many +strong absorption bands. These bands are so pronounced in the part of the +spectrum between the Fraunhofer lines F and D, as to leave the solar +spectrum unrecognizable.... Neptune’s spectrum is strikingly different +from that of <i>Uranus</i>, the bands in the latter planet all being reinforced +in <i>Neptune</i>. In this planet there are also new bands which have not been +observed in any of the other planets. The F line of hydrogen is remarkably +dark ... this band is of more than solar strength in the spectrum of +Uranus also. Thus free hydrogen seems to be present in the atmosphere of +both these planets. This and the other dark bands in these planets bear +evidence of an enveloping atmosphere of gases which is quite unlike that +which surrounds the earth.”<a name='fna_176' id='fna_176' href='#f_176'><small>[176]</small></a></p> + +<p>With the 18-inch equatorial telescope of the Strasburgh Observatory, M. +Wirtz measured the diameter of Neptune, and found from forty-nine measures +made between December 9, 1902, and March 28, 1903, a value of 2″·303 at a +distance of 30·1093 (earth’s distance from sun = 1). This gives a diameter +of 50,251 kilometres, or about 31,225 miles,<a name='fna_177' id='fna_177' href='#f_177'><small>[177]</small></a> and a mean density of +1·54 (water = 1;<span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span> earth’s mean density = 5·53). Prof. Barnard’s measures +gave a diameter of 32,900 miles, a fairly close agreement, considering the +difficulty of measuring so small a disc as that shown by Neptune.</p> + +<p>The satellite of Neptune was photographed at the Pulkown Observatory in +the year 1899. The name Triton has been suggested for it. In the old Greek +mythology Triton was a son of Neptune, so the name would be an appropriate +one.</p> + +<p>The existence of a second satellite of Neptune is suspected by Prof. +Schaeberle, who thinks he once saw it with the 36-inch telescope of the +Lick Observatory “on an exceptionally fine night” in 1895.<a name='fna_178' id='fna_178' href='#f_178'><small>[178]</small></a> But this +supposed discovery has not yet been confirmed. Lassell also thought he had +discovered a second satellite, but this supposed discovery was never +confirmed.<a href='#f_178'><small>[178]</small></a></p> + +<p>The ancient Burmese mention eight planets, the sun, the moon, Mercury, +Venus, Mars, Jupiter, Saturn, and another named Râhu, which is invisible. +It has been surmised that “Râhu” is Uranus, which is just visible to the +naked eye, and may possibly have been discovered by keen eyesight in +ancient times. The present writer has seen it several times without +optical aid in the West of Ireland, and with a binocular field-glass of 2 +inches aperture he found it quite a conspicuous object.</p> + +<p><span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span>When Neptune was <i>visually</i> discovered by Galle, at Berlin, he was +assisted in his observation by Prof. d’Arrest. The incident is thus +described by Dr. Dreyer, “On the night of June 14, 1874, while observing +Coggia’s comet together, I reminded Prof. d’Arrest how he had once said in +the course of a lecture, that he had been present at the finding of +Neptune, and that ‘he might say it would not have been found without him.’ +He then told me (and I wrote it down the next day), how he had suggested +the use of Bremiker’s map (as first mentioned by Dr. Galle in 1877) and +continued, ‘We then went back to the dome, where there was a kind of desk, +at which I placed myself with the map, while Galle, looking through the +refractor, described the configurations of the stars he saw. I followed +them on the map one by one, until he said: “And then there is a star of +the 8th magnitude, in such and such a position,” whereupon I immediately +exclaimed: “That star is not on the map.”’”<a name='fna_179' id='fna_179' href='#f_179'><small>[179]</small></a> This was the planet. But +it seems to the present writer that if Galle or d’Arrest had access to +Harding’s Atlas (as they probably had) they might easily have found the +planet with a good binocular field-glass. As a matter of fact Neptune is +shown in Harding’s Atlas (1822) as a star of the 8th magnitude, having +been mistaken for a star by Lalande on May 8 and 10, 1795; and the present +writer has<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> found Harding’s 8th magnitude stars quite easy objects with a +binocular field-glass having object-glasses of two inches diameter, and a +power of about six diameters.</p> + +<p><span class="smcap">Supposed Planet beyond Neptune.</span>—The possible existence of a planet beyond +Neptune has been frequently suggested. From considerations on the aphelia +of certain comets, Prof. Forbes in 1880 computed the probable position of +such a body. He thought this hypothetical planet would be considerably +larger than Jupiter, and probably revolve round the sun at a distance of +about 100 times the earth’s mean distance from the sun. The place +indicated was between R.A. 11<sup>h</sup> 24<sup>m</sup> and 12<sup>h</sup> 12<sup>m</sup>, and declination 0° +0′ to 6° 0′ north. With a view to its discovery, the late Dr. Roberts took +a series of eighteen photographs covering the region indicated. The result +of an examination of these photographs showed, Dr. Roberts says, that “no +planet of greater brightness than a star of the 15th magnitude exists on +the sky area herein indicated.” Prof. W. H. Pickering has recently revived +the question, and has arrived at the following results: Mean distance of +the planet from the sun, 51·9 (earth’s mean distance = 1); period of +revolution, 373½ years; mass about twice the earth’s mass; probable +position for 1909 about R.A. 7<sup>h</sup> 47<sup>m</sup>, north declination 21°, or about +5° south-east of the star κ Geminorum. The supposed planet would +be faint, its brightness<span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span> being from 11½ to 13½, according to the +“albedo” (or reflecting power) it may have.<a name='fna_180' id='fna_180' href='#f_180'><small>[180]</small></a></p> + +<p>Prof. Forbes has again attacked the question of a possible ultra-Neptunian +planet, and from a consideration of the comets of 1556, 1843 I, 1880 I, +and 1882 II, finds a mean distance of 105·4, with an inclination of the +orbit of 52° to the plane of the ecliptic. This high inclination implies +that “during the greatest part of its revolution it is beyond the zodiac,” +and this, Mr. W. T. Lynn thinks, “may partly account for its not having +hitherto been found by observation.”<a name='fna_181' id='fna_181' href='#f_181'><small>[181]</small></a></p> + +<p>From a consideration of the approximately circular shape of the orbits of +all the large planets of the solar system, Dr. See suggests the existence +of three planets outside Neptune, with approximate distances from the sun +of 42, 56, and 72 respectively (earth’s distance = 1), and recommends a +photographic search for them. He says, “To suppose the planetary system to +terminate with an orbit so round as that of Neptune is as absurd as to +suppose that Jupiter’s system terminates with the orbit of the fourth +satellite.”<a name='fna_182' id='fna_182' href='#f_182'><small>[182]</small></a></p> + +<p>According to Grant, even twenty years before the discovery of Neptune the +error of Prof. Adams’ first approximation amounted to little more than +10°.<a name='fna_183' id='fna_183' href='#f_183'><small>[183]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span></p> +<h2><a name="CHAPTER_XI" id="CHAPTER_XI"></a>CHAPTER XI</h2> +<p class="title">Comets</p> + +<p> </p> +<p class="dropcap"><span class="caps">We</span> learn from Pliny that comets were classified in ancient times, +according to their peculiar forms, into twelve classes, of which the +principal were: <i>Pogonias</i>, bearded; <i>Lampadias</i>, torch-like; <i>Xiphias</i>, +sword-like; <i>Pitheus</i>, tun-like; <i>Acontias</i>, javelin-like; <i>Ceratias</i>, +horn-like; <i>Disceus</i>, quoit-like; and <i>Hippias</i>, horse-mane-like.<a name='fna_184' id='fna_184' href='#f_184'><small>[184]</small></a></p> + +<p>Of the numerous comets mentioned in astronomical records, comparatively +few have been visible to the naked eye. Before the invention of the +telescope (1610) only those which were so visible <i>could</i>, of course, be +recorded. These number about 400. Of the 400 observed since then, some 70 +or 80 only have been visible by unaided vision; and most of these now +recorded could never have been seen without a telescope. During the last +century, out of 300 comets discovered, only 13 were very visible to the +naked eye. Hence, when we read in the newspapers that a comet has been +discovered the<span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span> chances are greatly against it becoming visible to the +naked eye.<a name='fna_185' id='fna_185' href='#f_185'><small>[185]</small></a></p> + +<p>Although comparatively few comets can be seen without a telescope, they +are sometimes bright enough to be visible in daylight! Such were those of +<span class="smcaplc">B.C.</span> 43, <span class="smcaplc">A.D.</span> 1106, 1402, 1532, 1577, 1744, 1843, and the “great September +comet” of 1882.</p> + +<p>If we except the great comet of 1861, through the tail of which the earth +is supposed to have passed, the comet which came nearest to the earth was +that of 1770, known as Lexell’s, which approached us within two millions +of miles, moving nearly in the plane of the ecliptic. It produced, +however, no effect on the tides, nor on the moon’s motion, which shows +that its mass must have been very small. It was computed by Laplace that +if its mass had equalled that of the earth, the length of our year would +have been shortened by 2 hours 47 minutes, and as there was no perceptible +change Laplace concluded that the comet’s mass did not exceed +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">5000</span>th of +the earth’s mass. This is the comet which passed so near to Jupiter that +its period was reduced to 5½ years. Owing to another near approach in +1779 it became invisible from the earth, and is now lost.<a name='fna_186' id='fna_186' href='#f_186'><small>[186]</small></a> Its +identity with the recently discovered eighth satellite of Jupiter has been +suggested by Mr. George Forbes (see under “Jupiter”). At the near approach +of Lexell’s comet to the earth in 1770, Messier, “the comet ferret,”<span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span> found +that its head had an apparent diameter of 2½°, or nearly five times +that of the moon!</p> + +<p>Another case of near approach to the earth was that of Biela’s comet at +its appearance in 1805. On the evening of December 9 of that year, the +comet approached the earth within 3,380,000 miles.<a name='fna_187' id='fna_187' href='#f_187'><small>[187]</small></a></p> + +<p>The comet of <span class="smcaplc">A.D.</span> 1106 is stated to have been seen in daylight close to +the sun. This was on February 4 of that year. On February 10 it had a tail +of 60° in length, according to Gaubil.<a name='fna_188' id='fna_188' href='#f_188'><small>[188]</small></a></p> + +<p>The comet of 1577 seems to have been one of the brightest on record. +According to Tycho Brahé, it was visible in broad daylight. He describes +the head as “round, bright, and of a yellowish light,” with a curved tail +of a reddish colour.<a name='fna_189' id='fna_189' href='#f_189'><small>[189]</small></a></p> + +<p>The comet of 1652 was observed for about three weeks only, and Hevelius +and Comiers state that it was equal to the moon in apparent size! This +would indicate a near approach to the earth. An orbit computed by Halley +shows that the least distance was about 12 millions of miles, and the +diameter of the comet’s head rather less than 110,000 miles, or about 14 +times the earth’s diameter.</p> + +<p>According to Mr. Denning, “most of the periodical comets at perihelion are +outside the earth’s orbit, and hence it follows that they escape<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> +observation unless the earth is on the same side of the sun as the +comet.”<a name='fna_190' id='fna_190' href='#f_190'><small>[190]</small></a></p> + +<p>It was computed by M. Faye that the <i>volume</i> of the famous Donati’s comet +(1858) was about 500 times that of the sun! On the other hand, he +calculated that its <i>mass</i> (or quantity of matter it contained) was only a +fraction of the earth’s mass. This shows how almost inconceivably tenuous +the material forming the comet must have been—much more rarefied, indeed, +than the most perfect vacuum which can be produced in an air-pump. This +tenuity is shown by the fact that stars were seen through the tail “as if +the tail did not exist.” A mist of a few hundred yards in thickness is +sufficient to hide the stars from our view, while a thickness of thousands +of miles of cometary matter does not suffice even to dim their brilliancy!</p> + +<p>At the time of the appearance of the great comet of 1843, it was doubtful +whether the comet had transited the sun’s disc. But it is now known, from +careful calculations by Prof. Hubbard, that a transit really took place +between 11<sup>h</sup> 28<sup>m</sup> and 12<sup>h</sup> 29<sup>m</sup> on February 27, 1843, and might have +been observed in the southern hemisphere. The distance of this remarkable +comet from the sun at its perihelion passage was less than that of any +known comet. A little before 10 p.m. on February 27, the comet passed +within 81,500 miles of<span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span> the sun’s surface with the enormous velocity of +348 miles a second! It remained less than 2¼ hours north of the +ecliptic, passing from the ascending to the descending node of its orbit +in 2<sup>h</sup> 13<sup>m</sup>·4.<a name='fna_191' id='fna_191' href='#f_191'><small>[191]</small></a> The great comet of 1882 transited the sun’s disc on +Sunday, September 17, of that year, the ingress taking place at 4<sup>h</sup> 50<sup>m</sup> +58<sup>s</sup>, Cape mean time. When on the sun the comet was absolutely invisible, +showing that there was nothing solid about it. It was visible near the sun +with the naked eye a little before the transit took place.<a name='fna_192' id='fna_192' href='#f_192'><small>[192]</small></a> This great +comet was found by several computors to have been travelling in an +elliptic orbit with a period of about eight centuries. Morrison found 712 +years; Frisby, 794; Fabritius, 823; and Kreutz, 843 years.<a name='fna_193' id='fna_193' href='#f_193'><small>[193]</small></a></p> + +<p>The great southern comet of 1887 may be described as a comet without a +head! The popular idea of a comet is a star with a tail. But in this case +there was no head visible—to the naked eye at least. Dr. Thome of the +Cordoba Observatory—its discoverer—describes it as “a beautiful +object—a narrow, straight, sharply defined, graceful tail, over 40° long, +shining with a soft starry light against a dark sky, beginning apparently +without a head, and gradually widening and fading as it extended +upwards.”<a name='fna_194' id='fna_194' href='#f_194'><small>[194]</small></a></p> + +<p><span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span>The great southern comet of 1901 had five tails on May 6 of that year. Two +were fairly bright, and the remaining three rather faint. Mr. Gale saw a +number of faint stars through the tails. The light of these seem to have +been “undimmed.” Mr. Cobham noticed that the stars Rigel and β +Eridani shone through one of the faint tails, and “showed no perceptible +difference.”<a name='fna_195' id='fna_195' href='#f_195'><small>[195]</small></a></p> + +<p>Prof. W. H. Pickering says that “the head of a comet, as far as our +present knowledge is concerned, seems therefore to be merely a meteor +swarm containing so much gaseous material that when electrified by its +approach to the sun it will be rendered luminous” (<i>Harvard Annual</i>, vol. +xxxii. part ii. p. 295) “... if the meteors and their atmospheres are +sufficiently widely separated from one another, the comet may be brilliant +and yet transparent at the same time.”</p> + +<p>In the case of Swift’s comet of 1892 some periodical differences of +appearance were due, according to Prof. W. H. Pickering, to a rotation of +the comet round an axis passing longitudinally through the tail, and he +estimated the period of rotation at about 94 to 97 hours. He computed that +in this comet the repulsive force exerted by the sun on the comet’s tail +was “about 39·5 times the gravitational force.”<a name='fna_196' id='fna_196' href='#f_196'><small>[196]</small></a></p> + +<p>The comet known as 1902<i>b</i> approached the<span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span> planet Mercury within two +millions of miles on November 29 of that year. Prof. O. C. Wendell, of +Harvard Observatory, made some observations on the transparency of this +comet. He found with the aid of a photometer and the 15-inch telescope of +the observatory that in the case of two faint stars over which the comet +passed on October 14, 1902, the absorption of light by the comet was +insensible, and possibly did not exceed one or two hundredths of a +magnitude,<a name='fna_197' id='fna_197' href='#f_197'><small>[197]</small></a> an amount quite imperceptible to the naked eye, and shows +conclusively how almost inconceivably rarefied the substance of this comet +must be.</p> + +<p>The comet known as Morehouse (1908<i>c</i>) showed some curious and wonderful +changes. Mr. Borelly found that five tails are visible on a photographic +plate taken on October 3, 1908, and the trail of an occulted star +indicates a slight absorption effect. According to M. L. Rabourdin, great +changes took place from day to day, and even during the course of an hour! +Similar changes were recorded by G. M. Gauthier; and Prof. Barnard, who +photographed the comet on 30 nights from September 2 to October 13, states +that the photographs of September 30 “are unique, whilst the +transformation which took place between the taking of these and the taking +of the next one on October 1 was very wonderful.”<a name='fna_198' id='fna_198' href='#f_198'><small>[198]</small></a> The spectrum<span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span> +showed the lines of cyanogen instead of the hydrocarbon spectrum shown by +most comets.</p> + +<p>Prof. Barnard has suggested that all the phenomena of comets’ tails cannot +be explained by a repulsive force from the sun. Short tails issuing from +the comet’s nucleus at considerable angles with the main tail point to +eruptive action in the comet itself. The rapid changes and distortions +frequently observed in the tails of some comets suggest motion through a +resisting medium; and the sudden increase of light also occasionally +observed points in the same direction.<a name='fna_199' id='fna_199' href='#f_199'><small>[199]</small></a></p> + +<p>It was computed by Olbers that if a comet having a mass of +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">2000</span>th of the +earth’s mass—which would form a globe of about 520 miles in diameter and +of the density of granite—collided with the earth, with a velocity of 40 +miles a second, our globe would be shattered into fragments.<a name='fna_200' id='fna_200' href='#f_200'><small>[200]</small></a> But that +any comet has a solid nucleus of this size seems very doubtful; and we may +further say that the collision of the earth with <i>any</i> comet is highly +improbable.</p> + +<p>It seems to be a common idea that harvests are affected by comets, and +even “comet wines” are sometimes spoken of. But we know that the earth +receives practically no heat from the brightest comet. Even in the case of +the brilliant comet of 1811, one of the finest on record, it was<span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span> found +that “all the efforts to concentrate its rays did not produce the +slightest effect on the blackened bulb of the most sensitive thermometer.” +Arago found that the year 1808, in which several comets were visible, was +a cold year, “and 1831, in which there was no comet, enjoyed a much higher +temperature than 1819, when there were three comets, one of which was very +brilliant.”<a name='fna_201' id='fna_201' href='#f_201'><small>[201]</small></a> We may, therefore, safely conclude that even a large +comet has no effect whatever on the weather.</p> + +<p>From calculations on the orbit of Halley’s comet, the next return of which +is due in 1910, Messrs. Cowell and Crommelin find that the identity of the +comet shown on the Bayeux Tapestry with Halley’s comet is now “fully +established.” They find that the date of perihelion passage was March 25, +1066, which differs by only 4 days from the date found by Hind. The +imposing aspect of the comet in 1066 described in European chronicles of +that time is confirmed by the Chinese Annals. In the latter records the +brightness is compared to that of Venus, and even with that of the moon! +The comparison with the moon was probably an exaggeration, but the comet +doubtless made a very brilliant show. In the Bayeux Tapestry the +inscription on the wall behind the spectators reads: “<i>isti mirant +stella</i>.” Now, this is bad Latin, and Mr. W. T.<span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span> Lynn has made the +interesting suggestion that some of the letters are hidden by the +buildings in front and that the real sentence is “<i>isti mirantur +stellam</i>.”<a name='fna_202' id='fna_202' href='#f_202'><small>[202]</small></a> The present writer has examined the copy of the Bayeux +Tapestry which is in the Dublin Museum, and thinks that Mr. Lynn’s +suggestion seems very plausible. But the last letter of <i>stellam</i> is +apparently hidden by the comet’s tail, which does not seem very probable!</p> + +<p>The conditions under which the comet will appear in 1910 are not unlike +those of 1066 and 1145. “In each year the comet was discovered as a +morning star, then lost in the sun’s rays; on its emergence it was near +the earth and moved with great rapidity, finally becoming stationary in +the neighbourhood of Hydra, where it was lost to view.”<a name='fna_203' id='fna_203' href='#f_203'><small>[203]</small></a> In 1910 it +will probably be an evening star before March 17, and after May 11, making +a near approach to the earth about May 12. About this time its apparent +motion in the sky will be very rapid. As, however, periodical comets—such +as Halley’s—seem to become fainter at each return, great expectations +with reference to its appearance in 1910 should not be indulged in.</p> + +<p>The appearance of Halley’s comet in <span class="smcaplc">A.D.</span> 1222 is thus described by +Pingré—a great authority on comets—(quoting from an ancient writer)—</p> + +<div class="blockquot"><p><span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span>“In autumn, that +is to say in the months of August and September, a star of the first magnitude was seen, very red, and accompanied by a +great tail which extended towards the top of the sky in the form of a +cone extremely pointed. It appeared to be very near the earth. It was +observed (at first?) near the place of the setting sun in the month of +December.”</p></div> + +<p>With reference to its appearance in the year 1456, when it was of “vivid +brightness,” and had a tail of 60° in length, Admiral Smyth says,<a name='fna_204' id='fna_204' href='#f_204'><small>[204]</small></a> “To +its malign influence were imputed the rapid successes of Mahomet II., +which then threatened all Christendom. The general alarm was greatly +aggravated by the conduct of Pope Callixtus III., who, though otherwise a +man of abilities, was a poor astronomer; for that pontiff daily ordered +the church bells to be rung at noon-tide, extra <i>Ave-Marias</i> to be +repeated, and a special protest and excommunication was composed, +exorcising equally the Devil, the Turks, and the comet.” With reference to +this story, Mr. G. F. Chambers points out<a name='fna_205' id='fna_205' href='#f_205'><small>[205]</small></a> that it is probably based +on a passage in Platina’s <i>Vitæ Pontificum</i>. But in this passage there is +no mention made of excommunication or exorcism, so that the story, which +has long been current, is probably mythical. In confirmation of this view, +the Rev. W. F. Rigge has shown conclusively<a name='fna_206' id='fna_206' href='#f_206'><small>[206]</small></a> that no bull was ever +issued<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> by Pope Callixtus III. containing a reference to <i>any</i> comet. The +story would therefore seem to be absolutely without foundation, and should +be consigned to the limbo of all such baseless myths.</p> + +<p>With reference to the appearance of Halley’s comet, at his last return in +1835, Sir John Herschel, who observed it at the Cape of Good Hope, says—</p> + +<div class="blockquot"><p>“Among the innumerable stars of all magnitudes, from the ninth +downwards, which at various times were seen through it, and some +extremely near to the nucleus (though not <i>exactly on it</i>) there never +appeared the least ground for presuming any extinction of their light +in traversing it. Very minute stars indeed, on entering its brightest +portions, were obliterated, as they would have been by an equal +illumination of the field of view; but stars which before their entry +appeared bright enough to bear that degree of illumination, were in no +case, so far as I could judge, affected to a greater extent than they +would have been by so much lamp-light artificially introduced.”<a name='fna_207' id='fna_207' href='#f_207'><small>[207]</small></a></p></div> + +<p>It is computed by Prof. J. Holetschak that, early in October, 1909, +Halley’s comet should have the brightness of a star of about 14½ +magnitude.<a name='fna_208' id='fna_208' href='#f_208'><small>[208]</small></a> It should then—if not detected before—be discoverable +with some of the large telescopes now available.</p> + +<p>According to the computations of Messrs. Cowell and Crommelin, the comet +should enter Pisces<span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span> from Aries in January, 1910. “Travelling westward +towards the star γ Piscium until the beginning of May, and then +turning eastward again, it will travel back through the constellations +Cetus, Orion, Monoceros, Hydra, and Sextans.” From this it seems that +observers in the southern hemisphere will have a better view of the comet +than those in northern latitudes. The computed brightness varies from 1 on +January 2, 1910, to 1112 on May 10. But the actual brightness of a comet +does not always agree with theory. It is sometimes brighter than +calculation would indicate.</p> + +<p>According to Prof. O. C. Wendell, Halley’s comet will, on May 12, 1910, +approach the earth’s orbit within 4·6 millions of miles; and he thinks +that possibly the earth may “encounter some meteors,” which are presumably +connected with the comet. He has computed the “radiant point” of these +meteors (that is, the point from which they appear to come), and finds its +position to be R.A. 22<sup>h</sup> 42<sup>m</sup>·9, Decl. N. 1° 18′. This point lies a +little south-west of the star β Piscium.</p> + +<p>According to Dr. Smart, the comet will, on June 2, “cross the Equator +thirteen degrees south of Regulus, and will then move slowly in the +direction of φ Leonis. The comet will be at its descending node +on the ecliptic in the morning of May 16, and the earth will pass through +the node on the comet’s orbit about two and a half<span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span> days later. The +comet’s orbit at the node is about 13 million miles within that of the +earth. Matter repelled from the comet’s nucleus by the sun with a velocity +of about 216,000 miles per hour, would just meet the earth when crossing +the comet’s orbit plane. Matter expelled with a velocity of 80,000 miles +per hour, as in the case of Comet Morehouse, would require seven days for +the journey. Cometary matter is said to have acquired greater velocities +than this, for (according to Webb, who quotes Chacornac) Comet II., 1862, +shot luminous matter towards the sun, with a velocity of nearly 2200 miles +per second. It is therefore possible that matter thrown off by the comet +at the node may enter our atmosphere, in which case we must hope that +cyanogen, which so often appears in cometary spectra, may not be +inconveniently in evidence.”<a name='fna_209' id='fna_209' href='#f_209'><small>[209]</small></a></p> + +<p>Cyanogen is, of course, a poisonous gas, but cometary matter is so +rarefied that injurious effects on the earth need not be feared.</p> + +<p>If we can believe the accounts which have been handed down to us, some +very wonderful comets were visible in ancient times. The following may be +mentioned:—</p> + +<p>B.C. 165. The sun is said to have been “seen for several hours in the +night.” If this was a comet it must have been one of extraordinary +brilliancy.<a name='fna_210' id='fna_210' href='#f_210'><small>[210]</small></a></p> + +<p><span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span>B.C. 146. “After the death of Demetrius, king of Syria, the father of +Demetrius and Antiochus, a little before the war in Achaia, there appeared +a comet as large as the sun. Its disc was first red, and like fire, +spreading sufficient light to dissipate the darkness of night; after a +little while its size diminished, its brilliancy became weakened, and at +length it entirely disappeared.”<a name='fna_211' id='fna_211' href='#f_211'><small>[211]</small></a></p> + +<p>B.C. 134. It is recorded that at the birth of Mithridates a great comet +appeared which “occupied the fourth part of the sky, and its brilliancy +was superior to that of the sun.” (?)<a name='fna_212' id='fna_212' href='#f_212'><small>[212]</small></a></p> + +<p>B.C. 75. A comet is described as equal in size to the moon, and giving as +much light as the sun on a cloudy day. (!)<a name='fna_213' id='fna_213' href='#f_213'><small>[213]</small></a></p> + +<p>A.D. 531. In this year a great comet was observed in Europe and China. It +is described as “a very large and fearful comet,” and was visible in the +west for three weeks. Hind thinks that this was an appearance of Halley’s +comet,<a name='fna_214' id='fna_214' href='#f_214'><small>[214]</small></a> and this has been confirmed by Mr. Crommelin.</p> + +<p>A.D. 813, August 4. A comet is said to have appeared on this date, of +which the following curious description is given: “It resembled two moons +joined together; they separated, and having taken different forms, at +length appeared like a man without a head.” (!)<a name='fna_215' id='fna_215' href='#f_215'><small>[215]</small></a></p> + +<p><span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span>A.D. 893. A great comet is said to have appeared in this year with a tail +100° in length, which afterwards increased to 200°!<a name='fna_216' id='fna_216' href='#f_216'><small>[216]</small></a></p> + +<p>A.D. 1402. A comet appeared in February of this year, which was visible in +daylight for eight days. “On Palm Sunday, March 19, its size was +prodigious.” Another comet, visible in the daytime, was seen from June to +September of the same year.</p> + +<p>When the orbit of the comet known as 1889 V was computed, it was found +that it had passed through Jupiter’s system in 1886 (July 18-21). The +calculations show that it must have passed within a distance of 112,300 +miles of the planet itself—or less than half the moon’s distance from the +earth—and “its centre may possibly have grazed the surface of +Jupiter.”<a name='fna_217' id='fna_217' href='#f_217'><small>[217]</small></a></p> + +<p>Sir John Herschel thought that the great comet of 1861 was by far the +brightest comet he had ever seen, those of 1811 and 1858 (Donati’s) not +excepted.<a name='fna_218' id='fna_218' href='#f_218'><small>[218]</small></a> Prof. Kreutz found its period of revolution round the sun +to be about 409 years, with the plane of the orbit nearly at right angles +to the plane of the ecliptic.</p> + +<hr style="width: 25%;" /> + +<p>On November 9, 1795, Sir William Herschel saw the comet of that year pass +centrally over<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> a small double star of the 11th and 12th magnitudes, and +the fainter of the two components remained distinctly visible during the +comet’s transit over the star. This comet was an appearance of the comet +now known as Encke’s.<a name='fna_219' id='fna_219' href='#f_219'><small>[219]</small></a> Struve saw a star of the 10th magnitude through +nearly the brightest part of Encke’s comet on November 7, 1828, but the +star’s light was not dimmed by the comet.</p> + +<p>Sir John Herschel saw a cluster of stars of the 16th or 17th magnitude +through Biela’s comet, although the interposed cometary matter must have +been at least 50,000 miles in thickness.<a name='fna_220' id='fna_220' href='#f_220'><small>[220]</small></a></p> + +<p>Bessel found that on September 29, 1835, a star of the 10th magnitude +shone with undimmed lustre through the tail of Halley’s comet within 8 +seconds of arc of the central point of the head. At Dorpat (Russia) Struve +saw the same star “in conjunction only 2″·2 from the brightest point of +the comet. The star remained continuously visible, and its light was not +perceptibly diminished whilst the nucleus of the comet seemed to be almost +extinguished before the radiance of the small star of the 9th or 10th +magnitude.”<a name='fna_221' id='fna_221' href='#f_221'><small>[221]</small></a></p> + +<p>Webb says—</p> + +<div class="blockquot"><p>“Donati saw a 7 mg. star enlarged so as to show a sensible disc, when +the nucleus of comet III.,<span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span> 1860, passed very near it. Stars are said +to have started, or become tremulous, during occultations by comets. +Birmingham observed the comet of Encke illuminated by a star over +which it passed, August 23, 1868; and Klein, in 1861, remarked an +exceptional twinkling in 5 mg. stars involved in the tail.”<a name='fna_222' id='fna_222' href='#f_222'><small>[222]</small></a></p></div> + +<p>The comet of 1729 had the greatest perihelion distance of any known +comet;<a name='fna_223' id='fna_223' href='#f_223'><small>[223]</small></a> that is, when nearest to the sun, it did not approach the +central luminary within four times the earth’s distance from the sun!</p> + +<p>Barnard’s comet, 1889 I., although it never became visible to the naked +eye, was visible with a telescope from September 2, 1888, to August 18, +1890, or 715 days—the longest period of visibility of any comet on +record. When last seen it was 6¼ times the earth’s distance from the +sun, or about 580 millions of miles,<a name='fna_224' id='fna_224' href='#f_224'><small>[224]</small></a> or beyond the orbit of Jupiter!</p> + +<p>Messier, who was called “the comet ferret,” discovered “all his comets +with a small 2-foot telescope of 2¼ inches aperture, magnifying 5 +times, and with a field of 4°.”<a name='fna_225' id='fna_225' href='#f_225'><small>[225]</small></a></p> + +<p>It is a very curious fact that Sir William Herschel, “during all his +star-gaugings and sweeps for nebulæ, never discovered a comet;”<a name='fna_226' id='fna_226' href='#f_226'><small>[226]</small></a> that +is<span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span> an object which was afterwards <i>proved</i> to be a comet. Possibly, +however, some of his nebulæ which are now missing, may have been really +comets.</p> + +<p>Sir William Herschel found the diameter of the head of the great comet of +1811 to be 127,000 miles. The surrounding envelope he estimated to be at +least 643,000 miles, or about three-fourths of the sun’s diameter.</p> + +<p>On a drawing of the tails of the great comet of 1744 given in a little +book printed in Berlin in that year, no less than 12 tails are shown! +These vary in length and brightness. A copy of this drawing is given in +<i>Copernicus</i>.<a name='fna_227' id='fna_227' href='#f_227'><small>[227]</small></a> The observations were made by “einen geschichten +Frauenzimmer,” who Dr. Dreyer identifies with Christian Kirch, or one of +her two sisters, daughters of the famous Gottfried and Maria Margaretta +Kirch (<i>Idem</i>, p. 107). Dr. Dreyer thinks that the drawing “seems to have +been carefully made, and not to be a mere rough sketch as I had at first +supposed” (<i>Idem</i>, p. 185).</p> + +<p>The tails of some comets were of immense length. That of the comet of 1769 +had an absolute length of 38 millions of miles. That of 1680, 96 million +of miles, or more than the sun’s distance from the earth. According to Sir +William Herschel, the tail of the great comet of 1811 was over 100 +millions of miles in length. That of the<span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span> great comet of 1843—one of the +finest in history—is supposed to have reached a length of 150 millions of +miles!<a name='fna_228' id='fna_228' href='#f_228'><small>[228]</small></a></p> + +<p>In width the tails of comets were in some cases enormous. According to Sir +William Herschel, the tail of the comet of 1811 had a diameter of 15 +millions of miles! Its volume was, therefore, far greater than that of the +sun!<a href='#f_228'><small>[228]</small></a></p> + +<p>According to Hevelius the comet of 1652 was of such a magnitude that it +“resembled the moon when half full; only it shone with a pale and dismal +light.”<a name='fna_229' id='fna_229' href='#f_229'><small>[229]</small></a></p> + +<p>Halley’s comet at its next appearance will be examined with the +spectroscope for the first time in its history. At its last return in +1835, the spectroscope had not been invented.</p> + +<p>For the great comet of 1811, Arago computed a period of 3065 years; and +Encke found a period of 8800 years for the great comet of 1680.<a name='fna_230' id='fna_230' href='#f_230'><small>[230]</small></a></p> + +<p>The variation in the orbital velocity of some comets is enormous. The +velocity of the comet of 1680 when passing round the sun (perihelion) was +about 212 miles a second! Whereas at its greatest distance from the sun +(aphelion) the velocity is reduced to about 10 feet a second!</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span></p> +<h2><a name="CHAPTER_XII" id="CHAPTER_XII"></a>CHAPTER XII</h2> +<p class="title">Meteors</p> + +<p> </p> +<p class="dropcap"><span class="caps">Mr. Denning</span> thinks that the meteor shower of the month of May, known as +the Aquarids, is probably connected with Halley’s comet. The meteors +should be looked for after 1 a.m. during the first week in May, and may +possibly show an enhanced display in May, 1910, when Halley’s comet will +be near the sun and earth.<a name='fna_231' id='fna_231' href='#f_231'><small>[231]</small></a></p> + +<p>On November 29, 1905, Sir David Gill observed a fireball with an apparent +diameter equal to that of the moon, which remained visible for 5 minutes +and disappeared in a hazy sky. Observed from another place, Mr. Fuller +found that the meteor was visible 2 hours later! Sir David Gill stated +that he does not know of any similar phenomenon.<a name='fna_232' id='fna_232' href='#f_232'><small>[232]</small></a></p> + +<p>Mr. Denning finds that swiftly moving meteors become visible at a greater +height above the earth’s surface than the slower ones. Thus, for the +Leonids and Perseids, which are both swift,<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> it has been found that the +Leonids appear at an average height of 84 miles, and disappear at a height +of 56 miles; and the Perseids at 80 and 54 miles respectively. “On the +other hand, the mean height of the very slow meteors average about 65 +miles at the beginning and 38 miles at the end of their appearance.”<a name='fna_233' id='fna_233' href='#f_233'><small>[233]</small></a></p> + +<p>During the night of July 21-22, 1896, Mr. William Brooks, the well-known +astronomer, and director of the Smith Observatory at Geneva (New York), +saw a round dark body pass slowly across the moon’s bright disc, the moon +being nearly full at the time. The apparent diameter of the object was +about one minute of arc, and the duration of the transit 3 or 4 seconds, +the direction of motion being from east to west. On August 22 of the same +year, Mr. Gathman (an American observer) saw a meteor crossing the <i>sun’s</i> +disc, the transit lasting about 8 seconds.<a name='fna_234' id='fna_234' href='#f_234'><small>[234]</small></a></p> + +<p>A meteor which appeared in Italy on July 7, 1892, was shown by Prof. von +Niessl to have had an <i>ascending</i> path towards the latter end of its +course! The length of its path was computed to be 683 miles. When first +seen, its height above the earth was about 42 miles, and when it +disappeared its height had increased to about 98 miles, showing that its +motion was directed upwards!<a name='fna_235' id='fna_235' href='#f_235'><small>[235]</small></a></p> + +<p><span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span>In the case of the fall of meteoric stones, which occasionally occur, it +has sometimes been noticed that the sound caused by the explosion of the +meteorite, or its passage through the air, is heard before the meteorite +is seen to fall. This has been explained by the fact that owing to the +resistance of the air to a body moving at first with a high velocity its +speed is so reduced that it strikes the earth with a velocity less than +that of sound. Hence the sound reaches the earth before the body strikes +the ground.<a name='fna_236' id='fna_236' href='#f_236'><small>[236]</small></a></p> + +<p>The largest meteoric stone preserved in a museum is that known as the +Anighita, which weighs 36½ tons, and was found at Cape York in +Greenland. It was brought to the American Museum of Natural History by +Commander R. E. Peary, the Arctic explorer.</p> + +<p>The second largest known is that of Bacubirito in Mexico, the weight of +which is estimated at 27½ tons.</p> + +<p>The third largest is that known as the Williamette, which was found in +1902 near the town of that name in Western Oregon (U.S.A.). It is composed +of metallic nickel-iron, and weighs about 13½ tons. It is now in the +American Museum of Natural History.</p> + +<p>A large meteorite was actually seen, from the deck of the steamer <i>African +Prince</i>, to fall into the Atlantic Ocean, on October 7, 1906! The captain<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> +of the vessel, Captain Anderson, describes it as having a train of light +resembling “an immense broad electric-coloured band, gradually turning to +orange, and then to the colour of molten metal. When the meteor came into +the denser atmosphere close to the earth, it appeared, as nearly as is +possible to describe it, like a molten mass of metal being poured out. It +entered the water with a hissing noise close to the ship.”<a name='fna_237' id='fna_237' href='#f_237'><small>[237]</small></a> This was a +very curious and perhaps unique phenomenon, and it would seem that the +vessel had a narrow escape from destruction.</p> + +<p>In Central Arizona (U.S.A.) there is a hill called Coon Butte, or Coon +Mountain. This so-called “mountain” rises to a height of only 130 to 160 +feet above the surrounding plain, and has on its top a crater of 530 to +560 feet deep; the bottom of the crater—which is dry—being thus 400 feet +below the level of the surrounding country. This so-called “crater” is +almost circular and nearly three-quarters of a mile in diameter. It has +been suggested that this “crater” was formed by the fall of an enormous +iron meteorite, or small asteroid. The “crater” has been carefully +examined by a geologist and a physicist. From the evidence and facts +found, the geologist (Mr. Barringer) states that “they do not leave, in my +mind, a scintilla of doubt that this mountain and its crater were produced +by the impact<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> of a huge meteorite or small asteroid.” The physicist (Mr. +Tilghmann) says that he “is justified, under due reserve as to +subsequently developed facts, in announcing that the formation at this +locality is due to the impact of a meteor of enormous and unprecedented +size.” There are numerous masses of meteoric iron in the vicinity of the +“crater.” The so-called Canyon Diabolo meteorite was found in a canyon of +that name about 2½ miles from the Coon Mountain. The investigators +estimate that the great meteoric fall took place “not more than 5000 years +ago, perhaps much less.” Cedar trees about 700 years old are now growing +on the rim of the mountain. From the results of artillery experiments, Mr. +Gilbert finds that “a spherical projectile striking solid limestone with a +velocity of 1800 feet a second will penetrate to a depth of something less +than two diameters,” and from this Mr. L. Fletcher concludes “that a +meteorite of large size would not be prevented by the earth’s atmosphere +from having a penetration effect sufficient for the production of such a +crater.”<a name='fna_238' id='fna_238' href='#f_238'><small>[238]</small></a></p> + +<p>The meteoric origin of this remarkable “crater” is strongly favoured by +Mr. G. P. Merrill, Head Curator of Geology, U.S. National Museum.</p> + +<p>The Canyon Diabolo meteorite above referred to was found to contain +diamonds! some black, others transparent. So some have said that “the<span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span> +diamond is a gift from Heaven,” conveyed to earth in meteoric +showers.<a name='fna_239' id='fna_239' href='#f_239'><small>[239]</small></a> But diamond-bearing meteorites would seem to be rather a +freak of nature. It does not follow that <i>all</i> diamonds had their origin +in meteoric stones. The mineral known as periodot is frequently found in +meteoric stones, but it is also a constituent of terrestrial rocks.</p> + +<p>In the year 1882 it was stated by Dr. Halm and Dr. Weinhand that they had +found fossil sponges, corals, and crinoids in meteoric stones! Dr. +Weinhand thought he had actually determined three genera!<a name='fna_240' id='fna_240' href='#f_240'><small>[240]</small></a> But this +startling result was flatly contradicted by Carl Vogt, who stated that the +supposed fossils are merely crystalline conformations.<a name='fna_241' id='fna_241' href='#f_241'><small>[241]</small></a></p> + +<p>Some meteorites contain a large quantity of occluded gases, hydrogen, +helium, and carbon oxides. It is stated that Dr. Odling once “lighted up +the theatre of the Royal Institution with gas brought down from +interstellar space by meteorites”!<a name='fna_242' id='fna_242' href='#f_242'><small>[242]</small></a></p> + +<p>On February 10, 1896, a large meteorite burst over Madrid with a loud +report. The concussion was so great that many windows in the city were +broken, and some partitions in houses were shaken down!<a name='fna_243' id='fna_243' href='#f_243'><small>[243]</small></a></p> + +<p><span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span>A very brilliant meteor or fireball was seen in daylight on June 9, 1900, +at 2<sup>h</sup> 55<sup>m</sup> p.m. from various places in Surrey, Sussex, and near London. +Calculations showed that “the meteor began 59 miles in height over a point +10 miles east of Valognes, near Cherbourg, France. Meteor ended 23 miles +in height, over Calais, France. Length of path 175 miles. Radiant point, +280°, 12°.”<a name='fna_244' id='fna_244' href='#f_244'><small>[244]</small></a></p> + +<p>It was decided some years ago “in the American Supreme Court that a +meteorite, though a stone fallen from heaven, belongs to the owner of the +freehold interest in the land on which it falls, and not to the +tenant.”<a name='fna_245' id='fna_245' href='#f_245'><small>[245]</small></a></p> + +<p>With reference to the fall of meteoric matter on the earth, Mr. Proctor +says, “It is calculated by Dr. Kleiber of St. Petersburgh that 4250 lbs. +of meteoric dust fall on the earth every hour—that is, 59 tons a day, and +more than 11,435 tons a year. I believe this to be considerably short of +the truth. It sounds like a large annual growth, and the downfall of such +an enormous mass of meteoric matter seems suggestive of some degree of +danger. But in reality, Dr. Kleiber’s estimate gives only about 25 +millions of pounds annually, which is less than 2 ounces annually to each +square mile of the earth’s surface,”<a name='fna_246' id='fna_246' href='#f_246'><small>[246]</small></a> a quantity which is, of course, +quite insignificant.</p> + +<p><span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span>According to Humboldt, Chladni states that a Franciscan monk was killed by +the fall of an aërolite at Milan in the year 1660.<a name='fna_247' id='fna_247' href='#f_247'><small>[247]</small></a> Humboldt also +mentions the death by meteoric stones of a monk at Crema on September 4, +1511, and two Swedish sailors on board ship in 1674.<a name='fna_248' id='fna_248' href='#f_248'><small>[248]</small></a></p> + +<p>It is a curious fact that, according to Olbers, “no fossil meteoric +stones” have ever been discovered.<a name='fna_249' id='fna_249' href='#f_249'><small>[249]</small></a> Considering the number which are +supposed to have fallen to the earth in the course of ages, this fact +seems a remarkable one.</p> + +<p>On May 10, 1879, a shower of meteorites fell at Eitherville, Iowa +(U.S.A.). Some of the fragments found weighed 437, 170, 92½, 28, +10½, 4 and 2 lbs. in weight. In the following year (1880) when the +prairie grass had been consumed by a fire, about “5000 pieces were found +from the size of a pin to a pound in weight.”<a name='fna_250' id='fna_250' href='#f_250'><small>[250]</small></a></p> + +<p>According to Prof. Silvestria of Catania, a shower of meteoric dust mixed +with rain fell on the night of March 29, 1880. The dust contained a large +proportion of iron in the metallic state. In size the particles varied +from a tenth to a hundredth of a millimetre.<a name='fna_251' id='fna_251' href='#f_251'><small>[251]</small></a></p> + +<p>It is sometimes stated that the average mass of a “shooting star” is only +a few grains. But from<span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span> comparisons with an electric arc light, Prof. W. +H. Pickering concludes that a meteor as bright as a third magnitude star, +composed of iron or stone, would probably have a diameter of 6 or 7 +inches. An average bright fireball would perhaps measure 5 or 6 feet in +diameter.<a name='fna_252' id='fna_252' href='#f_252'><small>[252]</small></a></p> + +<p>In the Book of Joshua we are told “that the <span class="smcap">Lord</span> cast down great stones +from heaven upon them unto Azekah, and they died” (Joshua x. 11). In the +latter portion of the verse “hailstones” are mentioned, but as the +original Hebrew word means stones in general (not hailstones), it seems +very probable that the stones referred to were aërolites.<a name='fna_253' id='fna_253' href='#f_253'><small>[253]</small></a></p> + +<p>The stone mentioned in the Acts of the Apostles, from which was found “the +<i>image</i> which fell down from Jupiter” (Acts xix. 35), was evidently a +meteoric stone.<a href='#f_253'><small>[253]</small></a></p> + +<p>The famous stone in the Caaba at Mecca, is probably a stone of meteoric +origin.<a href='#f_253'><small>[253]</small></a></p> + +<p class="poem"><span style="margin-left: 7em;">I</span><br /> +“Stones from Heaven! Can you wonder,<br /> +<span style="margin-left: 1em;">You who scrutinize the Earth,</span><br /> +At the love and veneration<br /> +<span style="margin-left: 1em;">They received before the birth</span><br /> +Of our scientific methods?<br /> +<br /> +<br /> +<span style="margin-left: 6.75em;">II</span><br /> +“Stones from Heaven! we can handle<br /> +<span style="margin-left: 1em;">Fragments fallen from realms of Space;</span><br /> +<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span>Oh! the marvel and the mystery,<br /> +<span style="margin-left: 1em;">Could we understand their place</span><br /> +In the scheme of things created!<br /> +<br /> +<br /> +<span style="margin-left: 6.5em;">III</span><br /> +“Stones from Heaven! With a mighty<br /> +<span style="margin-left: 1em;">Comet whirling formed they part?</span><br /> +Fell they from their lofty station<br /> +<span style="margin-left: 1em;">Like a brilliant fiery dart,</span><br /> +Hurl’d from starry fields of Night?”<a name='fna_254' id='fna_254' href='#f_254'><small>[254]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span></p> +<h2><a name="CHAPTER_XIII" id="CHAPTER_XIII"></a>CHAPTER XIII</h2> +<p class="title">The Zodiacal Light and Gegenschein</p> + +<p> </p> +<p class="dropcap"><span class="caps">According</span> to Gruson and Brugsch, the Zodiacal Light was known in ancient +times, and was even worshipped by the Egyptians. Strabo does not mention +it; but Diodorus Siculus seems to refer to it (<span class="smcaplc">B.C.</span> 373), and he probably +obtained his information from some Greek writers before his time, possibly +from Zenophon, who lived in the sixth century <span class="smcaplc">B.C.</span><a name='fna_255' id='fna_255' href='#f_255'><small>[255]</small></a> Coming to the +Christian era, it was noticed by Nicephorus, about 410 <span class="smcaplc">B.C.</span> In the Koran, +it is called the “false Aurora”; and it is supposed to be referred to in +the “Rubáiyát” of Omar Khayyam, the Persian astronomical poet, in the +second stanza of that poem (Edward Fitzgerald’s translation)—</p> + +<p class="poem">“Dreaming when Dawn’s Left Hand was in the Sky,<a name='fna_256' id='fna_256' href='#f_256'><small>[256]</small></a><br /> +I heard a voice within the Tavern cry,<br /> +Awake, my Little ones, and fill the Cup,<br /> +Before Life’s Liquor in its Cup be dry.”</p> + +<p>It was observed by Cassini in 1668,<a name='fna_257' id='fna_257' href='#f_257'><small>[257]</small></a> and by<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> Hooke in 1705. A short +description of its appearance will be found in Childrey’s <i>Britannia +Baconica</i> (1661), p. 183.</p> + +<p>The finest displays of this curious light seem to occur between the middle +of January and the middle of February. In February, 1856, Secchi found it +brighter than he had ever seen it before. It was yellowish towards the +axis of the cone, and it seemed to be brighter than the Milky Way in +Cygnus. He described it as “un grande spectacle.” In the middle of +February, 1866, Mr. Lassell, during his last residence in Malta, saw a +remarkable display of the Zodiacal Light. He found it at least twice as +bright as the brightest part of the Milky Way, and much brighter than he +had previously seen it. He found that the character of its light differed +considerably from that of the Milky Way. It was of a much redder hue than +the Galaxy. In 1874 very remarkable displays were seen in the +neighbourhood of London in January and February of that year; and in 1875 +on January 24, 25, and 30. On January 24 it was noticed that the “light” +was distinctly reddish and much excelled in brightness any portion of the +Milky Way.</p> + +<p>Humboldt, who observed it from Andes (at a height of 13,000 to 15,000 +feet), from Venezuela and from Cumana, tells us that he has seen the +Zodiacal Light equal in brightness to the Milky Way in Sagittarius.</p> + +<p><span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span>As probably many people have never seen the “light,” a caution may be +given to those who care to look for it. It is defined by the Rev. George +Jones, Chaplain to the “United States’ Japan Expedition” (1853-55), as “a +brightness that appears in the western sky after sunset, and in the east +before sunrise; following nearly or quite the line of the ecliptic in the +heavens, and stretching upwards to various elevations according to the +season of the year.” From the description some might suppose that the +light is visible <i>immediately</i> after sunset. But this is not so; it never +appears until twilight is over and “the night has fully set in.”</p> + +<p>The “light” is usually seen after sunset or before sunrise. But attempts +have recently been made by Prof. Simon Newcomb to observe it north of the +sun. To avoid the effects of twilight the sun must be only slightly more +than 18° below the horizon (that is, a little before or after the longest +day). This condition limits the place of observation to latitudes not much +south of 46°; and to reduce atmospheric absorption the observing station +should be as high as possible above the level of the sea. Prof. Newcomb, +observing from the Brienzer Rothorn in Switzerland (latitude 46° 47′ N., +longitude 8° 3′ E.), succeeded in tracing the “light” to a distance of 35° +north of the sun. It would seem, therefore, that the Zodiacal Light +envelops the sun on all<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> sides, but has a greater extension in the +direction of the ecliptic.<a name='fna_258' id='fna_258' href='#f_258'><small>[258]</small></a> From observations at the Lick Observatory, +Mr. E. A. Fath found an extension of 46° north of the sun.<a name='fna_259' id='fna_259' href='#f_259'><small>[259]</small></a></p> + +<p>From observations of the “light” made by Prof. Barnard at the Yerkes +Observatory during the summer of 1906, he finds that it extends to at +least 65° north of the sun, a considerably higher value than that found by +Prof. Newcomb.<a name='fna_260' id='fna_260' href='#f_260'><small>[260]</small></a> The difference may perhaps be explained by actual +variation of the meteoric matter producing the light. Prof. J. H. Poynting +thinks that possibly the Zodiacal Light is due to the “dust of long dead +comets.”<a name='fna_261' id='fna_261' href='#f_261'><small>[261]</small></a></p> + +<p>From careful observations of the “light,” Mr. Gavin J. Burns finds that +its luminosity is “some 40 or 50 per cent. brighter than the background of +the sky. Prof. Newcomb has made a precisely similar remark about the +luminosity of the Milky Way, viz. that it is surprisingly small.” This +agrees with my own observations during many years. It is only on the +finest and clearest nights that the Milky Way forms a conspicuous object +in the night sky. And this only in the country. The lights of a city +almost entirely obliterate it. Mr. Burns finds that the Zodiacal Light<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> +appears “to be of a yellowish tint; or if we call it white, then the Milky +Way is comparatively of a bluish tint.” During my residence in the Punjab +the Zodiacal Light seemed to me constantly visible in the evening sky in +the spring months. In the west of Ireland I have seen it nearly as bright +as the brightest portions of the Milky Way visible in this country +(February 20, 1890). The “meteoric theory” of the “light” seems to be the +one now generally accepted by astronomers, and in this opinion I fully +concur.</p> + +<p>From observations made in Jamaica in the years 1899 and 1901, Mr. Maxwell +Hall arrived at the conclusion that “the Zodiacal Light is caused by +reflection of sunlight from masses of meteoric matter still contained in +the invariable plane, which may be considered the original plane of the +solar system.”<a name='fna_262' id='fna_262' href='#f_262'><small>[262]</small></a> According to Humboldt, Cassini believed that the +Zodiacal Light “consisted of innumerably small planetary bodies revolving +round the sun.”<a name='fna_263' id='fna_263' href='#f_263'><small>[263]</small></a></p> + +<p><span class="smcap">The Gegenschein</span>, or <span class="smcap">Counter-glow</span>.—This is a faint patch of light seen +opposite the sun’s place in the sky, that is on the meridian at midnight. +It is usually elliptical in shape, with its longer axis lying nearly in +the plane of the ecliptic. It seems to have been first detected by Brorsen +(the discoverer of the short-period comet<span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span> of 1846) about the middle of +the nineteenth century. But it is not easy to see, for the famous Heis of +Münster, who had very keen eyesight, did not succeed in seeing it for +several years after Brorsen’s announcement.<a name='fna_264' id='fna_264' href='#f_264'><small>[264]</small></a> It was afterwards +independently discovered by Backhouse, and Barnard.</p> + +<p>Prof. Barnard’s earlier observations seemed to show that the Gegenschein +does not lie exactly opposite to the sun, but very nearly so. He found its +longitude is within one degree of 180°, and its latitude about 1°·3 north +of the ecliptic.<a name='fna_265' id='fna_265' href='#f_265'><small>[265]</small></a> But from subsequent observations he came to the +conclusion that the differences in longitude and apparent latitude are due +to atmospheric absorption, and that the object really lies in the ecliptic +and <i>exactly</i> opposite to the sun.<a name='fna_266' id='fna_266' href='#f_266'><small>[266]</small></a></p> + +<p>Barnard finds that the Gegenschein is not so faint as is generally +supposed. He says “it is best seen by averted vision, the face being +turned 60° or 70° to the right or left, and the eyes alone turned towards +it.” It is invisible in June and December, while in September it is round, +with a diameter of 20°, and very distinct. No satisfactory theory has yet +been advanced to account for this curious phenomenon. Prof. Arthur Searle +of Harvard attributes it to a number of<span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span> asteroids too small to be seen +individually. When in “opposition” to the sun these would be fully +illuminated and nearest to the earth. Its distance from the earth probably +exceeds that of the moon. Dr. Johnson Stoney thinks that the Gegenschein +may possibly be due to a “tail” of hydrogen and helium gases repelled from +the earth by solar action; this “tail” being visible to us by reflected +sunlight.</p> + +<p>It was observed under favourable circumstances in January and February, +1903, by the French astronomer, M. F. Quénisset. He found that it was +better seen when the atmosphere was less clear, contrary to his experience +of the Zodiacal Light. Prof. Barnard’s experience confirms this. M. +Quénisset notes that—as in the case of the Zodiacal Light—the southern +border of the Gegenschein is sharper than the northern. He found that its +brightness is less than that of the Milky Way between Betelgeuse and +γ Geminorum; and thinks that it is merely a strengthening of the +Zodiacal Light.<a name='fna_267' id='fna_267' href='#f_267'><small>[267]</small></a></p> + +<p>A meteoritic theory of the Gegenschein has been advanced by Prof. F. R. +Moulton, which explains it by light reflected from a swarm of meteorites +revolving round the sun at a distance of 930,240 miles outside the earth’s +orbit.</p> + +<p>Both the Zodiacal Light and Gegenschein were observed by Herr Leo Brenner +on the evening of<span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span> March 4, 1896. He found the Zodiacal Light on this +evening to be “<i>perhaps eight times brighter</i> than the Milky Way in +Perseus.” The “<i>Gegenschein distinctly visible</i> as a round, bright, +cloud-like nebula below Leo (Virgo), and about twice the brightness of the +Milky Way in Monoceros between Canis Major and Canis Minor.”<a name='fna_268' id='fna_268' href='#f_268'><small>[268]</small></a></p> + +<p>Humboldt thought that the fluctuations in the brilliancy of the Zodiacal +Light were probably due to a real variation in the intensity of the +phenomenon rather than to the elevated position of the observer.<a name='fna_269' id='fna_269' href='#f_269'><small>[269]</small></a> He +says that he was “astonished in the tropical climates of South America, to +observe the variable intensity of the light.”</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span></p> +<h2><a name="CHAPTER_XIV" id="CHAPTER_XIV"></a>CHAPTER XIV</h2> +<p class="title">The Stars</p> + +<p> </p> +<p class="dropcap"><span class="caps">Pliny</span> says that Hipparchus “ventured to count the stars, a work arduous +even for the Deity.” But this was quite a mistaken idea. Those visible to +the naked eye are comparatively few in number, and the enumeration of +those visible in an opera-glass—which of course far exceed those which +can be seen by unaided vision—is a matter of no great difficulty. Those +visible in a small telescope of 2¾ inches aperture have all been +observed and catalogued; and even those shown on photographs taken with +large telescopes can be easily counted. The present writer has made an +attempt in this direction, and taking an average of a large number of +counts in various parts of the sky, as shown on stellar photographs, he +finds a total of about 64 millions for the whole sky in both +hemispheres.<a name='fna_270' id='fna_270' href='#f_270'><small>[270]</small></a> Probably the total number will not exceed 100 millions. +But this is a comparatively small<span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span> number, even when compared with the +human population of our little globe.</p> + +<p>With reference to the charts made by photography in the International +scheme commenced some years ago, it has now been estimated that the charts +will probably contain a total of about 9,854,000 stars down to about the +14th magnitude (13·7). The “catalogue plates” (taken with a shorter +exposure) will, it is expected, include about 2,676,500 stars down to +11½ magnitude. These numbers may, however, be somewhat increased when +the work has been completed.<a name='fna_271' id='fna_271' href='#f_271'><small>[271]</small></a> If this estimate proves to be correct, +the number of stars visible down to the 14th magnitude will be +considerably less than former estimates have made it.</p> + +<p>Prof. E. C. Pickering estimates that the total number of stars visible on +photographs down to the 16th magnitude (about the faintest visible in the +great Lick telescope) will be about 50 millions.<a name='fna_272' id='fna_272' href='#f_272'><small>[272]</small></a> In the present +writer’s enumeration, above referred to, many stars fainter than the 16th +magnitude were included.</p> + +<p>Admiral Smyth says, with reference to Sir William Herschel—perhaps the +greatest observer that ever lived—“As to Sir William himself, he could +unhesitatingly call every star down to the 6th magnitude, by its name, +letter, or number.”<a name='fna_273' id='fna_273' href='#f_273'><small>[273]</small></a><span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span> This shows great powers of observation, and a +wonderful memory.</p> + +<p>On a photographic plate of the Pleiades taken with the Bruce telescope and +an exposure of 6 hours, Prof. Bailey of Harvard has counted “3972 stars +within an area 2° square, having Alcyone at its centre.”<a name='fna_274' id='fna_274' href='#f_274'><small>[274]</small></a> This would +give a total of about 41 millions for the whole sky, if of the same +richness.</p> + +<p>With an exposure of 16 hours, Prof. H. C. Wilson finds on an area of less +that 110′ square a total of 4621 stars. He thinks, “That all of these +stars belong to the Pleiades group is not at all probable. The great +majority of them probably lie at immense distances beyond the group, and +simply appear in it by projection.”<a href='#f_274'><small>[274]</small></a> He adds, “It has been found, +however, by very careful measurements made during the last 75 years at the +Königsbergh and Yale Observatories, that of the sixty-nine brighter stars, +including those down to the 9th magnitude, only eight show any certain +movement with reference to Alcyone. Since Alcyone has a proper motion or +drift of 6″ per century, this means that all the brightest stars except +the eight mentioned are drifting with Alcyone and so form a true cluster, +at approximately the same distance from the earth. Six of the eight stars +which show relative drift are moving in the opposite direction to the<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> +movement of Alcyone, and at nearly the same rate, so that their motion is +only apparent. They are really stationary, while Alcyone and the rest of +the cluster are moving past them.”<a name='fna_275' id='fna_275' href='#f_275'><small>[275]</small></a> This tends to show that the faint +stars are really <i>behind</i> the cluster, and are unconnected with it.</p> + +<p>It is a popular idea with some people that the Pole Star is the nearest of +all the stars to the celestial pole. But photographs show that there are +many faint stars nearer to the pole than the Pole Star. The Pole Star is +at present at a distance of 1° 13′ from the real pole of the heavens, but +it is slowly approaching it. The minimum distance will be reached in the +year 2104. From photographs taken by M. Flammarion at the Juvisy +Observatory, he finds that there are at least 128 stars nearer to the pole +than the Pole Star! The nearest star to the pole was, in the year 1902, a +small star of about 12½ magnitude, which was distant about 4 minutes of +arc from the pole.<a name='fna_276' id='fna_276' href='#f_276'><small>[276]</small></a> The estimated magnitude shows that the Pole Star +is nearly 10,000 times brighter than this faint star!</p> + +<p>It has been found that Sirius is bright enough to cast a shadow under +favourable conditions. On March 22, 1903, the distinguished French +astronomer Touchet succeeded in photographing<span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span> the shadow of a brooch cast +by this brilliant star. The exposure was 1<sup>h</sup> 5<sup>m</sup>.</p> + +<p>Martinus Hortensius seems to have been the first to see stars in daylight, +perhaps early in the seventeenth century. He mentions the fact in a letter +to Gassendi dated October 12, 1636, but does not give the date of his +observation. Schickard saw Arcturus in broad daylight early in 1632. Morin +saw the same bright star half an hour after sunset in March, 1635.</p> + +<p>Some interesting observations were made by Professors Payne and H. C. +Wilson, in the summer of 1904, at Midvale, Montana (U.S.A.), at a height +of 4790 feet above sea-level. At this height they found the air very clear +and transparent. “Many more stars were visible at a glance, and the +familiar stars appeared more brilliant.... In the great bright cloud of +the Milky Way, between β and γ Cygni, one could count +easily sixteen or seventeen stars, besides the bright ones η and +χ,<a name='fna_277' id='fna_277' href='#f_277'><small>[277]</small></a> while at Northfield it is difficult to distinctly see +eight or nine with the naked eye.” Some nebulæ and star fields were +photographed with good results by the aid of a 2½-inch Darlot lens and +3 hours’ exposure.<a name='fna_278' id='fna_278' href='#f_278'><small>[278]</small></a></p> + +<p>Prof. Barnard has taken some good stellar photographs with a lens of only +1½ inches in diameter,<span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span> and 4 or 5 inches focus belonging to an +ordinary “magic lantern”! He says that these “photographs with the small +lens show us in the most striking manner how the most valuable and +important information may be obtained with the simplest means.”<a name='fna_279' id='fna_279' href='#f_279'><small>[279]</small></a></p> + +<p>With reference to the rising and setting of the stars due to the earth’s +rotation on its axis, the late Sir George B. Airy, Astronomer Royal of +England, once said to a schoolmaster, “I should like to know how far your +pupils go into the first practical points for which reading is scarcely +necessary. Do they know that the stars rise and set? Very few people in +England know it. I once had a correspondence with a literary man of the +highest rank on a point of Greek astronomy, and found that he did not know +it!”<a name='fna_280' id='fna_280' href='#f_280'><small>[280]</small></a></p> + +<p>Admiral Smyth says, “I have been struck with the beautiful blue tint of +the smallest stars visible in my telescope. This, however, may be +attributed to some optical peculiarity.” This bluish colour of small stars +agrees with the conclusion arrived at by Prof. Pickering in recent years, +that the majority of faint stars in the Milky Way have spectra of the +Sirian type and, like that brilliant star, are of a bluish white colour. +Sir William Herschel saw many stars of a redder tinge than other observers +have noticed. Admiral Smyth<span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span> says, “This may be owing to the effect of his +metallic mirror or to some peculiarity of vision, or perhaps both.”<a name='fna_281' id='fna_281' href='#f_281'><small>[281]</small></a></p> + +<p>The ancient astronomers do not mention any coloured stars except white and +red. Among the latter they only speak of Arcturus, Aldebaran, Pollux, +Antares, and Betelgeuse as of a striking red colour. To these Al-Sufi adds +Alphard (α Hydræ).</p> + +<p>Sir William Herschel remarked that no decidedly green or blue star “has +ever been noticed unassociated with a companion brighter than itself.” An +exception to Herschel’s rule seems to be found in the case of the star +β Libræ, which Admiral Smyth called “pale emerald.” Mr. George +Knott observed it on May 19, 1852, as “beautiful pale green” (3·7 inches +achromatic, power 80), and on May 9, 1872, as “fine pale green” (5·5 +inches achromatic, power 65).</p> + +<p>The motion of stars in the line of sight, as shown by the +spectroscope—should theoretically alter their brightness in the course of +time; those approaching the earth becoming gradually brighter, while those +receding should become fainter. But the distance of the stars is so +enormous that even with very high velocities the change would not become +perceptible for ages. Prof. Oudemans found that to change the brightness +of a star by only one-tenth of a magnitude—a quantity barely<span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span> perceptible +to the eye-a number of years would be necessary, which is represented by +the formula</p> + +<table border="0" cellpadding="0" cellspacing="0" summary="table"> +<tr><td align="center" class="botbor">5916 years</td></tr> +<tr><td align="center">parallax × motion</td></tr></table> + +<p>for a star approaching the earth, and for a receding star</p> + +<table border="0" cellpadding="0" cellspacing="0" summary="table"> +<tr><td align="center" class="botbor">6195 years</td></tr> +<tr><td align="center">p × m</td></tr></table> + +<p>This is in geographical miles, 1 geographical mile being equal to 4·61 +English miles.</p> + +<p>Reducing the above to English miles, and taking an average for both +approaching and receding stars, we have</p> + +<table border="0" cellpadding="0" cellspacing="0" summary="table"> +<tr><td align="center" class="botbor">27,660 years</td></tr> +<tr><td align="center">p × m</td></tr></table> + +<p>where p = parallax in seconds of arc, and m = radial velocity in English +miles per second.</p> + +<p>Prof. Oudemans found that the only star which could have changed in +brightness by one-tenth of a magnitude since the time of Hipparchus is +Aldebaran. This is taking its parallax as 0″·52. But assuming the more +reliable parallax 0″·12 found by Dr. Elkin, this period is 4⅓ times +longer. For Procyon, the period would be 5500 years.<a name='fna_282' id='fna_282' href='#f_282'><small>[282]</small></a> The above +calculation shows how absurd it is to suppose that any star could have +gained or lost in brightness by motion in the line of sight during +historical times. The “secular variation” of stars<span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span> is quite another +thing. This is due to physical changes in the stars themselves.</p> + +<p>The famous astronomer Halley, the second Astronomer Royal at Greenwich, +says (<i>Phil. Trans.</i>, 1796), “Supposing the number of 1st magnitude stars +to be 13, at twice the distance from the sun there may be placed four +times as many, or 52; which with the same allowance would nearly represent +the star we find to be of the 2nd magnitude. So 9 × 13, or 117, for those +at three times the distance; and at ten times the distance 100 × 13, or +1300 stars; of which distance may probably diminish the light of any of +the stars of the 1st magnitude to that of the 6th, it being but the +hundredth part of what, at their present distance, they appear with.” This +agrees with the now generally accepted “light ratio” of 2·512 for each +magnitude, which makes a first magnitude star 100 times the light of a 6th +magnitude.</p> + +<p>On the 4th of March, 1796,<a name='fna_283' id='fna_283' href='#f_283'><small>[283]</small></a> the famous French astronomer Lalande +observed on the meridian a star of small 6th magnitude, the exact position +of which he determined. On the 15th of the same month he again observed +the star, and the places found for 1800 refer to numbers 16292-3 of the +reduced catalogue. In the observation of March 4 he attached the curious +remark, “Étoile singulière” (the observation of March 15 is without<span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span> +note). This remark of Lalande has puzzled observers who failed to find any +peculiarity about the star. Indeed, “the remark is a strange one for the +observer of so many thousands of stars to attach unless there was really +something singular in the star’s aspect at the time.” On the evening of +April 18, 1887, the star was examined by the present writer, and the +following is the record in his observing book, “Lalande’s étoile +singulière (16292-3) about half a magnitude less than η Cancri. +With the binocular I see two streams of small stars branching out from it, +north preceding like the tails of comet.” This may perhaps have something +to do with Lalande’s curious remark.</p> + +<p>The star numbered 1647 in Baily’s <i>Flamsteed Catalogue</i> is now known to +have been an observation of the planet Uranus.<a name='fna_284' id='fna_284' href='#f_284'><small>[284]</small></a></p> + +<p>Prof. Pickering states that the fainter stars photographed with the 8-inch +telescope at Cambridge (U.S.A.) are invisible to the eye in the 15-inch +telescope.<a name='fna_285' id='fna_285' href='#f_285'><small>[285]</small></a></p> + +<p>Sir Norman Lockyer finds that the lines of sulphur are present in the +spectrum of the bright star Rigel (β Orionis).<a name='fna_286' id='fna_286' href='#f_286'><small>[286]</small></a></p> + +<p>About 8½° south of the bright star Regulus (α Leonis) is a +faint nebula (H I, 4 Sextantis). On or near this spot the Capuchin monk De +Rheita fancied he saw, in the year 1643, a<span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span> group of stars representing +the napkin of S. Veronica—“sudarium Veronicæ sive faciem Domini maxima +similitudina in astris expressum.” And he gave a picture of the napkin and +star group. But all subsequent observers have failed to find any trace of +the star group referred to by De Rheita!<a name='fna_287' id='fna_287' href='#f_287'><small>[287]</small></a></p> + +<p>The Bible story of the star of the Magi is also told in connection with +the birth of the sun-gods Osiris, Horus, Mithra, Serapis, etc.<a name='fna_288' id='fna_288' href='#f_288'><small>[288]</small></a> The +present writer has also heard it suggested that the phenomenon may have +been an apparition of Halley’s comet! But as this famous comet is known to +have appeared in the year <span class="smcaplc">B.C.</span> 11, and as the date of the Nativity was +probably not earlier than <span class="smcaplc">B.C.</span> 5, the hypothesis seems for this (and other +reasons) to be inadmissible. It has also been suggested that the +phenomenon might have been an appearance of Tycho Brahé’s temporary star +of 1572, known as the “Pilgrim star”; but there seems to be no real +foundation for such an hypothesis. There is no reason to think that +“temporary” or new stars ever appear a second time.</p> + +<p>Admiral Smyth has well said, “It checks one’s pride to recollect that if +our sun with the whole system of planets, asteroids, and moons, and comets +were to be removed from the spectator<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> to the distance of the nearest +fixed star, not one of them would be visible, except the sun, which would +then appear but as a star of perhaps the 2nd magnitude. Nay, more, were +the whole system of which our globe forms an insignificant member, with +its central luminary, suddenly annihilated, no effect would be produced on +those unconnected and remote bodies; and the only annunciation of such a +catastrophe in the Sidereal “Times” would be that a small star once seen +in a distant quarter of the sky had ceased to shine.”<a name='fna_289' id='fna_289' href='#f_289'><small>[289]</small></a></p> + +<p>Prof. George C. Comstock finds that the average parallax of 67 selected +stars ranging in brightness between the 9th and the 12th magnitude, is of +the value of 0″·0051.<a name='fna_290' id='fna_290' href='#f_290'><small>[290]</small></a> This gives a distance representing a journey +for light of about 639 years!</p> + +<p>Mr. Henry Norris Russell thinks that nearly all the bright stars in the +constellation of Orion are practically at the same distance from the +earth. His reasons for this opinion are: (1) the stars are similar in +their spectra and proper motions, (2) their proper motions are small, +which suggests a small parallax, and therefore a great distance from the +earth. Mr. Russell thinks that the average parallax of these stars may +perhaps be 0″·005, which gives a distance of about 650 “light +years.”<a name='fna_291' id='fna_291' href='#f_291'><small>[291]</small></a></p> + +<p><span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span>According to Sir Norman Lockyer’s classification of the stars, the order +of <i>increasing</i> temperature is represented by the following, beginning +with those in the earliest stage of stellar evolution:—Nebulæ, Antares, +Aldebaran, Polaris, α Cygni, Rigel, ε Tauri, β +Crucis. Then we have the hottest stars represented by ε Puppis, +γ Argus, and Alnitam (ε Orionis). <i>Decreasing</i> +temperature is represented by (in order), Achernar, Algol, Markab, Sirius, +Procyon, Arcturus, 19 Piscium, and the “Dark Stars.”<a name='fna_292' id='fna_292' href='#f_292'><small>[292]</small></a> But other +astronomers do not agree with this classification. Antares and Aldebaran +are by some authorities considered to be <i>cooling</i> suns.</p> + +<p>According to Ritter’s views of the Constitution of the Celestial Bodies, +if we “divide the stars into three classes according to age corresponding +to these three stages of development, we shall assign to the first class, +A, those stars still in the nebular phase of development; to the second +class, B, those in the transient stage of greatest brilliancy; and to the +class C, those stars which have already entered into the long period of +slow extinction. It should be noted in this classification that we refer +to relative and not absolute age, since a star of slight mass passes +through the successive phases of its development more rapidly than the +star of greater mass.”<a name='fna_293' id='fna_293' href='#f_293'><small>[293]</small></a> Ritter<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> comes to the conclusion that “the +duration of the period in which the sun as a star had a greater brightness +than at present was very short in comparison with the period in which it +had and will continue to have a brightness differing only slightly from +its present value.”<a name='fna_294' id='fna_294' href='#f_294'><small>[294]</small></a></p> + +<p>In a valuable and interesting paper on “The Evolution of Solar +Stars,”<a name='fna_295' id='fna_295' href='#f_295'><small>[295]</small></a> Prof. Schuster says that “measurements by E. F. Nichols on +the heat of Vega and Arcturus indicated a lower temperature for Arcturus, +and confirms the conclusion arrived at on other grounds, that the hydrogen +stars have a higher temperature than the solar stars.” “An inspection of +the ultraviolet region of the spectrum gives the same result. These +different lines of argument, all leading to the same result, justify us in +saying that the surface temperature of the hydrogen stars is higher than +that of the solar stars. An extension of the same reasoning leads to the +belief that the helium stars have a temperature which is higher still.” +Hence we have Schuster, Hale, and Sir William Huggins in agreement that +the Sirian stars are hotter than the solar stars; and personally I agree +with these high authorities. The late Dr. W. E. Wilson, however, held the +opinion that the sun is hotter that Sirius!</p> + +<p>Schuster thinks that Lane’s law does not apply<span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span> to the temperature of the +photosphere and the absorbing layers of the sun and stars, but only to the +portions between the photosphere and the centre, which probably act like a +perfect gas. On this view he says the interior might become “hotter and +hotter until the condensation had reached a point at which the laws of +gaseous condensation no longer hold.”</p> + +<p>With reference to the stars having spectra of the 3rd and 4th type +(usually orange and red in colour), Schuster says—</p> + +<div class="blockquot"><p>“The remaining types of spectra belong to lower temperature still, as +in place of metallic lines, or in addition to them, certain bands +appear which experiments show us invariably belong to lower +temperature than the lines of the same element.</p> + +<p>“If an evolutionary process has been going on, which is similar for +all stars, there is little doubt that from the bright-line stars down +to the solar stars the order has been (1) helium or <i>Orion</i> stars, (2) +hydrogen or Sirian stars, (3) calcium or Procyon stars, (4) solar or +Capellan stars.”</p></div> + +<p>My investigations on “The Secular Variation of Starlight” (<i>Studies in +Astronomy</i>, chap. 17, and <i>Astronomical Essays</i>, chap. 12) based on a +comparison of Al-Sufi’s star magnitudes (tenth century) with modern +estimates and measures, tend strongly to confirm the above views.</p> + +<p>With regard to the 3rd-type stars, such as Betelgeuse and Mira Ceti, +Schuster says, “It has been already mentioned that observers differ as<span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span> to +whether their position is anterior to the hydrogen or posterior to the +solar stars, and there are valid arguments on both sides.”</p> + +<p>Scheiner, however, shows, from the behaviour of the lines of magnesium, +that stars of type I. (Sirian) are the hottest, and type III. the coolest, +and he says, we have “for the first time a direct proof of the correctness +of the physical interpretation of Vogel’s spectral classes, according to +which class II. is developed by cooling from I., and III. by a further +process of cooling from II.”<a name='fna_296' id='fna_296' href='#f_296'><small>[296]</small></a></p> + +<p>Prof. Hale says that “the resemblance between the spectra of sun-spots and +of 3rd-type stars is so close as to indicate that the same cause is +controlling the relative intensities of many lines in both instances. This +cause, as the laboratory work indicates, is to be regarded as reduced +temperature.”<a name='fna_297' id='fna_297' href='#f_297'><small>[297]</small></a></p> + +<p>According to Prof. Schuster, “a spectrum of bright lines may be given by a +mass of luminous gas, even if the gas is of great thickness. There is, +therefore, no difficulty in explaining the existence of stars giving +bright lines.” He thinks that the difference between “bright line” stars +and those showing dark lines depends upon the rate of increase of the +temperature from the surface towards the centre. If this rate is slow, +bright lines will be seen. If the rate of increase<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> is rapid, the +dark-line spectrum shown by the majority of the stars will appear. This +rate, he thinks, is regulated by the gravitational force. So that in the +early stages of condensation bright lines are more likely to occur. “If +the light is not fully absorbed,” both bright and dark lines of the same +element may be visible in the same star. Schuster considers it quite +possible that if we could remove the outer layers of the Sun’s atmosphere, +we should obtain a spectrum of bright lines.<a name='fna_298' id='fna_298' href='#f_298'><small>[298]</small></a></p> + +<p>M. Stratonoff finds that stars having spectra of the Orion and Sirian +types—supposed to represent an early stage in stellar evolution—tend to +congregate in or near the Milky Way. Star clusters in general show a +similar tendency, “but to this law the globular clusters form an +exception.”<a name='fna_299' id='fna_299' href='#f_299'><small>[299]</small></a> We may add that the spiral nebulæ—which seem to be +scattered indifferently over all parts of the sky—also seem to form an +exception; for the spectra of these wonderful objects seem to show that +they are really star clusters, in which the components are probably +relatively small; that is, small in comparison with our sun.</p> + +<p>If we accept the hypothesis that suns and systems were evolved from +nebulæ, and if we consider the comparatively small number of<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> nebulæ +hitherto discovered in the largest telescopes—about half a million; and +if we further consider the very small number of red stars, or those having +spectra of the third and fourth types—usually considered to be dying-out +suns—we seem led to the conclusion that our sidereal system is now at +about the zenith of its life-history; comparatively few nebulæ being left +to consolidate into stars, and comparatively few stars having gone far on +the road to the final extinction of their light.</p> + +<p>Prof. Boss of Albany (U.S.A.) finds that about forty stars of magnitudes +from 3½ to 7 in the constellation Taurus are apparently drifting +together towards one point. These stars are included between about R.A. +3<sup>h</sup> 47<sup>m</sup> to 5<sup>h</sup> 4<sup>m</sup>, and Declination + 5° to + 23° (that is, in the +region surrounding the Hyades). These motions apparently converge to a +point near R.A. 6<sup>h</sup>, Declination + 7° (near Betelgeuse). Prof. Boss has +computed the velocity of the stars in this group to be 45·6 kilometres +(about 28 miles) a second towards the “vanishing point,” and he estimated +the average parallax of the group to be 0″·025—about 130 years’ journey +for light. Although the motions are apparently converging to a point, it +does not follow that the stars in question will, in the course of ages, +meet at the “vanishing point.” On the contrary, the observed motions show +that the stars are moving in parallel lines through space.<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> About 15 +kilometres of the observed speed is due to the sun’s motion through space +in the opposite direction. Prof. Campbell finds from spectroscopic +measures that of these forty stars, nine are receding from the earth with +velocities varying from 12 to 60 kilometres a second, and twenty-three +others with less velocities than 38 kilometres.<a name='fna_300' id='fna_300' href='#f_300'><small>[300]</small></a> It will be obvious +that, as there is a “vanishing point,” the motion in the line of sight +must be one of <i>recession</i> from the earth.</p> + +<p>It has been found that on an average the parallax of a star is about +one-seventh of its “proper motion.”<a name='fna_301' id='fna_301' href='#f_301'><small>[301]</small></a></p> + +<p>Adopting Prof. Newcomb’s parallax of 0″·14 for the famous star 1830 +Groombridge, the velocity perpendicular to the line of sight is about 150 +miles a second. The velocity <i>in</i> the line of sight—as shown by the +spectroscope—is 59 miles a second approaching the earth. Compounding +these two velocities we find a velocity through space of about 161 miles a +second!</p> + +<p>An eminent American writer puts into the mouth of one of his characters, a +young astronomer, the following:—</p> + +<p class="poem"><span style="margin-left: 9em;">“I read the page</span><br /> +Where every letter is a glittering sun.”</p> + +<p>From an examination of the heat radiated by<span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span> some bright stars, made by +Dr. E. F. Nicholls in America with a very sensitive radiometer of his own +construction, he finds that “we do not receive from Arcturus more heat +than we should from a candle at a distance of 5 or 6 miles.”</p> + +<p>With reference to the progressive motion of light, and the different times +taken by light to reach the earth from different stars, Humboldt says, +“The aspect of the starry heavens presents to us objects of <i>unequal +date</i>. Much has long ceased to exist before the knowledge of its presence +reaches us; much has been otherwise arranged.”<a name='fna_302' id='fna_302' href='#f_302'><small>[302]</small></a></p> + +<p>The photographic method of charting the stars, although a great +improvement on the old system, seems to have its disadvantages. One of +these is that the star images are liable to disappear from the plates in +the course of time. The reduction of stellar photograph plates should, +therefore, be carried out as soon as possible after they are taken. The +late Dr. Roberts found that on a plate originally containing 364 stars, no +less than 130 had completely disappeared in 9¼ years!</p> + +<p>It has been assumed by some writers on astronomy that the faint stars +visible on photographs of the Pleiades are at practically the same +distance from the earth as the brighter stars of the cluster, and that +consequently there must be an enormous difference in actual size between +the<span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span> brighter and fainter stars. But there is really no warrant for any +such assumption. Photographs of the vicinity show that the sky all round +the Pleiades is equally rich in faint stars. It seems, therefore, more +reasonable to suppose that most of the faint stars visible in the Pleiades +are really far behind the cluster in space. For if <i>all</i> the faint stars +visible on photographs belonged to the cluster, then if we imagine the +cluster removed, a “hole” would be left in the sky, which is of course +utterly improbable, and indeed absurd. An examination of the proper +motions tends to confirm this view of the matter, and indicates that the +Pleiades cluster is a comparatively small one and simply projected on a +background of fainter stars.</p> + +<p>It has long been suspected that the famous star 61 Cygni, which is a +double star, forms a binary system—that is, that the two stars composing +it revolve round their common centre of gravity and move together through +space. But measures of parallax made by Herman S. Davis and Wilsing seem +to show a difference of parallax between the two components of about 0·08 +of a second of arc. This difference of parallax implies a distance of +about 2¼ “light years” between the two stars, and “if this is correct, +the stars are too remote to form a binary system. The proper motions of +5″·21 and 5″·15 seem to show that they are moving in nearly parallel +directions; but are<span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span> probably slowly separating.” Mr. Lewis, however, +thinks that a physical connection probably exists.<a name='fna_303' id='fna_303' href='#f_303'><small>[303]</small></a></p> + +<p>Dante speaks of the four bright stars of the Southern Cross as +emblematical of the four cardinal virtues, Justice, Temperance, Fortitude, +and Prudence; and he seems to refer to the stars Canopus, Achernar, and +Foomalhaut under the symbols of Faith, Hope, and Charity. The so-called +“False Cross” is said to be formed by the stars κ, δ, +ε, and ι of the constellation Argo Navis. But it seems +to me that a better (although larger) cross is formed by the stars α Centauri +and α, β, and γ of Triangulum Australis.</p> + +<p>Mr. Monck has pointed out that the names of the brightest stars seem to be +arranged alphabetically in order of colour, beginning with red and ending +with blue. Thus we have Aldebaran, Arcturus, Betelgeuse, Capella, Procyon, +Regulus, Rigel, Sirius, Spica and Vega. But as the origin of these names +is different, this must be merely a curious coincidence.<a name='fna_304' id='fna_304' href='#f_304'><small>[304]</small></a> And, to my +eye at least, Betelgeuse is redder than Arcturus.</p> + +<p>The poet Longfellow speaks of the—</p> + +<p class="poem">“Stars, the thoughts of God in the heavens,”<a name='fna_305' id='fna_305' href='#f_305'><small>[305]</small></a></p> + +<p>and Drayton says—</p> + +<p class="poem">“The stars to me an everlasting book<br /> +In that eternal register, the sky.”<a name='fna_306' id='fna_306' href='#f_306'><small>[306]</small></a></p> + +<p><span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span>Observing at a height of 12,540 feet on the Andes, the late Dr. Copeland +saw Sirius with the naked eye less than 10 minutes before sunset.<a name='fna_307' id='fna_307' href='#f_307'><small>[307]</small></a> He +also saw Jupiter 3<sup>m</sup> 47<sup>s</sup> before sunset; and the following bright +stars—Canopus, 0<sup>m</sup> 52<sup>s</sup> before sunset; Rigel (β Orionis) 16<sup>m</sup> +32<sup>s</sup> after sunset; and Procyon 11<sup>m</sup> 28<sup>s</sup> after sunset. From a height of +12,050 feet at La Paz, Bolivia, he saw with the naked eye in February, +1883, ten stars in the Pleiades in full moonlight, and seventeen stars in +the Hyades. He also saw σ Tauri double.<a name='fna_308' id='fna_308' href='#f_308'><small>[308]</small></a></p> + +<p>Humboldt says, “In whatever point the vault of heaven has been pierced by +powerful and far-penetrating telescopic instruments, stars or luminous +nebulæ are everywhere discoverable, the former in some cases not exceeding +the 20th or 24th degree of telescopic magnitude.”<a name='fna_309' id='fna_309' href='#f_309'><small>[309]</small></a> But this is a +mistake. No star of even the 20th magnitude has ever been seen by any +telescope. Even on the best photographic plates it is doubtful that any +stars much below the 18th magnitude are visible. To show a star of the +20th magnitude—if such stars exist—would require a telescope of 144 +inches or 12 feet in aperture. To show a star of the 24th magnitude—if +such there be—an aperture of 33 feet would be necessary!<a name='fna_310' id='fna_310' href='#f_310'><small>[310]</small></a></p> + +<p><span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span>It is a popular idea that stars may be seen in the daytime from the bottom +of a deep pit or high chimney. But this has often been denied. Humboldt +says, “While practically engaged in mining operations, I was in the habit, +during many years, of passing a great portion of the day in mines where I +could see the sky through deep shafts, yet I never was able to observe a +star.”<a name='fna_311' id='fna_311' href='#f_311'><small>[311]</small></a></p> + +<p>Stars may, however, be seen in the daytime with even small telescopes. It +is said that a telescope of 1 inch aperture will show stars of the 2nd +magnitude; 2 inches, stars of the 3rd magnitude; and 4 inches, stars of +the 4th magnitude. But I cannot confirm this from personal observation. It +may be so, but I have not tried the experiment.</p> + +<p>Sir George Darwin says—</p> + +<div class="blockquot"><p>“Human life is too short to permit us to watch the leisurely procedure +of cosmical evolution, but the celestial museum contains so many +exhibits that it may become possible, by the aid of theory, to piece +together, bit by bit, the processes through which stars pass in the +course of their evolutions.”<a name='fna_312' id='fna_312' href='#f_312'><small>[312]</small></a></p></div> + +<p>The so-called “telluric lines” seen in the solar spectrum, are due to +water vapour in the earth’s atmosphere. As the light of the stars also +passes through the atmosphere, it is evident that these lines should also +be visible in the spectra<span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span> of the stars. This is found to be the case by +Prof. Campbell, Director of the Lick Observatory, who has observed all the +principal bands in the spectrum of every star he has examined.<a name='fna_313' id='fna_313' href='#f_313'><small>[313]</small></a></p> + +<p>The largest “proper motion” now known is that of a star of the 8½ +magnitude in the southern hemisphere, known as Cordoba Zone V. No. 243. +Its proper motion is 8·07 seconds of arc per annum, thus exceeding that of +the famous “runaway star,” 1830 Groombridge, which has a proper motion of +7·05 seconds per annum. This greater motion is, however, only apparent. +Measures of parallax show that the southern “runaway” is much nearer to us +than its northern rival, its parallax being 0″·32, while that of +Groombridge 1830 is only 0″·14. With these data the actual velocity across +the line of sight can be easily computed. That of the southern star comes +out 80 miles a second, while that of Groombridge 1830 is 148 miles a +second. The actual velocity of Arcturus is probably still greater.</p> + +<p>The poet Barton has well said—</p> + +<p class="poem">“The stars! the stars! go forth at night,<br /> +<span style="margin-left: 1em;">Lift up thine eyes on high,</span><br /> +And view the countless orbs of light,<br /> +<span style="margin-left: 1em;">Which gem the midnight sky.</span><br /> +Go forth in silence and alone,<br /> +<span style="margin-left: 1em;">This glorious sight to scan,</span><br /> +And bid the humbled spirit own<br /> +<span style="margin-left: 1em;">The littleness of man.”</span></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span></p> +<h2><a name="CHAPTER_XV" id="CHAPTER_XV"></a>CHAPTER XV</h2> +<p class="title">Double and Binary Stars</p> + +<p> </p> +<p class="dropcap"><span class="caps">Prof. R. G. Aitken</span>, the eminent American observer of double stars, finds +that of all the stars down to the 9th magnitude—about the faintest +visible in a powerful binocular field-glass—1 in 18, or 1 in 20, on the +average, are double, with the component stars less than 5 seconds of arc +apart. This proportion of double stars is not, however, the same for all +parts of the sky; while in some regions double stars are very scarce, in +other places the proportion rises to 1 in 8.</p> + +<p>For the well-known binary star Castor (α Geminorum), several +orbits have been computed with periods ranging from 232 years (Mädler) to +1001 years (Doberck). But Burnham finds that “the orbit is absolutely +indeterminate at this time, and likely to remain so for another century or +longer.”<a name='fna_314' id='fna_314' href='#f_314'><small>[314]</small></a> Both components are spectroscopic binaries, and the system +is a most interesting one.</p> + +<p>The well-known companion of Sirius became<span class="pagenum"><a name="Page_161" id="Page_161">[Pg 161]</a></span> invisible in all telescopes in +the year 1890, owing to its near approach to its brilliant primary. It +remained invisible until August 20, 1896, when it was again seen by Dr. +See at the Lowell Observatory.<a name='fna_315' id='fna_315' href='#f_315'><small>[315]</small></a> Since then its distance has been +increasing, and it has been regularly measured. The maximum distance will +be attained about the year 1922.</p> + +<p>The star β Cephei has recently been discovered to be a +spectroscopic binary with the wonderfully short period of 4<sup>h</sup> 34<sup>m</sup> +11<sup>s</sup>. The orbital velocity is about 10½ miles a second, and as this +velocity is not very great, the distance between the components must be +very small, and possibly the two component bodies are revolving in actual +contact. The spectrum is of the “Orion type.”<a name='fna_316' id='fna_316' href='#f_316'><small>[316]</small></a></p> + +<p>According to Slipher the spectroscopic binary γ Geminorum has the +comparatively long period (for a spectroscopic binary) of about 3½ +years. This period is comparable with that of the telescopic binary +system, δ Equulei (period about 5·7 years). The orbit is quite +eccentric. I have shown elsewhere<a name='fna_317' id='fna_317' href='#f_317'><small>[317]</small></a> that γ Geminorum has +probably increased in brightness since the time of Al-Sufi (tenth +century). Possibly its spectroscopic duplicity may have something to do +with the variation in its light.</p> + +<p><span class="pagenum"><a name="Page_162" id="Page_162">[Pg 162]</a></span>With reference to the spectra of double stars, Mr. Maunder suggests that +the fact of the companion of a binary star showing a Sirian spectrum while +the brighter star has a solar spectrum may be explained by supposing that, +on the theory of fission, “the smaller body when thrown off consisted of +the lighter elements, the heavier remaining in the principal star. In +other words, in these cases spectral type depends upon original chemical +constitution, and not upon the stage of stellar development +attained.”<a name='fna_318' id='fna_318' href='#f_318'><small>[318]</small></a></p> + +<p>A curious paradox with reference to binary stars has recently come to +light. For many years it was almost taken for granted that the brighter +star of a pair had a larger mass than the fainter component. This was a +natural conclusion, as both stars are practically at the same distance +from the earth. But it has been recently found that in some binary stars +the fainter component has actually the larger mass! Thus, in the binary +star ε Hydræ, the “magnitude” of the component stars are 3 and 6, +indicating that the brighter star is about 16 times brighter than the +fainter component. Yet calculations by Lewis show that the fainter star +has 6 times the mass of the brighter, that is, contains 6 times the +quantity of matter! In the well-known binary 70 Ophiuchi, Prey finds that +the fainter star has about 4 times the<span class="pagenum"><a name="Page_163" id="Page_163">[Pg 163]</a></span> mass of the brighter! In 85 +Pegasi, the brighter star is about 40 times brighter than its companion, +while Furner finds that the mass of the fainter star is about 4 times that +of the brighter! And there are other similar cases. In fact, in these +remarkable combinations of suns the fainter star is really the “primary,” +and is, so far as mass is concerned, “the predominant partner.” This is a +curious anomaly, and cannot be well explained in the present state of our +knowledge of stellar systems. In the case of α Centauri the +masses of the components are about equal, while the primary star is about +3 times brighter than the other. But here the discrepancy is +satisfactorily explained by the difference in character of the spectra, +the brighter component having a spectrum of the solar type, while the +fainter seems further advanced on the downward road of evolution, that is, +more consolidated and having, perhaps, less intrinsic brightness of +surface.</p> + +<p>In the case of Sirius and its faint attendant, the mass of the bright star +is about twice the mass of the satellite, while its light is about 40,000 +times greater! Here the satellite is either a cooled-down sun or perhaps a +gaseous nebula. There seems to be no other explanation of this curious +paradox. The same remark applies to Procyon, where the bright star is +about 100,000 times brighter than its faint companion, although its mass +is only 5 times greater.</p> + +<p><span class="pagenum"><a name="Page_164" id="Page_164">[Pg 164]</a></span>The bright star Capella forms a curious anomaly or paradox. Spectroscopic +observations show that it is a very close binary pair. It has been seen +“elongated” at the Greenwich Observatory with the great 28-inch +refractor—the work of Sir Howard Grubb—and the spectroscopic and visual +measurements agree in indicating that its mass is about 18 times the mass +of the sun. But its parallax (about 0″·08) shows that it is about 128 +times brighter than the sun! This great brilliancy is inconsistent with +the star’s computed mass, which would indicate a much smaller brightness. +The sun placed at the distance of Capella would, I find, shine as a star +of about 5½ magnitude, while Capella is one of the brightest stars in +the sky. As the spectrum of Capella’s light closely resembles the solar +spectrum, we seem justified in assuming that the two bodies have pretty +much the same physical composition. The discrepancy between the computed +and actual brightness of the star cannot be explained satisfactorily, and +the star remains an astronomical enigma.</p> + +<p>Three remarkable double-star systems have been discovered by Dr. See in +the southern hemisphere. The first of these is the bright star α +Phœnicis, of which the magnitude is 2·4, or only very slightly fainter +than the Pole Star. It is attended by a faint star of the 13th magnitude +at a distance of less than 10 seconds (1897). The<span class="pagenum"><a name="Page_165" id="Page_165">[Pg 165]</a></span> bright star is of a +deep orange or reddish colour, and the great difference in brightness +between the component stars “renders the system both striking and +difficult.” The second is μ Velorum, a star of the 3rd magnitude, +which has a companion of the 11th magnitude, and only 2½″ from its +bright primary (1897). Dr. See describes this pair as “one of the most +extraordinary in the heavens.” The third is η Centauri, of 2½ +magnitude, with a companion of 13½ magnitude at a distance of 5″·65 +(1897); colours yellow and purple. This pair is “extremely difficult, +requiring a powerful telescope to see it.” Dr. See thinks that these three +objects “may be regarded as amongst the most splendid in the heavens.”</p> + +<p>The following notes are from Burnham’s recently published <i>General +Catalogue of Double Stars</i>.</p> + +<p>The Pole Star has a well-known companion of about the 9th magnitude, which +is a favourite object for small telescopes. Burnham finds that the bright +star and its faint companion are “relatively fixed,” and are probably only +an “optical pair.” Some other companions have been suspected by amateur +observers, but Burnham finds that “there is nothing nearer” than the known +companion within the reach of the great 36-inch telescope of the Lick +Observatory (<i>Cat.</i>, p. 299).</p> + +<p>The well-known companion to the bright star<span class="pagenum"><a name="Page_166" id="Page_166">[Pg 166]</a></span> Rigel (β Orionis) +has been suspected for many years to be a close double star. Burnham +concludes that it is really a binary star, and its “period may be shorter +than that of any known pair” (<i>Cat.</i>, p. 411).</p> + +<p>Burnham finds that the four brighter stars in the trapezium in the great +Orion nebula (in the “sword”) are relatively fixed (<i>Cat.</i>, p. 426).</p> + +<p>γ Leonis. This double star was for many years considered to be a +binary, but Burnham has shown that all the measures may be satisfactorily +represented by a straight line, and that consequently the pair merely +forms an “optical double.”</p> + +<p>42 Comæ Berenices. This is a binary star of which the orbit plane passes +nearly through the earth. The period is about 25½ years, and Burnham +says the orbit “is as accurately known as that of any known binary.”</p> + +<p>σ Coronæ Borealis. Burnham says that the orbits hitherto +computed—with periods ranging from 195 years (Jacob) to 846 years +(Doberck) are “mere guess work,” and it will require the measures of at +least another century, and perhaps a much longer time, to give an +approximate period (<i>Cat.</i>, p. 209). So here is some work left for +posterity to do in this field.</p> + +<p>70 Ophiuchi. With reference to this well-known binary star, Burnham says, +“the elements of the orbit are very accurately known.” The<span class="pagenum"><a name="Page_167" id="Page_167">[Pg 167]</a></span> periods +computed range from 86·66 years (Doolittle) to 98·15 years (Powell). The +present writer found a period of 87·84 years, which cannot be far from the +truth. Burnham found 87·75 years (<i>Cat.</i>, p. 774). In this case there is +not much left for posterity to accomplish.</p> + +<p>61 Cygni. With reference to this famous star Burnham says, “So far the +relative motion is practically rectilinear. If the companion is moving in +a curved path, it will require the measures of at least another +half-century to make this certain. The deviation of the measured positions +during the last 70 years from a right line are less than the average +errors of the observations.”</p> + +<p>Burnham once saw a faint companion to Sirius of the 16th magnitude, and +measured its position with reference to the bright star (280°·6: 40″·25: +1899·86). But he afterwards found that it was “not a real object but a +reflection from Sirius” (in the eye-piece). Such false images are called +“ghosts.”</p> + +<p>With reference to the well-known double (or rather quadruple) star ε +Lyræ, near Vega, and supposed faint stars near it, Burnham says, “From +time to time various small stars in the vicinity have been mapped, and +much time wasted in looking for and speculating about objects which only +exist in the imagination of the observer.” He believes that many of these +faint<span class="pagenum"><a name="Page_168" id="Page_168">[Pg 168]</a></span> stars, supposed to have been seen by various observers, are merely +“ghosts produced by reflection.”</p> + +<p>The binary star ζ Boötis, which has long been suspected of small +and irregular variation of light, showed remarkable spectral changes in +the year 1905,<a name='fna_319' id='fna_319' href='#f_319'><small>[319]</small></a> somewhat similar to those of a <i>nova</i>, or temporary +star. It is curious that such changes should occur in a star having an +ordinary Sirian type of spectrum!</p> + +<p>A curious quadruple system has been discovered by Mr. R. T. A. Innes in +the southern hemisphere. The star κ Toucani is a binary star with +components of magnitudes 5 and 7·7, and a period of revolution of perhaps +about 1000 years. Within 6′ of this pair is another star (Lacaille 353), +which is also a binary, with a period of perhaps 72 years. Both pairs have +the same proper motion through space, and evidently form a vast quadruple +system; for which Mr. Innes finds a possible period of 300,000 years.<a name='fna_320' id='fna_320' href='#f_320'><small>[320]</small></a></p> + +<p>It is a curious fact that the performance of a really good refracting +telescope actually exceeds what theory would indicate! at least so far as +double stars are concerned. For example, the famous double-star observer +Dawes found that the distance between the components of a double<span class="pagenum"><a name="Page_169" id="Page_169">[Pg 169]</a></span> star +which can just be divided, is found by dividing 4″·56 by the aperture of +the object-glass in inches. Now theory gives 5″·52 divided by the +aperture. “The actual telescope—if a really good one—thus exceeds its +theoretical requirements. The difference between theory and practice in +this case seems to be due to the fact that in the ‘spurious’ star disc +shown by good telescopes, the illumination at the edges of the star disc +is very feeble, so that its full size is not seen except in the case of a +very bright star.”<a name='fna_321' id='fna_321' href='#f_321'><small>[321]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_170" id="Page_170">[Pg 170]</a></span></p> +<h2><a name="CHAPTER_XVI" id="CHAPTER_XVI"></a>CHAPTER XVI</h2> +<p class="title">Variable Stars</p> + +<p> </p> +<p class="dropcap"><span class="caps">In</span> that interesting work <i>A Cycle of Celestial Objects</i>, Admiral Smyth +says (p. 275), “Geminiano Montanari, as far back as 1670, was so struck +with the celestial changes, that he projected a work to be intituled the +<i>Instabilities of the Firmament</i>, hoping to show such alterations as would +be sufficient to make even Aristotle—were he alive—reverse his opinion +on the incorruptibility of the spangled sky: ‘There are now wanting in the +heavens,’ said he, ‘two stars of the 2nd magnitude in the stem and yard of +the ship Argo. I and others observed them in the year 1664, upon occasion +of the comet that appeared in that year. When they first disappeared I +know not; only I am sure that on April 10, 1668, there was not the least +glimpse of them to be seen.’” Smyth adds, “Startling as this account +is—and I am even disposed to question the fact—it must be recollected +that Montanari was a man of integrity, and well versed in the theory and +practice of astronomy;<span class="pagenum"><a name="Page_171" id="Page_171">[Pg 171]</a></span> and his account of the wonder will be found—in +good set Latin—in page 2202 of the <i>Philosophical Transactions</i> for +1671.”</p> + +<p>There must be, I think—as Smyth suggests—some mistake in Montanari’s +observations, for it is quite certain that of the stars mentioned by +Ptolemy (second century <span class="smcaplc">A.D.</span>) there is no star of the 2nd magnitude now +missing. It is true that Al-Sufi (tenth century) mentions a star of the +<i>third</i> magnitude mentioned by Ptolemy in the constellation of the Centaur +(about 2° east of the star ε Centauri) which he could not find. +But this has nothing to do with Montanari’s stars. Montanari’s words are +very clear. He says, “<i>Desunt in Cœlo duæ stellæ</i> Secundæ Magnitudinis +<i>in</i> Puppi Navis <i>ejusve Transtris</i> Bayero β et γ, +<i>prope</i> Canem Majoris, <i>à me et aliis, occasione præsertim Cometæ</i> A. 1664 +<i>observatæ et recognitæ. Earum Disparitionem</i> cui Anno debeam, non novi; +<i>hoc indubium, quod à die</i> 10 April, 1668, <i>ne</i> vestigium quidem <i>illarum +adesse amplius observe; cæteris circa eas etium quartæ et quintæ +magnitudinis, immotis.</i>” So the puzzle remains unsolved.</p> + +<p>Sir William Herschel thought that “of all stars which are singly visible, +about one in thirty are undergoing an observable change.”<a name='fna_322' id='fna_322' href='#f_322'><small>[322]</small></a> Now taking +the number of stars visible to the naked eye at 6000, this would give +about 200 variable stars<span class="pagenum"><a name="Page_172" id="Page_172">[Pg 172]</a></span> visible at maximum to the unaided vision. But +this estimate seems too high. Taking all the stars visible in the largest +telescopes—possibly about 100 millions—the proportion of variable stars +will probably be much smaller still.</p> + +<p>The theory that the variation of light in the variable stars of the Algol +type is due to a partial eclipse by a companion star (not necessarily a +dark body) is now well established by the spectroscope, and is accepted by +all astronomers. The late Miss Clarke has well said “to argue this point +would be <i>enforcer une porte ouverte</i>.”</p> + +<p>According to Dr. A. W. Roberts, the components of the following “Algol +variables” “revolve in contact”: V Puppis, X Carinæ, β Lyræ, and +υ Pegasi. Of those V Puppis and β Lyræ are known +spectroscopic binaries. The others are beyond the reach of the +spectroscope, owing to their faintness.</p> + +<p>A very curious variable star of the Algol type is that known as R R +Draconis. Its normal magnitude is 10, but at minimum it becomes invisible +in a 7½-inch refracting telescope. The variation must, therefore, be +over 3 magnitudes, that is, at minimum its light must be reduced to about +one-sixteenth of its normal brightness. The period of variation from +maximum to minimum is about 2·83 days. The variation of light near minimum +is extraordinarily rapid, the<span class="pagenum"><a name="Page_173" id="Page_173">[Pg 173]</a></span> light decreasing by about 1 magnitude in +half an hour.<a name='fna_323' id='fna_323' href='#f_323'><small>[323]</small></a></p> + +<p>A very remarkable variable star has been recently discovered in the +constellation Auriga. Prof. Hartwig found it of the 9th magnitude on March +6, 1908, the star “having increased four magnitudes in one day, whilst +within eight days it was less than the 14th magnitude.”<a name='fna_324' id='fna_324' href='#f_324'><small>[324]</small></a> In other +words its light increased at least one-hundredfold in eight days!</p> + +<p>The period of the well-known variable star β Lyræ seems to be +slowly increasing. This Dr. Roberts (of South Africa) considers to be due +to the component stars slowly receding from each other. He finds that “a +very slight increase of one-thousandth part of the radius of the orbit +would account for the augmentation in time, 30<sup>m</sup> in a century.” According +to the theory of stellar evolution the lengthening of the period of +revolution of a binary star would be due to the “drag” caused by the tides +formed by each component on the other.<a name='fna_325' id='fna_325' href='#f_325'><small>[325]</small></a></p> + +<p>M. Sebastian Albrecht finds that in the short-period variable star known +as T Vulpeculæ (and other variables of this class, such as Y Ophiuchi), +there can be no eclipse to explain the variation of light (as in the case +of Algol). The star is a spectroscopic binary, it is true, but the +maximum<span class="pagenum"><a name="Page_174" id="Page_174">[Pg 174]</a></span> of light coincides with the greatest velocity of <i>approach</i> in +the line of sight, and the minimum with the greatest velocity of +<i>recession</i>. Thus the light curve and the spectroscopic velocity curve are +very similar in shape, but one is like the other turned upside down. “That +is, the two curves have a very close correspondence in phase in addition +to correspondence of shape and period.”<a name='fna_326' id='fna_326' href='#f_326'><small>[326]</small></a></p> + +<p>The star now known as W Ursæ Majoris (the variability of which was +discovered by Müller and Kempf in 1902), and which lies between the stars +θ and υ of that constellation, has the marvellously +short period of 4 hours (from maximum to maximum). Messrs. Jordan and +Parkhurst (U.S.A.), find from photographic plates that the star varies +from 7·24 to 8·17 magnitude.<a name='fna_327' id='fna_327' href='#f_327'><small>[327]</small></a> The light at maximum is, therefore, more +than double the light at minimum. A sun which loses more than half its +light and recovers it again in the short period of 4 hours is certainly a +curious and wonderful object.</p> + +<p>In contrast with the above, the same astronomers have discovered a star in +Perseus which seems to vary from about the 6th to the 7th magnitude in the +very long period of 7½ years! It is now known as X Persei, and its +position for 1900 is R.A. 3<sup>h</sup> 49<sup>m</sup> 8<sup>s</sup>, Dec. N. 30° 46′, or about one +degree south-east of the star ζ Persei.<span class="pagenum"><a name="Page_175" id="Page_175">[Pg 175]</a></span> It seems to be a +variable of the Algol type, as the star remained constant in light at +about the 6th magnitude from 1887 to 1891. It then began to fade, and on +December 1, 1897, it was reduced to about the 7th magnitude.</p> + +<p>On the night of August 20, 1886, Prof. Colbert, of Chicago, noticed that +the star ζ Cassiopeiæ increased in brightness “by quite half a +magnitude, and about half an hour afterwards began to return to its normal +magnitude.”<a name='fna_328' id='fna_328' href='#f_328'><small>[328]</small></a> This curious outburst of light in a star usually constant +in brightness is (if true) a very unusual phenomenon. But a somewhat +similar fluctuation of light is recorded by the famous German astronomer +Heis. On September 26, 1850, he noted that the star “ζ Lyræ +became, for a moment, <i>very bright</i>, and then again faint.” (The words in +his original observing book are: “ζ Lyræ wurde einen <i>Moment sehr +hell</i> und hierauf wieder dunkel.”) As Heis was a remarkably accurate +observer of star brightness, the above remark deserves the highest +confidence.<a name='fna_329' id='fna_329' href='#f_329'><small>[329]</small></a></p> + +<p>The variable star known as the V Delphini was found to be invisible in the +great 40-inch telescope of the Yerkes Observatory on July 20, 1900. Its +magnitude was, therefore, below the 17th. At its maximum brightness it is +about 7½, or easily visible in an ordinary opera-glass, so that its<span class="pagenum"><a name="Page_176" id="Page_176">[Pg 176]</a></span> +range of variation is nearly, or quite, ten magnitudes. That is, its light +at maximum is about 10,000 times its light at minimum. That a sun should +vary in light to this enormous extent is certainly a wonderful fact. A +variable discovered by Ceraski (and numbered 7579 in Chandlers’ Catalogue) +“had passed below the limit of the 40-inch in June, 1900, and was, +therefore, not brighter than 17 mag.”<a name='fna_330' id='fna_330' href='#f_330'><small>[330]</small></a></p> + +<p>The late Sir C. E. Peck and his assistant, Mr. Grover, made many valuable +observations of variable stars at the Rousden Observatory during many +years past. Among other interesting things noted, Peck sometimes saw faint +stars in the field of view of his telescope which were at other times +invisible for many months, and he suggested that these are faint variable +stars with a range of brightness from the 13th to the 20th magnitude. He +adds, “Here there is a practically unemployed field for the largest +telescopes.” Considering the enormous number of faint stars visible on +stellar photographs the number of undiscovered variable stars must be very +large.</p> + +<p>Admiral Smyth describes a small star near β Leonis, about 5′ +distant, of about 8th magnitude, and dull red. In 1864 Mr. Knott measured +a faint star close to Smyth’s position, but estimated it only 11·6 +magnitude. The Admiral’s star would thereupon seem to be variable.<a name='fna_331' id='fna_331' href='#f_331'><small>[331]</small></a></p> + +<p><span class="pagenum"><a name="Page_177" id="Page_177">[Pg 177]</a></span>The famous variable star η Argus, which Sir John Herschel, when +at the Cape of Good Hope in 1838, saw involved in dense nebulosity, was in +April, 1869, “seen on the bare sky,” with the great Melbourne telescope, +“the nebula having disappeared for some distance round it.” Other changes +were noticed in this remarkable nebula. The Melbourne observers saw “three +times as many stars as were seen by Herschel.” But of course their +telescope is much larger—48 inches aperture, compared with Herschel’s 20 +inches.</p> + +<p>Prof. E. C. Pickering thinks that the fluctuations of light of the +well-known variable star R Coronæ (in the Northern Crown), “are unlike +those of any known variable.” This very curious object—one of the most +curious in the heavens—sometimes remains for many months almost constant +in brightness (just visible to the naked eye), and then rapidly fades in +light by several magnitudes! Thus its changes of light in April and May, +1905, were as follows:—</p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td>1905,</td> + <td>April</td> + <td align="right">1</td> + <td> ... ... </td> + <td align="right">6·0</td> + <td>magnitude</td></tr> +<tr><td> </td> + <td align="center">"</td> + <td align="right">11</td> + <td> ... ... </td> + <td align="right">7·3</td> + <td align="center">"</td></tr> +<tr><td> </td> + <td align="center">"</td> + <td align="right">12</td> + <td> ... ... </td> + <td align="right">8·4</td> + <td align="center">"</td></tr> +<tr><td> </td> + <td>May</td> + <td align="right">1</td> + <td> ... ... </td> + <td align="right">11·4</td> + <td align="center">"</td></tr> +<tr><td> </td> + <td align="center">"</td> + <td align="right">7</td> + <td> ... ... </td> + <td align="right">12·5</td> + <td align="center">"</td></tr></table> + +<p>Thus between April 1 and May 1, its light was reduced by over 5 +magnitudes. In other words, the light of the star on May 1 was reduced to +less than one-hundredth of its light on April 1. If our<span class="pagenum"><a name="Page_178" id="Page_178">[Pg 178]</a></span> sun were to +behave in this way nearly all life would soon be destroyed on the face of +the earth.</p> + +<p>M. H. E. Lau finds that the short-period variable star δ Cephei +varies slightly in colour as well as in light, and that the colour curve +is parallel to the light curve. Near the minimum of light the colour is +reddish yellow, almost as red as ζ Cephei; a day later it is pure +yellow, and of about the same colour as the neighbouring ε +Cephei.<a name='fna_332' id='fna_332' href='#f_332'><small>[332]</small></a> But it would not be easy to fully establish such slight +variations of tint.</p> + +<p>A remarkably bright maximum of the famous variable Mira Ceti occurred in +1906. In December of that year it was fully 2nd magnitude. The present +writer estimated it 1·8, or nearly equal to the brightest on record—1·7 +observed by Sir William Herschel and Wargentin in the year 1779. From +photographs of the spectrum taken by Mr. Slipher at the Lowell Observatory +in 1907, he finds strong indications of the presence of the rather rare +element vanadium in the star’s surroundings. Prof. Campbell finds with the +Mills spectrograph attached to the great 36-inch telescope of the Lick +Observatory that Mira is receding from the earth at the apparently +constant velocity of about 38 miles a second.<a name='fna_333' id='fna_333' href='#f_333'><small>[333]</small></a> This, of course, has +nothing to do with the variation in the star’s light. Prof. Campbell +failed to see any trace of the green line<span class="pagenum"><a name="Page_179" id="Page_179">[Pg 179]</a></span> of hydrogen in the star’s +spectrum, while two other lines of the hydrogen series “glowed with +singular intensity.”</p> + +<p>Mr. Newall has found evidence of the element titanium in the spectrum of +Betelgeuse (α Orionis); Mr. Goatcher and Mr. Lunt (of the Cape +Observatory) find tin in Antares (and Scorpii). If the latter observation +is confirmed it will be the first time this metal has been found in a +star’s atmosphere.<a name='fna_334' id='fna_334' href='#f_334'><small>[334]</small></a></p> + +<p>It is a curious fact that Al-Sufi (tenth century) does not mention the +star ε Aquilæ, which lies closely north-west of ζ +Aquilæ, as it is now quite conspicuous to the naked eye. It was suspected +of variation by Sir William Herschel. It was first recorded by Tycho Brahé +about 1590, and he called it 3rd magnitude. Bayer also rated it 3, and +since his time it has been variously estimated from 3½ to 4. If it was +anything like its present brightness (4·21 Harvard) in the tenth century +it seems difficult to explain how it could have escaped Al-Sufi’s careful +scrutiny of the heavens, unless it is variable. Its colour seems reddish +to me.</p> + +<p>Mr. W. T. Lynn has shown—and I think conclusively—that the so-called +“new star” of <span class="smcaplc">A.D.</span> 389 (which is said to have appeared near Altair in the +Eagle) was really a comet.<a name='fna_335' id='fna_335' href='#f_335'><small>[335]</small></a></p> + +<p>Near the place of Tycho Brahé’s great new star<span class="pagenum"><a name="Page_180" id="Page_180">[Pg 180]</a></span> of 1572 (the “Pilgrim +Star”), Hind and W. E. Plummer observed a small star (No. 129 of +d’Arrest’s catalogue of the region) which seemed to show small +fluctuations of light, which “scarcely include a whole magnitude.” This +may possibly be identical with Tycho Brahé’s wonderful star, and should be +watched by observers. The place of this small star is (for 1865) R.A. 0<sup>h</sup> +17<sup>m</sup> 18<sup>s</sup>, N.P.D. 26° 37′·1. The region was examined by Prof. Burnham in +1890 with the 36-inch telescope of the Lick Observatory. “None of the +faint stars near the place presented any peculiarity worthy of remark, but +three double stars were found.”<a name='fna_336' id='fna_336' href='#f_336'><small>[336]</small></a></p> + +<p>With reference to the famous Nova (T) Coronæ—the “Blaze Star” of +1866—Prof. Barnard finds from careful comparisons with small stars in its +vicinity that “the Nova is now essentially of the same brightness it was +before the outburst of 1866 ... there seems to be no indication of motion +in the <i>Nova</i>.”</p> + +<p>With reference to the cause of “temporary” stars, or <i>novæ</i>, as they are +now called by astronomers—the late Prof. H. C. Vogel said—</p> + +<div class="blockquot"><p>“A direct collision of two celestial bodies is not regarded by Huggins +as an admissible explanation of the Nova; a partial collision has +little probability, and the most that can be admitted is perhaps the +mutual penetration and admixture of the outer<span class="pagenum"><a name="Page_181" id="Page_181">[Pg 181]</a></span> gaseous envelopes of +the two bodies at the time of their closest approach. A more probable +explanation is given by an hypothesis which we owe to Klinkerfues, and +which has more recently been further developed by Wilsing, viz. that +by the very close passage of two celestial bodies enormous tidal +disturbances are produced and thereby changes in the brightness of the +bodies. In the case of the two bodies which form the Nova, it must be +assumed that these phenomena are displayed in the highest degree of +development, and that changes of pressure have been produced which +have caused enormous eruptions from the heated interior of the bodies; +the eruptions are perhaps accompanied by electrical actions, and are +comparable with the outbursts in our own sun, although they are on a +much larger scale.”<a name='fna_337' id='fna_337' href='#f_337'><small>[337]</small></a></p></div> + +<p>It will be noticed that this hypothesis agrees with the fundamental +assumption of the “Planetesimal Hypothesis” advocated by Professors +Chamberlin and Moulton (see my <i>Astronomical Essays</i>, p. 324).</p> + +<p>The rush of a comparatively small body through a mass of gaseous matter +seems also a very plausible hypothesis. This idea was originally advanced +by Prof. Seeliger, and independently by Mr. Monck.</p> + +<p>With reference to the nebula which was observed round the great new star +of 1901—Nova Persei—Prof. Lewis Bell supports the theory of Seeliger, +which accounts for the apparent movements of the brightest portions of the +nebula by<span class="pagenum"><a name="Page_182" id="Page_182">[Pg 182]</a></span> supposing that the various parts of the highly tenuous matter +were successively lighted up by the effects of a travelling +electro-magnetic wavefront, and he shows that this theory agrees well with +the observed phenomenon.<a name='fna_338' id='fna_338' href='#f_338'><small>[338]</small></a> The “collision theory” which explained the +sudden outburst of light by the meeting of two dark bodies in space, seems +to be now abandoned by the best astronomers. The rapid cooling down of the +supposed bodies indicated by the rapid decrease of light is quite +inconsistent with this hypothesis.</p> + +<p>The rapid diminution in the light of some of these “new stars” is very +remarkable. Thus the new star which suddenly blazed out near the nucleus +of the great nebula in Andromeda in August, 1885, faded down in 5 months +from “the limit of visibility to the naked eye to that of a 26-inch +telescope”! A <i>large</i> body could not cool in this way.</p> + +<p>Mr. Harold K. Palmer thinks that the “complete and astonishingly rapid +changes of spectral type observed in the case of <i>Nova Cygni</i> and <i>Nova +Aurigæ</i>, and likewise those observed in <i>Nova Normæ</i>, <i>Nova Sagittarii</i> +and <i>Nova Persei</i>, leave little doubt that the masses of these objects are +small.”<a name='fna_339' id='fna_339' href='#f_339'><small>[339]</small></a></p> + +<p>No less than 3748 variable stars had been discovered up to May, 1907. Of +these 2909 were<span class="pagenum"><a name="Page_183" id="Page_183">[Pg 183]</a></span> found at Harvard Observatory (U.S.A.) chiefly by means of +photography.<a name='fna_340' id='fna_340' href='#f_340'><small>[340]</small></a></p> + +<p>The star 14. 1904 Cygni has a period of only 3 hours 14 minutes, which is +the shortest period known for a variable star.</p> + +<p>A very interesting discovery has recently been made with reference to the +star μ Herculis. It has been long suspected of variable light +with a period of 35 or 40 days, or perhaps irregular. Frost and Adams now +find it to be a spectroscopic binary, and further observations at Harvard +Observatory show that it is a variable of the Algol (or perhaps β +Lyræ) type. The Algol variation of light was suggested by MM. Baker and +Schlesinger. The period seems to be about 2·05 days.<a name='fna_341' id='fna_341' href='#f_341'><small>[341]</small></a></p> + +<p>The northern of the two “pointers” in the Plough (so called because they +nearly point to the Pole Star) is about the 2nd magnitude, as Al-Sufi +rated it. It was thought to be variable in colour by Klein, Konkoly, and +Weber; and M. Lau has recently found a period of 50 days with a maximum of +“jaune rougeâtre” on April 2, 1902.</p> + +<p>The famous variable star η Argus did “not exceed the 8th +magnitude” in February, 1907, according to Mr. Tebbutt.<a name='fna_342' id='fna_342' href='#f_342'><small>[342]</small></a> This is the +faintest ever recorded for this wonderful star.</p> + +<p><span class="pagenum"><a name="Page_184" id="Page_184">[Pg 184]</a></span>It is stated in <i>Knowledge</i> (vol. 5, p. 3, January 4, 1884) that the +temporary star of 1876 (in the constellation of Cygnus) “had long been +known and catalogued as a telescopic star of the 9th magnitude with +nothing to distinguish it from the common herd.” But this is quite +erroneous. The star was quite unknown before it was discovered by Schmidt +at Athens on November 24 of that year. The remark apparently refers to the +“Blaze Star” of 1866 in Corona Borealis, which <i>was</i> known previously as a +star of about the 9th magnitude before its sudden outburst on May 12 of +that year.</p> + +<p>This “new star” of 1866—T Coronæ, as it is now called—was, with the +possible exception of Nova Persei (1901), the only example of a <i>nova</i> +which was known to astronomers as a small star previous to the great +outburst of light. It is the brightest of the <i>novæ</i> still visible. It was +the first of these interesting objects to be examined with the +spectroscope. It was observed by Burnham in the years 1904-1906 with the +great 40-inch telescope of the Yerkes Observatory (U.S.A.). He found its +colour white, or only slightly tinged with yellow. In August and +September, 1906, he estimated its magnitude at about 9·3, and “it would +seem therefore that the Nova is now essentially of the same brightness it +was before the outburst in 1866.” It shows no indication of motion. +Burnham found no<span class="pagenum"><a name="Page_185" id="Page_185">[Pg 185]</a></span> peculiarity about its telescopic image. A small and very +faint nebula was found by Burnham a little following (that is east of) the +<i>nova</i>.<a name='fna_343' id='fna_343' href='#f_343'><small>[343]</small></a></p> + +<p>The following details of the great new star of 1572—the “Pilgrim Star” of +Tycho Brahé—are given by Delambre.<a name='fna_344' id='fna_344' href='#f_344'><small>[344]</small></a> In November, 1572, it was +brighter than Sirius, Vega, and Jupiter, and almost equal to Venus at its +brightest. During December it resembled Jupiter in brightness. In January, +1573, it was fainter and only a little brighter than stars of the 1st +magnitude. In February and March it was equal to 1st magnitude stars, and +in April and May was reduced to the 2nd magnitude. In June and July it was +3rd magnitude; in September of the 4th, and at the end of 1573 it was +reduced to the 5th magnitude. In February, 1574, it was 6th magnitude, and +in March of the same year it became invisible to the naked eye.</p> + +<p>From this account it will be seen that the decrease in light of this +curious object was much slower than that of Nova Persei (1901) (“the new +star of the new century”). This would suggest that it was a much larger +body.</p> + +<p>There were also changes in its colour. When it was of the brightness of +Venus or Jupiter it shone with a white light. It then became golden, and +afterwards reddish like Mars, Aldebaran, or<span class="pagenum"><a name="Page_186" id="Page_186">[Pg 186]</a></span> Betelgeuse. It afterwards +became of a livid white colour like Saturn, and this it retained as long +as it was visible. Tycho Brahé thought that its apparent diameter might +have been about 3½ minutes of arc, and that it was possibly 361 times +smaller than the earth(!) But we now know that these estimates were +probably quite erroneous.</p> + +<p>Temporary stars were called by the ancient Chinese “Ke-sing,” or guest +stars.<a name='fna_345' id='fna_345' href='#f_345'><small>[345]</small></a></p> + +<p>A temporary star recorded by Ma-tuan-lin (Chinese Annals) in February, +1578, is described as “a star as large as the sun.” But its position is +not given.<a name='fna_346' id='fna_346' href='#f_346'><small>[346]</small></a></p> + +<p>About the middle of September, 1878, Mr. Greely, of Boston (U.S.A.), +reported to Mr. E. F. Sawyer (the eminent observer of variable stars) +that, about the middle of August of that year, he had seen the famous +variable star Mira Ceti of about the 2nd magnitude, although the star did +not attain its usual maximum until early in October, 1878. Mr. Greely +stated that several nights after he first saw Mira it had faded to the 4th +or 5th magnitude. If there was no mistake in this observation (and Sawyer +could find none) it was quite an unique phenomenon, as nothing of the sort +has been observed before or since in the history of this famous star. It +looks as if Mr. Greely had observed a new or “temporary” star near the<span class="pagenum"><a name="Page_187" id="Page_187">[Pg 187]</a></span> +place of Mira Ceti; but as the spot is far from the Milky Way, which is +the usual seat of such phenomena, this hypothesis seems improbable.</p> + +<p>In the so-called Cepheid and Geminid variables of short period, the +principal characteristics of the light variation are as follows:—</p> + +<div class="blockquot"><p>“1. The light varies without pause.</p> + +<p>“2. The amount of their light variation is usually about 1 magnitude.</p> + +<p>“3. Their periods are short—a few days only.</p> + +<p>“4. They are of a spectral type approximately solar; no Orion, Sirian +or Arcturian stars having been found among them.</p> + +<p>“5. They seem to be found in greater numbers in certain parts of the +sky, notably in the Milky Way, but exhibit no tendency to form +clusters.</p> + +<p>“6. All those stars whose radial velocities have been studied have +been found to be binaries whose period of orbital revolution coincides +with that of their light change.</p> + +<p>“7. The orbits, so far as determined, are all small, <i>a</i> sin <i>i</i> being +2,000,000 kilometres or less.</p> + +<p>“8. Their maximum light synchronizes with their maximum velocity of +approach, and minimum light with maximum velocity of recession.</p> + +<p>“9. No case has been found in which the spectrum of more than one +component has been bright enough to be recorded in the +spectrograms.”<a name='fna_347' id='fna_347' href='#f_347'><small>[347]</small></a></p></div> + +<p>It is very difficult to find an hypothesis which will explain +satisfactorily <i>all</i> these characteristics, and attempts in this direction +have not proved very successful. Mr. J. C. Duncan suggests the<span class="pagenum"><a name="Page_188" id="Page_188">[Pg 188]</a></span> action of +an absorbing atmosphere surrounding the component stars.</p> + +<p>On March 30, 1612, Scheiner saw a star near Jupiter. It was at first equal +in brightness to Jupiter’s satellites. It gradually faded, and on April 8 +of the same year it was only seen with much difficulty in a very clear +sky. “After that date it was never seen again, although carefully looked +for under favourable conditions.”</p> + +<p>An attempted identification of Scheiner’s star was made in recent years by +Winnecke. He found that its position, as indicated by Scheiner, agrees +with that of the Bonn <i>Durchmusterung</i> star 15°, 2083 (8½ magnitude). +This star is not a known variable. Winnecke watched it for 17 years, but +found no variation of light. From Scheiner’s recorded observations his +star seems to have reached the 6th magnitude, which is considerably +brighter than the <i>Durchmusterung</i> star watched by Winnecke.<a name='fna_348' id='fna_348' href='#f_348'><small>[348]</small></a></p> + +<p>With reference to the colours of the stars, the supposed change of colour +in Sirius from red to white is well known, and will be considered in the +chapter on the Constellations. The bright star Arcturus has also been +suspected of variation in colour. About the middle of the nineteenth +century Dr. Julius Schmidt, of Athens, the well-known observer of variable +stars, thought it one of the reddest stars in the sky, especially in the +year<span class="pagenum"><a name="Page_189" id="Page_189">[Pg 189]</a></span> 1841, when he found its colour comparable with that of the planet +Mars.<a name='fna_349' id='fna_349' href='#f_349'><small>[349]</small></a> In 1852, however, he was surprised to find it yellow and devoid +of any reddish tinge; in colour it was lighter than that of Capella. In +1863, Mr. Jacob Ennis found it “decidedly orange.” Ptolemy and Al-Sufi +called it red.</p> + +<p>Mr. Ennis speaks of Capella as “blue” (classing it with Rigel), and +comparing its colour with that of Vega!<a name='fna_350' id='fna_350' href='#f_350'><small>[350]</small></a> But the present writer has +never seen it of this colour. To his eye it seems yellowish or orange. It +was called red by Ptolemy, El Fergani, and Riccioli; but Al-Sufi says +nothing about its colour.</p> + +<p>Of β Ursæ Minoris, Heis, the eminent German astronomer said, “I +have had frequent opportunities of convincing myself that the colour of +this star is not always equally red; at times it is more or less yellow, +at others most decidedly red.”<a name='fna_351' id='fna_351' href='#f_351'><small>[351]</small></a></p> + +<p>Among double stars there are many cases in which variation of colour has +been suspected. In some of these the difference in the recorded colour may +possibly be due to “colour blindness” in some of the observers; but in +others there seems to be good evidence in favour of a change. The +following may be mentioned:—</p> + +<p><span class="pagenum"><a name="Page_190" id="Page_190">[Pg 190]</a></span>η Cassiopeiæ. Magnitudes of the components about 4 and 7½. +Recorded as red and green by Sir John Herschel and South; but yellow and +orange by Sestini.</p> + +<p>ι Trianguli. Magnitudes 5½ and 7. Secchi estimated them as +white or yellow and blue; but Webb called them yellow and green (1862).</p> + +<p>γ Leonis, 2 and 3½. Sir William Herschel noted them white and +reddish white; but Webb, light orange and greenish yellow.</p> + +<p>12 Canum Venaticorum, 2½ and 6½. White and red, Sir William +Herschel; but Sir John Herschel says in 1830, “With all attention I could +perceive no contrast of colours in the two stars.” Struve found them both +white in 1830, thus agreeing with Sir John Herschel. Sestini saw them +yellow and blue in 1844; Smyth, in 1855, pale reddish white and lilac; +Dembowski, in 1856, white and pale olive blue; and Webb, in 1862, flushed +white and pale lilac.</p> + +<p>On October 13, 1907, Nova Persei, the great new star of 1901, was +estimated to be only 11·44 magnitude, or about 11½. When at its +brightest this famous star was about zero magnitude; so that it has in +about 6 years faded about 11½ magnitudes in brightness; in other words, +it has been reduced to <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">40000</span> of its greatest brilliancy!</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_191" id="Page_191">[Pg 191]</a></span></p> +<h2><a name="CHAPTER_XVII" id="CHAPTER_XVII"></a>CHAPTER XVII</h2> +<p class="title">Nebulæ and Clusters</p> + +<p> </p> +<p class="dropcap"><span class="caps">In</span> his interesting and valuable work on “The Stars,” the late Prof. +Newcomb said—</p> + +<div class="blockquot"><p>“Great numbers of the nebulæ are therefore thousands of times the +dimensions of the earth’s orbit, and most of them are thousands of +times the dimensions of the whole solar system. That they should be +completely transparent through such enormous dimensions shows their +extreme tenuity. Were our solar system placed in the midst of one of +them it is probable that we should not be able to find any evidence of +its existence”!</p></div> + +<p>Prof. Perrine thinks that the total number of the nebulæ will ultimately +be found to exceed a million.<a name='fna_352' id='fna_352' href='#f_352'><small>[352]</small></a></p> + +<p>Dr. Max Wolf has discovered a number of small nebulæ in the regions near +Algol and Nova Persei (the great “new star” of 1901). He says, “They +mostly lie in two bands,” and are especially numerous where the two bands +meet, a region of 12 minutes of arc square containing no less than 148 of +them. They are usually “round with<span class="pagenum"><a name="Page_192" id="Page_192">[Pg 192]</a></span> central condensation,” and form of +Andromeda nebula.<a name='fna_353' id='fna_353' href='#f_353'><small>[353]</small></a></p> + +<p>Some small nebulæ have been found in the vicinity of the globular +clusters. They are described by Prof. Perrine as very small and like an +“out of focus” image of a small star. “They appear to be most numerous +about clusters which are farthest from the galaxy.” Prof. Perrine says, +“Practically all the small nebulæ about the globular clusters are +elliptical or circular. Those large enough to show structure are spirals. +Doubtless the majority of these are spirals.”<a name='fna_354' id='fna_354' href='#f_354'><small>[354]</small></a> This seems further +evidence in favour of the “spiral nebular hypothesis” of Chamberlin and +Moulton.</p> + +<p>A great photographic nebula in Orion was discovered by Prof. Barnard in +1894. In a drawing he gives of the nebula,<a name='fna_355' id='fna_355' href='#f_355'><small>[355]</small></a> it forms a long streak +beginning a little south of γ Orionis (Bellatrix), passing +through the star 38 Orionis north of 51 and south of 56 and 60 Orionis. +Then turning south it sweeps round a little north of κ Orionis; +then over 29 Orionis, and ends a little to the west of η Orionis. +There is an outside patch west of Rigel. Barnard thinks that the whole +forms a vast spiral structure; probably connected with the “great nebula” +in the “sword of Orion,” which it surrounds.</p> + +<p><span class="pagenum"><a name="Page_193" id="Page_193">[Pg 193]</a></span>From calculations of the brightness of surface (“intrinsic brightness”) of +several “planetary” nebulæ made by the present writer in the year 1905, he +finds that the luminosity is very small compared with that of the moon. +The brightest of those examined (<i>h</i> 3365, in the southern hemisphere, +near the Southern Cross) has a surface luminosity of only +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">400</span> of that of +the moon.<a name='fna_356' id='fna_356' href='#f_356'><small>[356]</small></a> The great nebulæ in Orion and Andromeda seem to have “still +smaller intrinsic brightness.”</p> + +<p>Arago says—</p> + +<div class="blockquot"><p>“The spaces which precede or which follow simple nebulæ, and <i>a +fortiori</i> groups of nebulæ, contain generally few stars. Herschel +found this rule to be invariable. Thus every time that, during a short +interval, no star appeared, in virtue of the diurnal motion, to place +itself in the field of his motionless telescope, he was accustomed to +say to the secretary who assisted him (Miss Caroline Herschel), +‘Prepare to write; nebulæ are about to arrive.’”<a name='fna_357' id='fna_357' href='#f_357'><small>[357]</small></a></p></div> + +<p>Commenting on this remark of Arago, the late Herbert Spencer says—</p> + +<div class="blockquot"><p>“How does this fact consist with the hypothesis that nebulæ are remote +galaxies? If there were but one nebula, it would be a curious +coincidence were this one nebula so placed in the distant regions of +space as to agree in direction with a starless spot in our sidereal +system! If there were but two nebulæ, and both were so placed, the +coincidence would be excessively strange.<span class="pagenum"><a name="Page_194" id="Page_194">[Pg 194]</a></span> What shall we say on +finding that they are habitually so placed? (the last five words +replace some that are possibly a little too strong).... When to the +fact that the general mass of nebulæ are antithetical in position to +the general mass of the stars, we add the fact that local regions of +nebulæ are regions where stars are scarce, and the further fact that +single nebulæ are habitually found in comparatively starless spots, +does not the proof of a physical connection become overwhelming?”<a name='fna_358' id='fna_358' href='#f_358'><small>[358]</small></a></p></div> + +<p>With reference to the small elongated nebula discovered by Miss Caroline +Herschel in 1783 near the great nebula in Andromeda, Admiral Smyth says, +“It lies between two sets of stars, consisting of four each, and each +disposed like the figure 7, the preceding group being the smallest.”<a name='fna_359' id='fna_359' href='#f_359'><small>[359]</small></a></p> + +<p>Speaking of the “nebula” Messier 3—a globular cluster in Canes +Venatici—Admiral Smyth says, “This mass is one of those balls of compact +and wedged stars whose laws of aggregation it is so impossible to assign; +but the rotundity of the figure gives full indication of some general +attractive bond of union.”<a name='fna_360' id='fna_360' href='#f_360'><small>[360]</small></a> The terms “compact and wedged” are, +however, too strong, for we know that in the globular clusters the +component stars must be separated from each other by millions of miles!</p> + +<p>Prof. Chamberlin suggests that the secondary nebula (as it is called) in +the great spiral in Canes<span class="pagenum"><a name="Page_195" id="Page_195">[Pg 195]</a></span> Venatici (Messier 51) may possibly represent +the body which collided with the other (the chief nucleus) in a grazing +collision, and is now escaping. He considers this secondary body to have +been “a dead sun”—that is, a dark body.<a name='fna_361' id='fna_361' href='#f_361'><small>[361]</small></a> This would be very +interesting if it could be proved. But it seems to me more probable that +the secondary nucleus is simply a larger portion of the ejected matter, +which is now being gradually detached from the parent mass.</p> + +<p>Scheiner says “the previous suspicion that the spiral nebulæ are star +clusters is now raised to a certainty,” and that the spectrum of the +Andromeda nebula is very similar to that of the sun. He says there is “a +surprising agreement of the two, even in respect to the relative intensity +of the separate spectral regions.”<a name='fna_362' id='fna_362' href='#f_362'><small>[362]</small></a></p> + +<p>In the dynamical theory of spiral nebulæ, Dr. E. J. Wilczynski thinks that +the age of a spiral nebula may be indicated by the number of its coils; +those having the largest number of coils being the oldest, from the point +of view of evolution.<a name='fna_363' id='fna_363' href='#f_363'><small>[363]</small></a> This seems to be very probable.</p> + +<p>In the spectrum of the gaseous nebulæ, the F line of hydrogen (Hβ) +is visible, but not the C line (Hα). The invisibility of the +C line is explained by Scheiner as due to a physiological<span class="pagenum"><a name="Page_196" id="Page_196">[Pg 196]</a></span> cause, “the eye +being less sensitive to that part of the spectrum in which the line +appears than to the part containing the F line.”<a name='fna_364' id='fna_364' href='#f_364'><small>[364]</small></a></p> + +<p>An apparent paradox is found in the case of the gaseous nebulæ. The +undefined outlines of these objects render any attempt at measuring their +parallax very difficult, if not impossible. Their distance from the earth +is therefore unknown, and perhaps likely to remain so for many years to +come. It is possible that they may not be farther from us than some of the +stars visible in their vicinity. On the other hand, they may lie far +beyond them in space. But whatever their distance from the earth may be, +it may be easily shown that their attraction on the sun is directly +proportioned to their distance—that is, the greater their distance, the +greater the attraction! This is evidently a paradox, and rather a +startling one too. But it is nevertheless mathematically true, and can be +easily proved. For, <i>their distance being unknown</i>, they may be of any +dimensions. They might be comparatively small bodies relatively near the +earth, or they may be immense masses at a vast distance from us. The +latter is, of course, the more probable. In either case the <i>apparent</i> +size would be the same. Take the case of any round gaseous nebula. +Assuming it to be of a globular form, its <i>real</i> diameter will depend on +its distance from<span class="pagenum"><a name="Page_197" id="Page_197">[Pg 197]</a></span> the earth—the greater the distance, the greater the +diameter. Now, as the volumes of spheres vary as the cubes of their +diameters, it follows that the volume of the nebula will vary as the cube +of its distance from the earth. As the mass of an attracting body depends +on its volume and density, its real mass will depend on the cube of its +distance, the density (although unknown) being a fixed quantity. If at a +certain distance its mass is <i>m</i>, at double the distance (the <i>apparent</i> +diameter being the same) it would have a mass of eight times <i>m</i> (8 being +the cube of 2), and at treble the distance its mass would be 27 <i>m</i>, and +so on, its <i>apparent</i> size being known, but not its <i>real</i> size. This is +obvious. Now, the attractive power of a body varies directly as its +mass—the greater the mass, the greater the attraction. Again, the +attraction varies <i>inversely</i> as the square of the distance, according to +the well-known law of Newton. Hence if <i>d</i> be the unknown distance of the +nebula, we have its attractive power varying as <i>d</i><sup>3</sup> divided by <i>d</i><sup>2</sup>, +or directly as the distance <i>d</i>. We have then the curious paradox that for +a nebula whose distance from the earth is unknown, its attractive power on +the sun (or earth) will vary directly as the distance—the greater the +distance the greater the attraction, and, of course, conversely, the +smaller the distance the less the attractive power. This result seems at +first sight absurd and incredible,<span class="pagenum"><a name="Page_198" id="Page_198">[Pg 198]</a></span> but a little consideration will show +that it is quite correct. Consider a small wisp of cloud in our +atmosphere. Its mass is almost infinitesimal and its attractive power on +the earth practically <i>nil</i>. But a gaseous nebula having the same +<i>apparent size</i> would have an enormous volume, and, although probably +formed of very tenuous gas, its mass would be very great, and its +attractive power considerable. The large apparent size of the Orion nebula +shows that its volume is probably enormous, and as its attraction on the +sun is not appreciable, its density must be excessively small, less than +the density of the air remaining in the receiver of the best air-pump +after the air has been exhausted. How such a tenuous gas can shine as it +does forms another paradox. Its light is possibly due to some +phosphorescent or electrical action.</p> + +<p>The apparent size of “the great nebula in Andromeda” shows that it must be +an object of vast dimensions. The nearest star to the earth, Alpha +Centauri, although probably equal to our sun in volume, certainly does not +exceed one-hundredth of a second in diameter as seen from the earth. But +in the case of the Andromeda nebula we have an object of considerable +apparent size, not measured by seconds of arc, but showing an area about +three times greater than that of the full moon. The nebula certainly lies +in the region of the stars—much farther off than<span class="pagenum"><a name="Page_199" id="Page_199">[Pg 199]</a></span> Alpha Centauri—and its +great apparent size shows that it must be of stupendous dimensions. A +moment’s consideration will show that whatever its distance may be, the +farther it is from the earth the larger it must be in actual size. The sun +is vastly larger than the moon, but its apparent size is about the same +owing to its greater distance. Sir William Herschel thought the Andromeda +nebula to be “undoubtedly the nearest of all the great nebulæ,” and he +estimated its distance at 2000 times the distance of Sirius. This would +not, however, indicate a relatively near object, as it would imply a +“light journey” of over 17,000 years! (The distance of Sirius is about 88 +“light years.”)</p> + +<p>It has been generally supposed that this great nebula lies at a vast +distance from the earth, possibly far beyond most of the stars seen in the +same region of the sky; but perhaps not quite so far as Herschel’s +estimate would imply. Recently, however, Prof. Bohlin of Stockholm has +found from three series of measures made in recent years a parallax of +0″·17.<a name='fna_365' id='fna_365' href='#f_365'><small>[365]</small></a></p> + +<p>This indicates a distance of 1,213,330 times the sun’s distance from the +earth, and a “light journey” of about 19 years. This would make the +distance of the nebula more than twice the distance of Sirius, about four +times the distance of α Centauri, but less than that of Capella.</p> + +<p><span class="pagenum"><a name="Page_200" id="Page_200">[Pg 200]</a></span>Prof. Bohlin’s result is rather unexpected, and will require confirmation +before it can be accepted. But it will be interesting to inquire what this +parallax implies as to the real dimensions and probable mass of this vast +nebula. The extreme length of the nebula may be taken to represent its + +diameter considered as circular. For, although a circle seen obliquely is +always foreshortened into an ellipse, still the longer axis of the ellipse +will always represent the real diameter of the circle. This may be seen by +holding a penny at various angles to the eye. Now, Dr. Roberts found that +the apparent length of the Andromeda nebula is 2⅓ degrees, or 8400 +seconds of arc. The diameter in seconds divided by the parallax will give +the real diameter of the nebula in terms of the sun’s distance from the +earth taken as unity. Now, 8400 divided by 0″·17 gives nearly 50,000, that +is, the real diameter of the Andromeda nebula would be—on Bohlin’s +parallax—nearly 50,000 times the sun’s distance from the earth. As light +takes about 500 seconds to come from the sun to the earth, the above +figures imply that light would take about 290 days, or over 9 months to +cross the diameter of this vast nebula.</p> + +<p>Elementary geometrical considerations will show that if the Andromeda +nebula lies at a greater distance from the earth than that indicated by +Bohlin’s parallax, its real diameter, and therefore its volume and mass, +will be greater. If, therefore,<span class="pagenum"><a name="Page_201" id="Page_201">[Pg 201]</a></span> we assume the parallax found by Bohlin, +we shall probably find a <i>minimum</i> value for the size and mass of this +marvellous object.</p> + +<p>Among Dr. Roberts’ photographs of spiral nebulæ (and the Andromeda nebula +is undoubtedly a spiral) there are some which are apparently seen nearly +edgeways, and show that these nebulæ are very thin in proportion to their +diameter. From a consideration of these photographs we may, I think, +assume a thickness of about one-hundredth of the diameter. This would give +a thickness for the Andromeda nebulæ of about 500 times the sun’s distance +from the earth. This great thickness will give some idea of the vast +proportions of the object we are dealing with. The size of the whole solar +system—large as it is—is small in comparison. The diameter and thickness +found above can easily be converted into miles, and from these dimensions +the actual volume of the nebula can be compared with that of the sun. It +is merely a question of simple mensuration, and no problem of “high +mathematics” is involved. Making the necessary calculations, I find that +the volume of the Andromeda nebula would be about 2·32 trillion times +(2·32 × 10<sup>18</sup>) the sun’s volume! Now, assuming that the nebulous matter +fills only one-half of the apparent volume of the nebula (allowing for +spaces between the spiral branches), we have the volume = 1·16 × 10<sup>18</sup>. +If the nebula had the same<span class="pagenum"><a name="Page_202" id="Page_202">[Pg 202]</a></span> density as the sun, this would be its mass in +terms of the sun’s mass taken as unity, a mass probably exceeding the +combined mass of all the <i>stars</i> visible in the largest telescopes! But +this assumption is, of course, inadmissible, as the sun is evidently quite +opaque, whereas the nebula is, partially at least, more or less +transparent. Let us suppose that the nebula has a <i>mean</i> density equal to +that of atmospheric air. As water is about 773 times heavier than air, and +the sun’s density is 1·4 (water = 1) we have the mass of the nebula equal +to 1·16 × 10<sup>18</sup> divided by 773 × 1·4, or about 10<sup>15</sup> times the sun’s +mass, which is still much greater than the probable combined mass of all +the <i>visible</i> stars. As it seems unreasonable to suppose that the mass of +an individual member of our sidereal system should exceed the combined +mass of the remainder of the system, we seem compelled to further reduce +the density of the Andromeda nebula. Let us assume a mean density of, say, +a millionth of hydrogen gas (a sufficiently low estimate) which is about +14·44 times lighter than air, and we obtain a mass of about 8 × 10<sup>7</sup> or +80 million times the mass of the sun, which is still an enormous mass.</p> + +<p>As possibly I may have assumed too great a thickness for the nebula, let +us take a thickness of one-tenth of that used above, or one thousandth of +the length of the nebula. This gives a mass of 8 million times the sun’s +mass. This seems<span class="pagenum"><a name="Page_203" id="Page_203">[Pg 203]</a></span> a more probable mass if the nebula is—as Bohlin’s +parallax implies—a member of our sidereal system.</p> + +<p>If we assume a parallax of say 0″·01—or one-hundredth of a second of +arc—which would still keep the nebula within the bounds of our sidereal +system—we have the dimensions of the nebula increased 17 times, and hence +its mass nearly 5000 times greater (17<sup>3</sup>) than that found above. The mass +would then be 40,000 million times the sun’s mass! This result seems +highly improbable, for even this small parallax would imply a light +journey of only 326 years, whereas the distance of the Milky Way has been +estimated by Prof. Newcomb at about 3000 years’ journey for light.</p> + +<p>In Dr. Roberts’ photograph many small stars are seen scattered over the +surface of the nebula; but these do not seem to be quite so numerous as in +the surrounding sky. If the nebula lies nearer to us than the fainter +stars visible on the photograph, some of them may be obscured by the +denser portions of the nebula; some may be visible through the openings +between the spiral branches; while others may be nearer to us and simply +projected on the nebula.</p> + +<p>To add to the difficulty of solving this celestial problem, the +spectroscope shows that the Andromeda nebula is not gaseous. The spectrum +is, according to Scheiner, very similar to that of the sun, and “there is +a surprising agreement of<span class="pagenum"><a name="Page_204" id="Page_204">[Pg 204]</a></span> the two, even in respect to the relative +intensities of the separate spectral regions.”<a name='fna_366' id='fna_366' href='#f_366'><small>[366]</small></a> He thinks that “the +greater part of the stars comprising the nucleus of the nebula belong to +the second spectral class” (solar), and that the nebula “is now in an +advanced stage of development. No trace of bright nebular lines are +present, so that the interstellar space in the Andromeda nebula, just as +in our stellar system, is not appreciably occupied by gaseous +matter.”<a href='#f_366'><small>[366]</small></a> He suggests that the inner part of the nebula [the +“nucleus”] “corresponds to the complex of those stars which do not belong +to the Milky Way, while the latter corresponds to the spirals of the +Andromeda nebula.”<a href='#f_366'><small>[366]</small></a> On this view of the matter we may suppose that the +component particles are small bodies widely separated, and in this way the +<i>mean</i> density of the Andromeda nebula may be very small indeed. They +cannot be large bodies, as the largest telescopes have failed to resolve +the nebula into stars, and photographs show no sign of resolution.</p> + +<p>It has often been suggested, and sometimes definitely stated, that the +Andromeda nebula may possibly be an “external” universe, that is an +universe entirely outside our sidereal system, and comparable with it in +size. Let us examine the probability of such hypothesis. Assuming that the +nebula has the same diameter as the Milky<span class="pagenum"><a name="Page_205" id="Page_205">[Pg 205]</a></span> Way, or about 6000 “light +years,” as estimated by Prof. Newcomb, I find that its distance from the +earth would be about 150,000 “light years.” As this is about 8000 times +the distance indicated by Bohlin’s parallax, its dimensions would be 8000 +times as great, and hence its volume and mass would be 8000 cubed, or +512,000,000,000 times greater than that found above. That is, about 4 +trillion (4 × 10<sup>18</sup>) times the sun’s mass! As this appears an incredibly +large mass to be compressed into a volume even so large as that of our +sidereal system, we seem compelled to reject the hypothesis that the +nebula represents an external universe. The sun placed at the distance +corresponding to 150,000 light years would, I find, shine as a star of +less than the 23rd magnitude, a magnitude which would be invisible in the +largest telescope that man could ever construct. But the combined light of +4 trillion of stars of even the 23rd magnitude would be equal to one of +minus 23·5 magnitude, that is, 23½ magnitude brighter than the zero +magnitude, or not very much inferior to the sun in brightness. As the +Andromeda nebula shines only as a star of about the 5th magnitude the +hypothesis of an external universe seems to be untenable.</p> + +<p>It is evident, however, that the mass of the Andromeda nebula must be +enormous; and if it belongs to our sidereal system, and if the other great +nebulæ have similar masses, it seems quite<span class="pagenum"><a name="Page_206" id="Page_206">[Pg 206]</a></span> possible that the mass of the +<i>visible</i> universe may much exceed that of the <i>visible</i> stars, and may be +equal to 1000 million times the sun’s mass—as supposed by the late Lord +Kelvin—or even much more.</p> + +<p>With reference to the small star which suddenly blazed out near the +nucleus of the Andromeda nebula in August, 1885, Prof. Seeliger has +investigated the decrease in the light of the star on the hypothesis that +it was a cooling body which had suddenly been raised to an intense heat by +the shock of a collision, and finds a fair agreement between theory and +observation. Prof. Auwers points out the similarity between this outburst +and that of the “temporary star” of 1860, which appeared in the cluster 80 +Messier, and he thinks it very probable that both phenomena were due to +physical changes in the nebulæ in which they appeared.</p> + +<p>The appearance of this temporary star in the Andromeda nebula seems to +afford further evidence against the hypothesis of the nebula being an +external universe. For, as I have shown above, our sun, if placed at a +distance of 150,000 light years, would shine only as a star of the 23rd +magnitude, or over 15 magnitudes fainter than the temporary star. This +would imply that the star shone with a brightness of over a million times +that of the sun, and would therefore indicate a body of enormous size. But +the rapid<span class="pagenum"><a name="Page_207" id="Page_207">[Pg 207]</a></span> fading of its light would, on the contrary, imply a body of +comparatively small dimensions. We must, therefore, conclude that the +nebula, whatever it may be, is not an external universe, but forms a +member of our own sidereal system.</p> + +<p>In Sir John Herschel’s catalogue of Nebulæ and Clusters of Stars, +published in 1833, in the <i>Philosophical Transactions</i> of the Royal +Society, there are many curious objects mentioned. Of these I have +selected the following:—</p> + +<p>No. 496 is described as “a superb cluster which fills the whole field; +stars 9, 10 ... 13 magnitude and none below, but the whole ground of the +sky on which it stands is singularly dotted over with infinitely minute +points.” This is No. 22 of Sir William Herschel’s 6th class, and will be +found about 3 degrees south and a little east of the triple star 29 +Monocerotis.</p> + +<p>No. 650. This object lies about 3 degrees north of the star μ +Leonis, the most northern of the bright stars in the well-known “Sickle,” +and is thus described by Sir John Herschel: “A star 12th magnitude with an +extremely faint nebulous atmosphere about 10″ to 12″. It is between a star +8-9 magnitude north preceding, and one 10th magnitude south following, +neither of which are so affected. A curious object.”</p> + +<p>No. 1558. Messier 53. A little north-east of the star α Comæ +Berenices. Described as “a most beautiful highly compressed cluster. +Stars<span class="pagenum"><a name="Page_208" id="Page_208">[Pg 208]</a></span> very small, 12th ... 20th magnitude, with scattered stars to a +considerable distance; irregularly round, but not globular. Comes up to a +blaze in the centre; indicating a round mass of pretty equable density. +Extremely compressed. A most beautiful object. A mass of close-wedged +stars 5′ in diameter; a few 12th magnitude, the rest of the smallest size +and innumerable.” Webb says, “Not very bright with 3<span style="font-size: 0.8em;"><sup>7</sup></span>⁄<span style="font-size: 0.6em;">10</span> inches; +beautiful with 9 inches.” This should be a magnificent object with a very +large telescope, like the Lick or Yerkes.</p> + +<p>No. 2018. “A more than usually condensed portion of the enormous cluster +of the Milky Way. The field has 200 or 300 stars in it at once.” This lies +about 2° south-west of the star 6 Aquilæ, which is near the northern edge +of the bright spot of Milky Way light in “Sobieski’s Shield”—one of the +brightest spots in the sky.</p> + +<p>No. 2093. “A most wonderful phenomenon. A very large space 20′ or 30′ +broad in Polar Distance, and 1<sup>m</sup> or 2<sup>m</sup> in Right Ascension, full of +nebula and stars mixed. The nebula is decidedly attached to the stars, and +is as decidedly not stellar. It forms irregular lace-work marked out by +stars, but some parts are decidedly nebulous, wherein no star can be +seen.” Sir John Herschel gives a figure of this curious spot, which he +says represents its “general character, but not the minute<span class="pagenum"><a name="Page_209" id="Page_209">[Pg 209]</a></span> details of +this object, which would be extremely difficult to give with any degree of +fidelity.” It lies about 3 degrees west of the bright star ζ +Cygni.</p> + +<p>Among the numerous curious objects observed by Sir John Herschel during +his visit to the Cape of Good Hope, the following may be mentioned:—</p> + +<p><i>h</i> 2534 (H iv. 77). Near τ<sup>4</sup> Eridani. Sir John Herschel says, +“Attached cometically to a 9th magnitude star which forms its head. It is +an exact resemblance to Halley’s comet as seen in a night glass.”... “A +complete telescopic comet; a perfect miniature of Halley’s comet, only the +tail is rather broader in proportion.”<a name='fna_367' id='fna_367' href='#f_367'><small>[367]</small></a></p> + +<p><i>h</i> 3075. Between γ Monocerotis and γ Canis Majoris. “A +very singular nebula, and much like the profile of a bust (head, neck, and +shoulders) or a silhouette portrait, very large, pretty well defined, +light nearly uniform, about 12′ diameter. In a crowded field of Milky Way +stars, many of which are projected on it.”<a name='fna_368' id='fna_368' href='#f_368'><small>[368]</small></a></p> + +<p><i>h</i> 3315 (Dunlop 323). In the Milky Way; about 3° east of the Eta Argûs +nebula. Sir John Herschel says, “A glorious cluster of immense magnitude, +being at least 2 fields in extent every way. The stars are 8, 9, 10, and +11th magnitudes, but chiefly 10th magnitude, of which there must be at +least 200. It is the most brilliant object of the kind I have ever seen” +... “has several<span class="pagenum"><a name="Page_210" id="Page_210">[Pg 210]</a></span> elegant double stars, and many orange-coloured +stars.”<a name='fna_369' id='fna_369' href='#f_369'><small>[369]</small></a> This should form a fine object in even a comparatively small +telescope, and may be recommended to observers in the southern hemisphere. +A telescope of 3-inches aperture should show it well.</p> + +<p>Among astronomical curiosities may be counted “clusters within clusters.” +A cluster in Gemini (N.G.C. 2331) has a small group of “six or seven stars +close together and well isolated from the rest.”</p> + +<p>Lord Rosse describes No. 4511 of Sir John Herschel’s General Catalogue of +Nebulæ and Clusters (<i>Phil. Trans.</i>, 1864) as “a most gorgeous cluster, +stars 12-15 magnitude, full of holes.”<a name='fna_370' id='fna_370' href='#f_370'><small>[370]</small></a> His sketch of this cluster +shows 3 rings of stars in a line, each ring touching the next on the +outside. Sir John Herschel described it as “Cluster; very large; very +rich; stars 11-15 magnitude (Harding, 1827),” but says nothing about the +rings. This cluster lies about 5 degrees south of δ Cygni.</p> + +<p>Dr. See, observing with the large telescope of the Lowell Observatory, +found that when the sky is clear, the moon absent, and the seeing perfect, +“the sky appeared in patches to be of a brownish colour,” and suggests +that this colour owes its existence to immense cosmical clouds, which are +shining by excessively feeble light!<span class="pagenum"><a name="Page_211" id="Page_211">[Pg 211]</a></span> Dr. See found that these brown +patches seem to cluster in certain regions of the Milky Way.<a name='fna_371' id='fna_371' href='#f_371'><small>[371]</small></a></p> + +<p>From a comparison of Trouvelot’s drawing of the small elongated nebula +near the great nebula in Andromeda with recent photographs, Mr. Easton +infers that this small nebula has probably rotated through an angle of +about 15° in 25 years. An examination I have made of photographs taken in +different years seems to me to confirm this suspicion, which, if true, is +evidently a most interesting phenomenon.</p> + +<p>Dr. Max Wolf of Heidelberg finds, by spectrum photography, that the +well-known “ring nebula” in Lyra consists of four rings composed of four +different gases. Calling the inner ring A, the next B, the next C, and the +outer D, he finds that A is the smallest ring, and is composed of an +unknown gas; the next largest, B, is composed of hydrogen gas; the next, +C, consists of helium gas; and the outer and largest ring, D, is +composed—like A—of an unknown gas. As the molecular weight of hydrogen +is 2·016, and that of helium is 3·96, Prof. Bohuslav Brauner suggests that +the molecular weight of the gas composing the inner ring A is smaller than +that of hydrogen, and the molecular weight of the gas forming the outer +ring D is greater than that of helium. He also suggests that the gas of +ring A may possibly be identical with the “coronium” of the solar<span class="pagenum"><a name="Page_212" id="Page_212">[Pg 212]</a></span> corona, +for which Mendelief found a hypothetical atomic and molecular weight of +0·4.<a name='fna_372' id='fna_372' href='#f_372'><small>[372]</small></a></p> + +<p>With reference to the nebular hypothesis of Laplace, Dr. A. R. Wallace +argues that “if there exists a sun in a state of expansion in which our +sun was when it extended to the orbit of Neptune, it would, even with a +parallax of <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">60</span>th of a second, show a disc of half a second, which could +be seen with the Lick telescope.” My reply to this objection is, that with +such an expansion there would probably be very little “intrinsic +brightness,” and if luminous enough to be visible the spectrum would be +that of a gaseous nebula, and no known <i>star</i> gives such a spectrum. But +some planetary nebulæ look like small stars, and with high powers on large +telescopes would probably show a disc. On these considerations, Dr. +Wallace’s objection does not seem to be valid.</p> + +<p>It is usually stated in popular works on astronomy that the spectra of +gaseous nebulæ show only three or four bright lines on a faint continuous +background. But this is quite incorrect. No less than forty bright lines +have been seen and measured in the spectra of gaseous nebulæ.<a name='fna_373' id='fna_373' href='#f_373'><small>[373]</small></a> This +includes 2 lines of “nebulium,” 11 of hydrogen, 5 of helium, 1 of oxygen +(?), 3 of nitrogen (?), 1 of silicon (?), and 17 of an unknown substance. +In the great nebulæ in Orion 30 bright lines have been photographed.<a name='fna_374' id='fna_374' href='#f_374'><small>[374]</small></a></p> + +<p><span class="pagenum"><a name="Page_213" id="Page_213">[Pg 213]</a></span>D’Arrest found that “gaseous +nebulæ are rarely met with outside the Milky Way, and never at a considerable distance from it.”<a name='fna_375' id='fna_375' href='#f_375'><small>[375]</small></a></p> + +<p>Mr. A. E. Fath thinks that “no spiral nebula investigated has a truly +continuous spectrum.” He finds that so feeble is the intensity of the +light of the spiral nebulæ that, while a spectrogram of Arcturus can be +secured with the Mills spectrograph “in less than two minutes,” “an +exposure of about 500 hours would be required for the great nebula in +Andromeda, which is of the same spectral type.”<a name='fna_376' id='fna_376' href='#f_376'><small>[376]</small></a> Mr. Fath thinks that +in the case of the Andromeda nebula, the “star cluster” theory “seems to +be the only one that can at all adequately explain the spectrum +obtained.”<a name='fna_377' id='fna_377' href='#f_377'><small>[377]</small></a></p> + +<p>Prof. Barnard finds that the great cluster in Hercules (Messier 13) is +“composed of stars of different spectral types.” This result was confirmed +by Mr. Fath.<a name='fna_378' id='fna_378' href='#f_378'><small>[378]</small></a></p> + +<p>From observations with the great 40-inch telescope of the Yerkes +Observatory (U.S.A.), Prof. Barnard finds that the nucleus of the planetary +nebula H. iv. 18 in Andromeda is variable to the extent of at least 3 +magnitudes. At its brightest it is about the 12th magnitude; and the +period seems to be about 28 days. Barnard says, “I think this is the first +case in<span class="pagenum"><a name="Page_214" id="Page_214">[Pg 214]</a></span> which the nucleus of a planetary or other nebula has been shown +to be certainly variable.” “The normal condition seems to be faint—the +nucleus remaining bright for a few days only. In an ordinary telescope it +looks like a small round disc of a bluish green colour.” He estimated the +brightness of the nebula as that of a star of 8·2 magnitude.<a name='fna_379' id='fna_379' href='#f_379'><small>[379]</small></a> Even in +a telescope of 4 inches aperture, this would be a fairly bright object. It +lies about 3½ degrees south-west of the star ι Andromedæ.</p> + +<p>The so-called “globular clusters” usually include stars of different +brightness; comparatively bright telescopic stars of the 10th to 13th +magnitude with faint stars of the 15th to 17th magnitude. Prof. Perrine of +the Lick Observatory finds that (<i>a</i>) “the division of the stars in +globular clusters into groups, differing widely in brightness, is +characteristic of these objects”; (<i>b</i>) “the globular clusters are devoid +of true nebulosity”; and (<i>c</i>) “stars fainter than 15th magnitude +predominate in the Milky Way and globular clusters, but elsewhere are +relatively scarce.” He found that “exposures of one hour or thereabouts +showed as many stars as exposures four to six times as long; the only +effect of the longer exposures being in the matter of density.” This last +result confirms the late Dr. Roberts’ conclusions. Perrine finds that for +clusters in the Milky Way, the faint stars (15th to 17th magnitude) “are +about as<span class="pagenum"><a name="Page_215" id="Page_215">[Pg 215]</a></span> numerous in proportion to the bright stars (10th to 13th +magnitude) as in the globular clusters themselves.” This is, however, not +the case with globular clusters at a distance from the Milky Way. In these +latter clusters he found that “in the regions outside the limits of the +cluster there are usually very few faint stars, hardly more than +one-fourth or one-tenth as many as there are bright stars”; and he thinks +that “this paucity of faint stars” in the vicinity of these clusters +“gives rise to the suspicion that all regions at a distance from the +Galaxy may be almost devoid of these very faint stars.” The late Prof. +Keeler’s series of nebular photographs “in or near the Milky Way” tend to +confirm the above conclusions. Perrine finds the northernmost region of +the Milky Way “to be almost, if not entirely, devoid of globular +clusters.”<a name='fna_380' id='fna_380' href='#f_380'><small>[380]</small></a></p> + +<p>According to Sir John Herschel, “the sublimity of the spectacle afforded” +by Lord Rosse’s great telescope of 6 feet in diameter of some of the +“larger globular and other clusters” “is declared by all who have +witnessed it, to be such that no words can express.”<a name='fna_381' id='fna_381' href='#f_381'><small>[381]</small></a></p> + +<p>In his address to the British Association at Leicester in 1907, Sir David +Gill said—</p> + +<div class="blockquot"><p>“Evidence upon evidence has accumulated to show that nebulæ consist of +the matter out of<span class="pagenum"><a name="Page_216" id="Page_216">[Pg 216]</a></span> which stars have been and are being evolved.... The +fact of such an evolution with the evidence before us, can hardly be +doubted. I most fully believe that, when the modifications of +terrestrial spectra under sufficiently varied conditions of +temperature, pressure, and environment, have been further studied, +this connection will be greatly strengthened.”</p></div> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_217" id="Page_217">[Pg 217]</a></span></p> +<h2><a name="CHAPTER_XVIII" id="CHAPTER_XVIII"></a>CHAPTER XVIII</h2> +<p class="title">Historical</p> + +<p> </p> +<p class="dropcap"><span class="caps">The</span> grouping of the stars into constellations is of great antiquity. The +exact date of their formation is not exactly known, but an approximate +result may be arrived at from the following considerations. On the +celestial spheres, or “globes,” used by the ancient astronomers, a portion +of the southern heavens of a roughly circular form surrounding the South +Pole was left blank. This space presumably contained the stars in the +southern hemisphere which they could not see from their northern stations. +Now, the centre of this circular blank space most probably coincided with +the South Pole of the heavens at the time when the constellations were +first formed. Owing to the “Precession of the Equinoxes” this centre has +now moved away from the South Pole to a considerable distance. It can be +easily computed at what period this centre coincided with the South Pole, +and calculations show that this was the case about 2700 <span class="smcaplc">B.C.</span> The position +of this circle also indicates that the<span class="pagenum"><a name="Page_218" id="Page_218">[Pg 218]</a></span> constellations were formed at a +place between 36° and 40° north latitude, and therefore probably somewhere +in Asia Minor north of Mesopotamia. Again, the most ancient observations +refer to Taurus as the equinoxial constellation. Virgil says—</p> + +<p class="poem">“Candidus auratis aperit cum cornibus annum Taurus.”<a name='fna_382' id='fna_382' href='#f_382'><small>[382]</small></a></p> + +<p>This would indicate a date about 3000 <span class="smcaplc">B.C.</span> There is no tradition, however, +that the constellation Gemini was ever <i>seen</i> to occupy this position, so +that 3000 <span class="smcaplc">B.C.</span> seems to be the earliest date admissible.<a name='fna_383' id='fna_383' href='#f_383'><small>[383]</small></a></p> + +<p>Prof. Sayce thinks that the “signs of the Zodiac” had their origin in the +plains of Mesopotamia in the twentieth or twenty-third century <span class="smcaplc">B.C.</span>, and +Brown gives the probable date as 2084 <span class="smcaplc">B.C.</span><a name='fna_384' id='fna_384' href='#f_384'><small>[384]</small></a></p> + +<p>According to Seneca, the study of astronomy among the Greeks dates back to +about 1400 <span class="smcaplc">B.C.</span>; and the ancient constellations were already classical in +the time of Eudoxus in the fourth century <span class="smcaplc">B.C.</span> Eudoxus (408-355 <span class="smcaplc">B.C.</span>) +observed the positions of forty-seven stars visible in Greece, thus +forming the most ancient star catalogue which has been preserved. He was a +son of<span class="pagenum"><a name="Page_219" id="Page_219">[Pg 219]</a></span> Eschinus, and a pupil of Archytas and probably Plato.</p> + +<p>The work of Eudoxus was put into verse by the poet Aratus (third century +<span class="smcaplc">B.C.</span>). This poem describes all the old constellations now known, except +Libra, the Balance, which was at that time included in the Claws of the +Scorpion. About <span class="smcaplc">B.C.</span> 50, the Romans changed the Claws, or Chelæ, into +Libra. Curious to say, Aratus states that the constellation Lyra contained +no bright star!<a name='fna_385' id='fna_385' href='#f_385'><small>[385]</small></a> Whereas its principal star, Vega, is now one of the +brightest stars in the heavens!</p> + +<p>With reference to the origin of the constellations, Aratus says—</p> + +<p class="poem"><span style="margin-left: 7.5em;">“Some men of yore</span><br /> +A nomenclature thought of and devised<br /> +And forms sufficient found.”</p> + +<p>This shows that even in the time of Aratus the constellations were of +great antiquity.</p> + +<p>Brown says—</p> + +<div class="blockquot"><p>“Writers have often told us, speaking only from the depths of their +ignorance, how ‘Chaldean’ shepherds were wont to gaze at the brilliant +nocturnal sky, and to <i>imagine</i> that such and such stars resemble this +or that figure. But all this is merely the old effort to make capital +out of nescience, and the stars are before our eyes to prove the +contrary. Having already certain fixed ideas and figures in his mind, +the constellation-former, when he came to his task, applied his<span class="pagenum"><a name="Page_220" id="Page_220">[Pg 220]</a></span> +figures to the stars and the stars to his figures as harmoniously as +possible.”<a name='fna_386' id='fna_386' href='#f_386'><small>[386]</small></a> “Thus <i>e.g.</i> he arranged the stars of <i>Andromeda</i> into +the representation of a chained lady, not because they naturally +reminded him (or anybody else) of such a figure, but because he +desired to express that idea.”</p></div> + +<p>A coin of Manius Aquillus, <span class="smcaplc">B.C.</span> 94, shows four stars in Aquila, and seems +to be the oldest representation extant of a star group. On a coin of <span class="smcaplc">B.C.</span> +43, Dr. Vencontre found five stars, one of which was much larger than the +others, and concludes that it represents the Hyades (in Taurus). He +attributes the coin to P. Clodius Turrinus, who probably used the +constellation Taurus or Taurinus as a phonetic reference to his surname. A +coin struck by L. Lucretius Trio in 74 <span class="smcaplc">B.C.</span>, shows the seven stars of the +Plough, or as the ancients called them Septem Triones. Here we have an +allusion to the name of the magistrate Trio.<a name='fna_387' id='fna_387' href='#f_387'><small>[387]</small></a></p> + +<p>In a work published in Berne in 1760, Schmidt contends that the ancient +Egyptians gave to the constellations of the Zodiac the names of their +divinities, and expressed them by the signs which were used in their +hieroglyphics.<a name='fna_388' id='fna_388' href='#f_388'><small>[388]</small></a></p> + +<p>Hesiod mentions Orion, the Pleiades, Sirius, Aldebaran, and Arcturus; and +Homer refers to Orion, Arcturus, the Pleiades, the Hyades, the<span class="pagenum"><a name="Page_221" id="Page_221">[Pg 221]</a></span> Great Bear +(under the name of Amaxa, the Chariot), and the tail of the Little Bear, +or “Cynosura.”</p> + +<p>Hipparchus called the constellations Asterisms (ἀστερίσμος), +Aristotle and Hyginus Σομάτα (bodies), and Ptolemy +Σχημάτα (figures). By some they were called Μορφώσεις +(configurations), and by others Μετεώρε. Proclus called those +near the ecliptic Ζωδία (animals). Hence our modern name Zodiac.</p> + +<p>Hipparchus, Ptolemy, and Al-Sufi referred the positions of the stars to +the ecliptic. They are now referred to the equator. Aboul Hassan in the +thirteenth century (1282) was the first to use Right Ascensions and +Declinations instead of Longitudes and Latitudes. The ancient writers +described the stars by their positions in the ancient figures. Thus they +spoke of “the star in the head of Hercules,” “the bright star in the left +foot of Orion” (Rigel); but Bayer in 1603 introduced the Greek letters to +designate the brighter stars, and these are now universally used by +astronomers. These letters being sometimes insufficient, Hevelius added +numbers, but the numbers in <i>Flamsteed’s Catalogue</i> are now generally +used.</p> + +<p>Ptolemy and all the ancient writers described the constellation figures as +they are seen on globes, that is from the outside. Bayer in his Atlas, +published in 1603, reversed the figures to show them as they would be seen +from the <i>interior</i><span class="pagenum"><a name="Page_222" id="Page_222">[Pg 222]</a></span> of a hollow globe and as, of course, they are seen in +the sky. Hevelius again reversed Bayer’s figures to make them correspond +with those of Ptolemy. According to Bayer’s arrangement, Betelgeuse +(α Orionis) would be on the left shoulder of Orion, instead of +the right shoulder according to Ptolemy and Al-Sufi, and Rigel (β +Orionis) on the right foot (Bayer) instead of the left foot (Ptolemy). +This change of position has led to some confusion; but at present the +positions of the stars are indicated by their Right Ascensions and +Declinations, without any reference to their positions in the ancient +figures.</p> + +<p>The classical constellations of Hipparchus and Ptolemy number forty-eight, +and this is the number described by Al-Sufi in his “Description of the +Fixed Stars” written in the tenth century <span class="smcaplc">A.D.</span></p> + +<p>Firminicus gives the names of several constellations not mentioned by +Ptolemy. M. Fréret thought that these were derived from the Egyptian +sphere of Petosiris. Of these a Fox was placed north of the Scorpion; a +constellation called Cynocephalus near the southern constellation of the +Altar (Ara); and to the north of Pisces was placed a Stag. But all these +have long since been discarded. Curious to say neither the Dragon nor +Cepheus appears on the old Egyptian sphere.<a name='fna_389' id='fna_389' href='#f_389'><small>[389]</small></a></p> + +<p><span class="pagenum"><a name="Page_223" id="Page_223">[Pg 223]</a></span>Other small constellations have also been formed by various astronomers +from time to time, but these have disappeared from our modern star maps. +The total number of constellations now recognized in both hemispheres +amounts to eighty-four.</p> + +<p>The first catalogue formed was nominally that of Eudoxus in the fourth +century <span class="smcaplc">B.C.</span> (about 370 <span class="smcaplc">B.C.</span>). But this can hardly be dignified by the +name of catalogue, as it contained only forty-seven stars, and it omits +several of the brighter stars, notably Sirius! The first complete (or +nearly complete) catalogue of stars visible to the naked eye was that of +Hipparchus about 129 <span class="smcaplc">B.C.</span> Ptolemy informs us that it was the sudden +appearance of a bright new or “temporary star” in the year 134 <span class="smcaplc">B.C.</span> in the +constellation Scorpio which led Hipparchus to form his catalogue, and +there seems to be no reason to doubt the accuracy of this statement, as +the appearance of this star is recorded in the Chinese Annals. The +Catalogue of Hipparchus contains only 1080 stars; but as many more are +visible to the naked eye, Hipparchus must have omitted those which are not +immediately connected with the old constellation figures of men and +animals.</p> + +<p>Hipparchus’ Catalogue was revised by Ptolemy in his famous work the +<i>Almagest</i>. Ptolemy reduced the positions of the stars given by Hipparchus +to the year 137 <span class="smcaplc">A.D.</span>; but used a<span class="pagenum"><a name="Page_224" id="Page_224">[Pg 224]</a></span> +wrong value of the precession which only corresponded to about 50 <span class="smcaplc">A.D.</span>; and he probably adopted the star magnitudes +of Hipparchus without any revision. Indeed, it seems somewhat doubtful +whether Ptolemy made any observations of the brightness of the stars +himself. Ptolemy’s catalogue contains 1022 stars.</p> + +<p>Prof. De Morgan speaks of Ptolemy as “a splendid mathematician and an +indifferent observer”; and from my own examination of Al-Sufi’s work on +the Fixed Stars, which was based on Ptolemy’s work, I think that De +Morgan’s criticism is quite justified.</p> + +<p>Al-Sufi’s <i>Description of the Fixed Stars</i> was written in the tenth +century and contains 1018 stars. He seems to have adopted the <i>positions</i> +of the stars given by Ptolemy, merely correcting them for the effects of +precession; but he made a very careful revision of the star magnitudes of +Ptolemy (or Hipparchus) from his own observations, and this renders his +work the most valuable, from this point of view, of all the ancient +catalogues.</p> + +<p>Very little is known about Al-Sufi’s life, and the few details we have are +chiefly derived from the works of the historians Abu’-l-faradji and +Casiri, and the Oriental writers Hyde, Caussin, Sedillot, etc. Al-Sufi’s +complete name was Abd-al-Rahmän Bin Umar Bin Muhammad Bin Sahl +Abu’l-husaïn al-Sufi al-Razi. The name Sufi indicates that he<span class="pagenum"><a name="Page_225" id="Page_225">[Pg 225]</a></span> belonged to +the sect of Sufis (Dervishes), and the name Razi that he lived in the town +of Raï in Persia, to the east of Teheran. He was born on December 7, 903 +<span class="smcaplc">A.D.</span>, and died on May 25, 986, so that, like many other astronomers, he +lived to a good old age. According to ancient authorities, Al-Sufi—as he +is usually called—was a very learned man, who lived at the courts of +Schiraz and Baghdad under Adhad-al-Davlat—of the dynasty of the +Buïdes—who was then the ruler of Persia. Al-Sufi was held in high esteem +and great favour by this prince, who said of him, “Abd-al-Rahmän al-Sufi +taught me to know the names and positions of the fixed stars, Scharif Ibn +al-Aalam the use of astronomical tables, and Abu Ali al-Farisi instructed +me in the principles of grammar.” Prince Adhad-al-Davlat died on March 26, +983. According to Caussin, Al-Sufi also wrote a book on astrology, and a +work entitled <i>Al-Ardjouze</i>, which seems to have been written in verse, +but its subject is unknown. He also seems to have determined the exact +length of the year, and to have undertaken geodetic measurements. The +al-Aalam mentioned above was also an able astronomer, and in addition to +numerous observations made at Baghdad, he determined with great care the +precession of the equinoxes. He found the annual constant of precession to +be 51″·4, a value which differs but little from modern results.</p> + +<p><span class="pagenum"><a name="Page_226" id="Page_226">[Pg 226]</a></span>In the year 1874, the late M. Schjellerup, the eminent Danish astronomer, +published a French translation of two Arabic manuscripts written by +Al-Sufi and entitled “A Description of the Fixed Stars.” One of these +manuscripts is preserved in the Royal Library at Copenhagen, and the other +in the Imperial Library at St. Petersburgh.<a name='fna_390' id='fna_390' href='#f_390'><small>[390]</small></a></p> + +<p>Al-Sufi seems to have been a most careful and accurate observer, and +although, as a rule, his estimates of the relative brightness of stars are +in fairly good agreement with modern estimates and photometric measures, +there are many remarkable and interesting differences. Al-Sufi’s +observations have an important bearing on the supposed “secular variation” +of the stars; that is, the slow variation in light which may have occurred +in the course of ages in certain stars, apart from the periodical +variation which is known to occur in the so-called variable stars. More +than 900 years have now elapsed since the date of Al-Sufi’s observations +(about <span class="smcaplc">A.D.</span> 964) and over 2000 years in the case of Hipparchus, and +although these periods are of course very short in the life-history of any +star, still <i>some</i> changes may possibly have taken place in the brightness +of some of them.<span class="pagenum"><a name="Page_227" id="Page_227">[Pg 227]</a></span> There are several cases in which a star seems to have +diminished in light since Al-Sufi’s time. This change seems to have +certainly occurred in the case of θ Eridani, β Leonis, +ζ Piscis Australis, and some others. On the other hand, some +stars seem to have certainly increased in brightness, and the bearing of +these changes on the question of “stellar evolution” will be obvious.</p> + +<p>In most cases Al-Sufi merely mentions the magnitude which he estimated a +star to be; such as “third magnitude,” “fourth,” “small third magnitude,” +“large fourth,” etc. In some cases, however, he directly states that a +certain star is a little brighter than another star near it. Such +cases—unfortunately not numerous—are very valuable for comparison with +modern estimates and measures, when variation is suspected in the light of +a star. The estimates of Argelander, Heis, and Houzeau are based on the +same scale as that used by Ptolemy and Al-Sufi. Al-Sufi’s estimates are +given in thirds of a magnitude. Thus, “small third magnitude” means 3⅓, +or 3·33 magnitude in modern measures; “large fourth,” 3⅔ or 3·66 +magnitude. These correspond with the estimates of magnitude given by +Argelander, Heis, and Houzeau in their catalogues of stars visible to the +naked eye, and so the estimates can be directly compared.</p> + +<p>I have made an independent identification of all the stars mentioned by +Al-Sufi. In the<span class="pagenum"><a name="Page_228" id="Page_228">[Pg 228]</a></span> majority of cases my identifications concur with those of +Schjellerup; but in some cases I cannot agree with him. In a few cases I +have found that Al-Sufi himself, although accurately describing the +position of the stars observed by <i>him</i>, has apparently misidentified the +star observed by Hipparchus and Ptolemy. This becomes evident when we plot +Ptolemy’s positions (as given by Al-Sufi) and compare them with Al-Sufi’s +descriptions of the stars observed by him. This I have done in all cases +where there seemed to be any doubt; and in this way I have arrived at some +interesting results which have escaped the notice of Schjellerup. This +examination shows clearly, I think, that Al-Sufi did not himself measure +the <i>positions</i> of the stars he observed, but merely adopted those of +Ptolemy, corrected for the effect of precession. The great value of his +work, however, consists in his estimates of star magnitudes, which seem to +have been most carefully made, and from this point of view, his work is +invaluable. Prof. Pierce says, “The work which the learning of M. +Schjellerup has brought to light is so important that the smallest errors +of detail become interesting.”<a name='fna_391' id='fna_391' href='#f_391'><small>[391]</small></a></p> + +<p>Although Al-Sufi’s work is mentioned by the writers referred to above, no +complete translation of his manuscript was made until the task was +undertaken by Schjellerup, and even now Al-Sufi’s<span class="pagenum"><a name="Page_229" id="Page_229">[Pg 229]</a></span> name is not mentioned +in some popular works on astronomy! But he was certainly the best of all +the old observers, and his work is deserving of the most careful +consideration.</p> + +<p>Al-Sufi’s descriptions of the stars were, it is true, based on Ptolemy’s +catalogue, but his work is not a mere translation of that of his +predecessor. It is, on the contrary, a careful and independent survey of +the heavens, made from his own personal observations, each of Ptolemy’s +stars having been carefully examined as to its position and magnitude, and +Ptolemy’s mistakes corrected. In examining his descriptions, Schjellerup +says, “We soon see the vast extent of his labours, his perseverance, and +the minute accuracy and almost modern criticism with which he executed his +work.” In fact, Al-Sufi has given us a careful description of the starry +sky as it appeared in his time, and one which deserves the greatest +confidence. It far surpasses the work of Ptolemy, which had been without a +rival for eight centuries previously, and it has only been equalled in +modern times by the surveys of Argelander, Gould, Heis, and Houzeau. Plato +remarked with reference to the catalogue of Hipparchus, <i>Cœlam posteris +in hereditatem relictum</i>, and the same may be said of Al-Sufi’s work. In +addition to his own estimates of star magnitudes, Al-Sufi adds the +magnitudes given by Ptolemy whenever Ptolemy’s estimate differs<span class="pagenum"><a name="Page_230" id="Page_230">[Pg 230]</a></span> from his +own; and this makes his work still more valuable, as Ptolemy’s magnitudes +given in all the editions of the <i>Almagest</i> now extant are quite +untrustworthy.</p> + +<p>In the preface to his translation of Al-Sufi’s work, Schjellerup mentions +some remarkable discrepancies between the magnitudes assigned to certain +stars by Ptolemy and Argelander. This comparison is worthy of confidence +as it is known that both Al-Sufi and Argelander adopted Ptolemy’s (or +Hipparchus’) scale of magnitudes. For example, all these observers agree +that β Ursæ Minoris (Ptolemy’s No. 6 of that constellation) is of +the 2nd magnitude, while in the case of γ Ursæ Minoris (Ptolemy’s +No. 7), Ptolemy called it 2nd, and Argelander rated it 3rd; Argelander +thus making γ one magnitude fainter than Ptolemy’s estimate. Now, +Al-Sufi, observing over 900 years ago, rated γ of the 3rd +magnitude, thus correcting Ptolemy and agreeing with Argelander. Modern +photometric measures confirm the estimates of Al-Sufi and Argelander. But +it is, of course, possible that one or both stars may be variable in +light, and β has actually been suspected of variation. Almost all +the constellations afford examples of this sort. In the majority of cases, +however, Al-Sufi agrees well with Argelander and Heis, but there are in +some cases differences which suggest a change in relative brightness.</p> + +<p><span class="pagenum"><a name="Page_231" id="Page_231">[Pg 231]</a></span>Among other remarkable things contained in Al-Sufi’s most interesting work +may be mentioned the great nebula in Andromeda, which was first noticed in +Europe as visible to the naked eye by Simon Marius in 1612. Al-Sufi, +however, speaks of it as a familiar object in his time.</p> + +<p>Schjellerup says—</p> + +<div class="blockquot"><p>“For a long time many of the stars in Ptolemy’s catalogue could not be +identified in the sky. Most of these discordances were certainly due +to mistakes in copying, either in longitude or latitude. Many of these +differences were, however, corrected by the help of new manuscripts. +For this purpose Al-Sufi’s work is of great importance. By a direct +examination of the sky he succeeded in finding nearly all the stars +reported by Ptolemy (or Hipparchus). And even if his criticism may +sometimes seem inconclusive, his descriptions are not subject to +similar defects, his positions not depending solely on the places +given in Ptolemy’s catalogue. For, in addition to the longitudes and +latitudes quoted from Ptolemy, he has described by alignment the +positions of the stars referred to. In going from the brightest and +best known stars of each constellation he indicates the others either +by describing some peculiarity in their position, or by giving their +mutual distance as so many cubits (<i>dzirâ</i>), or a span (<i>schibr</i>), +units of length which were used at that time to measure apparent +celestial distances. The term <i>dzirâ</i> means literally the fore-arm +from the bone of the elbow to the tip of the middle finger, or an ell. +We should not, however, conclude from this that the Arabians were so +unscientific as to measure celestial distances by an ell, as this +would be quite in contradiction to<span class="pagenum"><a name="Page_232" id="Page_232">[Pg 232]</a></span> their well-known knowledge of +Geometry and Trigonometry.”</p></div> + +<p>With reference to the arc or angular distance indicated by the “cubit,” +Al-Sufi states in his description of the constellation Auriga that the +<i>dzirâ</i> (or cubit) is equal to 2° 20′. Three cubits, therefore, represent +7°, and 4 cubits 9° 20′.</p> + +<p>In Al-Sufi’s own preface to his work, after first giving glory to God and +blessings on “his elected messenger Muhammed and his family,” he proceeds +to state that he had often “met with many persons who wished to know the +fixed stars, their positions on the celestial vault, and the +constellations, and had found that these persons may be divided into two +classes. One followed the method of astronomers and trust to spheres +designed by artists, who not knowing, the stars themselves, take only the +longitudes and latitudes which they find in the books, and thus place the +stars on the sphere, without being able to distinguish truth from error. +It then follows that those who really know the stars in the sky find on +examining these spheres that many stars are otherwise than they are in the +sky. Among these are Al-Battani, Atârid and others.”</p> + +<p>Al-Sufi seems rather hard on Al-Battani (or Albategnius as he is usually +called) for he is generally considered to have been the most<span class="pagenum"><a name="Page_233" id="Page_233">[Pg 233]</a></span> +distinguished of the Arabian astronomers. His real name was Mohammed Ibn +Jaber Ibn Senan Abu Abdallah Al-Harrani. He was born about <span class="smcaplc">A.D.</span> 850 at +Battan, near Harran in Mesopotamia, and died about <span class="smcaplc">A.D.</span> 929. He was the +first to make use of sines instead of chords, and versed sines. The +<i>Alphonsine Tables</i> of the moon’s motions were based on his observations.</p> + +<p>After some severe criticisms on the work of Al-Battani and Atârid, Al-Sufi +goes on to say that the other class of amateurs who desire to know the +fixed stars follow the method of the Arabians in the science of +<i>Anva</i><a name='fna_392' id='fna_392' href='#f_392'><small>[392]</small></a> and the mansions of the moon and the books written on this +subject. Al-Sufi found many books on the <i>anva</i>, the best being those of +Abu Hanifa al-Dînavari. This work shows that the author knew the Arabic +tradition better than any of the other writers on the subject. Al-Sufi, +however, doubts that he had a good knowledge of the stars themselves, for +if he had he would not have followed the errors of his predecessors.</p> + +<p>According to Al-Sufi, those who know one of these methods do not know the +other. Among these is Abu-Hanifa, who states in his book that the names of +the twelve signs (of the Zodiac) did not originate from the arrangement +or<span class="pagenum"><a name="Page_234" id="Page_234">[Pg 234]</a></span> configuration of the stars resembling the figure from which the name +is derived. The stars, Abu-Hanifa said, “change their places, and although +the names of the signs do not change, yet the arrangement of the stars +ceases to be the same. This shows that he was not aware of the fact that +the arrangement of the stars does not change, and their mutual distances +and their latitudes, north and south of the ecliptic, are neither +increased nor diminished.” “The stars,” Al-Sufi says, “do not change with +regard to their configurations, because they are carried along together by +a physical motion and by a motion round the poles of the ecliptic. This is +why they are called fixed. Abu-Hanifa supposed that they are termed fixed +because their motion is very slow in comparison with that of the planets.” +“These facts,” he says, “can only be known to those who follow the method +of the astronomers and are skilled in mathematics.”</p> + +<p>Al-Sufi says that the stars of the Zodiac have a certain movement +following the order of the signs, which according to Ptolemy and his +predecessors is a degree in 100 years. But according to the authors of +<i>al-mumtahan</i> and those who have observed subsequently to Ptolemy, it is a +degree in 66 years. According to modern measures, the precession is about +50″·35 per annum, or one degree in 71½ years.</p> + +<p>Al-Sufi says that the Arabians did not make<span class="pagenum"><a name="Page_235" id="Page_235">[Pg 235]</a></span> use of the figures of the +Zodiac in their proper signification, because they divided the +circumference of the sky by the number of days which the moon took to +describe it—about 28 days—and they looked for conspicuous stars at +intervals which, to the eye, the moon appeared to describe in a day and a +night. They began with <i>al-scharataïn</i>, “the two marks” (α and +β Arietis) which were the first striking points following the +point of the spring equinox. They then sought behind these two marks +another point at a distance from them, equal to the space described by the +moon in a day and a night. In this way they found <i>al-butaïn</i> (ε, +δ, and ρ Arietis); after that <i>al-tsuraija</i>, the +Pleiades; then <i>al-dabaran</i>, the Hyades, and thus all the “mansions” of +the moon. They paid no attention to the signs of the Zodiac, nor to the +extent of the figures which composed them. This is why they reckoned among +the “mansions” <i>al-haka</i> (λ Orionis) which forms no part of the +signs of the Zodiac, since it belongs to the southern constellation of the +Giant (Orion). And similarly for other stars near the Zodiac, of which +Al-Sufi gives some details. He says that Regulus (α Leonis) was +called by the Arabians <i>al-maliki</i>, the Royal Star, and that <i>al-anva</i> +consists of five stars situated in the two wings of the Virgin. These +stars seem to be β, η, γ, δ, and +ε Virginis, which form with Spica (α Virginis) a +Y-shaped<span class="pagenum"><a name="Page_236" id="Page_236">[Pg 236]</a></span> figure. Spica was called <i>simak al-azal</i>, the unarmed <i>simak</i>; +the “armed <i>simak</i>” being Arcturus, <i>simak al-ramih</i>. These old Arabic +names seem very fanciful.</p> + +<p>Al-Sufi relates that in the year 337 of the Hegira (about <span class="smcaplc">A.D.</span> 948) he +went to Ispahan with Prince Abul-fadhl, who introduced him to an +inhabitant of that city, named Varvadjah, well known in that country, and +famous for his astronomical acquirements. Al-Sufi asked him the names of +the stars on an astrolabe which he had, and he named Aldebaran, the two +bright stars in the Twins (Castor and Pollux), Regulus, Sirius, and +Procyon, the two Simaks, etc. Al-Sufi also asked him in what part of the +sky <i>Al-fard</i> (α Hydræ) was, but he did not know! Afterwards, in +the year 349, this same man was at the court of Prince Adhad-al-Davlat, +and in the presence of the Prince, Al-Sufi asked him the name of a bright +star—it was <i>al-nasr al-vaki</i>, the falling Vulture (Vega), and he +replied, “That is <i>al-aijuk</i>” (Capella)! thus showing that he only knew +the <i>names</i> of the stars, but did not know them when he saw them in the +sky. Al-Sufi adds that all the women “who spin in their houses” knew this +star (Vega) by the name of <i>al-atsafi</i>, the Tripod. But this could not be +said even of “educated women” at the present day.</p> + +<p>With reference to the number of stars which<span class="pagenum"><a name="Page_237" id="Page_237">[Pg 237]</a></span> can be seen with the naked +eye, Al-Sufi says, “Many people believe that the total number of fixed +stars is 1025, but this is an evident error. The ancients only observed +this number of stars, which they divided into six classes according to +magnitude. They placed the brightest in the 1st magnitude; those which are +a little smaller in the 2nd; those which are a little smaller again in the +3rd; and so on to the 6th. As to those which are below the 6th magnitude, +they found that their number was too great to count; and this is why they +have omitted them. It is easy to convince one’s self of this. If we +attentively fix our gaze on a constellation of which the stars are well +known and registered, we find in the spaces between them many other stars +which have not been counted. Take, for example, the Hen [Cygnus]; it is +composed of seventeen internal stars, the first on the beak, the brightest +on the tail, the others on the wings, the neck and the breast; and below +the left wing are two stars which do not come into the figure. Between +these different stars, if you examine with attention, you will perceive a +multitude of stars, so small and so crowded that we cannot determine their +number. It is the same with all the other constellations.” These remarks +are so correct that they might have been written by a modern astronomer. +It should be added, however, that <i>all</i> the faint stars referred to by +Al-Sufi—and thousands of<span class="pagenum"><a name="Page_238" id="Page_238">[Pg 238]</a></span> others still fainter—have now been mapped down +and their positions accurately determined.</p> + +<p>About the year 1437, Ulugh Beigh, son of Shah Rokh, and grandson of the +Mogul Emperor Tamerlane, published a catalogue of stars in which he +corrected Ptolemy’s positions. But he seems to have accepted Al-Sufi’s +star magnitudes without any attempt at revision. This is unfortunate, for +an <i>independent</i> estimate of star magnitudes made in the fifteenth century +would now be very valuable for comparison with Al-Sufi’s work and with +modern measures. Ulugh Beigh’s catalogue contains 1018 stars, nearly the +same number as given by Ali-Sufi.<a name='fna_393' id='fna_393' href='#f_393'><small>[393]</small></a></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_239" id="Page_239">[Pg 239]</a></span></p> +<h2><a name="CHAPTER_XIX" id="CHAPTER_XIX"></a>CHAPTER XIX</h2> +<p class="center"><span class="title">The Constellations</span><a name='fna_394' id='fna_394' href='#f_394'><small>[394]</small></a></p> + +<p> </p> +<p class="dropcap"><span class="caps">Curious</span> to say, Al-Sufi rated the Pole Star as 3rd magnitude; for it is +now only slightly less than the 2nd. At present it is about the same +brightness as β of the same constellation (Ursa Minor) which +Al-Sufi rated 2nd magnitude. It was, however, also rated 3rd magnitude by +Ptolemy (or Hipparchus), and it may possibly have varied in brightness +since ancient times. Admiral Smyth says that in his time (1830) it was +“not even a very bright third size” (!)<a name='fna_395' id='fna_395' href='#f_395'><small>[395]</small></a> Spectroscopic measures show +that it is approaching the earth at the rate of 16 miles a second; but +this would have no perceptible effect on its brightness in historical +times. This may seem difficult to understand, and to some perhaps<span class="pagenum"><a name="Page_240" id="Page_240">[Pg 240]</a></span> +incredible; but the simple explanation is that its distance from the earth +is so great that a journey of even 2000 years with the above velocity +would make no <i>appreciable</i> difference in its distance! This is +undoubtedly true, as a simple calculation will show, and the fact will +give some idea of the vast distance of the stars. The well-known 9th +magnitude companion to the Pole Star was seen <i>by day</i> in the Dorpat +telescope by Struve and Wrangel; and “on one occasion by Encke and +Argelander.”<a name='fna_396' id='fna_396' href='#f_396'><small>[396]</small></a></p> + +<p>The star β Ursæ Minoris was called by the Arabians <i>Kaukab +al-shamáli</i>, the North Star, as it was—owing to the precession of the +Equinoxes—nearer to the Pole in ancient times than our present Pole Star +was <i>then</i>.</p> + +<p>The “Plough” (or Great Bear) is supposed to represent a waggon and horses. +“Charles’ Wain” is a corruption of “churl’s wain,” or peasant’s cart. The +Arabians thought that the four stars in the quadrilateral represented a +bier, and the three in the “tail” the children of the deceased following +as mourners! In the Greek mythology, Ursa Major represented the nymph +Callisto, a daughter of Lycaon, who was loved by Jupiter, and turned into +a bear by the jealous Juno. Among the old Hindoos the seven stars +represented the seven Rishis. It is the Otawa of the great Finnish epic, +the “Kalevala.” It was also called<span class="pagenum"><a name="Page_241" id="Page_241">[Pg 241]</a></span> +“David’s Chariot,” and in America it is known as “The Dipper.”</p> + +<p>Closely north of the star θ in Ursa Major is a small star known +as Flamsteed 26. This is not mentioned by Al-Sufi, but is now, I find from +personal observation, very visible, and indeed conspicuous, to the naked +eye. I find, however, that owing to the large “proper motion” of the +bright star (1″·1 per annum) the two stars were much closer together in +Al-Sufi’s time than they are at present, and this probably accounts for +Al-Sufi’s omission. This is an interesting and curious fact, and shows the +small changes which occur in the heavens during the course of ages.</p> + +<p>Close to the star ζ, the middle star of the “tail” of Ursa Major +(or handle of the “Plough”), is a small star known as Alcor, which is +easily visible to good eyesight without optical aid. It is mentioned by +Al-Sufi, who says the Arabians called it <i>al-suha</i>, “the little unnoticed +one.” He says that “Ptolemy does not mention it, and it is a star which +seems to test the powers of the eyesight.” He adds, however, an Arabian +proverb, “I show him <i>al-suha</i>, and he shows me the moon,” which seems to +suggest that to some eyes, at least, it was no test of sight at all. It +has, however, been suspected of variation in light. It was rated 5th +magnitude by Argelander, Heis, and Houzeau, but was measured 4·02 at +Harvard<span class="pagenum"><a name="Page_242" id="Page_242">[Pg 242]</a></span> Observatory. It has recently been found to be a spectroscopic +binary.</p> + +<p>The constellation of the Dragon (Draco) is probably referred to in Job +(chap. xxvi. v. 13), where it is called “the crooked serpent.” In the +Greek mythology it is supposed to represent the dragon which guarded the +golden apples in the Garden of the Hesperides. Some have suggested that it +represented the serpent which tempted Eve. Dryden says, in his translation +of Virgil—</p> + +<p class="poem">“Around our Pole the spiry Dragon glides,<br /> +And like a wand’ring stream the Bears divides.”</p> + +<p>The fact that the constellation Boötis rises quickly and sets slowly, +owing to its lying horizontally when rising and vertically when setting, +was noted by Aratus, who says—</p> + +<p class="poem">“The Bearward now, past seen,<br /> +But more obscured, near the horizon lies;<br /> +For with the four Signs the Ploughman, as he sinks,<br /> +The deep receives; and when tired of day<br /> +At even lingers more than half the night,<br /> +When with the sinking sun he likewise sets<br /> +These nights from his late setting bear their name.”<a name='fna_397' id='fna_397' href='#f_397'><small>[397]</small></a></p> + +<p>The cosmical setting of Boötis—that is, when he sets at sunset—is stated +by Ovid to occur on March 5 of each year.</p> + +<p>With reference to the constellation Hercules, Admiral Smyth says—</p> + +<div class="blockquot"><p><span class="pagenum"><a name="Page_243" id="Page_243">[Pg 243]</a></span>“The kneeling posture has given rise to momentous discussion; and +whether it represents Lycaon lamenting his daughter’s transformation, +or Prometheus sentenced, or Ixion ditto, or Thamyrus mourning his +broken fiddle, remains still uncertain. But in process of time, this +figure became a lion, and Hyginus mentions both the lion’s skin and +the club; while the right foot’s being just over the head of the +Dragon, satisfied the mythologists that he was crushing the Lernæan +hydra.... Some have considered the emblem as typifying the serpent +which infested the vicinity of Cape Tænarus, whence a sub-genus of +Ophidians still derives its name. At all events a poet, indignant at +the heathen exaltation of Hevelius, has said—</p> + +<p class="poem">“‘To Cerberus, too, a place is given—<br /> +His home of old was far from heaven.’”<a name='fna_398' id='fna_398' href='#f_398'><small>[398]</small></a></p></div> + +<p>Aratus speaks of Hercules as “the Phantom whose name none can tell.”</p> + +<p>There were several heroes of the name of Hercules, but the most famous was +Hercules the Theban, son of Jupiter and Alcmene wife of Amphitryon, King +of Thebes, who is said to have lived some years before the siege of Troy, +and went on the voyage of the Argonauts about 1300 <span class="smcaplc">B.C.</span> According to some +ancient writers, another Hercules lived about 2400 <span class="smcaplc">B.C.</span>, and was a +contemporary of Atlas and Theseus. But according to Pétau, Atlas lived +about 1638 <span class="smcaplc">B.C.</span>, and Lalande thought that this chronology is the more +probable.</p> + +<p>The small constellation Lyra, which contains<span class="pagenum"><a name="Page_244" id="Page_244">[Pg 244]</a></span> the bright star Vega, is +called by Al-Sufi the Lyre, the Goose, the Persian harp, and the Tortoise. +In his translation of Al-Sufi’s work, Schjellerup suggests that the name +“Goose” may perhaps mean a plucked goose, which somewhat resembles a Greek +lyre, and also a tortoise. The name of the bright star Vega is a +corruption of the Arabic <i>vâki</i>. Ptolemy and Al-Sufi included all the very +brightest stars in the “first magnitude,” making no distinction between +them, but it is evident at a glance that several of them, such as Arcturus +and Vega, are brighter than an average star of the first magnitude, like +Aldebaran.</p> + +<p>The constellation Perseus, which lies south-east of “Cassiopeia’s Chair,” +may be recognized by the festoon formed by some of its stars, the bright +star α Persei being among them. It is called by Al-Sufi +“<i>barschânsch</i>, Περσεύς, Perseus, who is <i>hamil râs al-gul</i>, the +Bearer of the head of <i>al-gul</i>.” According to Kazimirski, “<i>Gul</i> was a +kind of demon or ogre who bewilders travellers and devours them, beginning +at the feet. In general any mischievous demon capable of taking all sorts +of forms.” In the Greek mythology Perseus was supposed to be the son of +Jupiter and Danæ. He is said to have been cast into the sea with his +mother and saved by King Polydectus. He afterwards cut off the head of +Medusa, one of the Gorgons, while she slept, and armed with this he +delivered Andromeda from the sea-monster.</p> + +<p><span class="pagenum"><a name="Page_245" id="Page_245">[Pg 245]</a></span>The constellation Auriga lies east of Perseus and contains the bright star +Capella, one of the three brightest stars in the northern hemisphere (the +others being Arcturus and Vega). Theon, in his commentary on Aratus, says +that Bellerophon invented the chariot, and that it is represented in the +heavens by Auriga, the celestial coachman. According to Dupuis, Auriga +represents Phæton, who tried to drive the chariot of the sun, and losing +his head fell into the river Eridanus. The setting of Eridanus precedes by +a few minutes that of Auriga, which was called by some of the ancient +writers Amnis Phaï-tontis.<a name='fna_399' id='fna_399' href='#f_399'><small>[399]</small></a> Auriga is called by Al-Sufi <i>numsick +al-ainna</i>—He who holds the reins, the Coachman; also <i>al-inâz</i>, the +She-goat. M. Dorn found in Ptolemy’s work, the Greek name ‘Ηνίοχοι, +Auriga, written in Arabic characters. Al-Sufi says, “This +constellation is represented by the figure of a standing man behind ‘He +who holds the head of <i>al-gûl</i>’ [Perseus], and between the Pleiades and +the Great Bear.”</p> + +<p>Capella is, Al-Sufi says, “the bright and great star of the first +magnitude which is on the left shoulder [of the ancient figure] on the +eastern edge of the Milky Way. It is that which is marked on the astrolabe +as <i>al-aijûk</i>.” The real meaning of this name is unknown. Schjellerup +thought, contrary to what Ideler says, that the name is<span class="pagenum"><a name="Page_246" id="Page_246">[Pg 246]</a></span> identical with +the Greek word Αϊξ (a goat). Capella was observed at Babylon +about 2000 <span class="smcaplc">B.C.</span>, and was then known as Dilgan. The Assyrian name was +<i>Icu</i>, and the Persian name <i>colca</i>. It was also called Capra Hircus, +Cabrilla, Amalthea, and Olenia. In ancient times the rising of Capella was +supposed to presage the approach of storms. Ovid says, “Olenia sidus +pluviale Capellæ.”</p> + +<p>The constellation Aquila is called by Al-Sufi <i>al-ukab</i>, the Eagle, or +<i>al-nasr al-tâïr</i>, the flying vulture. According to the ancient poets the +eagle carried nectar to Jupiter when he was hidden in a cave in Crete. +This eagle also assisted Jupiter in his victory over the Giants and +contributed to his other pleasures. For these reasons the eagle was +consecrated to Jupiter, and was placed in the sky. Al-Sufi says, “There +are in this figure three famous stars [γ, α, and β +Aquilæ], which are called <i>al-nasr al-tâïr</i>.” Hence is derived the +modern name Altair for the bright star α Aquilæ. Al-Sufi says +that the “common people” call “the three famous stars” <i>al-mîzân</i>, the +Balance, on account of the equality of the stars.” This probably refers to +the approximately equal distances between γ and α, and +α and β, and not to their relative brightness. He says +“Between the bright one of the tail [ξ Aquilæ] and the star in +the beak of the Hen [β Cygni] in the thinnest part of the Milky +Way, we see the figure of a little earthen jar, of which the<span class="pagenum"><a name="Page_247" id="Page_247">[Pg 247]</a></span> stars begin +at the bright one in the tail, and extend towards the north-west. [This +seems to refer to ε Aquilæ and the small stars near it.] They +then turn towards the east in the base of the jar, and then towards the +south-east to a little cloud [4, 5, etc. Vulpeculæ, a well-known group of +small stars] which is found to the north of the two stars in the shaft of +the Arrow [α and β Sagittæ]. The cloud is on the eastern +edge of the jar, and the bright one on the tail on the western edge; the +orifice is turned towards the flying Vulture [Aquila], and the base +towards the north. Among these are distinguished some of the fourth, +fifth, and sixth magnitudes [including, probably, 110, 111, 112, 113 +Hercules, and 1 Vulpeculæ] and Ptolemy says nothing of this figure, except +the bright star in the tail of the<span class="pagenum"><a name="Page_248" id="Page_248">[Pg 248]</a></span> Eagle” (see figure). The above is a +good example of the minute accuracy of detail in Al-Sufi’s description.</p> + +<p> </p> +<div class="figcenter"><img src="images/img1.jpg" alt="" /></div> +<p class="caption">AL-SUFI’S “EARTHEN JAR.”</p> +<p> </p> + +<p>The southern portion of Aquila was formerly called Antinous, who was said +to have been a young man of great beauty born at Claudiopolis in Bithynia, +and drowned in the Nile. Others say that he sacrificed his life to save +that of the Emperor Hadrian, who afterwards raised altars in his honour +and placed his image on coins.<a name='fna_400' id='fna_400' href='#f_400'><small>[400]</small></a></p> + +<p>The constellation Pegasus, Al-Sufi says, “is represented by the figure of +a horse, which has the head, legs, and forepart of the body to the end of +the back, but it has neither hind quarters nor hind legs.” According to +Brown, Pegasus was the horse of Poseidon, the sea god. Half of it was +supposed to be hidden in the sea, into which the river Eridanus +flowed.<a name='fna_401' id='fna_401' href='#f_401'><small>[401]</small></a> In the Greek mythology it was supposed to represent the +winged horse produced by the blood which fell from the head of Medusa when +she was killed by Perseus! Some think that it represents Bellerophon’s +horse, and others the horse of Nimrod. It was also called Sagmaria and +Ephippiatus, and was sometimes represented with a saddle instead of wings.</p> + +<p>In describing the constellation Andromeda, Al-Sufi speaks of two series of +stars which start from the great nebula in Andromeda; one series<span class="pagenum"><a name="Page_249" id="Page_249">[Pg 249]</a></span> going +through 32 Andromedæ, π, δ, and ε to ζ and +η; and the other through ν, μ, β Andromedæ into the +constellation Pisces. He says they enclose a fish-shaped figure called by +the Arabians <i>al-hût</i>, the Fish, <i>par excellence</i>. He speaks of two other +series of stars which begin at τ and υ, and diverging +meet again at χ Persei, forming another “fish-like figure.” The +eastern stream starts from τ and passes through 55, γ, +60, 62, 64, and 65 Andromedæ; and the western stream from υ +through χ 51, 54, and <i>g</i> Persei up to<span class="pagenum"><a name="Page_250" id="Page_250">[Pg 250]</a></span> χ Persei. The +head of the first “fish,” <i>al-hût</i>, is turned towards the north, and that +of the second towards the south (see figure).</p> + +<p> </p> +<div class="figcenter"><img src="images/img2.jpg" alt="" /></div> +<p class="caption">AL-SUFI’S “FISHES” IN ANDROMEDA.</p> +<p> </p> + +<p>Al-Sufi says that the stars α Persei, γ, β, δ, and +α Andromedæ, and β Pegasi form a curved line. This is +quite correct, and this fine curve of bright stars may be seen at a glance +on a clear night in September, when all the stars are high in the sky.</p> + +<p>The first constellation of the Zodiac, Aries, the Ram, was called, +according to Aratus and Eratosthenes, κρίος. It is mentioned by +Ovid under the name of Hellas. It was also called by the ancients the Ram +with the golden horns. Manilius (fourth century <span class="smcaplc">B.C.</span>) called it “The +Prince.” It is supposed to have represented the god Bel. Among the +Accadians the sign meant “He who dwells on the altar of uprightness.” It +first appears on the Egyptian Zodiac; and it was sacred to Jupiter Ammon. +In the Greek mythology it was supposed to represent the ram, the loss of +whose fleece led to the voyage of the Argonauts. In the time of +Hipparchus, about 2000 years ago, it was the first sign of the Zodiac, or +that in which the sun is situated at the Vernal Equinox (about March 21 in +each year). But owing to the precession of the equinoxes, this point has +now moved back into Pisces.</p> + +<p>The brightest star of Aries (α) is sometimes<span class="pagenum"><a name="Page_251" id="Page_251">[Pg 251]</a></span> called Hamal, +derived from the Arabic <i>al-hamal</i>, a name given to the constellation +itself by Al-Sufi. In the Accadian language it was called <i>Dilkur</i>, “the +dawn proclaimer.” Ali-Sufi says that close to α, “as if it were +attached to it,” is a small star of the 6th magnitude, not mentioned by +Ptolemy. This is clearly κ Arietis. The fact of Al-Sufi having +seen and noticed this small star, which modern measures show to be below +the 5th magnitude, is good evidence of his keen eyesight and accuracy of +observation.</p> + +<p>According to Al-Sufi, the stars β and γ Arietis were +called by the Arabians <i>al-scharatain</i>, “the two marks.” They marked the +“first mansion of the moon,” and ε, δ, and ρ the second +mansion. With reference to these so-called “mansions of the moon,” Admiral +Smyth says—</p> + +<div class="blockquot"><p>“The famous <i>Manazil al-kamar</i>, i.e. Lunar mansions, constituted a +supposed broad circle in Oriental astronomy divided into twenty-eight +unequal parts, corresponding with the moon’s course, and therefore +called the abodes of the moon. This was not a bad arrangement for a +certain class of gazers, since the luminary was observed to be in or +near one or other of these parts, or constellations every night. +Though tampered with by astrologers, these Lunar mansions are probably +the earliest step in ancient astronomy.”<a name='fna_402' id='fna_402' href='#f_402'><small>[402]</small></a></p></div> + +<p>Taurus, the second constellation of the Zodiac,<span class="pagenum"><a name="Page_252" id="Page_252">[Pg 252]</a></span> was in ancient times +represented by the figure of a bull, the hinder part of which is turned +towards the south-west, and the fore part towards the east. It had no hind +legs, and the head was turned to one side, with the horns extended towards +the east. Its most ancient name was <i>Te</i>, possibly a corruption of the +Accadian <i>dimmena</i>, “a foundation-stone.” The Greek name is ἀθώρ +(θωώρ, Eusebius). In the old Egyptian mythology Taurus +represented the god Apis. According to Dupuis it also represented the 10th +“labour of Hercules,” namely, his victory over the cows of Geryon, King of +Spain.<a name='fna_403' id='fna_403' href='#f_403'><small>[403]</small></a> It was also supposed to represent the bull under the form of +which Jupiter carried off Europa, daughter of Agenor, King of the +Phœnicians. It may also refer to Io or Isis, who is supposed to have +taught the ancient Egyptians the art of agriculture.</p> + +<p>Aldebaran is the well-known bright red star in the Hyades. It was called +by Ptolemy <i>Fulgur succularum</i>. Ali-Sufi says it was marked on the old +astrolabes as <i>al-dabaran</i>, “the Follower” (because it follows the Hyades +in the diurnal motion), and also <i>ain al-tsaur</i>, the eye of the bull. It +may be considered as a standard star of the 1st magnitude. Modern +observations show that it has a parallax of 0″·107. It is receding from +the earth, according to Vogel, at the rate<span class="pagenum"><a name="Page_253" id="Page_253">[Pg 253]</a></span> of about 30 miles a second; +but even with this high velocity it will take thousands of years before +its brightness is perceptibly diminished. It has a faint companion of +about the 10th magnitude at the distance of 118″, which forms a good +“light test” for telescopes of 3 or 4 inches aperture. I saw it well with +a 4-inch Wray in the Punjab sky. The Hyades were called <i>Succulæ</i> by the +Romans, and in the Greek mythology were said to be children of Atlas.</p> + +<p>The star β Tauri, sometimes called Nath, from the Arabic +<i>al-nátih</i>, the butting, is a bright star between Capella and γ +Orionis (Bellatrix). It is on the tip of the horn in the ancient figure of +Taurus, and “therefore” (says Admiral Smyth) “at the greatest distance +from the hoof; can this have given rise to the otherwise pointless sarcasm +of not knowing B from a bull’s foot?”<a name='fna_404' id='fna_404' href='#f_404'><small>[404]</small></a> Al-Sufi says that an imaginary +line drawn from the star now known as A Tauri to τ Tauri would +pass between υ and κ Tauri, which is quite correct, +another proof of the accuracy of his observations. He also says that the +star ω Tauri is exactly midway between A and ε, which is +again correct. He points out that Ptolemy’s position of ω is +incorrect. This is often the case with Ptolemy’s positions, and tends to +show that Ptolemy adopted the position given by Hipparchus without +attempting to verify their position in the sky.<span class="pagenum"><a name="Page_254" id="Page_254">[Pg 254]</a></span> Al-Sufi himself adopts +the longitudes and latitudes of the stars as given by Ptolemy in the +<i>Almagest</i>, but corrects the positions in his <i>descriptions</i>, when he +found Ptolemy’s places erroneous.</p> + +<p>The famous group of the Pleiades is well known; but there is great +difficulty in understanding Al-Sufi’s description of the cluster. He says, +“The 29th star (of Taurus) is the more northern of the anterior side of +the Pleiades themselves, and the 30th is the southern of the same side; +the 31st is the following vertex of the Pleiades, and is in the more +narrow part. The 32nd is situated outside the northern side. Among these +stars, the 32nd is of the 4th magnitude, the others of the 5th.” Now, it +is very difficult or impossible to identify these stars with the stars in +the Pleiades as they are at present. The brightest of all, Alcyone +(η Tauri), now about 3rd magnitude, does not seem to be mentioned +at all by Al-Sufi! as he says distinctly that “the brightest star” (No 32 +of Taurus) is “outside” the Pleiades “on the northern side.” It seems +impossible to suppose that Al-Sufi could have overlooked Alcyone had it +the same brightness it has now. The 32nd star seems to have disappeared, +or at least diminished greatly in brightness, since the days of Al-Sufi. +More than four stars were, however, seen by Al-Sufi, for he adds, “It is +true that the stars of the Pleiades must exceed the four<span class="pagenum"><a name="Page_255" id="Page_255">[Pg 255]</a></span> mentioned above, +but I limit myself to these four because they are very near each other and +the largest [that is, the brightest]; this is why I have mentioned them, +neglecting the others.” A full examination of the whole question is given +by Flammarion in his interesting work <i>Les Étoiles</i> (pp. 289-307), and I +must refer my readers to this investigation for further details.</p> + +<p>According to Brown, Simonides of Keos (<span class="smcaplc">B.C.</span> 556-467) says, “Atlas was the +sire of seven daughters with violet locks, who are called the heavenly +<i>Peleiades</i>.”<a name='fna_405' id='fna_405' href='#f_405'><small>[405]</small></a> The name is by some supposed to be derived from the +Greek πλείων, full. The Old Testament word <i>Kimah</i> (Job ix. 9 and +xxviii. 31) and Amos (v. 8) is derived from the Assyrian <i>Kimta</i>, a +“family.” Aratus describes the Pleiades in the following lines:—</p> + +<p class="poem">“Near his<a name='fna_406' id='fna_406' href='#f_406'><small>[406]</small></a> left thigh together sweep along<br /> +The flock of Clusterers. Not a mighty span<br /> +Holds all, and they themselves are dim to see,<br /> +And seven paths aloft men say they take,<br /> +Yet six alone are viewed by mortal eye.<br /> +These seven are called by name Alkyonî<br /> +Kelainî, Meropî and Steropî<br /> +Taygetî, Elecktrî, Maia queen.<br /> +They thus together small and faint roll on<br /> +Yet notable at morn and eve through Zeus.”<a name='fna_407' id='fna_407' href='#f_407'><small>[407]</small></a></p> + +<p>The Pleiades are mentioned by Ovid. According to the ancient poets they +were supposed to<span class="pagenum"><a name="Page_256" id="Page_256">[Pg 256]</a></span> represent the children of Atlas and Hesperus, and on +this account they were called Atlantids or Hesperides. From the +resemblance in sound to the word πλείας, a pigeon, they were +sometimes called “the doves,” and for the same reason the word +πλεῖν, to navigate, led to their being called the “shipping stars.” The +word πλείας was also applied to the priestesses of the god Zeus +(Jupiter) at Dordona, in the groves of which temple there were a number of +pigeons. This is, perhaps, what Aratus refers to in the last line of the +extract quoted above. According to Neapolitan legends, the name of +Virgil’s mother was Maia. The mother of Buddha, the Hindoo <i>avatar</i>, was +also named Maia. In Italy the Pleiades were called <i>Gallinata</i>, and in +France <i>poussinière</i>, both of which mean the hen and chickens, a term also +given to them by Al-Sufi. The old Blackfoot Indians called them “The Seven +Perfect Ones.” The Crees and Ojibway Indians called them the “Fisher +Stars.” The Adipones of Brazil and some other nations claimed that they +sprang from the Pleiades! The Wyandot Indians called them “The Singing +Maidens.”</p> + +<p>Photographs show that the brighter stars of the Pleiades are involved in +nebulosity. That surrounding Maia seems to be of a spiral form. Now, there +is a Sanscrit myth which represents Maia as “weaving the palpable +universe,” for which reason she was “typified as a spider.”<span class="pagenum"><a name="Page_257" id="Page_257">[Pg 257]</a></span> This seems +very appropriate, considering the web of nebulous light which surrounds +the stars of the group. Maia was also considered as a type of the +universe, which again seems appropriate, as probably most of the stars +were evolved from spiral nebulæ.</p> + +<p>The name Hyades is supposed to be derived from the Greek word ὑεῖν, +to rain, because in ancient times they rose at the rainy season.</p> + +<p>In ancient Egypt, Aldebaran was called <i>ary</i>; and the Pleiades <i>chooa</i>, a +word which means “thousands.” The name Aldebaran seems to have been +originally applied to the whole of the Hyades group. Aldebaran was also +called by the Arabians <i>al-fanik</i>, the great Camel, and the Hyades +<i>al-kilas</i>, the young Camels. The two close stars υ and κ +Tauri were called <i>al-kalbaïn</i>, the dogs of Aldebaran. La Condamine +states that the Indians of the Amazon saw in the Hyades the head of a +bull.</p> + +<p>Gemini, the Twins, is the third constellation of the Zodiac. It was also +called Gemelli, etc. According to Dupuis it represents the 11th “labour of +Hercules”—his triumph over the dog Cerberus.<a name='fna_408' id='fna_408' href='#f_408'><small>[408]</small></a> But some of Dupuis’ +ideas seem very fanciful. The Twins are usually called Castor and Pollux, +but they were also called by the ancient writers Apollo and Hercules; +Jason and Triptolemus; Amphion and Zethus; and Theseus<span class="pagenum"><a name="Page_258" id="Page_258">[Pg 258]</a></span> and Peritheus. In +Egypt they represented the deities Horus and Hippocrates. Brown thinks +that the “Great Twins” were originally the sun and moon, “who live +alternately. As one is born the other dies; as one rises the other +sets.”<a name='fna_409' id='fna_409' href='#f_409'><small>[409]</small></a> This applies to the full moon, but does not seem applicable to +the other lunar phases.</p> + +<p>Gemini was the constellation to which Dante supposed himself transported +when he visited the stellar heavens.<a name='fna_410' id='fna_410' href='#f_410'><small>[410]</small></a> He says he was born under the +influence of this “sign.”</p> + +<p>Cancer, the Crab, is the next sign of the Zodiac. In the Greek mythology +it was supposed to have been placed in the sky by Juno to commemorate the +crab which pinched the toes of Hercules in the Lernæan marsh. The Greek +name was τυβί. According to Dupuis it represents the 12th “labour +of Hercules”—his capture of the golden apples in the Garden of the +Hesperides, which were guarded by a Dragon. This Dragon is Draco, which +was also called Custos Hesperidum.<a name='fna_411' id='fna_411' href='#f_411'><small>[411]</small></a> But the connection between a crab +and the myth of the golden apples is not obvious—unless some reference to +“crab apples” is intended! Among the Romans, Cancer was consecrated to +Mercury, and by the ancient Egyptians to their god Anubis.</p> + +<p>The well-known cluster in Cancer called the<span class="pagenum"><a name="Page_259" id="Page_259">[Pg 259]</a></span> Præsape, Al-Sufi says, is “a +little spot which resembles a cloud, and is surrounded by four stars, two +to the west [η and θ Cancri] and two to the east” +[γ and δ]. This cluster is mentioned by Aratus, who +calls it the “Manger.” The word Præsape is often translated “Beehive,” but +there can be no doubt that it really means “Manger,” referring to the +stars γ and δ Cancri, which the ancients called Aselli, +the ass’s colts. These were supposed to represent the asses which in the +war of Jupiter against the Giants helped his victory by their braying!</p> + +<p>Admiral Smyth says in his <i>Bedford Catalogue</i> (p. 202) that he found +γ and δ Cancri both of 4th magnitude; but the +photometric measures show that δ is now distinctly brighter than +γ. An occultation of δ Cancri by the moon is recorded as +having occurred on September 3, <span class="smcaplc">B.C.</span> 240.</p> + +<p>The fine constellation Leo, the Lion, is the next “sign” of the Zodiac, +and is marked by the well-known “Sickle.” According to Dupuis, it +represents the first “labour of Hercules”—the killing of the Nemælian +lion. Manilius called it Nemæus. It was also called Janonus sidus, Bacchi +sidus, etc. The Greek name was μεχίρ, μεχείρ, or +μεχός. In ancient Egypt, Leo was sacred to Osiris, and many of +the Egyptian monuments are ornamented with lions’ heads. It is stated in +the Horapolla that its appearance was supposed to announce the annual +rising of the Nile.</p> + +<p><span class="pagenum"><a name="Page_260" id="Page_260">[Pg 260]</a></span>Regulus (α Leonis) is the brightest and most southern of the +stars in the “Sickle.” Al-Sufi says “it is situated in the heart and is of +the 1st magnitude. It is that which is called <i>al-maliki</i>, the royal star. +It is marked on the astrolabe as <i>kalb al-asad</i>, the Heart of the Lion” +(whence the name Cor Leonis). Modern photometric measures make it about +1·3 magnitude. It has an 8½ magnitude companion at about 177″ distance +(Burnham) which is moving through space with the bright star, and is +therefore at probably the same distance from the earth as its brilliant +primary. This companion is double (8·5, 12·5: 3″·05, Burnham). The +spectroscope shows that Regulus is approaching the earth at the rate of +5½ miles a second. Its parallax is very small—about 0″·022, according +to Dr. Elkin—which indicates that it is at a vast distance from the +earth; and its brightness shows that it must be a sun of enormous size. +Ptolemy called it βασιλίσκος, whence its Latin name Regulus, +first used by Copernicus as the diminutive of <i>rex</i>.<a name='fna_412' id='fna_412' href='#f_412'><small>[412]</small></a></p> + +<p>The next constellation of the Zodiac is Virgo, the Virgin. It was also +called by the ancients Ceres, Isis, Erigone, Fortuna, Concorda, Astræa, +and Themis. The Greek name was φαμένωθ. Ceres was the goddess +of the harvest. Brown thinks that it probably represents the ancient +goddess Istar, and also Ashtoreth. According to Prof.<span class="pagenum"><a name="Page_261" id="Page_261">[Pg 261]</a></span> Sayce it is the +same as the Accadian sign of “the errand of Istar, a name due to the +belief that it was in August that the goddess Astarte descended into Hades +in search of her betrothed, the sun god Tammuz, or Adonis, who had been +slain by the boar’s tusk.”<a name='fna_413' id='fna_413' href='#f_413'><small>[413]</small></a> The ear of corn (Spica) is found on the +ancient Egyptian monuments, and is supposed to represent the fertility +caused by the annual rising of the Nile. According to Aratus, the Virgin +lived on earth during the golden age under the name of Justice, but that +in the bronze age she left the earth and took up her abode in the heavens.</p> + +<p class="poem">“Justice, loathing that race of men,<br /> +Winged her flight to heaven.”</p> + +<p>The Sphinx near the Great Pyramid has the head of a virgin on the body of +a lion, representing the goddess Isis (Virgo) and her husband Osiris +(Leo).</p> + +<p>Al-Sufi’s 5th star of Virgo is Flamsteed 63 Virginis. Al-Sufi says it is a +double star of the 5th magnitude. In Al-Sufi’s time it formed a “naked-eye +double” with 61 Virginis, but owing to large proper motion, 61 has now +moved about 26 minutes of arc towards the south, and no longer forms a +double with 63. This interesting fact was first pointed out by Flammarion +in his work <i>Les Étoiles</i> (p. 373).</p> + +<p><span class="pagenum"><a name="Page_262" id="Page_262">[Pg 262]</a></span>Libra, the Balance, is one of the “signs” of the Zodiac, but originally +formed the claws of the Scorpion. It was called Juguna by Cicero, and +Mochos by Ampelius. The Greek name was φαρμουθέ. Virgil +suggests that it represented the justice of the emperor Augustus, honoured +by the name of a constellation; but probably this refers to the birth of +Augustus under the sign of Libra, as Scaliger has pointed out. According +to Brown, “the daily seizing of the dying western sun by the claws of the +Scorpion of darkness is reduplicated annually at the Autumnal Equinox, +when the feeble waning sun of shortening days falls ever earlier into his +enemy’s grasp;”<a name='fna_414' id='fna_414' href='#f_414'><small>[414]</small></a> and he says, “The Balance or Scales (Libra), which it +will be observed is in itself neither diurnal nor nocturnal, is the only +one of the zodiacal signs not Euphratean in origin, having been imported +from Egypt and representing originally the balance of the sun at the +horizon between the upper and under worlds; and secondarily the equality +of the days and nights at the equinox.”<a name='fna_415' id='fna_415' href='#f_415'><small>[415]</small></a></p> + +<p>According to Houzeau, Libra was formed at the beginning of the second +century <span class="smcaplc">B.C.</span>, and it does not appear in any writings before those of +Geminus and Varron.<a name='fna_416' id='fna_416' href='#f_416'><small>[416]</small></a></p> + +<p><span class="pagenum"><a name="Page_263" id="Page_263">[Pg 263]</a></span>Milton says in <i>Paradise Lost</i>:—</p> + +<p class="poem">“The Eternal to prevent such horrid fray,<br /> +Hung forth in heaven his golden scales, yet seen<br /> +Betwixt Astræa and the Scorpion’s sign.”</p> + +<p>(Here Astræa is Virgo.)</p> + +<p>It is worth noticing that both Ptolemy and Al-Sufi rated the star κ +Libræ as two magnitudes brighter than λ Libræ. The two stars +are now practically of equal brightness (5th magnitude), and it seems +impossible to believe that this could have been the case in Al-Sufi’s +time. Surely a careful observer like Al-Sufi, who estimated the relative +brightness of stars to a third of a magnitude, could not possibly have +made an error of two magnitudes in the brightness of two stars near each +other! It should be stated, however, that κ Libræ was rated 5th +magnitude by Argelander and Heis, and λ, 6th magnitude by the +same excellent observers.</p> + +<p>The next “sign” of the Zodiac, Scorpion, was consecrated by the Romans to +Mars, and by the Egyptians to Typhon.<a name='fna_417' id='fna_417' href='#f_417'><small>[417]</small></a> It was called <i>Nepa</i> by Cicero, +<i>Martis sidus</i> by Manilius, and <i>Fera magna</i> by Aratus. The Greek name was +πάχον.</p> + +<p>Mr. E. B. Knobel has called attention to a curious remark of Ptolemy with +reference to the bright star Antares (α Scorpii), “Media earum +quæ <i>tendit ad rapinam</i> quæ dicitur Cor Scorpionis”; and he made a similar +remark with<span class="pagenum"><a name="Page_264" id="Page_264">[Pg 264]</a></span> reference to Betelgeuse (α Orionis) and others. But +Mr. Robert Brown<a name='fna_418' id='fna_418' href='#f_418'><small>[418]</small></a> explains the remark by the fact that in ancient +times these stars rose in the morning at a time when caravans were exposed +to dangers from robbers. Thus the term had nothing to do with the aspect +or colour of these stars, but was merely a reference to their supposed +astrological influence on human affairs.</p> + +<p>In the Egyptian <i>Book of the Dead</i>, Silkit was a goddess who assumed the +form of a scorpion in the sky. She was supposed to be the daughter of +<i>Ra</i>.</p> + +<p>With reference to stars “outside” the ancient figure of Scorpio, the +first, Al-Sufi says, “is a star which immediately follows <i>al-schaulat</i>” +[λ] and κ, “it is of small 4th magnitude; Ptolemy calls +it νεφελοείδης” [nebulous]. Schjelerup, in his translation of +Al-Sufi’s work, does not identify this object; but it is very evidently +γ Telescopii, which lies exactly in the position described by +Al-Sufi. Now, it is a very interesting and curious fact that Ptolemy +called it nebulous, for in the same telescopic field with it is the nebula +<i>h</i> 3705 (= Dunlop 557). Dunlop describes it as a “small well-defined +rather bright nebula, about 20″ in diameter; a very small star precedes +it, but is not involved; following γ Telescopii.” Sir John +Herschel at the Cape found it fairly resolved into very faint stars, and +adds, “The whole <i>ground</i><span class="pagenum"><a name="Page_265" id="Page_265">[Pg 265]</a></span> of the heavens, for an immense extent is +thickly sown with such stars. A beautiful object.”<a name='fna_419' id='fna_419' href='#f_419'><small>[419]</small></a> This perhaps +accounts for the nebulous appearance of the star as seen by Ptolemy.</p> + +<p>Several <i>novæ</i> or temporary stars are recorded as having appeared in +Scorpio. One in the year <span class="smcaplc">B.C.</span> 134 is stated by Pliny to have induced +Hipparchus to form his catalogue of stars. This star was also observed in +China. Its exact position is unknown, but Flammarion thinks it may +possibly have appeared about 4° north of the star β Scorpii. +Another new star is said to have appeared in <span class="smcaplc">A.D.</span> 393, somewhere in the +Scorpion’s tail. One in <span class="smcaplc">A.D.</span> 1203 and another in 1584 are also mentioned, +the latter near π Scorpii.</p> + +<p>The constellation Scorpio seems to be referred to by Dante in his +<i>Purgatorio</i> (ix. 4-6) in the lines—</p> + +<p class="poem">“De gemma la sua fronte era lucenta<br /> +Poste in figura del fredda animale<br /> +Che con la coda percota la genta,”</p> + +<p>perhaps suggested by Ovid’s remark—</p> + +<p class="poem">“Scorpius exhibit caudaque menabitur unca.”<a name='fna_420' id='fna_420' href='#f_420'><small>[420]</small></a></p> + +<p>Next to Scorpio comes Sagittarius, the Archer. It is said to have been +placed in the sky as a symbol of Hercules, a hero who was held in the +greatest veneration by the ancient Egyptians.<span class="pagenum"><a name="Page_266" id="Page_266">[Pg 266]</a></span> The horse, usually +associated with this constellation, was a symbol of war. It was also +called by the ancients Chiron, Arcitenens, Minotaurus, Croton, etc. The +Greek name was παυνί, or παωνί. Chiron was supposed to +be the son of Saturn and Phillyra, and first taught men to ride on horses. +The name is derived from the Greek χείρ, a hand. Some writers, +however, think that Chiron is represented by the constellation of the +Centaur, and others say that Sagittarius represents the Minotaur loved by +Persephone. According to Dupuis, Sagittarius represents the 5th “labour of +Hercules,” which consisted in hunting the birds of the lake Stymphalus, +which ravaged the neighbouring countries. These birds are perhaps +represented by Cygnus, Altair, and the Vulture (Lyra). The Lyre probably +represents the musical instrument which Hercules used to frighten the +birds.<a name='fna_421' id='fna_421' href='#f_421'><small>[421]</small></a></p> + +<p>According to Al-Sufi, the Arabians called the stars γ, δ, ε, and +η Sagittarii which form a quadrilateral figure, “the Ostrich +which goes to the watering place,” because they compared the Milky Way to +a river. They compared the stars σ, φ, τ, and ζ +Sagittarii, which form another quadrilateral, to an ostrich which has +drunk and returns from the “watering place.” He says that the star λ +Sagittarii forms with these two “ostriches” a tent, and certainly the +figure formed by λ, φ, ζ, ε,<span class="pagenum"><a name="Page_267" id="Page_267">[Pg 267]</a></span> and δ is not unlike a +tent. Al-Sufi says more about these “ostriches”; but the ideas of the old +Arabians about the stars seem very fanciful.</p> + +<p>A “temporary star” is recorded in the Chinese Annals of Ma-touan-lin as +having appeared in May, <span class="smcaplc">B.C.</span> 48, about 4° distant from μ +Sagittarii. Another in the year 1011 <span class="smcaplc">A.D.</span> appeared near the quadrilateral +figure formed by the stars σ, τ, ζ, and φ Sagittarii. +This may perhaps be identified with the object referred to by Hepidannus +in the year 1012, which was of extraordinary brilliancy, and remained +visible “in the southern part of the heavens during three months.” Another +is mentioned near the same place in <span class="smcaplc">A.D.</span> 386 (April to July).<a name='fna_422' id='fna_422' href='#f_422'><small>[422]</small></a> The +number of “temporary stars” recorded in this part of the heavens is very +remarkable.</p> + +<p>According to Brown, Sagittarius is depicted on a stone, cir. <span class="smcaplc">B.C.</span> 1100, +found at Bâbilu, and now in the British Museum.<a name='fna_423' id='fna_423' href='#f_423'><small>[423]</small></a></p> + +<hr style="width: 25%;" /> + +<p>The next of the “signs of the Zodiac” is Capricornus, the Goat. In the +Arabo-Latin edition of Ptolemy’s <i>Almagest</i> it is called Alcaucurus. It is +supposed to represent Amalthea, the goat which nursed Jupiter. According +to Dupuis it represented the 6th “labour of Hercules,” which was the +cleaning out of the Augean stables.<a name='fna_424' id='fna_424' href='#f_424'><small>[424]</small></a></p> + +<p><span class="pagenum"><a name="Page_268" id="Page_268">[Pg 268]</a></span>α<sub>2</sub> Capricorni is the northern of two stars of the 4th +magnitude (α and β Capricorni). It really consists of +two stars visible to the naked eye. The second of these two stars (α<sub>1</sub>) +is not mentioned by Al-Sufi, but I find that, owing to proper +motion, they were nearer together in his time (tenth century), and were +evidently seen by him as one star. β Capricorni (about 3rd +magnitude) is a very wide double star (3½, 6; 205″), which may be seen +with any small telescope. The fainter star was found to be a close double +by Burnham. At present β is brighter than α, although +rated of the same brightness by Al-Sufi.</p> + +<p>Aquarius is the next “sign of the Zodiac.” It is supposed to represent a +man pouring water out of an urn or bucket. Other names given to this +constellation were Aristæus, Ganymede, Cecrops, Amphora, Urna, and Aqua +tyrannus. According to Dupuis it represents the 7th “labour of Hercules,” +which was his victory over the famous bull which ravaged Crete.<a name='fna_425' id='fna_425' href='#f_425'><small>[425]</small></a> But +the connection between a bull and a bucket is not obvious. Aquarius is +represented in several places on the Egyptian monuments. Some of the +ancient poets supposed that it represented Deucalion (the Noah of the +Greek story of the Deluge); others thought that it represented Cecrops, +who came to Greece from Egypt, built Athens, and was also called Bifornis. +Others say that he was Ganymede, the cup-bearer of the gods.</p> + +<p><span class="pagenum"><a name="Page_269" id="Page_269">[Pg 269]</a></span>There is some difficulty about the identification of some of Al-Sufi’s +stars in Aquarius. His sixth star (Fl. 7) is nearly 10° south-west of +β Aquarii, and is, Al-Sufi says, “the following of three stars in +the left hand, and precedes the fourth [β] ... it is of the 6th +magnitude. Ptolemy calls it third, but in reality it is very faint” [now +about 6th magnitude]. The seventh [μ] is the middle one of the +three and about 4½ magnitude, although Al-Sufi calls it “small fifth” +[Ptolemy rated it 4]. The eighth star, ε, is the preceding of the +three and about 3·8, agreeing closely with Al-Sufi’s 4·3. Ptolemy rated it +3. This star is mentioned under the name <i>nou</i> in the time of +<i>Tcheou-Kong</i> in the twelfth century <span class="smcaplc">B.C.</span> Al-Sufi says, “These three stars +are followed by a star of the 5th magnitude which Ptolemy has not +mentioned. It is brighter than the sixth star” [Fl. 7]. This is evidently +ν Aquarii. If, however, we plot Ptolemy’s positions as given by +Al-Sufi, it seems probable that <i>Ptolemy’s</i> sixth star was really ν, +and that either μ or Fl. 7 was not seen by him. As Ptolemy +called his seventh star 4th magnitude, and his sixth and eighth stars 3rd +magnitude, some considerable change of brightness seems to have taken +place in these stars; as ν is now only 4½ and Fl. 7 only a +bright sixth. Variation was suspected in Fl. 7<a name='fna_426' id='fna_426' href='#f_426'><small>[426]</small></a> by Gould. I found it +very<span class="pagenum"><a name="Page_270" id="Page_270">[Pg 270]</a></span> reddish with binocular in October, 1892. Burnham found it to be a +close double star, the companion being about 12th magnitude at a distance +of only 2″. It is probably a binary.</p> + +<p>According to Al-Sufi, the Arabians called the second and third stars of +the figure (α and ο Aquarii) <i>sad al-malik</i> (<i>malk</i> or +<i>mulk</i>), “the Good Fortune of the king.” They called the fourth and fifth +stars (β and ξ Aquarii) with the twenty-eighth star of +Capricornus (<i>c</i>) <i>sad al-sund</i>, “the Good Fortune of the Happy Events.” +“This is the 24th mansion of the moon.” These stars rose at the time of +year when the cold ends, and they set at the time the heat ends. Hence, +Al-Sufi says, “when they rise the rains begin, and when they set the +unhealthy winds cease, fertility abounds, and the dew falls.” Hence +probably the Arabic names. This, of course, applies to the climate of +Persia and Arabia, and not to the British Isles. Al-Sufi says, “They call +the 6th, 7th, and 8th stars <i>sad bula</i>, ‘The Good Fortune which swallows +up!’ This is the 23rd mansion of the moon. They say that it is so called +because that at the time of the Deluge it rose at the moment when God +said, ‘O earth! absorb the waters’ (Koran, chap, xi., v. 46). They called +the stars γ, π, ζ and η Aquarii <i>sad al-achbija</i>, ‘the +the Good Fortune of the tents’; this is the 25th mansion of the moon, and +they give them this name because of these four stars, three form a +triangle, the fourth [ζ] being in the<span class="pagenum"><a name="Page_271" id="Page_271">[Pg 271]</a></span> middle.” The three were +considered to form a tent.</p> + +<p>The Arabians called the bright star Fomalhaut “in the mouth of the +southern fish <i>al-dhifda al-auval</i>, ‘the first Frog,’ as the bright one on +the southern point of the tail of Kîtus [Cetus] is called <i>al-dhifda +al-tsani</i> [β Ceti], ‘the second Frog.’” Fomalhaut was also called +<i>al-zhalim</i>, “the male ostrich.”</p> + +<p>Al-Sufi says, “Some of the Arabians state that a ship is situated to the +south of Aquarius.” The stars in the Southern Fish (Piscis Australis) seem +to be here referred to.</p> + +<p>The constellation Pisces, the Fishes, is the last of the “signs of the +Zodiac.” The Fishes appear on an ancient Greek obelisk described by +Pococke. Among the Greeks this sign was consecrated to Venus; and in Egypt +to Nepthys, wife of Typhon and goddess of the sea. Pisces is said to end +the Zodiac as the Mediterranean Sea terminated Egypt. This idea was +suggested by Schmidt, who also conjectured that the Ram (Aries) was placed +at the beginning of the Zodiac because Thebes, a town sacred to Jupiter +Ammon, was at the beginning of Egypt in ancient times; and he thought that +the constellation Triangulum, the Triangle, represented the Nile Delta, +Eridanus being the Nile.<a name='fna_427' id='fna_427' href='#f_427'><small>[427]</small></a> The constellation was represented in ancient +times by two fishes connected by a cord<span class="pagenum"><a name="Page_272" id="Page_272">[Pg 272]</a></span> tied to their tails. The southern +of these “fishes” lies south of the “Square of Pegasus,” and the northern +between Andromeda and Aries. According to Manilius, the origin of these +fishes is as follows: Venus, seeing Typhon on the banks of the river +Euphrates, cast herself with her son into the river and they were +transformed into fishes!</p> + +<p>Some of the Arabians substituted a swallow for the northern of the two +fishes—the one below Andromeda. The swallow was a symbol of Spring. +According to Dupuis, Pisces represents the 8th “labour of Hercules,” his +triumph over the mares of Diomed which emitted fire from their +nostrils.<a name='fna_428' id='fna_428' href='#f_428'><small>[428]</small></a> But the connection between fishes and mares is not obvious, +and some of Dupuis’ ideas seem very fanciful. Here he seems to have found +a “mare’s nest.”</p> + +<p>The constellation Cetus, the Whale, represents, according to ancient +writers, the sea monster sent by Neptune to devour Andromeda when she was +chained to the rock. Aratus calls Cetus the “dusky monster,” and Brown +remarks that “the ‘Dusky Star’ would be peculiarly appropriate to Mira +(the wondrous ο Ceti).”<a name='fna_429' id='fna_429' href='#f_429'><small>[429]</small></a> Cetus was also called Canis +Tritonis, or Dog of the Sea, Bayer in his Atlas (1603) shows a dragon +instead of a whale, finding it so represented on some ancient spheres. +Al-Sufi calls it Kîtus or κητος, the whale. He says,<span class="pagenum"><a name="Page_273" id="Page_273">[Pg 273]</a></span> “it is +represented by the figure of a marine animal, of which the fore part is +turned towards the east, to the south of the Ram, and the hinder part +towards the west behind the three ‘extern’ stars of Aquarius.”</p> + +<p>Al-Sufi does not mention the variable star ο Ceti, now called +Mira, or the “wonderful,” nor does he refer to any star in its immediate +vicinity. We may, therefore, conclude that it was near a minimum of light +at the time of his observation of the stars of Cetus.</p> + +<p>The constellation of Orion, one of the finest in the heavens, was called +by Al-Sufi <i>al-djabbar</i>, “the Giant,” and also <i>al-djauza</i>, “the Spouse.” +The poet Longfellow says—</p> + +<p class="poem">“Sirius was rising in the east<br /> +And, slow ascending one by one,<br /> +The kindling constellations shone<br /> +Begirt with many a blazing star<br /> +Stood the great giant Al-gebar<br /> +Orion, hunter of the beast!<br /> +His sword hung gleaming at his side<br /> +And on his arm, the lion’s hide—<br /> +Scattered across the midnight air<br /> +The golden radiance of its hair.”</p> + +<p>Al-Sufi says it “is represented by the figure of a standing man, to the +south of the sun’s path. This constellation very much resembles a human +figure with a head and two shoulders. It is called <i>al-djabbar</i>, ‘the +Giant,’ because it has two thrones, holds a club in his hand, and is +girded with a sword.” Orion is supposed to have been a son of<span class="pagenum"><a name="Page_274" id="Page_274">[Pg 274]</a></span> Neptune; +but there are many stories of the origin of the name. It is also said to +be derived from the Greek word ὤρα, because the constellation was +used to mark the different times of the year. According to the ancient +fable, Orion was killed by a scorpion, and was placed in the sky at the +request of Diana. According to Houzeau, the name comes from <i>oriri</i>, to be +born. Scorpio rises when Orion sets, and he thinks that the idea of the +ancients was that the Scorpion in this way kills the giant Orion.</p> + +<p>In ancient Egypt Orion was called <i>Sahu</i>. This name occurs on the +monuments of the Ptolemies, and also on those of the Pharaohs. It is also +mentioned in the <i>Book of the Dead</i>. It seems to have been considered of +great importance in ancient Egypt, as its heliacal rising announced that +of Sirius, which heralded the annual rising of the Nile.</p> + +<p>The constellation Eridanus lies south of Taurus, east of Cetus, and west +of Lepus. In ancient times it was supposed to represent the Nile or the +Po. Ptolemy merely calls it Ποταμοῦ +ἀστερισμὸς, or asterism of +the river. It was called Eridanus by the Greeks, and Fluvius by the +Romans. It appears to correspond with the Hebrew Shicor. Al-Sufi calls it +<i>al-nahr</i>, “the River.”</p> + +<p>One of the most interesting points in Al-Sufi’s most interesting work is +the identity of the bright star known to the ancient astronomers as<span class="pagenum"><a name="Page_275" id="Page_275">[Pg 275]</a></span> +<i>achir al-nahr</i>, “the End of the River,” and called by Ptolemy +’Εσχατος τοῦ ποταμοῦ, +“the Last in the River.” Some astronomers have +identified this star with α Eridani (Achernar), a bright southern +star of the 1st magnitude, south of Eridanus. But Al-Sufi’s description +shows clearly that the star he refers to is really θ Eridani; +and the reader will find it interesting to follow his description with a +star map before him. Describing Ptolemy’s 34th star of Eridanus (the star +in question), he says, “the 34th star is found before [that is west of] +these three stars [the 31st, 32nd, and 33rd, which are υ<sup>2</sup>, Du, +and υ′ in Proctor’s Atlas], the distance between it and that of +the three which is nearest being about 4 cubits [9° 20′]. It is of the +first magnitude; it is that which is marked on the southern astrolabe, and +called <i>achir al-nahr</i>, ‘the End of the River.’ There are before this +bright one two stars, one to the south, [σ Eridani, not shown in +Proctor’s small Atlas], the other to the north [ι Eridani]; +Ptolemy does not mention these. One of these stars is of the 4th +magnitude, the other of the 5th. There is behind the same [that is, east +of it] a star of the 4th magnitude distant from it two cubits [ε +Eridani]. To the south of the three stars which follow the bright one +there are some stars of the 4th and 5th magnitudes, which he [Ptolemy] has +not mentioned.”</p> + +<p>Now, a glance at a star map of this region will<span class="pagenum"><a name="Page_276" id="Page_276">[Pg 276]</a></span> show clearly that the +bright star referred to by Al-Sufi is undoubtedly θ Eridani, +which is therefore the star known to the ancients as the “End of the +River,” or the “Last in the River.”</p> + +<p>The position given by Ptolemy agrees fairly well with Al-Sufi’s +description, although the place is slightly erroneous, as is also the case +with Fomalhaut and β Centauri. It is impossible to suppose that +either Ptolemy or Al-Sufi could have seen α Eridani, as it is too +far south to be visible from their stations, and, owing to the precession +of the equinoxes, the star was still further south in ancient times. +Al-Sufi says distinctly that the distance between Ptolemy’s 33rd star +(which is undoubtedly <i>h</i> Eridani, or Proctor’s υ′) and the 34th +star was “4 cubits,” or 9° 20′. The actual distance is about 9° 11′, so +that Al-Sufi’s estimate was practically correct. Halley, in his <i>Catalogus +Stellarium Australium</i>, identifies Ptolemy’s star with θ +Eridani, and Baily agreed with him.<a name='fna_430' id='fna_430' href='#f_430'><small>[430]</small></a> Ulugh Beigh also identifies the +“Last in the River” with θ Eridani. The Arabic observer Mohammed +Ali Achsasi, who observed in the seventeenth century, called θ +Eridani <i>Achr al-nahr</i>, and rated it first magnitude.<a name='fna_431' id='fna_431' href='#f_431'><small>[431]</small></a> To argue, as +Bode and Flammarion have done, that Ptolemy and Al-Sufi may have heard of +α Eridani from travellers in the southern<span class="pagenum"><a name="Page_277" id="Page_277">[Pg 277]</a></span> hemisphere, is to beg +the whole question at issue. This is especially true with reference to +Al-Sufi, who says, in the preface to his work, that he has described the +stars “as seen with my own eyes.” α Eridani is over 11 “cubits” +from <i>h</i> Eridani instead of “4 cubits” as Al-Sufi says. This shows +conclusively that the star seen by Al-Sufi was certainly <i>not</i> α +Eridani. The interest of the identification is that Al-Sufi rated θ +Eridani of the <i>first</i> magnitude, whereas it is now only 3rd +magnitude! It was measured 3·06 at Harvard and estimated 3·4 by Stanley +Williams, so that it has evidently diminished greatly in brightness since +Al-Sufi’s time. There is an interesting paper on this subject by Dr. +Anderson (the discoverer of Nova Aurigæ and Nova Persei) in <i>Knowledge</i> +for July, 1893, in which he states that the “Last in the River,” according +to the statements of Hipparchus and Ptolemy, <i>did</i> rise above their +horizon at a certain time of the year, which α Eridani could not +possibly have done. This seems sufficient to settle the question in favour +of θ Eridani. Dr. Anderson says, “It is much to be regretted +that Professor Schjellerup, the able and industrious translator of Sufi, +has allowed this to escape his notice, and helped in the preface and note +to his work to propagate the delusion that α Eridani is Ptolemy’s +‘Last in the River’”; and in this opinion I fully concur. Al-Sufi’s clear +account places it beyond a doubt that the star<span class="pagenum"><a name="Page_278" id="Page_278">[Pg 278]</a></span> known to Hipparchus, +Ptolemy, Al-Sufi, and Ulugh Beigh as the “Last in the River” was θ +Eridani. θ must have diminished greatly in brightness since +Al-Sufi’s time, for in ranking it as 1st magnitude he placed it in a very +select list. He only rated thirteen stars in the whole heavens as being of +the 1st magnitude. These are: Arcturus, Vega, Capella, Aldebaran, Regulus, +β Leonis, Fomalhaut, Rigel, θ Eridani, Sirius, Procyon, +Canopus, and α Centauri. <i>All</i> these stars were actually <i>seen</i> +by Al-Sufi, <i>and described from his own observations</i>. He does not mention +α Eridani, as it was not visible from his station in Persia.</p> + +<p>θ Eridani is a splendid double star (3·40, 4·49: 8″·38, 1902, +Tebbutt). I found the components white and light yellow with 3-inch +refractor in the Punjab. Dr. Gould thinks that one of the components is +variable to some extent. This is interesting, considering the brilliancy +of the star in Al-Sufi’s time. The brighter component was found to be a +spectroscopic binary by Wright, so that on the whole the star is a most +interesting object.</p> + +<p>The small constellation Lepus, the Hare, lies south of Orion. Pliny calls +it Dasypus, and Virgil Auritus. In ancient Egypt it was the symbol of +vigilance, prudence, fear, solitude, and speed.<a name='fna_432' id='fna_432' href='#f_432'><small>[432]</small></a> It may perhaps +represent the hare hunted by Orion;<span class="pagenum"><a name="Page_279" id="Page_279">[Pg 279]</a></span> but some say it was placed in the sky +to commemorate a terrible plague of hares which occurred in Sicily in +ancient times.</p> + +<p>A little north-west of the star μ Leporis is Hind’s “crimson +star” (R.A. 4<sup>h</sup> 53<sup>m</sup>, S. 14° 57′, 1900) described by him as “of the most +intense crimson, resembling a blood drop on the background of the sky; as +regards depth of colour, no other star visible in these latitudes could be +compared with it.” It is variable from about the 6th to the 8th magnitude, +with a period of about 436 days from maximum to maximum.</p> + +<p>The constellation Canis Major, the Great Dog, is remarkable for containing +Sirius, the brightest star in the heavens. In the Greek mythology it was +supposed to represent a dog given by Aurora to Cephalus as the swiftest of +all dogs. Cephalus wished to match it against a fox which he thought +surpassed all animals for speed. They both ran for so long a time, so the +story goes, that Jupiter rewarded the dog by placing it among the stars. +But probably the dog comes from Anubis, the dog-headed god of the ancient +Egyptians. According to Brown, Theogirius (<span class="smcaplc">B.C.</span> 544) refers to the +constellation of the Dog.<a name='fna_433' id='fna_433' href='#f_433'><small>[433]</small></a> He thinks that Canis Major is probably “a +reduplication” of Orion; Sirius and β Canis Majoris corresponding +to α and γ Orionis; δ, 22, and ε Canis +Majoris to the stars in Orion’s belt (δ, ε, and<span class="pagenum"><a name="Page_280" id="Page_280">[Pg 280]</a></span> ζ +Orionis); and η; and κ Canis Majoris with κ and +β Orionis.<a name='fna_434' id='fna_434' href='#f_434'><small>[434]</small></a></p> + +<p>The Arabic name of Sirius was <i>al-schira</i>, which might easily be corrupted +into Sirius. The Hebrew name was Sihor. According to Plutarch, the +Ethiopians paid regal honours to the Celestial Dog. The Romans used to +sacrifice a dog in its honour at the fetes called Robigalia, which were +held on the seventh day before the Calends of May, and nine days after the +entry of the sun into Taurus. Pliny says, “Hoc tempus Varro determinat +sole decimam partem Tauri obtinenti quod canis occidit, sidus per se +vehemens,” etc.<a name='fna_435' id='fna_435' href='#f_435'><small>[435]</small></a></p> + +<p>Owing to some remarks of Cicero, Horace, and Seneca, it has been supposed +that in ancient times Sirius was of red colour. Seneca says, “Nec mirum +est, si terra omnis generis et varia evaporatio est; quam in cœlo +quoque non unus appareat color rerum, sed acrior sit Caniculæ rubor, +Nartis remissior, Jovis nullus, in lucem puram nitore perducto.”<a name='fna_436' id='fna_436' href='#f_436'><small>[436]</small></a> It +is now brilliantly white with a bluish tinge. But this change of colour is +somewhat doubtful. The remarks of the ancient writers may possibly refer +to its great brilliancy rather than its colour. Al-Sufi says nothing about +its colour, and it was probably<span class="pagenum"><a name="Page_281" id="Page_281">[Pg 281]</a></span> a white star in his time. If it were red +in his day he would most probably have mentioned the fact, as he does in +the case of several red stars. Brown, however, quotes the following from +Ibn Alraqqa, an Arabian observer:—</p> + +<p class="poem">“I recognize Sirius <i>shining red</i>, whilst the morning is becoming white.<br /> +The night fading away, has risen and left him,<br /> +The night is not afraid to lose him, since he follows her.”</p> + +<p>Schjellerup thinks that it is very doubtful that Sirius was really red as +seen by Hipparchus and Ptolemy. But in an exhaustive inquiry made by Dr. +See on the supposed change of colour,<a name='fna_437' id='fna_437' href='#f_437'><small>[437]</small></a> he comes to the conclusion that +Sirius was really red in ancient times. Seneca states distinctly that it +was redder than Mars (see extract above), and other ancient writers refer +to its red colour. It has been generally supposed that the Arabian +astronomer Alfraganus, in his translation of Ptolemy’s <i>Almagest</i>, refers +to only five red stars observed by Ptolemy, namely, Arcturus, Aldebaran, +Betelgeuse, Antares, and Pollux. But Dr. See shows that this idea is due +to a mistranslation of Alfraganus by Plato Tibertinus in 1537, and that +Ptolemy did not speak of “five red stars,” but five <i>nebulous</i> stars, as +stated by Christmann and Golius. Ptolemy described Sirius as ὑπόκιρρος, +“fiery red,” the same word used with reference to the other +stars mentioned above. The change<span class="pagenum"><a name="Page_282" id="Page_282">[Pg 282]</a></span> of colour, if any, probably took place +before Al-Sufi’s time.</p> + +<p>Dr. See says—</p> + +<div class="blockquot"><p>“Prof. Newcomb rejects the former well-authenticated redness of +Sirius, because he cannot explain the fact. But the ink was scarcely +dry on his new book on the stars, in which he takes this position, +when Nova Persei blazed forth in 1901; and observers saw it change +colour from day to day and week to week. Could any one explain the +cause of these numerous and conspicuous changes of colour? Shall we, +then, deny the changes of colour in Nova Persei, some of which were +noticed when it was nearly as bright as Sirius?”<a name='fna_438' id='fna_438' href='#f_438'><small>[438]</small></a></p></div> + +<p>On the ceiling of the Memnonium at Thebes the heliacal rising of Sirius is +represented under the form and name of Isis. The coincidence of this +rising with the annual rising of the Nile is mentioned by Tibullus and +Aclian. About 4000 <span class="smcaplc">B.C.</span> the heliacal rising of Sirius coincided with the +summer solstice (about June 21) and the beginning of the rising of the +Nile. The festival in honour of this event was held by the Egyptians about +July 20, and this marked the beginning of the sacred Egyptian year. On the +summit of Mount Pelion in Thessaly there was a temple dedicated to Zeus, +where sacrifices were offered at the rising of Sirius by men of rank who +were chosen for the purpose by the priests and wore fresh sheepskins.</p> + +<p><span class="pagenum"><a name="Page_283" id="Page_283">[Pg 283]</a></span>Sirius seems to have been worshipped by the ancient Egyptians under the +name of Sothis, and it was regarded as the star of Isis and Osiris. The +last name without the initial O very much resembles our modern name.</p> + +<p>According to Al-Sufi, the Arabians called Sirius <i>al-schira al-abûr</i>, +“Sirius which has passed across,” also <i>al-schira al Jamânija</i>, “the +Sirius of Yémen.” He says it is called <i>al-abûr</i>, “because it has passed +across the Milky Way into the southern region.” He relates a mythological +story why Sirius “fled towards the south” and passed across the Milky Way +towards Suhail (Canopus). The same story is told by Albufaragius<a name='fna_439' id='fna_439' href='#f_439'><small>[439]</small></a> +(thirteenth century). (The story was probably derived from Al-Sufi.) Now, +it seems to me a curious and interesting fact that the large proper motion +of Sirius would have carried it across the Milky Way from the eastern to +the western border in a period of 60,000 years. Possibly the Arabian story +may be based on a tradition of Sirius having been seen on the opposite, or +eastern, side of the Milky Way by the men of the early Stone Age. However +this may be, we know from the amount and direction of the star’s proper +motion that it must have passed across the Milky Way from east to west +within the period above stated. The Arabic name <i>al-abûr</i> is not, +therefore, a merely fanciful<span class="pagenum"><a name="Page_284" id="Page_284">[Pg 284]</a></span> one, but denotes an <i>actual fact</i>. The +proper motion of Sirius could not possibly have been known to the +ancients, as it was only revealed by accurate modern observations.</p> + +<p>The little constellation Canis Minor, the Little Dog, lies south of Gemini +and Cancer. Small as it is, it was one of the original forty-eight +constellations of Ptolemy. In the Greek mythology it was supposed to +represent either one of Diana’s hunting dogs, or one of Orion’s hounds. +Ovid calls it the dog of Icarus. Others say it was the dog of Helen, who +was carried off by Paris. According to the old poets, Orion’s dog, or the +dog of Icarus, threw himself into a well after seeing his master perish. +The name Fovea, given to the constellation by Bayer, signifies a pit where +corn was deposited. This comes from the fact that the rising of the star +Procyon (α Canis Minoris) indicated the season of abundance. But +Lalande thought it more probable that the idea of a pit came from the +Greek σειρὸς, which means a corn store, and that it was +confounded with Sirius.</p> + +<p>The name of the bright star Procyon (α Canis Minoris) is derived +from the Greek προκύων, “the advanced day,” because it appeared +in the morning sky before Sirius. Procyon was called by the Hindoos +Hanouman after their famous monkey god, from whose tail a bridge is said +to have been formed to enable the army of Rama to pass from India to +Ceylon. Al-Sufi says that the star was<span class="pagenum"><a name="Page_285" id="Page_285">[Pg 285]</a></span> marked on the old astrolabes as +<i>al-schira al-schamia</i>, “the Syrian Sirius.” It was also called, he says, +<i>al-schira al-gumaisa</i>, “the Sirius with blear eyes” (!) from weeping +because Sirius had passed across the Milky Way, Procyon remaining on the +eastern side. Here we have the same legend again. The proper motion of +Procyon (about the same in amount and direction as that of Sirius) shows +that the star has been on the eastern side of the Milky Way for many ages +past. About 60,000 years hence, Procyon will be near the star θ +Canis Majoris, and will then—like Sirius—have passed across the Milky +Way.</p> + +<p>Argo, the Ship, is a large constellation south of Hydra, Monoceros, and +Canis Major. It is called by Al-Sufi <i>al-safîna</i>, “the Ship.” It is +supposed to represent the first ship ever built. The name is derived from +the builder Argo, or from the Greek word ’Αργὸς. This ship is said +to have been built in Thessaly by order of Minerva and Neptune, to go on +the expedition for the conquest of the golden fleece. The date of this +expedition, commanded by Jason, is usually fixed at 1300 or 1400 <span class="smcaplc">B.C.</span> With +reference to the position of this supposed ship in the sky, Proctor says, +“It is noteworthy that when we make due correction for the effects of +precession during the past 4000 years, the old constellation Argo is set +on an even keel, instead of being tilted some 45° to the horizon, as at +present when<span class="pagenum"><a name="Page_286" id="Page_286">[Pg 286]</a></span> due south.” He connects Argo with Noah’s Ark.</p> + +<p>The brightest star of Argo is Canopus, called Suhaïl by Al-Sufi. It is the +second brightest star in the heavens; but it is not visible in northern +latitudes. The Harvard photometric measures make it nearly one magnitude +brighter than the zero magnitude, about two magnitudes brighter than +Aldebaran, and about half the brightness of Sirius. This fine star has +been suspected of variable light. Webb says, “It was thought (1861) in +Chili brighter than Sirius.” Observing it in the Punjab, the present +writer found it on several occasions but little inferior to Sirius, +although very low on the southern horizon. From recent observations by Mr. +H. C. McKay in Australia, he believes that it is variable to the extent of +at least half a magnitude.<a name='fna_440' id='fna_440' href='#f_440'><small>[440]</small></a> But it is difficult to establish +variations of light in very bright stars. The parallax of Canopus is +<i>very</i> small, so its distance from the earth is very great, and it must be +a sun of gigantic size. According to Al-Fargani, Canopus was called the +star of St. Catherine by the Christian pilgrims in the tenth century.<a name='fna_441' id='fna_441' href='#f_441'><small>[441]</small></a> +It was called Suhaïl by the old Arabians, a name apparently derived from +the root <i>sahl</i>, “a plain”; and Schjellerup suggests that the name was +probably applied to this and some other southern<span class="pagenum"><a name="Page_287" id="Page_287">[Pg 287]</a></span> stars because they seem +to move along a plain near the southern horizon. Al-Sufi says that he +measured the latitude of Schiraz in Persia, where he observed, and found +it to be 29° 36′; and hence for that place Canopus, when on the meridian, +had an altitude of about 9°. Canopus was the ancient name of Aboukir in +Egypt, and is said to have derived its name from the pilot of Menelaus, +whose name was Kanobus, and who died there from the bite of a snake. The +star is supposed to have been named after him, and it was worshipped by +the ancient Egyptians.</p> + +<p>Al-Sufi does not mention the famous variable star η Argûs, which, +owing to the precession of the equinoxes, he might possibly have seen +<i>close to the horizon</i>, if it had been a bright star in his day. It lies +between φ Velorum and α Crucis. Both of these stars are +mentioned by Al-Sufi, but he says nothing of any bright star (or indeed +any star) between them. This negative evidence tends to show that η +Argûs was not visible to the naked eye in Al-Sufi’s time. This +extraordinary star has in modern times varied through all degrees of +brightness from Sirius down to the 8th magnitude! Schönfeld thought that a +regular period is very improbable. It seems to be a sort of connecting +link between the long period variables and the <i>novæ</i> or temporary stars. +It is reddish in colour, and the spectrum of its light is very similar to +that of the temporary stars. Whether it will<span class="pagenum"><a name="Page_288" id="Page_288">[Pg 288]</a></span> ever become a brilliant +object again, time alone can tell; but from the fact that it was +presumably faint in Al-Sufi’s time, and afterwards increased to the +brightness of Sirius, it seems possible that its light may again revive.</p> + +<p>The long constellation Hydra lies south of Cancer, Leo, Crater, Corvus, +Virgo, and Libra. It was also called Asina, Coluber, Anguis, Sublimatus, +etc. In the Greek mythology it was supposed to represent the Lernæan +serpent killed by Hercules. According to Ovid, who fixed its acronycal +rising for February 14, it had a common origin with Corvus and Crater. +Apollo, wishing to sacrifice to Jupiter, sent the Crow with a cup to fetch +water. On his way to the well the Crow stopped at a fig tree and waited +for the fruit to ripen! Afterwards, to excuse his delay, he said that a +serpent had prevented him from drawing the water. But Apollo, to punish +the Crow for his deception, changed his plumage from white to black, and +ordered the serpent to prevent the Crow from drinking.<a name='fna_442' id='fna_442' href='#f_442'><small>[442]</small></a> Hydra was +called by Al-Sufi <i>al-schudja</i>, “the Serpent, or Hydra.” He says that “it +contains twenty-five stars in the figure and two ‘outside’, and its head +is to the south of the southern scale of the Balance” (α Libræ). +But this is clearly a mistake (one of the very few errors to be found in +Al-Sufi’s work), for he goes on to say that the head is composed of four +stars<span class="pagenum"><a name="Page_289" id="Page_289">[Pg 289]</a></span> forming a figure like the head of a horse, and he adds, “This head +is in the middle between <i>al-shira al-gumaisa</i> [Procyon] and <i>Kalb +al-asad</i> [Regulus] the Heart, inclining from these two stars a little to +the south.” This clearly indicates the stars δ, ε, η, and σ +Hydræ which, with ζ Hydræ, have always been considered as +forming the Hydra’s head. These stars lie south of α and β +Cancri, not south of Libra as Al-Sufi says (doubtless by a slip of the +pen).</p> + +<p>Ptolemy’s 12th star of Hydra (α Hydræ) is, Al-Sufi says, “the +bright red star which is found at the end of the neck where the back +begins; it is of the 2nd magnitude. It is that which is marked on the +astrolabe as <i>unk al-schudja</i>, ‘the neck of the serpent,’ also <i>al-fard</i>, +‘the solitary one.’” Al-Sufi’s estimate of its brightness agrees well with +modern measures; but it has been suspected of variable light. Sir John +Herschel’s estimates at the Cape of Good Hope varied from 1·75 to 2·58 +magnitude. He thought that its apparent variation might be due to its +reddish colour, and compares it to the case of α Cassiopeiæ. But +as this latter star is now <i>known</i> to be irregularly variable it seems +probable that α Hydræ may be variable also. Gemmill found it +remarkably bright on May 9, 1883, when he thought it nearly equal to +Pollux (1·2 magnitude). On the other hand, Franks thought it nearer the +3rd than the 2nd magnitude on March 2, 1878. On April 9, 1884, the<span class="pagenum"><a name="Page_290" id="Page_290">[Pg 290]</a></span> +present writer found it only slightly less than Regulus (1·3 magnitude). +On April 6, 1886, how-ever, it was considerably less than Regulus, but +half a magnitude brighter than β Canis Minoris, or about 2½ +magnitude. In the Chinese Annals it is called the “Red Bird.” In a list of +thirty stars found on a tablet at Birs-Nimroud, it is called “The son of +the supreme temple.” Although to the naked eye deserving the name of +Alphard or “the solitary one,” it is by no means an isolated star when +examined with a telescope. It has a faint and distant companion, observed +by Admiral Smyth; and about 25′ to the west of it Ward saw a small double +star (8, 13: 90°: 50″). With a 3-inch refractor in the Punjab, I saw a +small star of about 8½ magnitude to the south and a little east of the +bright star, probably identical with Smyth’s companion. Farther off in the +same direction I saw a fainter star, and others at greater distances in +the field. There is also a faint star a little to the north. I also saw +Ward’s double with the 3-inch telescope.</p> + +<p>There is some difficulty in identifying the stars numbered by Ptolemy 13, +14, and 15 in Hydra. Having plotted a map from Ptolemy’s positions (as +given by Al-Sufi), I have come to the conclusion that Ptolemy’s stars are +13 = κ Hydræ; 14 = υ; and 15 = λ Hydræ, +probably. From the clear description given by Al-Sufi of the stars +<span class="pagenum"><a name="Page_291" id="Page_291">[Pg 291]</a></span>observed by <i>him</i>, I find that <i>his</i> stars are 13 = υ<sub>1</sub>; 14 = +υ<sub>2</sub>; and 15 = λ Hydræ. We must, therefore, conclude +that Ptolemy and Al-Sufi saw only three stars where now there are +four,<a name='fna_443' id='fna_443' href='#f_443'><small>[443]</small></a> and that κ Hydræ was not seen, or at least is not +mentioned by Al-Sufi. κ is, therefore, probably variable. It was +rated 4 by Tycho Brahé, Bayer, and Hevelius; it is at present about 5th +magnitude. If Ptolemy did not see υ<sub>2</sub> it is probably variable +also, and, indeed, it has been suspected of variable light.<a name='fna_444' id='fna_444' href='#f_444'><small>[444]</small></a></p> + +<p>The small constellation of Crater, the Cup, lies north of Hydra, and south +of Leo and Virgo. Al-Sufi calls it <i>al-batija</i>, “the Jar, or Cup.” He says +the Arabians called it <i>al-malif</i>, “the Crib, or Manger.” According to +Brown, the stars of Crater exactly form a Bakhian κάνθαρος, with +its two handles rising above the two extremities of the +circumference.<a name='fna_445' id='fna_445' href='#f_445'><small>[445]</small></a> An Asia Minor legend “connected Crater with the mixing +of human blood with wine in a bowl.” Crater is referred to by Ovid in the +lines—</p> + +<p class="poem">“Dixit et antiqui monumenta perennia facti<br /> +Anguis, Avis, Crater sidera, juncta micunt.”</p> + +<p>The star α Crateris was rated 4th magnitude by<span class="pagenum"><a name="Page_292" id="Page_292">[Pg 292]</a></span> Al-Sufi and all +other observers, and the Harvard measures make it 4·20, a satisfactory +agreement. It has three companions noted by Admiral Smyth. One of these he +called “intense blood colour.” This is R Crateris, now known to be +variable from above the 8th magnitude to below the 9th. Sir John Herschel +called it an “intense scarlet star, a curious colour.” With 3-inch +refractor in the Punjab I found it “full scarlet.” It is one of an open +pair, the further of the two from α. There is a third star about +9th magnitude a little south of it. Ward saw a 13th magnitude star between +α and R with a 2⅞-inch (Wray) refractor. This I saw “readily” +with my 3-inch. Smyth does not mention this faint star, although he used a +much larger telescope.</p> + +<p>Corvus, the Crow, is a small constellation, north of Hydra. Aratus says +“the Crow form seems to peck the fold of the water snake” (Hydra). The +victory which Valerius Corvinus is said to have owed to a crow has given +it the name of Pomptina, because the victory took place near the Pontine +marshes.<a name='fna_446' id='fna_446' href='#f_446'><small>[446]</small></a> A quadrilateral figure is formed by its four brightest +stars, γ, δ, β, and ε Corvi. This figure has sometimes +been mistaken for the Southern Cross by those who are not familiar with +the heavens. But the stars of the Southern Cross are much brighter.</p> + +<p>The constellation Centaurus, the Centaur, lies<span class="pagenum"><a name="Page_293" id="Page_293">[Pg 293]</a></span> south of Hydra and Libra, +and north of the Southern Cross. According to Dupuis, Centaurus represents +the 3rd “labour of Hercules,” his triumph over the Centaurs.<a name='fna_447' id='fna_447' href='#f_447'><small>[447]</small></a> The +Centaurs were supposed to be a people living in the vicinity of Mount +Ossa, who first rode on horses. The constellation was also called Semivir, +Chiron, Phobos, Minotaurus, etc. Al-Sufi says it “is represented by the +figure of an animal, of which the forepart is the upper part of a man from +the head to end of the back, and its hinder part is the hinder part of a +horse, from the beginning of the back to the tail. It is to the south of +the Balance [Libra] turning its face towards the east, and the hinder part +of the beast towards the west.”</p> + +<p>Al-Sufi describes very clearly the four bright stars of the famous +“Southern Cross.” Owing to precession these stars were some 7° further +north in the tenth century than they are at present, and they could have +been all seen by Al-Sufi, when on the meridian. In the time of Ptolemy and +Hipparchus, they were still further north, and about 5000 years ago they +were visible in the latitude of London. Dante speaks of these four stars +as emblematical of the four cardinal virtues, Justice, Temperance, +Fortitude, and Prudence.</p> + +<p>Closely south-east of α and β Crucis is the dark spot in +the Milky Way known as the “Coal Sack,”<span class="pagenum"><a name="Page_294" id="Page_294">[Pg 294]</a></span> which forms such a conspicuous +object near the Southern Cross. It was first described by Pinzon in 1499; +and afterwards by Lacaille in 1755. Although to the naked eye apparently +black, photographs show that it contains many faint stars, but, of course, +much less numerous than in the surrounding regions. The dark effect is +chiefly caused by contrast with the brilliancy of the Milky Way +surrounding it.</p> + +<p>Al-Sufi also mentions the bright stars α and β Centauri +which follow the Southern Cross. He says that the distance between them +“is four cubits,” that is about 9° 20′, but it is less than this now. +α has a large “proper motion” of 3″·67 per annum, and was farther +from β in Al-Sufi’s time than it is at present. This, however, +would not <i>wholly</i> account for the difference, and Al-Sufi’s over-estimate +is probably due to the well-known effect by which the distance between two +stars is <i>apparently</i> increased when they are near the horizon. Several of +Al-Sufi’s distances between southern stars are over-estimated, probably +for the same reason.</p> + +<p>The constellation Lupus, the Wolf, is south of Libra and Scorpio. It lies +along the western border of the Milky Way. According to ancient writers it +represents Lycaon, King of Arcadia, a contemporary of Cecrops, who is said +to have sacrificed human victims, and on account of his cruelty was +changed into a wolf. Another fable<span class="pagenum"><a name="Page_295" id="Page_295">[Pg 295]</a></span> is that it represents a wolf +sacrificed by the Centaur Chiron. According to Brown, Lupus appears on the +Euphratian planisphere discovered by George Smyth in the palace of +Sennacherib. Al-Sufi called it <i>al-sabu</i>, “the Wild Beast.” It was also +called <i>al-fand</i>, “the Leopard,” and <i>al-asada</i>, “the Lioness.”</p> + +<p>Ara, the Altar, lies south of Scorpio. According to ancient writers it +represents an altar built by Vulcan, when the gods made war against the +Titans. It is called by Al-Sufi <i>al-midjman</i>, “the Scent Box,” or “the +Altar.”</p> + +<p>The little constellation Corona Australis, the Southern Crown, lies south +and west of Sagittarius, east of Scorpio, and west of Telescopium. Aratus +refers to the stars in Corona Australis as—</p> + +<p class="poem"><span style="margin-left: 9em;">“Other few</span><br /> +Before the Archer under his forefeet<br /> +Led round in circle roll without a name.”<a name='fna_449' id='fna_449' href='#f_449'><small>[449]</small></a></p> + +<p>But the constellation was known by the names Caduceus, Orbiculus, Corona +Sagittarii, etc. The ancient poets relate that Bacchus placed this crown +in the sky in honour of his mother Semele.<a name='fna_450' id='fna_450' href='#f_450'><small>[450]</small></a> Others say that it +represents the crown conferred on Corinne of Thebes, famous as a poet.</p> + +<p>The small constellation Piscis Australis, or the<span class="pagenum"><a name="Page_296" id="Page_296">[Pg 296]</a></span> Southern Fish, lies +south of Capricornus and Aquarius. In the most ancient maps it is +represented as a fish drinking the water which flows from the urn of +Aquarius.</p> + +<hr style="width: 25%;" /> + +<p>A good many constellations have been added to the heavens since the days +of Al-Sufi, and notes on some of these may be of interest.</p> + +<p><span class="smcap">Camelopardalis.</span>—This constellation first appears on a celestial +planisphere published by Bartschius in the year 1624. It was not formed by +Bartschius himself, but by the navigators of the sixteenth century. It +lies south of Ursa Minor, north of Perseus and Auriga, east of Draco, and +west of Cassiopeia. It contains no star brighter than the 4th magnitude.</p> + +<p><span class="smcap">Lynx.</span>—This constellation is south of Camelopardalis and Ursa Major, and +north of Gemini and Cancer. It was formed by Hevelius in 1660, and he +called it the Lynx, because, he said, it contained only faint stars and +“it was necessary to have the eyes of a lynx” to see them! Some of them +were, however, observed by Ptolemy and Al-Sufi, and are mentioned by the +latter under Ursa Major.</p> + +<p><span class="smcap">Canes Venatici</span>, or the Hunting Dogs.—This was formed by Hevelius in 1660. +It lies south of the Great Bear’s tail, north of Coma Berenices, east of +Ursa Major, and west of Boötis. Its brightest stars α (12) and +β (8) were observed by Al-Sufi,<span class="pagenum"><a name="Page_297" id="Page_297">[Pg 297]</a></span> and included by him in the +“extern” stars of Ursa Major.</p> + +<p><span class="smcap">Coma Berenices.</span>—This constellation lies between Canes Venatici and Virgo. +Although it was not included among the old forty-eight constellations of +Ptolemy, it is referred to by Al-Sufi as the Plat, or Tress of Hair, and +he included its stars Flamsteed 12, 15, and 21 in the “extern” stars of +Leo. It was originally formed by the poet Callimachus in the third century +<span class="smcaplc">B.C.</span>, but was not generally accepted until reformed by Hevelius. +Callimachus lived at Alexandria in the reigns of Ptolemy Philadelphus and +Ptolemy Euergetes, and was chief librarian of the famous library of +Alexandria from about <span class="smcaplc">B.C.</span> 260 until his death in <span class="smcaplc">B.C.</span> 240. Eratosthenes +was one of his pupils. The history of the constellation is as follows: +Berenice, wife of Ptolemy Euergetes, made a vow, when her husband was +leaving her on a military expedition, that if he returned in safety she +would cut off her hair and consecrate it in the temple of Mars. Her +husband returned, and she fulfilled her vow. But on the next day the hair +had disappeared—stolen from the temple—and Conon the mathematician +showed Ptolemy seven stars near the constellation of the Lion which did +not belong to any constellation. These were formed into a constellation +and called Berenice’s Hair. Conon is referred to by Catullus in the +lines—</p> + +<p class="poem"><span class="pagenum"><a name="Page_298" id="Page_298">[Pg 298]</a></span> +“Idem me ille Conon cœleste numine vidit<br /> +E. Berenico vertice Cæsariem.”</p> + +<p>Coma Berenices first occurs as a distinct constellation in the catalogue +contained in the Rudolphine Tables formed by Kepler (epoch 1600) from the +observations of Tycho Brahé.<a name='fna_451' id='fna_451' href='#f_451'><small>[451]</small></a> Bayer substituted a sheaf of corn, an +idea derived from an ancient manuscript.</p> + +<p><span class="smcap">Leo Minor.</span>—This small constellation lies between Ursa Major and Leo, and +east of the Lynx. It was formed by Halley about the year 1660; but is +referred to by Al-Sufi, who includes one of its stars (Fl. 41) in the +“extern” stars of Leo. There are, however, several brighter stars in the +group. The brightest, Fl. 46, was measured 3·92 at Harvard. The star Fl. +37 was called <i>præcipua</i> (or brightest) by Tycho Brahé, and rated 3, but +as it was measured only 4·77 at Harvard it may possibly have diminished in +brightness.</p> + +<p><span class="smcap">Sextans.</span>—This constellation lies south of Leo, and north and east of +Hydra. It was formed by Hevelius about the year 1680. According to the +Harvard photometric measures its brightest star is Fl. 15 (4·50).</p> + +<p><span class="smcap">Monoceros</span>, or the Unicorn, lies south of Gemini and Canis Minor, north of +Canis Major and Argo, east of Orion, and west of Hydra. It appears on the +planisphere of Bartschius, published in<span class="pagenum"><a name="Page_299" id="Page_299">[Pg 299]</a></span> 1624. According to Scaliger it is +shown on an old Persian sphere. One of its stars, Fl. 22, is mentioned by +Al-Sufi among the “extern” stars of Canis Major (No. 1). Another, Fl. 30, +is given under Hydra (“Extern” No. 1) and Fl. 8, 13, and 15 are apparently +referred to in Gemini. The star 15 Monocerotis is a little south of +ξ Geminorum, and was measured 4·59 magnitude at Harvard. It was +at one time supposed to be variable with a short period (about 3½ +days), but this variation has not been confirmed. The spectrum is of the +fifth type—with bright lines—a very rare type among naked-eye stars. It +is a triple star (5, 8·8, 11·2: 2″·9, 16″·3) and should be seen with a +4-inch telescope. It has several other small companions, one of which +(139°·2: 75″·7) has been suspected of variation in light. It was estimated +8½ by Main in 1863, but only 12 by Sadler in 1875. Observing it on +March 28, 1889, with 3-inch refractor, I found it about one magnitude +brighter than a star closely preceding, and estimated it 8 or 8½ +magnitude. It is probably variable and should be watched.</p> + +<p><span class="smcap">Scutum Sobieski.</span>—This is, or was, a small constellation in the southern +portion of Aquila, which was formed by Hevelius in 1660 in honour of the +Polish hero Sobieski. Its principal stars, which lie south-west of λ +Aquilæ, were mentioned by Al-Sufi and are referred to by him under that +constellation. It contains a very bright spot of<span class="pagenum"><a name="Page_300" id="Page_300">[Pg 300]</a></span> Milky Way light, which +may be well seen in the month of July just below the star λ +Aquilæ. Closely south of the star 6 Aquilæ is a remarkable variable star R +Scuti (R.A. 18<sup>h</sup> 42<sup>m</sup>·2, S. 5° 49′). It varies from 4·8 to 7·8 with an +irregular period. All the light changes can be observed with a good +opera-glass.</p> + +<p><span class="smcap">Vulpecula</span>, the Fox.—This modern constellation lies south of Cygnus, north +of Sagitta and Delphinus, east of Hercules, and west of Pegasus. It was +formed by Hevelius in 1660. One of its stars, 6 Vulpeculæ, is mentioned by +Al-Sufi in describing the constellation Cygnus. Closely north-west of 32 +Vulpeculæ is the short-period variable T Vulpeculæ. It varies from 5·5 to +6·2 magnitude, and its period is 4·436 days. This is an interesting +object, and all the changes of light can be observed with an opera-glass.</p> + +<p><span class="smcap">Lacerta.</span>—This little constellation lies south of Cepheus and north of +Pegasus. Its formation was first suggested by Roger and Anthelm in 1679, +and it was called by them “The Sceptre and the Hand of Justice.” It was +named Lacerta by Hevelius in 1690, and this name it still retains. Al-Sufi +seems to refer to its stars in his description of Andromeda, but does not +mention any star in particular. It brightest star Fl. 7 (α +Lacertæ) is about the 4th magnitude. About one degree south-west of 7 is 5 +Lacertæ, a deep orange star with a blue companion in a fine field.</p> + +<p><span class="pagenum"><a name="Page_301" id="Page_301">[Pg 301]</a></span>There are some constellations south of the Equator which, although above +Al-Sufi’s horizon when on the meridian, are not described by him, as they +were formed since his time. These are as follows:—</p> + +<p><span class="smcap">Sculptor.</span>—This constellation lies south of Aquarius and Cetus, and north +of Phœnix. Some of its stars are referred to by Al-Sufi under Eridanus +as lying within the large triangle formed by β Ceti, Fomalhaut, +and α Phœnicis. The brightest star is α, about 12° +south of β Ceti (4·39 magnitude Harvard). About 7° south-east of +α is the red and variable star R Sculptoris; variable from 6·2 to +8·8 magnitude, with a period of about 376 days. Gould describes it as +“intense scarlet.” It has a spectrum of the fourth type.</p> + +<p><span class="smcap">Phœnix.</span>—This constellation lies south of Sculptor. Some of its stars +are referred to by Al-Sufi, under Eridanus, as forming a boat-shaped +figure. These are evidently α, κ, μ, β, ν, and γ. +α is at the south-eastern angle of Al-Sufi’s triangle referred to +above (under “Sculptor”). (See Proctor’s Atlas, No. 3.)</p> + +<p><span class="smcap">Fornax</span>, the Furnace, lies south of Cetus, west of Eridanus, and east of +Sculptor and Phœnix. It was formed by Lacaille, and is supposed to +represent a chemical furnace with an alembic and receiver! Its brightest +star, α Fornacis, is identical with 12 Eridani.</p> + +<p><span class="pagenum"><a name="Page_302" id="Page_302">[Pg 302]</a></span><span class="smcap">Cælum</span>, +the Sculptor’s Tools, is a small constellation east of Columba, and +west of Eridanus. It was formed by Lacaille. The brightest stars are +α and γ, which are about 4½ magnitude. α has +a faint companion; and γ is a wide double star to the naked eye.</p> + +<p><span class="smcap">Antlia</span>, the Air Pump, lies south of Hydra, east and north of Argo, and +west of Centaurus. It was formed by Lacaille. It contains no star brighter +than 4th magnitude. The brightest, α, has been variously rated +from 4 to 5, and Stanley Williams thinks its variability “highly +probable.”</p> + +<p><span class="smcap">Norma</span>, the Rule, lies south of Scorpio. It contains no star brighter than +the 4th magnitude.</p> + +<p><span class="smcap">Telescopium.</span>—This modern constellation lies south of Corona Australis, +and north of Pavo. Its stars α, δ, and ζ, which lie near +the northern boundary of the constellation, are referred to by Al-Sufi in +his description of Ara.</p> + +<p><span class="smcap">Microscopium.</span>—This small constellation is south of Capricornus, and west +of Piscis Australis. Its stars seem to be referred to by Al-Sufi as having +been seen by Ptolemy, but he does not specify their exact positions. It +contains no star brighter than 4½ magnitude.</p> + +<hr style="width: 25%;" /> + +<p>South of Al-Sufi’s horizon are a number of constellations surrounding the +south pole, which, of course, he could not see. Most of these have been +formed since his time, and these will now be<span class="pagenum"><a name="Page_303" id="Page_303">[Pg 303]</a></span> considered; beginning with +that immediately surrounding the South Pole (Octans), and then following +the others as nearly as possible in order of Right Ascension.</p> + +<p><span class="smcap">Octans.</span>—This is the constellation surrounding the South Pole of the +heavens. There is no bright star near the Pole, the nearest visible to the +naked eye being σ Octantis, which is within one degree of the +pole. It was estimated 5·8 at Cordoba. The brightest star in the +constellation is ν Octantis (α, Proctor), which lies +about 12 degrees from the pole in the direction of Indus and Microscopium. +The Harvard measure is 3·74 magnitude.</p> + +<p><span class="smcap">Hydrus</span>, the Water-Snake, is north of Octans in the direction of Achernar +(α Eridani). The brightest star is β, which lies close +to θ Octantis. The Harvard measure is 2·90. Gould says its +colour is “clear yellow.” It has a large proper motion of 2″·28 per annum. +Sir David Gill found a parallax of 0″·134, and this combined with the +proper motion gives a velocity of 50 miles a second at right angles to the +line of sight. γ Hydri is a comparatively bright star of about +the 3rd magnitude, about 15½ degrees from the South Pole. It is +reddish, with a spectrum of the third type.</p> + +<p><span class="smcap">Horologium</span>, the Clock, is north of Hydra, and south of Eridanus. Three of +its stars, α, δ, and ψ, at the extreme northern end of +the constellation,<span class="pagenum"><a name="Page_304" id="Page_304">[Pg 304]</a></span> seem to be referred to by Al-Sufi in his description +of Eridanus, but he does not give their exact positions. Most of the stars +forming this constellation were below Al-Sufi’s horizon.</p> + +<p><span class="smcap">Reticulum</span>, the Net, is a small constellation to the east of Hydrus and +Horologium. The brightest star of the constellation is α (3·36 +Harvard, 3·3 Cordoba, and “coloured”).</p> + +<p><span class="smcap">Dorado</span>, the Sword Fish, lies east of Reticulum and west of Pictor. It +contains only two stars brighter than the 4th magnitude. These are α +(3·47 Harvard) and β (3·81 Harvard, but suspected of +variation). About 3° east of α Reticuli is the variable star R +Doradus. It varies from 4·8 to 6·8, and its period is about 345 days. +Gould calls it “excessively red.” It may be followed through all its +fluctuations of light with an opera-glass.</p> + +<p><span class="smcap">Mensa</span>, or Mons Mensa, the Table Mountain, lies between Dorado and the +South Pole, and represents the Table Mountain of the Cape of Good Hope. It +contains no star brighter than the 5th magnitude.</p> + +<p><span class="smcap">Pictor</span>, the Painter’s Easel, lies north of Doradus, and south of Columba. +It contains no very bright stars, the brightest being α (3·30 +Harvard).</p> + +<p><span class="smcap">Volans</span>, the Flying Fish, is north of Mensa, and south and west of Argo. +Its brighter stars, with the exception of α and β, form +an irregular six-sided figure. Its brightest star is β (3·65) +according<span class="pagenum"><a name="Page_305" id="Page_305">[Pg 305]</a></span> to the Harvard measures. The Cordoba estimates, however, range +from 3·6 to 4·4, and Gould says its colour is “bright yellow.” Williams +rated it 3·8.</p> + +<p><span class="smcap">Chamælion.</span>—This small constellation lies south of Volans, and north of +Mensa and Octans. None of its stars are brighter than the 4th magnitude, +its brightest being α (4·08 Harvard) and γ (4·10).</p> + +<p><span class="smcap">Argo.</span>—This large constellation extends much further south than Al-Sufi +could follow it. The most southern star he mentions is ε Carinæ, +but south of this are several bright stars. β Carinæ is 1·80 +according to the Harvard measures; υ Carinæ, 3·08; θ, +3·03; ω, 3·56; and others. A little north-west of ι is +the long-period variable R Carinæ (9<sup>h</sup> 29<sup>m</sup>·7, S. 62° 21′, 1900). It +varies from 4·5 at maximum to 10 at minimum, and the period is about 309·7 +days. A little east of R Carinæ is another remarkable variable star, <i>l</i> +Carinæ (R.A. 9<sup>h</sup> 42<sup>m</sup>·5, S. 62° 3′). It varies from 3·6 to 5·0 +magnitude, with a period of 35½ days from maximum to maximum. All the +light changes can be observed with an opera-glass, or even with the naked +eye. It was discovered at Cordoba. The spectrum is of the solar type (G).</p> + +<p><span class="smcap">Musca</span>, the Bee, is a small constellation south of the Southern Cross and +Centaurus. Its brightest stars are α (2·84 Harvard) and β +(3·26). These two stars form a fine pair south of<span class="pagenum"><a name="Page_306" id="Page_306">[Pg 306]</a></span> α Crucis. +Closely south-east of α is the short-period variable R Muscæ. It +varies from 6·5 to 7·6 magnitude, and its period is about 19 hours. All +its changes of light may be observed with a good opera-glass.</p> + +<p><span class="smcap">Apus</span>, the Bird of Paradise, lies south-east of Musca, and north of Octans. +Its brightest star is α, about the 4th magnitude. Williams calls +it “deep yellow.” About 3° north-west of α, in the direction of +the Southern Cross, is θ Apodis, which was found to be variable +at Cordoba from 5½ to 6½. The spectrum is of the third type, which +includes so many variable stars.</p> + +<p><span class="smcap">Triangulum Australis</span>, the Southern Triangle, is a small constellation +north of Apus, and south of Norma. A fine triangle, nearly isosceles, is +formed by its three bright stars, α, β, γ, the brightest α +being at the vertex. These three stars form with α Centauri an +elongated cross. The stars β and γ are about 3rd +magnitude. β is reddish. ε (4·11, Harvard) is also +reddish, and is nearly midway between β and γ, and near +the centre of the cross above referred to. α is a fine star (1·88 +Harvard) and is one of the brightest stars in the sky—No. 33 in a list of +1500 highest stars given by Pickering. About 1° 40′ west of ε is +the short-period variable R Trianguli Australis (R.A. 15<sup>h</sup> 10<sup>m</sup>·8, S. +66° 8′) discovered at Cordoba in 1871. It varies from 6·7 to 7·4, and the +period is about 3<sup>d</sup> 7<sup>h</sup>·2. Although not visible to ordinary<span class="pagenum"><a name="Page_307" id="Page_307">[Pg 307]</a></span> eyesight it +is given here, as it is an interesting object and all its light changes +may be well seen with an opera-glass. A little south-east of β is +another short-period variable, S Trianguli Australis (R.A. 15<sup>h</sup> 52<sup>m</sup>·2, +S. 63° 30′), which varies from 6·4 to 7·4, with a period of 6·3 days; and +all its fluctuations of light may also be observed with a good +opera-glass.</p> + +<p><span class="smcap">Circinus</span>, the Compass, is a very small constellation lying between +Triangulum and Centaurus. Its brightest star, α, is about 3½ +magnitude, about 4° south of α Centauri.</p> + +<p><span class="smcap">Pavo</span>, the Peacock, lies north of Octans and Apus, and south of +Telescopium. Its brightest star is α, which is a fine bright star +(2·12 Harvard). κ is a short-period variable. It varies from 3·8 +to 5·2, and the period is about 9 days. This is an interesting object, as +all the fluctations of light can be observed by the naked eye or an +opera-glass. ε Pavonis was measured 4·10 at Harvard, but the +Cordoba estimates vary from 3·6 to 4·2. Gould says “it is of a remarkably +blue colour.”</p> + +<p><span class="smcap">Indus.</span>—This constellation lies north of Octans, and south of Sagittarius, +Microscopium, and Grus. One of its stars, α, is probably referred +to by Al-Sufi in his description of Sagittarius; it lies nearly midway +between β Sagittarii and α Gruis, and is the brightest +star of the constellation. The star ε Indi (4·74 Harvard) has a +remarkably large<span class="pagenum"><a name="Page_308" id="Page_308">[Pg 308]</a></span> proper motion of 4″·68 per annum. Its parallax is about +0″·28, and the proper motion indicates a velocity of about 49 miles a +second at right angles to the line of sight.</p> + +<p><span class="smcap">Toucan.</span>—This constellation lies north of Octans, and south of Phœnix +and Grus, east of Indus, and west of Hydrus. Its brightest star is α, of about the 3rd magnitude.</p> + +<hr style="width: 25%;" /> + +<p>There are seven “celestial rivers” alluded to by the ancient +astronomers:—</p> + +<p>1. The Fish River, which flows from the urn of Aquarius.</p> + +<p>2. The “River of the Bird,” or the Milky Way in Cygnus.</p> + +<p>3. The River of the Birds—2, including Aquila.</p> + +<p>4. The River of Orion—Eridanus.</p> + +<p>5. The River of the god Marduk—perhaps the Milky Way in Perseus.</p> + +<p>6. The River of Serpents (Serpens, or Hydra).</p> + +<p>7. The River of Gan-gal (The High Cloud)—probably the Milky Way as a +whole.</p> + +<p>There are four serpents represented among the constellations. These are +Hydra, Hydrus, Serpens, and Draco.</p> + +<p>According to the late Mr. Proctor the date of the building of the Great +Pyramid was about 3400 <span class="smcaplc">B.C.</span><a name='fna_452' id='fna_452' href='#f_452'><small>[452]</small></a> At this time the Spring +Equinox was in<span class="pagenum"><a name="Page_309" id="Page_309">[Pg 309]</a></span> +Taurus, and this is referred to by Virgil. But this was not so in Virgil’s +time, when—on account of the precession of the equinoxes—the equinoctial +point had already entered Pisces, in which constellation it still remains. +At the date 3400 <span class="smcaplc">B.C.</span> the celestial equator ran along the whole length of +the constellation Hydra, nearly through Procyon, and a little north of the +bright red star Antares.</p> + +<p>The star Fomalhaut (α Piscis Australis) is interesting as being +the most southern 1st magnitude star visible in England, its meridian +altitude at Greenwich being little more than eight degrees.<a name='fna_453' id='fna_453' href='#f_453'><small>[453]</small></a></p> + +<p>With reference to the Greek letters given to the brighter stars by Bayer +(in his Atlas published in 1603), and now generally used by astronomers, +Mr. Lynn has shown that although “Bayer did uniformly designate the +brightest stars in each constellation by the letter α,”<a name='fna_454' id='fna_454' href='#f_454'><small>[454]</small></a> it +is a mistake to suppose—as has often been stated in popular books on +astronomy—that he added the other Greek letters <i>in order of brightness</i>. +That this is an error clearly appears from Bayer’s own “Explicatio” to his +Atlas, and was long since pointed out by Argelander (1832), and by Dr. +Gould in his <i>Uranometria Argentina</i>. Gould says,<span class="pagenum"><a name="Page_310" id="Page_310">[Pg 310]</a></span> “For the stars of each +order, the sequence of the letters in no manner represents that of their +brightness, but depended upon the positions of the stars in the figure, +beginning usually at the head, and following its course until all the +stars of that order of magnitude were exhausted.” Mr. Lynn says, “Perhaps +one of the most remarkable instances in which the lettering is seen at a +glance not to follow the order of the letters is that of the three +brightest stars in Aquila [Al-Sufi’s ‘three famous stars’], γ +being evidently brighter than β. But there is no occasion to +conjecture from this that any change of relative brightness has taken +place. Bayer reckoned both of these two of the third magnitude, and +appears to have arranged β before γ, according to his +usual custom, simply because β is in the neck of the supposed +eagle, and γ at the root of one of the wings.”<a name='fna_455' id='fna_455' href='#f_455'><small>[455]</small></a> Another good +example is found in the stars of the “Plough,” in which the stars are +evidently arranged in the order of the figure and not in the order of +relative brightness. In fact, Bayer is no guide at all with reference to +star magnitudes. How different Al-Sufi was in this respect!</p> + +<p>The stars Aldebaran, Regulus, Antares, and Fomalhaut were called royal +stars by the ancients. The reason of this was that they lie roughly about +90° apart, that is 6 hours of Right Ascension. So, if through the north +and south poles of the<span class="pagenum"><a name="Page_311" id="Page_311">[Pg 311]</a></span> heavens and each of these stars we draw great +circles of the sphere, these circles will divide the sphere into four +nearly equal parts, and the ancients supposed that each of these stars +ruled over a quarter of the sphere, an idea probably connected with +astrology. As the position of Aldebaran is R.A. 4<sup>h</sup> 30<sup>m</sup>, Declination +North 16° 19′, and that of Antares is R.A. 16<sup>h</sup> 15<sup>m</sup>, Declination South +25° 2′, these two stars lie at nearly opposite points of the celestial +sphere. From this it follows that our sun seen from Aldebaran would lie +not very far from Antares, and seen from Antares it would appear not far +from Aldebaran.</p> + +<p>The following may be considered as representative stars of different +magnitudes. For those of first magnitude and fainter I have only given +those for which all the best observers in ancient and modern times agree, +and which have been confirmed by modern photometric measures. The Harvard +measures are given:—</p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td colspan="2">Brighter than</td> + <td>“zero magnitude”</td> + <td>Sirius (-1·58); Canopus (-0·86)</td></tr> +<tr><td colspan="2">Zero magnitude</td> + <td align="center">... ... ...</td> + <td>α Centauri (0·06)</td></tr> +<tr><td colspan="2">0 to 0·4 magnitude</td> + <td align="center">... ... ...</td> + <td>Vega (0·14); Capella (0·21);<br /><span style="margin-left: 1em;">Arcturus (0·24); Rigel (0·34)</span></td></tr> +<tr><td>0·5</td> + <td>magnitude</td> + <td align="center">... ... ...</td> + <td>Procyon (0·48)</td></tr> +<tr><td>1st</td> + <td align="center">"</td> + <td align="center">... ... ...</td> + <td>Aldebaran (1·06)</td></tr> +<tr><td>2nd</td> + <td align="center">"</td> + <td align="center">... ... ...</td> + <td>α Persei (1·90); β Aurigæ (2·07)</td></tr> +<tr><td><span class="pagenum"><a name="Page_312" id="Page_312">[Pg 312]</a></span>3rd</td> + <td align="center">"</td> + <td align="center">... ... ...</td> + <td>η Boötis (3·08); ζ Capricorni (2·98)</td></tr> +<tr><td>4th</td> + <td align="center">"</td> + <td align="center">... ... ...</td> + <td>ρ Leonis (3·85); λ Scorpii (4·16);<br /> + <span style="margin-left: 1em;">γ Crateris(4·14); ρ Herculis (4·14)</span></td></tr> +<tr><td>5th</td> + <td align="center">"</td> + <td align="center">... ... ...</td> + <td>ο Pegasi (4·85); μ Capricorni (5·10)</td></tr></table> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_313" id="Page_313">[Pg 313]</a></span></p> +<h2><a name="CHAPTER_XX" id="CHAPTER_XX"></a>CHAPTER XX</h2> +<p class="title">The Visible Universe</p> + +<p> </p> +<p class="dropcap"><span class="caps">Some</span> researches on the distribution of stars in the sky have recently been +made at the Harvard Observatory (U.S.A.). The principal results are:—(1) +The number of stars on any “given area of the Milky Way is about twice as +great as in an equal area of any other region.” (2) This ratio does not +increase for faint stars down to the 12th magnitude. (3) “The Milky Way +covers about one-third of the sky and contains about half of the stars.” +(4) There are about 10,000 stars of magnitude 6·6 or brighter, 100,000 +down to magnitude 8·7, one million to magnitude 11, and two millions to +magnitude 11·9. It is estimated that there are about 18 millions of stars +down to the 15th magnitude visible in a telescope of 15 inches +aperture.<a name='fna_456' id='fna_456' href='#f_456'><small>[456]</small></a></p> + +<p>According to Prof. Kapteyn’s researches on stellar distribution, he finds +that going out from the earth into space, the “star density”—that is,<span class="pagenum"><a name="Page_314" id="Page_314">[Pg 314]</a></span> +the number of stars per unit volume of space—is fairly constant until we +reach a distance of about 200 “light years.” From this point the density +gradually diminishes out to a distance of 2500 “light years,” at which +distance it is reduced to about one-fifth of the density in the sun’s +vicinity.<a name='fna_457' id='fna_457' href='#f_457'><small>[457]</small></a></p> + +<p>In a letter to the late Mr. Proctor (<i>Knowledge</i>, November, 1885, p. 21), +Sir John Herschel suggested that our Galaxy (or stellar system) “contained +within itself miniatures of itself.” This beautiful idea is probably true. +In his account of the greater “Magellanic cloud,” Sir John Herschel +describes one of the numerous objects it contains as follows:—</p> + +<div class="blockquot"><p>“Very bright, very large; oval; very gradually pretty, much brighter +in the middle; a beautiful nebula; it has very much the resemblance to +the Nubecula Major itself as seen with the naked eye, but it is far +brighter and more impressive in its general aspect as if it were +doubled in intensity. Note—July 29, 1837. I well remember this +observation, it was the result of repeated comparisons between the +object seen in the telescope and the actual nubecula as seen high in +the sky on the meridian, and no vague estimate carelessly set down. +And who can say whether in this object, magnified and analysed by +telescopes infinitely superior to what we now possess, there may not +exist all the complexity of detail that the nubecula itself presents +to our examination?”<a name='fna_458' id='fna_458' href='#f_458'><small>[458]</small></a></p></div> + +<p><span class="pagenum"><a name="Page_315" id="Page_315">[Pg 315]</a></span>The late Lord Kelvin, in a remarkable address delivered before the +Physical Science Section of the British Association at its meeting at +Glasgow in 1901, considered the probable quantity of matter contained in +our Visible Universe. He takes a sphere of radius represented by the +distance of a star having a parallax of one-thousandth of a second (or +about 3000 years’ journey for light), and he supposes that uniformly +distributed within this sphere there exists a mass of matter equal to 1000 +million times the sun’s mass. With these data he finds that a body placed +originally at the surface of the sphere would in 5 million years acquire +by gravitational force a velocity of about 12½ miles a second, and +after 25 million of years a velocity of about 67 miles a second. As these +velocities are of the same order as the observed velocities among the +stars, Lord Kelvin concludes that there <i>is</i> probably as much matter in +our universe as would be represented by a thousand million suns. If we +assumed a mass of ten thousand suns the velocities would be much too high. +The most probable estimate of the total number of the visible stars is +about 100 millions; so that if Lord Kelvin’s calculations are correct we +seem bound to assume that space contains a number of dark bodies. The +nebulæ, however, probably contain vast masses of matter, and this may +perhaps account—partially, at least—for the large amount of<span class="pagenum"><a name="Page_316" id="Page_316">[Pg 316]</a></span> matter +estimated by Lord Kelvin. (See Chapter on “Nebulæ.”)</p> + +<p>In some notes on photographs of the Milky Way, Prof. Barnard says with +reference to the great nebula near ρ Ophiuchi, “The peculiarity +of this region has suggested to me the idea that the apparently small +stars forming the ground work of the Milky Way here, are really very small +bodies compared with our own sun”; and again, referring to the region near +β Cygni, “One is specially struck with the apparent extreme +smallness of the general mass of the stars in this region.” Again, with +reference to χ Cygni, he says, “The stars here also are +remarkably uniform in size.”<a name='fna_459' id='fna_459' href='#f_459'><small>[459]</small></a></p> + +<p>Eastman’s results for parallax seem to show that “the fainter rather than +the brighter stars are nearest to our system.” But this apparent paradox +is considered by Mr. Monck to be very misleading;<a name='fna_460' id='fna_460' href='#f_460'><small>[460]</small></a> and the present +writer holds the same opinion.</p> + +<p>Prof. Kapteyn finds “that stars whose proper motions exceed 0″·05 are not +more numerous in the Milky Way than in other parts of the sky; or, in +other words, if only the stars having proper motions of 0″·05 or upwards +were mapped, there would be no aggregation of stars showing the existence +of the Milky Way.”<a name='fna_461' id='fna_461' href='#f_461'><small>[461]</small></a></p> + +<p><span class="pagenum"><a name="Page_317" id="Page_317">[Pg 317]</a></span>With reference to the number of stars visible on photographs, the late Dr. +Isaac Roberts says—</p> + +<div class="blockquot"><p>“So far as I am able at present to judge, under the atmospheric +conditions prevalent in this country, the limit of the photographic +method of delineation will be reached at stellar, or nebular, light of +the feebleness of about 18th-magnitude stars. The reason for this +inference is that the general illumination of the atmosphere by +starlight concentrated upon a film by the instrument will mask the +light of objects that are fainter than about 18th-magnitude +stars.”<a name='fna_462' id='fna_462' href='#f_462'><small>[462]</small></a></p></div> + +<p>With reference to blank spaces in the sky, the late Mr. Norman Pogson +remarked—</p> + +<div class="blockquot"><p>“Near S Ophiuchi we find one of the most remarkable vacuities in this +hemisphere—an elliptic space of about 65′ in length in the direction +of R.A., and 40′ in width, in which there exists <i>no</i> star larger than +the 13th magnitude ... it is impossible to turn a large telescope in +that direction and, if I may so express it, view such black darkness, +without a feeling that we are here searching into the remote regions +of space, far beyond the limits of our own sidereal system.”<a name='fna_463' id='fna_463' href='#f_463'><small>[463]</small></a></p></div> + +<p>Prof. Barnard describes some regions in the constellation Taurus +containing “dark lanes” in a groundwork of faint nebulosity. He gives two +beautiful photographs of the regions referred to, and says that the dark +holes and lanes are<span class="pagenum"><a name="Page_318" id="Page_318">[Pg 318]</a></span> apparently darker than the sky in the immediate +vicinity. He says, “A very singular feature in this connection is that the +stars also are absent in general from the lanes.” A close examination of +these photographs has given the present writer the impression that the +dark lanes and spots are <i>in</i> the nebulosity, and that the nebulosity is +mixed up with the stars. This would account for the fact that the stars +are in general absent from the dark lanes. For if there is an intimate +relation between the stars and the nebulosity, it would follow that where +there is no nebulosity in this particular region there would be no stars. +Prof. Barnard adds that the nebulosity is easily visible in a 12-inch +telescope.<a name='fna_464' id='fna_464' href='#f_464'><small>[464]</small></a></p> + +<p>With reference to the life of the universe, Prof. F. R. Moulton well +says—</p> + +<div class="blockquot"><p>“The lifetime of a man seems fairly long, and the epoch when Troy was +besieged, or when the Pharaohs piled up the pyramids in the valley of +the Nile, or when our ancestors separated on the high plateaux of +Asia, seems extremely remote, but these intervals are only moments +compared to the immense periods required for geological evolutions and +the enormously greater ones consumed in the developement of worlds +from widely extended nebulous masses. We recognize the existence of +only those forces whose immediate consequences are appreciable, and it +may be that those whose effects are yet unseen are really of the +highest importance. A little creature whose<span class="pagenum"><a name="Page_319" id="Page_319">[Pg 319]</a></span> life extended over only +two or three hours of a summer’s day might be led, if he were +sufficiently endowed with intelligence, to infer that passing clouds +were the chief influence at work in changing the climate instead of +perceiving that the sun’s slow motion across the sky would bring on +the night and its southward motion the winter.”<a name='fna_465' id='fna_465' href='#f_465'><small>[465]</small></a></p></div> + +<p>In a review of my book <i>Astronomical Essays</i> in <i>The Observatory</i>, +September, 1907, the following words occur. They seem to form a good and +sufficient answer to people who ask, What is there beyond our visible +universe? “If the stellar universe is contained in a sphere of say 1000 +stellar units radius, what is there beyond? To this the astronomer will +reply that theories and hypotheses are put forward for the purpose of +explaining observed facts; when there are no facts to be explained, no +theory is required. As there are no observed facts as to what exists +beyond the farthest stars, the mind of the astronomer is a complete blank +on the subject. Popular imagination can fill up the blank as it pleases.” +With these remarks I fully concur.</p> + +<p>In his address to the British Association, Prof. G. H. Darwin (now Sir +George Darwin) said—</p> + +<div class="blockquot"><p>“Man is but a microscopic being relatively to astronomical space, and +he lives on a puny planet circling round a star of inferior rank. Does +it not, then, seem futile to imagine that he can discover<span class="pagenum"><a name="Page_320" id="Page_320">[Pg 320]</a></span> the origin +and tendency of the Universe as to expect a housefly to instruct us as +to the theory of the motions of the planets? And yet, so long as he +shall last, he will pursue his search, and will no doubt discover many +wonderful things which are still hidden. We may indeed be amazed at +all that man has been able to find out, but the immeasurable magnitude +of the undiscovered will throughout all time remain to humble his +pride. Our children’s children will still be gazing and marvelling at +the starry heavens, but the riddle will never be read.”</p></div> + +<p>The ancient philosopher Lucretius said—</p> + +<p class="poem">“Globed from the atoms falling slow or swift<br /> +I see the suns, I see the systems lift<br /> +Their forms; and even the system and the suns<br /> +Shall go back slowly to the eternal drift.”<a name='fna_466' id='fna_466' href='#f_466'><small>[466]</small></a></p> + +<p>But it has been well said that the structure of the universe “has a +fascination of its own for most readers quite apart from any real progress +which may be made towards its solution.”<a name='fna_467' id='fna_467' href='#f_467'><small>[467]</small></a></p> + +<p>The Milky Way itself, Mr. Stratonoff considers to be an agglomeration of +immense condensations, or stellar clouds, which are scattered round the +region of the galactic equator. These clouds, or masses of stars, +sometimes leave spaces between them, and sometimes they overlap, and in +this way he accounts for the great rifts, like the Coal Sack, which allow +us to see through this great<span class="pagenum"><a name="Page_321" id="Page_321">[Pg 321]</a></span> circle of light. He finds other +condensations of stars; the nearest is one of which our sun is a member, +chiefly composed of stars of the higher magnitudes which “thin out rapidly +as the Milky Way is approached.” There are other condensations: one in +stars of magnitudes 6·5 to 8·5; and a third, farther off, in stars of +magnitudes 7·6 to 8. These may be called opera-glass, or field-glass +stars.</p> + +<p>Stratonoff finds that stars with spectra of the first type (class A, B, C, +and D of Harvard) which include the Sirian and Orion stars, are +principally situated near the Milky Way, while those of type II. (which +includes the solar stars) “are principally condensed in a region +coinciding roughly with the terrestrial pole, and only show a slight +increase, as compared with other stars, as the galaxy is approached.”<a name='fna_468' id='fna_468' href='#f_468'><small>[468]</small></a></p> + +<p>Prof. Kapteyn thinks that “undoubtedly one of the greatest difficulties, +if not the greatest of all, in the way of obtaining an understanding of +the real distribution of the stars in space, lies in our uncertainty about +the amount of loss suffered by the light of the stars on its way to the +observer.”<a name='fna_469' id='fna_469' href='#f_469'><small>[469]</small></a> He says, “There can be little doubt in my opinion, about +the existence of absorption in space, and I think that even a good guess +as to the order of its amount can be made. For, first<span class="pagenum"><a name="Page_322" id="Page_322">[Pg 322]</a></span> we know that space +contains an enormous mass of meteoric matter. This matter must necessarily +intercept some part of the star-light.”</p> + +<p>This absorption, however, seems to be comparatively small. Kapteyn finds a +value of 0·016 (about <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">60</span>th) of a magnitude for a star at a distance +corresponding to a parallax of one-tenth of a second (about 33 “light +years”). This is a quantity almost imperceptible in the most delicate +photometer. But for very great distances—such as 3000 “light years”—the +absorption would evidently become very considerable, and would account +satisfactorily for the gradual “thinning out” of the fainter stars. If +this were fully proved, we should have to consider the fainter stars of +the Milky Way to be in all probability fairly large suns, the light of +which is reduced by absorption.</p> + +<p>That some of the ancients knew that the Milky Way is composed of stars is +shown by the following lines translated from Ovid:—</p> + +<p class="poem">“A way there is in heaven’s extended plain<br /> +Which when the skies are clear is seen below<br /> +And mortals, by the name of Milky, know;<br /> +The groundwork is of stars, through which the road<br /> +Lies open to great Jupiter’s abode.”<a name='fna_470' id='fna_470' href='#f_470'><small>[470]</small></a></p> + +<p>From an examination of the distribution of the faint stars composing the +Milky Way, and those shown in Argelander’s charts of stars down to the<span class="pagenum"><a name="Page_323" id="Page_323">[Pg 323]</a></span> +9½ magnitude, Easton finds that there is “a real connection between the +distribution of 9th and 10th magnitude stars, and that of the faint stars +of the Milky Way, and that consequently the faint or very faint stars of +the galactic zone are at a distance which does not greatly exceed that of +the 9th and 10th magnitude stars.”<a name='fna_471' id='fna_471' href='#f_471'><small>[471]</small></a> A similar conclusion was, I think, +arrived at by Proctor many years ago. Now let us consider the meaning of +this result. Taking stars of the 15th magnitude, if their faintness were +merely due to greater distance, their actual brightness—if of the same +size—would imply that they are at 10 times the distance of stars of the +10th magnitude. But if at the same distance from us, a 10th magnitude star +would be 100 times brighter than a 15th magnitude star, and if of the same +density and “intrinsic brightness” (or luminosity of surface) the 10th +magnitude would have 10 times the diameter of the fainter star, and hence +its volume would be 1000 times greater (10<sup>3</sup>), and this great difference +is not perhaps improbable.</p> + +<p>The constitution of the Milky Way is not the same in all its parts. The +bright spot between β and γ Cygni is due to relatively +bright stars. Others equally dense but fainter regions in Auriga and +Monoceros are only evident in stars of the 8th and 9th magnitude, and the +light of the well-known luminous spot in “Sobieski’s Shield,”<span class="pagenum"><a name="Page_324" id="Page_324">[Pg 324]</a></span> closely +south of λ Aquilæ, is due to stars below magnitude 9½.</p> + +<p>The correspondence in distribution between the stars of Argelander’s +charts and the fainter stars of the Milky Way shows, as Easton points out, +that Herschel’s hypothesis of a uniform distribution of stars of +approximately equal size is quite untenable.</p> + +<p>It has been suggested that the Milky Way may perhaps form a ring of stars +with the sun placed nearly, but not exactly, in the centre of the ring. +But were it really a ring of uniform width with the sun eccentrically +placed within it, we should expect to find the Milky Way wider at its +nearest part, and gradually narrowing towards the opposite point. Now, +Herschel’s “gages” and Celoria’s counts show that the Galaxy is wider in +Aquila than in Monoceros. This is confirmed by Easton, who says, “<i>for the +faint stars taken as a whole, the Milky Way is widest in its brightest +part</i>” (the italics are Easton’s). From this we should conclude that the +Milky Way is nearer to us in the direction of Aquila than in that of +Monoceros. Sir John Herschel suggested that the southern parts of the +galactic zone are nearer to us on account of their greater <i>brightness</i> in +those regions.<a name='fna_472' id='fna_472' href='#f_472'><small>[472]</small></a> But greater width is a safer test of distance than +relative brightness. For it may be easily shown than the <i>intrinsic</i> +brightness of an<span class="pagenum"><a name="Page_325" id="Page_325">[Pg 325]</a></span> area containing a large number of stars would be the +same for <i>all</i> distances (neglecting the supposed absorption of light in +space). For suppose any given area crowded with stars to be removed to a +greater distance. The light of each star would be diminished inversely as +the square of the distance. But the given area would also be diminished +<i>directly</i> as the square of the distance, so we should have a diminished +amount of light on an equally diminished area, and hence the intrinsic +brightness, or luminosity of the area per unit of surface, would remain +unaltered. The increased brightness of the Milky Way in Aquila is +accounted for by the fact that Herschel’s “gages” show an increased number +of stars, and hence the brightness in Aquila and Sagittarius does not +necessarily imply that the Milky Way is nearer to us in those parts, but +that it is richer in small stars than in other regions.</p> + +<p>Easton is of opinion that the annular hypothesis of the Milky Way is +inconsistent with our present knowledge of the galactic phenomena, and he +suggests that its actual constitution resembles more that of a spiral +nebula.<a name='fna_473' id='fna_473' href='#f_473'><small>[473]</small></a> On this hypothesis the increase in the number of stars in the +regions above referred to may be due to our seeing one branch of the +supposed “two-branched spiral” projected on another branch of the same +spiral. This seems supported by Sir John Herschel’s<span class="pagenum"><a name="Page_326" id="Page_326">[Pg 326]</a></span> observations in the +southern hemisphere, where he found in some places “a tissue as it were of +large stars spread over another of very small ones, the immediate +magnitudes being wanting.” Again, portions of the spiral branches may be +richer than others, as photographs of spiral nebulæ seem to indicate. +Celoria, rejecting the hypothesis of a single ring, suggests the existence +of <i>two</i> galactic rings inclined to each other at an angle of about 20°, +one of these including the brighter stars, and the other the fainter. But +this seems to be a more artificial arrangement then the hypothesis of a +spiral. Further, the complicated structure of the Milky Way cannot be well +explained by Celoria’s hypothesis of two distinct rings one inside the +other. From analogy the spiral hypothesis seems much more probable.</p> + +<p>Considering the Milky Way to represent a colossal spiral nebula viewed +from a point not far removed from the centre of the spiral branches, +Easton suggests that the bright region between β and γ +Cygni, which is very rich in comparatively bright stars, may possibly +represent the “<i>central accumulations of the Milky Way</i>,” that is, the +portion corresponding to the nucleus of a spiral nebula. If this be so, +this portion of the Milky Way should be nearer to us than others. Easton +also thinks that the so-called “solar cluster” of Gould, Kapteyn, and +Schiaparelli may perhaps be “the expression of<span class="pagenum"><a name="Page_327" id="Page_327">[Pg 327]</a></span> the central condensation +of the galactic system itself, composed of the most part of suns +comparable with our own, and which would thus embrace most of the bright +stars to the 9th or 10th magnitude. The distance of the galactic streams +and convolutions would thus be comparable with the distances of these +stars.” He thinks that the sun lies within a gigantic spiral, “in a +comparatively sparse region between the central nucleus and Orion.”</p> + +<p>Scheiner thinks that “the irregularities of the Milky Way, especially in +streams, can be quite well accounted for, as Easton has attempted to do, +if they are regarded as a system of spirals, and not as a ring system.”</p> + +<p>Evidence in favour of the spiral hypothesis of the Milky Way, as advocated +by Easton and Scheiner, may be found in Kapteyn’s researches on the proper +motions of the stars. This eminent astronomer finds that stars with +measurable proper motions—and therefore in all probability relatively +near the earth—have mostly spectra of the solar type, and seem to cluster +round “a point adjacent to the sun, in total disregard to the position of +the Milky Way,” and that stars with little or no proper motion collect +round the galactic plain. He is also of opinion that the Milky Way +resembles the Andromeda nebula, “the globular nucleus representing the +solar cluster, and the far spreading wings or whorls the<span class="pagenum"><a name="Page_328" id="Page_328">[Pg 328]</a></span> compressed layer +of stars enclosed by the rings of the remote Galaxy.”</p> + +<p>With reference to the plurality of inhabited worlds, it has been well said +by the ancient writer Metrodorus (third century <span class="smcaplc">B.C.</span>), “The idea that +there is but a single world in all infinitude would be as absurd as to +suppose that a vast field had been formed to produce a single blade of +wheat.”<a name='fna_474' id='fna_474' href='#f_474'><small>[474]</small></a> With this opinion the present writer fully concurs.</p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_329" id="Page_329">[Pg 329]</a></span></p> +<h2><a name="CHAPTER_XXI" id="CHAPTER_XXI"></a>CHAPTER XXI</h2> +<p class="title">General</p> + +<p> </p> +<p class="dropcap"><span class="caps">The</span> achievements of Hipparchus in astronomy were very remarkable, +considering the age in which he lived. He found the amount of the apparent +motion of the stars due to the precession of the equinoxes (of which he +was the discoverer) to be 59″ per annum. The correct amount is about 50″. +He measured the length of the year to within 9 minutes of its true value. +He found the inclination of the ecliptic to the plane of the equator to be +23° 51′. It was then 23° 46′—as we now know by modern calculations—so +that Hipparchus’ estimation was a wonderfully close approximation to the +truth. He computed the moon’s parallax to be 57′, which is about its +correct value. He found the eccentricity of the sun’s apparent orbit round +the earth to be one twenty-fourth, the real value being then about +one-thirteenth. He determined other motions connected with the earth and +moon; and formed a catalogue of 1080 stars. All this work has earned for +him the well-merited title of “The Father of Astronomy.”<a name='fna_475' id='fna_475' href='#f_475'><small>[475]</small></a></p> + +<p><span class="pagenum"><a name="Page_330" id="Page_330">[Pg 330]</a></span>The following is a translation of a Greek passage ascribed to Ptolemy: “I +know that I am mortal and the creature of a day, but when I search out the +many rolling circles of the stars, my feet touch the earth no longer, but +with Zeus himself I take my fill of ambrosia, the food of the gods.”<a name='fna_476' id='fna_476' href='#f_476'><small>[476]</small></a> +This was inscribed (in Greek) on a silver loving cup presented to the late +Professor C. A. Young, the famous American astronomer.<a name='fna_477' id='fna_477' href='#f_477'><small>[477]</small></a></p> + +<p>Some curious and interesting phenomena are recorded in the old Chinese +Annals, which go back to a great antiquity. In 687 <span class="smcaplc">B.C.</span> “a night” is +mentioned “without clouds and without stars” (!) This may perhaps refer to +a total eclipse of the sun; but if so, the eclipse is not mentioned in the +Chinese list of eclipses. In the year 141 <span class="smcaplc">B.C.</span>, it is stated that the sun +and moon appeared of a deep red colour during 5 days, a phenomenon which +caused great terror among the people. In 74 <span class="smcaplc">B.C.</span>, it is related that a +star as large as the moon appeared, and was followed in its motion by +several stars of ordinary size. This probably refers to an unusually large +“bolide” or “fireball.” In 38 <span class="smcaplc">B.C.</span>, a fall of meteoric stones is recorded +“of the size of a walnut.” In <span class="smcaplc">A.D.</span> 88, another fall of stones is +mentioned. In <span class="smcaplc">A.D.</span> 321, sun-spots were visible to the naked eye.</p> + +<p><span class="pagenum"><a name="Page_331" id="Page_331">[Pg 331]</a></span>Homer speaks of a curious darkness which occurred during one of the great +battles in the last year of the Trojan war. Mr. Stockwell identifies this +with an eclipse of the sun which took place on August 28, 1184 <span class="smcaplc">B.C.</span> An +eclipse referred to by Thucydides as having occurred during the first year +of the Peloponnesian War, when the darkness was so great that some stars +were seen, is identified by Stockwell with a total eclipse of the sun, +which took place on August 2, 430 <span class="smcaplc">B.C.</span></p> + +<p>A great eclipse of the sun is supposed to have occurred in the year 43 or +44 <span class="smcaplc">B.C.</span>, soon after the death of Julius Cæsar. Baron de Zach and Arago +mention it as the first annular eclipse on record. But calculations show +that no solar eclipse whatever, visible in Italy, occurred in either of +these years. The phenomenon referred to must therefore have been of +atmospherical origin, and indeed this is suggested by a passage in +Suetonius, one of the authors quoted on the subject.</p> + +<p>M. Guillaume thinks that the ninth Egyptian plague, the thick “darkness” +(Exodus x. 21-23), may perhaps be explained by a total eclipse of the sun +which occurred in 1332 <span class="smcaplc">B.C.</span> It is true that the account states that the +darkness lasted “three days,” but this, M. Guillaume thinks, may be due to +an error in the translation.<a name='fna_478' id='fna_478' href='#f_478'><small>[478]</small></a> This explanation, however, seems very +improbable.</p> + +<p>According to Hind, the moon was eclipsed on<span class="pagenum"><a name="Page_332" id="Page_332">[Pg 332]</a></span> the generally received date +of the Crucifixion, <span class="smcaplc">A.D.</span> 33, April 3. He says, “I find she had emerged +from the earth’s dark shadow a quarter of an hour before she rose at +Jerusalem (6<sup>h</sup> 36<sup>m</sup> p.m.); but the penumbra continued upon her disc for +an hour afterwards.” An eclipse could not have had anything to do with the +“darkness over all the land” during the Crucifixion. For this lasted for +three hours, and the totality of a solar eclipse can only last a few +minutes at the most. As a matter of fact the “eclipse of Phlegon,” a +partial one (<span class="smcaplc">A.D.</span> 29, November 24) was “the only solar eclipse that could +have been visible in Jerusalem during the period usually fixed for the +ministry of Christ.”</p> + +<p>It is mentioned in the Anglo-Saxon Chronicle that a total eclipse of the +sun took place in the year after King Alfred’s great battle with the +Danes. Now, calculation shows that this eclipse occurred on October 29, +878 <span class="smcaplc">A.D.</span> King Alfred’s victory over the Danes must, therefore, have taken +place in 877 <span class="smcaplc">A.D.</span>, and his death probably occurred in 899 <span class="smcaplc">A.D.</span> This solar +eclipse is also mentioned in the Annals of Ulster. From this it will be +seen that in some cases the dates of historical events can be accurately +fixed by astronomical phenomena.</p> + +<p>It is stated by some historians that an eclipse of the sun took place on +the morning of the battle of<span class="pagenum"><a name="Page_333" id="Page_333">[Pg 333]</a></span> Crecy, August 26, 1346. But calculation +shows that there was no eclipse of the sun visible in England in that +year. At the time of the famous battle the moon had just entered on her +first quarter, and she was partially eclipsed six days afterwards—that is +on the 1st of September. The mistake seems to have arisen from a +mistranslation of the old French word <i>esclistre</i>, which means lightning. +This was mistaken for <i>esclipse</i>. The account seems to indicate that there +was a heavy thunderstorm on the morning of the battle.</p> + +<p>A dark shade was seen on the waning moon by Messrs. Hirst and J. C. +Russell on October 21, 1878, “as dark as the shadow during an eclipse of +the moon.”<a name='fna_479' id='fna_479' href='#f_479'><small>[479]</small></a> If this observation is correct, it is certainly most +difficult to explain. Another curious observation is recorded by Mr. E. +Stone Wiggins, who says that a partial eclipse of the sun by a dark body +was observed in the State of Michigan (U.S.A.) on May 16, 1884, at 7 p.m. +The “moon at that moment was 12 degrees south of the equator and the sun +as many degrees north of it.” The existence of a dark satellite of the +earth has been suggested, but this seems highly improbable.</p> + +<p>The sun’s corona seems to have been first noticed in the total eclipse of +the sun which occurred at the death of the Roman emperor<span class="pagenum"><a name="Page_334" id="Page_334">[Pg 334]</a></span> +Domitian, <span class="smcaplc">A.D.</span> 95. Philostratus in his <i>Life of Apollonius</i> says, with reference to this +eclipse, “In the heavens there appeared a prodigy of this nature: a +certain <i>corona</i> resembling the Iris surrounded the orb of the sun, and +obscured its light.”<a name='fna_480' id='fna_480' href='#f_480'><small>[480]</small></a> In more modern times the corona seems to have +been first noticed by Clavius during the total eclipse of April 9, +1567.<a name='fna_481' id='fna_481' href='#f_481'><small>[481]</small></a> Kepler proved that this eclipse was total, not annular, so that +the ring seen by Clavius must have been the corona.</p> + +<p>With reference to the visibility of planets and stars during total +eclipses of the sun; in the eclipse of May 12, 1706, Venus, Mercury, and +Aldebaran, and several other stars were seen. During the totality of the +eclipse of May 3, 1715, about twenty stars were seen with the naked +eye.<a name='fna_482' id='fna_482' href='#f_482'><small>[482]</small></a> At the eclipse of May 22, 1724, Venus and Mercury, and a few +fixed stars were seen.<a name='fna_483' id='fna_483' href='#f_483'><small>[483]</small></a> The corona was also noticed. At the eclipse of +May 2, 1733, Jupiter, the stars of the “Plough,” Capella, and other stars +were visible to the naked eye; and the corona was again seen.<a href='#f_483'><small>[483]</small></a></p> + +<p>During the total eclipses of February 9, 1766, June 24, 1778, and June 16, +1806, the corona was again noticed. But its true character was then +unknown.</p> + +<p>At the eclipse of July 8, 1842, it was noticed by<span class="pagenum"><a name="Page_335" id="Page_335">[Pg 335]</a></span> observers at Lipesk +that the stars Aldebaran and Betelgeuse (α Orionis), which are +usually red, “appeared quite white.”<a name='fna_484' id='fna_484' href='#f_484'><small>[484]</small></a></p> + +<p>There will be seven eclipses in the years 1917, 1935, and 1985. In the +year 1935 there will be five eclipses of the sun, a rare event; and in +1985 there will be three total eclipses of the moon, a most unusual +occurrence.<a name='fna_485' id='fna_485' href='#f_485'><small>[485]</small></a></p> + +<p>Among the ancient Hindoos, the common people believed that eclipses were +caused by the interposition of a monstrous demon called Raha. This absurd +idea, and others equally ridiculous, were based on declarations in their +sacred books, and no pious Hindoo would think of denying it.</p> + +<p>The following cases of darkenings of the sun are given by Humboldt:—</p> + +<p>According to Plutarch the sun remained pale for a whole year at the death +of Julius Cæsar, and gave less than its usual heat.<a name='fna_486' id='fna_486' href='#f_486'><small>[486]</small></a></p> + +<p>A sun-darkening lasting for two hours is recorded on August 22, 358 <span class="smcaplc">A.D.</span>, +before the great earthquake of Nicomedia.</p> + +<p>In 360 <span class="smcaplc">A.D.</span> there was a sun-darkening from early morn till noon. The +description given by the historians of the time corresponds to an eclipse +of the sun, but the duration of the obscurity is inexplicable.</p> + +<p>In 409 <span class="smcaplc">A.D.</span>, when Alaric lay siege to Rome, +<span class="pagenum"><a name="Page_336" id="Page_336">[Pg 336]</a></span> “there was so great a +darkness that the stars were seen by day.”</p> + +<p>In 536 <span class="smcaplc">A.D.</span> the sun is said to have been darkened for a year and two +months!</p> + +<p>In 626 <span class="smcaplc">A.D.</span>, according to Abul Farag, half the sun’s disc was darkened for +eight months!</p> + +<p>In 934 <span class="smcaplc">A.D.</span> the sun lost its brightness for two months in Portugal.</p> + +<p>In 1090 <span class="smcaplc">A.D.</span> the sun was darkened for three hours.</p> + +<p>In 1096, sun-spots were seen with the naked eye on March 3.</p> + +<p>In 1206 <span class="smcaplc">A.D.</span> on the last day of February, “there was complete darkness for +six hours, turning the day into night.” This seems to have occurred in +Spain.</p> + +<p>In 1241 the sun was so darkened that stars could be seen at 3 p.m. on +Michaelmas day. This happened in Vienna.<a name='fna_487' id='fna_487' href='#f_487'><small>[487]</small></a></p> + +<p>The sun is said to have been so darkened in the year 1547 <span class="smcaplc">A.D.</span> for three +days that stars were visible at midday. This occurred about the time of +the battle of Mühlbergh.<a name='fna_488' id='fna_488' href='#f_488'><small>[488]</small></a></p> + +<p>Some of these darkenings may possibly have been due to an enormous +development of sun-spots; but in some cases the darkness is supposed by +Chladni and Schnurrer to have been caused by “the passage of meteoric +masses before the sun’s disc.”</p> + +<p><span class="pagenum"><a name="Page_337" id="Page_337">[Pg 337]</a></span>The first observer of a transit of Venus was Jeremiah Horrocks, who +observed the transit of November 24 (O.S.), 1639. He had previously +corrected Kepler’s predicted time of the transit from 8<sup>h</sup> 8<sup>m</sup> a.m. at +Manchester to 5<sup>h</sup> 57<sup>m</sup> p.m. At the end of 1875 a marble scroll was +placed on the pedestal of the monument of John Conduitt (nephew of Sir +Isaac Newton, and who adopted Horrocks’ theory of lunar motions) at the +west end of the nave of Westminster Abbey, bearing this inscription from +the pen of Dean Stanley—</p> + +<table style="margin-left: 15%;" border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td align="center">“Ad majora avocatus<br /> +quæ ob hæc parerga negligi non decuit”<br /> +<span class="smcap">In Memory of</span><br /> +JEREMIAH HORROCKS<br /> +Curate of Hoole in Lancashire<br /> +Who died on the 3<sup>d</sup> of January, 1641, in or near his<br /> +22<sup>d</sup> year<br /> +Having in so short a life<br /> +Detected the long inequality in the mean motion of<br /> +Jupiter and Saturn<br /> +Discovered the orbit of the Moon to be an ellipse;<br /> +Determined the motion of the lunar aspe,<br /> +Suggested the physical cause of its revolution;<br /> +And predicted from his own observations, the<br /> +Transit of Venus<br /> +Which was seen by himself and his friend<br /> +WILLIAM CRABTREE<br /> +On Sunday, the 24th November (O.S.) 1639;<br /> +This Tablet, facing the Monument of Newton<br /> +Was raised after the lapse of more than two centuries<br /> +December 9, 1874.<a name='fna_489' id='fna_489' href='#f_489'><small>[489]</small></a></td></tr></table> + +<p><span class="pagenum"><a name="Page_338" id="Page_338">[Pg 338]</a></span>The transit of Venus which occurred in 1761 was observed on board ship(!) +by the famous but unfortunate French astronomer Le Gentil. The ship was +the frigate <i>Sylphide</i>, sent to the help of Pondicherry (India) which was +then being besieged by the English. Owing to unfavourable winds the +<i>Sylphide</i> was tossed about from March 25, 1761, to May 24 of the same +year. When, on the later date, off the coast of Malabar, the captain of +the frigate learned that Pondicherry had been captured by the English, the +vessel returned to the Isle of France, where it arrived on June 23, after +touching at Point de Galle on May 30. It was between these two places that +Le Gentil made his observations of the transit of Venus under such +unfavourable conditions. He had an object-glass of 15 feet (French) focus, +and this he mounted in a tube formed of “four pine planks.” This rough +instrument was fixed to a small mast set up on the quarter-deck and worked +by ropes. The observations made under such curious conditions, were not, +as may be imagined, very satisfactory. As another transit was to take +place on June 3, 1769, Le Gentil made the heroic resolution of remaining +in the southern hemisphere to observe it! This determination was duly +carried out, but his devotion to astronomy was not rewarded; for on the +day of the long waited for transit the sky at Pondicherry (where he had +gone to observe it) was clouded over<span class="pagenum"><a name="Page_339" id="Page_339">[Pg 339]</a></span> during the whole phenomenon, +“although for many days previous the sky had been cloudless.” To add to +his feeling of disappointment he heard that at Manilla, where he had been +staying some time previously, the sky was quite clear, and two of his +friends there had seen the transit without any difficulty.<a name='fna_490' id='fna_490' href='#f_490'><small>[490]</small></a> Truly the +unfortunate Le Gentil was a martyr to science.</p> + +<p>The famous German astronomer Bessel once said “that a practical astronomer +could make observations of value if he had only a cart-wheel and a gun +barrel”; and Watson said that “the most important part of the instrument +is the person at the small end.”<a name='fna_491' id='fna_491' href='#f_491'><small>[491]</small></a></p> + +<p>With reference to Father Hell’s supposed forgery of his observations of +the transit of Venus in 1769, and Littrow’s criticism of some of the +entries in Hell’s manuscript being corrected with a different coloured +ink, Professor Newcomb ascertained from Weiss that Littrow was colour +blind, and could not distinguish between the colour of Aldebaran and the +whitest star. Newcomb adds, “For half a century the astronomical world +had based an impression on the innocent but mistaken evidence of a +colour-blind man respecting the tint of ink in a manuscript.”</p> + +<p>It is recorded that on February 26, <span class="smcaplc">B.C.</span> 2012, the moon, Mercury, Venus, +Jupiter, and Saturn,<span class="pagenum"><a name="Page_340" id="Page_340">[Pg 340]</a></span> were in the same constellation, and within 14 +degrees of each other. On September 14, 1186 <span class="smcaplc">A.D.</span>, the sun, moon, and all +the planets then known, are said to have been situated in Libra.<a name='fna_492' id='fna_492' href='#f_492'><small>[492]</small></a></p> + +<p>In the Sanscrit epic poem, “The Ramaya,” it is stated that at the birth of +Rama, the moon was in Cancer, the sun in Aries, Mercury in Taurus, Venus +in Pisces, Mars in Capricornus, Jupiter in Cancer, and Saturn in Libra. +From these data, Mr. Walter R. Old has computed that Rama was born on +February 10, 1761 <span class="smcaplc">B.C.</span><a name='fna_493' id='fna_493' href='#f_493'><small>[493]</small></a></p> + +<p>A close conjunction of Mars and Saturn was observed by Denning on +September 29, 1889, the bright star Regulus (α Leonis) being at +the time only 47′ distant from the planets.<a name='fna_494' id='fna_494' href='#f_494'><small>[494]</small></a></p> + +<p>An occultation of the Pleiades by the moon was observed by Timocharis at +Alexandria on January 29, 282 <span class="smcaplc">B.C.</span> Calculations by Schjellerup show that +Alcyone (η Tauri) was occulted; but the exact time of the day +recorded by Timocharis differs very considerably from that computed by +Schjellerup.<a name='fna_495' id='fna_495' href='#f_495'><small>[495]</small></a> Another occultation of the Pleiades is recorded by +Agrippa in the reign of Domitian. According to Schjellerup the phenomenon +occurred on November 29, <span class="smcaplc">A.D.</span> 92.</p> + +<p>“Kepler states that on the 9th of January, 1591,<span class="pagenum"><a name="Page_341" id="Page_341">[Pg 341]</a></span> Mæstlin and himself +witnessed an occultation of Jupiter by Mars. The red colour of the latter +on that occasion plainly indicated that it was the inferior planet.”<a name='fna_496' id='fna_496' href='#f_496'><small>[496]</small></a> +That is, that Mars was nearer to the sun than Jupiter. But as the +telescope had not then been invented, this may have been merely a near +approach of the two planets.</p> + +<p>According to Kepler, Mæstlin saw an occultation of Mars by Venus on +October 3, 1590. But this may also have been merely a near approach.<a href='#f_496'><small>[496]</small></a></p> + +<p>A curious paradox is that one can discover an object without seeing it, +and see an object without discovering it! The planet Neptune was +discovered by Adams and Leverrier by calculation before it was seen in the +telescope by Galle; and it was actually seen by Lalande on May 8 and 10, +1795, but he took it for a <i>star</i> and thus missed the discovery. In fact, +he <i>saw</i> the planet, but did not <i>discover</i> it. It actually appears as a +star of the 8th magnitude in Harding’s Atlas (1822). The great “new star” +of February, 1901, known as Nova Persei, was probably seen by some people +before its discovery was announced; and it was actually noticed by a +well-known American astronomer, who thought it was some bright star with +which he was not familiar! But this did not amount to a discovery. Any one +absolutely ignorant of astronomy might have made the same observation. An +object must be <i>identified</i> as a<span class="pagenum"><a name="Page_342" id="Page_342">[Pg 342]</a></span> <i>new</i> object before a discovery can be +claimed. Some years ago a well-known Irish naturalist discovered a spider +new to science, and after its discovery he found that it was common in +nearly every house in Dublin! But this fact did not detract in the least +from the merit of its scientific discovery.</p> + +<p>There is a story of an eminent astronomer who had been on several eclipse +expeditions, and yet was heard to remark that he had never seen a total +eclipse of the sun. “But your observations of several eclipses are on +record,” it was objected. “Certainly, I have on several occasions made +observations, but I have always been too busy to look at the eclipse.” He +was probably in a dark tent taking photographs or using a spectroscope +during the totality. This was observing an eclipse without seeing it!</p> + +<p>Humboldt gives the credit of the invention of the telescope to Hans +Lippershey, a native of Wesel and a spectacle-maker at Middleburgh; to +Jacob Adreaansz, surnamed Metius, who is also said to have made +burning-glasses of ice; and to Zachariah Jansen.<a name='fna_497' id='fna_497' href='#f_497'><small>[497]</small></a></p> + +<p>With reference to the parabolic figure of the large mirrors of reflecting +telescopes, Dr. Robinson remarked at the meeting of the British +Association at Cork in 1843, “between the spherical and parabolic figures +the extreme difference is so<span class="pagenum"><a name="Page_343" id="Page_343">[Pg 343]</a></span> slight, even in the telescope of 6-feet +aperture [Lord Rosse’s] that if the two surfaces touched at their vertex, +the distance at the edge would not amount to the <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">10000</span> +of an inch, a space which few can measure, and none without a microscope.”<a name='fna_498' id='fna_498' href='#f_498'><small>[498]</small></a></p> + +<p>In the year 1758, Roger Long, Lowndean Professor of Astronomy at +Cambridge, constructed an “orrery” on a novel principle. It was a hollow +metal sphere of about 18 feet in diameter with its fixed axis parallel to +the earth’s axis. It was rotated, by means of a winch and rackwork. It +held about thirty persons in its interior, where astronomical lectures +were delivered. The constellations were painted on the interior surface; +and holes pierced through the shell and illuminated from the outside +represented the stars according to their different magnitudes. This +ingenious machine was much neglected for many years, but was still in +existence in Admiral Smyth’s time, 1844.<a name='fna_499' id='fna_499' href='#f_499'><small>[499]</small></a></p> + +<p>A “temporary star” is said to have been seen by Hepidanus in the +constellation Aries in either 1006 or 1012 <span class="smcaplc">A.D.</span> The late M. Schönfeld, a +great authority on variable stars, found from an Arabic and Syrian +chronicle that 1012 is the correct year (396 of the Hegira), but that the +word translated Aries would by a probable emendation mean<span class="pagenum"><a name="Page_344" id="Page_344">[Pg 344]</a></span> Scorpio. The +word in the Syrian record is not the word for Aries.<a name='fna_500' id='fna_500' href='#f_500'><small>[500]</small></a></p> + +<p>Mr. Heber D. Curtis finds that the faintest stars mentioned in Ptolemy’s +Catalogue are about 5·38 magnitude on the scale of the Harvard +<i>Photometric Durchmustering</i>.<a name='fna_501' id='fna_501' href='#f_501'><small>[501]</small></a> Heis and Houzeau saw stars of 6-7 +magnitude (about 6·4 on Harvard scale). The present writer found that he +could see most of Heis’ faintest stars in the west of Ireland (Co. Sligo) +without optical aid (except short-sighted spectacles).</p> + +<p>With reference to the apparent changes in the stellar heavens produced by +the precession of the equinoxes, Humboldt says—</p> + +<div class="blockquot"><p>“Canopus was fully 1° 20′ below the horizon of Toledo (39° 54′ north +latitude) in the time of Columbus; and now the same star is almost as +much above the horizon of Cadiz. While at Berlin, and in northern +latitudes, the stars of the Southern Cross, as well as α and +β Centauri, are receding more and more from view, the +Magellanic Clouds are slowly approaching our latitudes. Canopus was at +its greatest northern approximation during last century [eighteenth], +and is now moving nearer and nearer to the south, although very +slowly, owing to its vicinity to the south pole of the ecliptic. The +Southern Cross began to become invisible in 52° 30′ north latitude +2900 years before our era, since, according to Galle, this +constellation might previously have reached an altitude of more than +10°. When it<span class="pagenum"><a name="Page_345" id="Page_345">[Pg 345]</a></span> had disappeared from the horizon of the countries of the +Baltic, the great pyramid of Cheops had already been erected more than +five hundred years. The pastoral tribe of the Hyksos made their +incursion seven hundred years earlier. The past seems to be visibly +nearer to us when we connect its measurement with great and memorable +events.”<a name='fna_502' id='fna_502' href='#f_502'><small>[502]</small></a></p></div> + +<p>With reference to the great Grecian philosopher and scientist Eratosthenes +of Cyrene, keeper of the Alexandrian Library under Ptolemy Euergetes, Carl +Snyder says, “Above all the Alexanders, Cæsars, Tadema-Napoleons, I set +the brain which first spanned the earth, over whose little patches these +fought through their empty bootless lives. Why should we have no poet to +celebrate so great a deed?”<a name='fna_503' id='fna_503' href='#f_503'><small>[503]</small></a> And with reference to Aristarchus he +says, “If grandeur of conceptions be a measure of the brain, or ingenuity +of its powers, then we must rank Aristarchus as one of the three or four +most acute intellects of the ancient world.”<a name='fna_504' id='fna_504' href='#f_504'><small>[504]</small></a></p> + +<p>Lagrange, who often asserted Newton to be the greatest genius that ever +existed, used to remark also—“and the most fortunate; we do not find more +than once a system of the world to establish.”<a name='fna_505' id='fna_505' href='#f_505'><small>[505]</small></a></p> + +<p>Grant says—</p> + +<div class="blockquot"><p><span class="pagenum"><a name="Page_346" id="Page_346">[Pg 346]</a></span>“Lagrange deserves +to be ranked among the greatest mathematical geniuses of ancient or modern times. In this respect he is worthy of a +place with Archimedes or Newton, although he was far from possessing +the sagacity in physical enquiries which distinguished these +illustrious sages. From the very outset of his career he assumed a +commanding position among the mathematicians of the age, and during +the course of nearly half a century previous to his death, he +continued to divide with Laplace the homage due to pre-eminence in the +exact sciences. His great rival survived him fourteen years, during +which he reigned alone as the prince of mathematicians and theoretical +astronomers.”<a name='fna_506' id='fna_506' href='#f_506'><small>[506]</small></a></p></div> + +<p>A writer in <i>Nature</i> (May 25, 1871) relates the following anecdote with +reference to Sir John Herschel: “Some time after the death of Laplace, the +writer of this notice, while travelling on the continent in company with +the celebrated French <i>savant</i> Biot, ventured to put to him the question, +not altogether a wise one, ‘And whom of all the philosophers of Europe do +you regard as the most worthy successor of Laplace?’ Probably no man was +better able than Biot to form a correct conclusion, and the reply was more +judicious than the question. It was this, ‘If I did not love him so much I +should unhesitatingly say, Sir John Herschel.’” Dr. Gill (now Sir David +Gill), in an address at the Cape of Good Hope in June, 1898, spoke of Sir +John Herschel as “the prose poet of science; his popular scientific works +are models of<span class="pagenum"><a name="Page_347" id="Page_347">[Pg 347]</a></span> clearness, and his presidential addresses teem with +passages of surpassing beauty. His life was a pure and blameless one from +first to last, full of the noblest effort and the noblest aim from the +time when as a young Cambridge graduate he registered a vow ‘to try to +leave the world wiser than he found it’—a vow that his life amply +fulfilled.”<a name='fna_507' id='fna_507' href='#f_507'><small>[507]</small></a></p> + +<p>Prof. Newcomb said of Adams, the co-discoverer of Neptune with Leverrier, +“Adams’ intellect was one of the keenest I ever knew. The most difficult +problem of mathematical astronomy and the most recondite principles that +underlie the theory of the celestial motions were to him but child’s +play.” Airy he regarded as “the most commanding figure in the astronomy of +our time.”<a name='fna_508' id='fna_508' href='#f_508'><small>[508]</small></a> He spoke of Delaunay, the great French astronomer, as a +most kindly and attractive man, and says, “His investigations of the +moon’s motion is one of the most extraordinary pieces of mathematical work +ever turned out by a single person. It fills two quarto volumes, and the +reader who attempts to go through any part of the calculations will wonder +how one man could do the work in a lifetime.”<a name='fna_509' id='fna_509' href='#f_509'><small>[509]</small></a></p> + +<p>Sir George B. Airy and Prof. J. C. Adams died in the same month. The +former on January 2,<span class="pagenum"><a name="Page_348" id="Page_348">[Pg 348]</a></span> 1892, and the latter on January 22 of the same year.</p> + +<p>It is known from the parish register of Burstow in Surrey that Flamsteed +(Rev. John Flamsteed), the first Astronomer Royal at Greenwich, was buried +in the church at that place on January 12, 1720; but a search for his +grave made by Mr. J. Carpenter in 1866 and by Mr. Lynn in 1880 led to no +result. In Mrs. Flamsteed’s will a sum of twenty-five pounds was left for +the purpose of erecting a monument to the memory of the great astronomer +in Burstow Church; but it does not appear that any monument was ever +erected. Flamsteed was Rector of the Parish of Burstow.<a name='fna_510' id='fna_510' href='#f_510'><small>[510]</small></a> He was +succeeded in 1720 by the Rev. James Pound, another well-known astronomer. +Pound died in 1724.<a name='fna_511' id='fna_511' href='#f_511'><small>[511]</small></a></p> + +<p>Evelyn says in his Diary, 1676, September 10, “Dined with Mr. Flamsteed, +the learned astrologer and mathematician, whom his Majesty had established +in the new Observatory in Greenwich Park furnished with the choicest +instruments. An honest sincere man.”<a name='fna_512' id='fna_512' href='#f_512'><small>[512]</small></a> This shows that in those days +the term “astrologer” was synonymous with “astronomer.”</p> + +<p>In an article on “Our Debt to Astronomy,” by Prof. Russell Tracy Crawford +(Berkeley<span class="pagenum"><a name="Page_349" id="Page_349">[Pg 349]</a></span> Astronomical Department, California, U.S.A.), the following +remarks occur:—</p> + +<div class="blockquot"><p>“Behind the artisan is a chemist, behind the chemist is a physicist, +behind the physicist is a mathematician, and behind the mathematician +is an astronomer.” “Were it not for the data furnished by astronomers, +commerce by sea would practically stop. The sailing-master on the high +seas could not determine his position, nor in what direction to head +his ship in order to reach a desired harbour. Think what this means in +dollars and cents, and estimate it if you can. For this one service +alone the science of astronomy is worth more in dollars and cents to +the world in one week than has been expended upon it since the +beginning of civilization. Do you think that Great Britain, for +instance, would take in exchange an amount equal to its national debt +for what astronomy gives it? I answer for you most emphatically, +‘No.’”</p></div> + +<p>In his interesting book, <i>Reminiscences of an Astronomer</i>, Prof. Simon +Newcomb says with reference to the calculations for the <i>Nautical Almanac</i> +(referred to in the above extract)—</p> + +<div class="blockquot"><p>“A more hopeless problem than this could not be presented to the +ordinary human intellect. There are tens of thousands of men who could +be successful in all the ordinary walks of life, hundreds who could +wield empires, thousands who could gain wealth, for one who could take +up this astronomical problem with any hope of success. The men who +have done it are, therefore, in intellect the select few of the human +race—an aristocracy ranking above all others in the scale of being. +The astronomical ephemeris is the last outcome of their productive +genius.”</p></div> + +<p><span class="pagenum"><a name="Page_350" id="Page_350">[Pg 350]</a></span>In a paper on the “Aspects of American Astronomy,” Prof. Newcomb says, “A +great telescope is of no use without a man at the end of it, and what the +telescope may do depends more upon this appendage than upon the instrument +itself. The place which telescopes and observatories have taken in +astronomical history are by no means proportional to their dimensions. +Many a great instrument has been a mere toy in the hands of its owner. +Many a small one has become famous. Twenty years ago there was here in +your city [Chicago] a modest little instrument which, judged by its size, +could not hold up its head with the great ones even of that day. It was +the private property of a young man holding no scientific position and +scarcely known to the public. And yet that little telescope is to-day +among the famous ones of the world, having made memorable advances in the +astronomy of double stars, and shown its owner to be a worthy successor of +the Herschels and Struves in that line of work.”<a name='fna_513' id='fna_513' href='#f_513'><small>[513]</small></a> Here Prof. Newcomb +evidently refers to Prof. Burnham, and the 6-inch telescope with which he +made many of his remarkable discoveries of double stars. With reference to +Burnham’s work, Prof. Barnard says—</p> + +<div class="blockquot"><p>“It represents the labour of a struggling amateur, who during the day +led the drudging life of a stenographer in the United States court<span class="pagenum"><a name="Page_351" id="Page_351">[Pg 351]</a></span> in +Chicago, and at night worked among the stars for the pure love of it. +Such work deserves an everlasting fame, and surely this has fallen to +Mr. Burnham.”</p></div> + +<p>Admiral Smyth says—</p> + +<div class="blockquot"><p>“A man may prove a good astronomer without possessing a spacious +observatory: thus Kepler was wont to observe on the bridge at Prague; +Schröter studied the moon, and Harding found a planet from a +<i>gloriette</i>; while Olbers discovered two new planets from an attic of +his house.”<a name='fna_514' id='fna_514' href='#f_514'><small>[514]</small></a></p></div> + +<p>It is probably not generally known that “some of the greatest astronomers +of modern times, such as Kepler, Newton, Hansen, Laplace, and Leverrier, +scarcely ever looked through a telescope.”<a name='fna_515' id='fna_515' href='#f_515'><small>[515]</small></a></p> + +<p>Kepler, who always signed himself Keppler in German, is usually supposed +to have been born on December 21, 1571, in the imperial town of Weil, but +according to Baron von Breitschwert,<a name='fna_516' id='fna_516' href='#f_516'><small>[516]</small></a> he was really born on December +27, 1571, in the village of Magstadt in Wurtemberg.</p> + +<p>According to Lieut. Winterhalter, M. Perrotin of the Nice Observatory +declared “that two hours’ work with a large instrument is as fatiguing as +eight with a small one, the labour involved increasing in proportion to +the cube of the aperture, the chances of seeing decreasing in the same +ratio,<span class="pagenum"><a name="Page_352" id="Page_352">[Pg 352]</a></span> while it can hardly be said that the advantages increase in like +proportion.”<a name='fna_517' id='fna_517' href='#f_517'><small>[517]</small></a></p> + +<p>The late Mr. Proctor has well said—</p> + +<div class="blockquot"><p>“It is well to remember that the hatred which many entertain against +the doctrine of development as applied to solar systems and stellar +galaxies is not in reality a sign, as they imagine, of humility, but +is an effort to avoid the recognition of the nothingness of man in the +presence of the infinities of space and time and vitality presented +within the universe of God.”<a name='fna_518' id='fna_518' href='#f_518'><small>[518]</small></a></p></div> + +<p>Humboldt says—</p> + +<div class="blockquot"><p>“That arrogant spirit of incredulity, which rejects facts without +attempting to investigate them, is in some cases almost more injurious +than an unquestioning credulity. Both are alike detrimental to the +force of investigations.”<a name='fna_519' id='fna_519' href='#f_519'><small>[519]</small></a></p></div> + +<p>With reference to the precession of the equinoxes and the changes it +produces in the position of the Pole Star, it is stated in a recent book +on science that the entrance passage of the Great Pyramid of Ghizeh is +inclined at an angle of 30° to the horizon, and therefore points to the +celestial pole. But this is quite incorrect. The Great Pyramid, it is +true, is situated close to the latitude of 30°. But the entrance passage +does not point exactly to the pole. The inclination was measured by Col. +Vyse, and found to be<span class="pagenum"><a name="Page_353" id="Page_353">[Pg 353]</a></span> 26° 45′. For six out of the nine pyramids of +Ghizeh, Col. Vyse found an <i>average</i> inclination of 26° 47′, these +inclinations ranging from 25° 55′ (2nd, or pyramid of Mycerinus) to 28° 0′ +(9th pyramid).<a name='fna_520' id='fna_520' href='#f_520'><small>[520]</small></a> Sir John Herschel gives 3970 <span class="smcaplc">B.C.</span> as the probable date +of the erection of the Great Pyramid.<a href='#f_520'><small>[520]</small></a> At that time the distance of +α Draconis (the Pole Star of that day) from the pole was 3° 44′ +25″, so that when on the meridian <i>below</i> the pole (its lower culmination +as it is termed) its altitude was 30° - 3° 44′ 25″ = 26° 15′ 35″, which +agrees fairly well with the inclination of the entrance passage. Letronne +found a date of 3430 <span class="smcaplc">B.C.</span>; but the earlier date agrees better with the +evidence derived from Egyptology.</p> + +<p>Emerson says—</p> + +<p class="poem">“I am brother to him who squared the pyramids<br /> +By the same stars I watch.”</p> + +<p>From February 6 to 15, 1908, all the bright planets were visible together +at the same time. Mercury was visible above the western horizon after +sunset, Venus very brilliant with Saturn a little above it, Mars higher +still, all ranged along the ecliptic, and lastly Jupiter rising in the +east.<a name='fna_521' id='fna_521' href='#f_521'><small>[521]</small></a> This simultaneous visibility of all the bright planets is +rather a rare occurrence.</p> + +<p>With reference to the great improbability of<span class="pagenum"><a name="Page_354" id="Page_354">[Pg 354]</a></span> Laplace’s original Nebular +Hypothesis being true, Dr. See says, “We may calculate from the +preponderance of small bodies actually found in the solar system—eight +principal planets, twenty-five satellites (besides our moon), and 625 +asteroids—that the chances of a nebula devoid of hydrostatic pressure +producing small bodies is about 2<sup>658</sup> to 1, or a decillion decillion +(10<sup>66</sup>)<sup>6</sup> to the sixth power, to unity. This figure is so very large +that we shall content ourselves with illustrating a decillion decillion, +and for this purpose we avail ourselves of a method employed by <span class="smcap">Archimedes</span> +to illustrate his system of enumeration. Imagine sand so fine that 10,000 +grains will be contained in the space occupied by a poppy seed, itself +about the size of a pin’s head; and then conceive a sphere described about +our sun with a radius of 200,000 astronomical units<a name='fna_522' id='fna_522' href='#f_522'><small>[522]</small></a> (α +Centauri being at a distance of 275,000) entirely filled with this fine +sand. The number of grains of sand in this sphere of the fixed stars would +be a decillion decillion<a name='fna_523' id='fna_523' href='#f_523'><small>[523]</small></a> (10<sup>66</sup>)<sup>6</sup>. All these grains of sand +against one is the probability that a nebula devoid of hydrostatical +pressure, such as that which formed the planets and satellites, will lead +to the genesis of such small bodies revolving about a greatly predominant<span class="pagenum"><a name="Page_355" id="Page_355">[Pg 355]</a></span> +central mass.”<a name='fna_524' id='fna_524' href='#f_524'><small>[524]</small></a> In other words, it is practically certain that the +solar system was <i>not</i> formed from a gaseous nebula in the manner +originally proposed by Laplace. On the other hand, the evolution of the +solar system from a rotating spiral nebula seems very probable.</p> + +<hr style="width: 25%;" /> + +<p>Some one has said that “the world knows nothing of its greatest men.” The +name of Mr. George W. Hill will probably be unknown to many of my readers. +But the late Prof. Simon Newcomb said of him that he “will easily rank as +the greatest master of mathematical astronomy during the last quarter of +the nineteenth century.”<a name='fna_525' id='fna_525' href='#f_525'><small>[525]</small></a> Of Prof. Newcomb himself—also a great +master in the same subject—Sir Robert Ball says he was “the most +conspicuous figure among the brilliant band of contemporary American +astronomers.”<a name='fna_526' id='fna_526' href='#f_526'><small>[526]</small></a></p> + +<p>An astronomer is supposed to say, with reference to unwelcome visitors to +his observatory, “Who steals my purse steals trash; but he that filches +from me my clear nights, robs me of that which not enriches him, and makes +me poor indeed.”<a name='fna_527' id='fna_527' href='#f_527'><small>[527]</small></a></p> + +<p>Cicero said, “In the heavens there is nothing fortuitous, unadvised, +inconstant, or variable; all there is order, truth, reason, and +constancy”; and he adds, “The creation is as plain a signal<span class="pagenum"><a name="Page_356" id="Page_356">[Pg 356]</a></span> of the being +of a God, as a globe, a clock, or other artificial machine, is of a +man.”<a name='fna_528' id='fna_528' href='#f_528'><small>[528]</small></a></p> + +<p>“Of all the epigrams attributed rightly or wrongly to Plato, the most +famous has been expanded by Shelley into the four glorious lines—</p> + +<p class="poem">“‘Thou wert the morning star among the living<br /> +<span style="margin-left: 1em;">Ere thy pure light had fled,</span><br /> +Now having died, thou art as Hesperus, giving<br /> +<span style="margin-left: 1em;">New splendour to the dead.’”<a name='fna_529' id='fna_529' href='#f_529'><small>[529]</small></a></span></p> + +<p>Sir David Brewster has well said,<a name='fna_530' id='fna_530' href='#f_530'><small>[530]</small></a> “Isaiah furnishes us with a +striking passage, in which the occupants of the earth and the heavens are +separately described, ‘I have made the earth, and created man upon it: I, +even My hands, have stretched out the heavens, and all <i>their</i> host have I +commanded’ (Isaiah xlv. 12). But in addition to these obvious references +to life and things pertaining to life, we find in Isaiah the following +remarkable passage: ‘For thus saith the Lord that created the heavens; God +Himself that formed the earth and made it; He hath established it, <i>He +created it not</i> <span class="smcaplc">IN VAIN</span>, He formed <i>it to be inhabited</i>’ (Isaiah xlv. 18). +Here we have a distinct declaration from the inspired prophet that the +<i>earth would have been created</i> <span class="smcaplc">IN VAIN</span> <i>if it had not been formed to be +inhabited</i>; and hence we draw the conclusion that as the Creator cannot be +supposed to have made the worlds of<span class="pagenum"><a name="Page_357" id="Page_357">[Pg 357]</a></span> our system and those in the sidereal +system in vain, they must have been formed to be inhabited.” This seems to +the present writer to be a good and sufficient reply to Dr. Wallace’s +theory that our earth is the only inhabited world in the Universe!<a name='fna_531' id='fna_531' href='#f_531'><small>[531]</small></a> +Such a theory seems incredible.</p> + +<p>The recent discovery made by Prof. Kapteyn, and confirmed by Mr. +Eddington, of two drifts of stars, indicating the existence of <i>two</i> +universes, seems to render untenable Dr. Wallace’s hypothesis of the +earth’s central position in a single universe.<a href='#f_531'><small>[531]</small></a></p> + + +<p> </p><p> </p> +<div class="note"> +<p class="center"><span class="smcap">Note added in the Press.</span></p> + +<p>While these pages were in the Press, it was announced, by Dr. Max Wolf of +Heidelberg, that he found Halley’s comet on a photograph taken on the +early morning of September 12, 1909. The discovery has been confirmed at +Greenwich Observatory. The comet was close to the position predicted by +the calculations of Messrs. Cowell and Crommelin of Greenwich Observatory +(<i>Nature</i>, September 16, 1908).</p></div> + +<p><span class="pagenum"><a name="Page_358" id="Page_358">[Pg 358]</a></span></p> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_359" id="Page_359">[Pg 359]</a></span></p> +<p class="title">INDEX</p> + + +<p class="index"> +<span class="large">A</span><br /> +<br /> +Aboukir, <a href="#Page_287">287</a><br /> +<br /> +Aboul Hassan, <a href="#Page_221">221</a><br /> +<br /> +Abu Ali al Farisi, <a href="#Page_225">225</a><br /> +<br /> +Abu-Hanifa, <a href="#Page_233">233</a>, <a href="#Page_234">234</a><br /> +<br /> +Abul-fadl, <a href="#Page_236">236</a><br /> +<br /> +Accadians, <a href="#Page_250">250</a>, <a href="#Page_252">252</a><br /> +<br /> +Achernar, <a href="#Page_275">275</a><br /> +<br /> +Aclian, <a href="#Page_282">282</a><br /> +<br /> +Adam, <a href="#Page_96">96</a>, <a href="#Page_347">347</a><br /> +<br /> +Adhad-al-Davlat, <a href="#Page_225">225</a>, <a href="#Page_236">236</a><br /> +<br /> +Adonis, <a href="#Page_261">261</a><br /> +<br /> +Adreaansz, <a href="#Page_342">342</a><br /> +<br /> +Airy, Sir G. B., <a href="#Page_87">87</a>, <a href="#Page_140">140</a>, <a href="#Page_347">347</a>, <a href="#Page_357">357</a><br /> +<br /> +Aitken, <a href="#Page_160">160</a><br /> +<br /> +Al-Battani, <a href="#Page_232">232</a>, <a href="#Page_233">233</a><br /> +<br /> +Albrecht, <a href="#Page_173">173</a><br /> +<br /> +Albufaragius, <a href="#Page_283">283</a><br /> +<br /> +Alcor, <a href="#Page_241">241</a><br /> +<br /> +Alcyone, <a href="#Page_137">137</a><br /> +<br /> +Aldebaran, <a href="#Page_60">60</a>, <a href="#Page_156">156</a>, <a href="#Page_236">236</a>, <a href="#Page_252">252</a>, <a href="#Page_257">257</a>, <a href="#Page_310">310</a>, <a href="#Page_311">311</a><br /> +<br /> +Alfard, <a href="#Page_236">236</a>, <a href="#Page_289">289</a><br /> +<br /> +Alfargani, <a href="#Page_286">286</a><br /> +<br /> +Alfraganus, <a href="#Page_281">281</a><br /> +<br /> +Almagest, <a href="#Page_281">281</a><br /> +<br /> +Al-Sufi, <a href="#Page_47">47</a>, <a href="#Page_149">149</a>, <a href="#Page_179">179</a>, <a href="#Page_189">189</a>, <a href="#Page_221">221</a>, <a href="#Page_224">224</a>, <a href="#Page_225">225-238</a>, <a href="#Page_244">244</a>, <a href="#Page_246">246</a>, <a href="#Page_250">250</a>, <a href="#Page_251">251</a>, <a href="#Page_253">253</a>, <a href="#Page_254">254</a>, <a href="#Page_261">261</a>, <a href="#Page_263">263</a>, <a href="#Page_264">264</a>, <a href="#Page_266">266-270</a>, <a href="#Page_272">272</a>, <a href="#Page_274">274-278</a>, <a href="#Page_285">285</a>, <a href="#Page_287">287</a>, <a href="#Page_289">289</a>, <a href="#Page_290">290</a>, <a href="#Page_293">293</a>, <a href="#Page_298">298</a>, <a href="#Page_300">300-302</a>, <a href="#Page_304">304</a>, <a href="#Page_307">307</a><br /> +<br /> +Altair, <a href="#Page_246">246</a><br /> +<br /> +Ampelius, <a href="#Page_262">262</a><br /> +<br /> +Amphion, <a href="#Page_257">257</a><br /> +<br /> +Ancient eclipses, <a href="#Page_52">52</a>, <a href="#Page_53">53</a><br /> +<br /> +Anderson, <a href="#Page_120">120</a>, <a href="#Page_277">277</a><br /> +<br /> +Andromeda nebula, <a href="#Page_198">198-206</a>, <a href="#Page_231">231</a><br /> +<br /> +Annals of Ulster, <a href="#Page_332">332</a><br /> +<br /> +Antares, <a href="#Page_60">60</a>, <a href="#Page_179">179</a>, <a href="#Page_310">310</a>, <a href="#Page_311">311</a><br /> +<br /> +Anthelm, <a href="#Page_300">300</a><br /> +<br /> +Antinous, <a href="#Page_248">248</a><br /> +<br /> +Antlia, <a href="#Page_302">302</a><br /> +<br /> +Apollo, <a href="#Page_257">257</a><br /> +<br /> +Apparent diameter of moon, <a href="#Page_49">49</a><br /> +<br /> +Apple, <a href="#Page_79">79</a><br /> +<br /> +“Apples, golden,” <a href="#Page_258">258</a><br /> +<br /> +Apus, <a href="#Page_306">306</a><br /> +<br /> +Aquarius, <a href="#Page_268">268</a><br /> +<br /> +Aquila, <a href="#Page_246">246</a><br /> +<br /> +Aquillus, <a href="#Page_220">220</a><br /> +<br /> +Ara <a href="#Page_295">295</a><br /> +<br /> +Arago, <a href="#Page_26">26</a>, <a href="#Page_30">30</a>, <a href="#Page_57">57</a>, <a href="#Page_116">116</a>, <a href="#Page_193">193</a>, <a href="#Page_331">331</a><br /> +<br /> +Aratus, <a href="#Page_219">219</a>, <a href="#Page_242">242</a>, <a href="#Page_245">245</a>, <a href="#Page_250">250</a>, <a href="#Page_255">255</a>, <a href="#Page_256">256</a>, <a href="#Page_261">261</a>, <a href="#Page_263">263</a>, <a href="#Page_272">272</a><br /> +<br /> +Archimedes, <a href="#Page_346">346</a>, <a href="#Page_354">354</a><br /> +<br /> +Arcturus, <a href="#Page_148">148</a>, <a href="#Page_188">188</a>, <a href="#Page_244">244</a><br /> +<br /> +Argelander, <a href="#Page_29">29</a>, <a href="#Page_227">227</a>, <a href="#Page_229">229</a>, <a href="#Page_230">230</a>, <a href="#Page_240">240</a><br /> +<br /> +Argo, <a href="#Page_285">285-288</a>, <a href="#Page_305">305</a><br /> +<br /> +Argon in sun, <a href="#Page_4">4</a><br /> +<br /> +Argonauts, <a href="#Page_243">243</a>, <a href="#Page_250">250</a><br /> +<br /> +Aries, <a href="#Page_250">250</a><br /> +<br /> +Aristotle, <a href="#Page_49">49</a>, <a href="#Page_67">67</a><br /> +<br /> +Arrhenius, <a href="#Page_4">4</a>, <a href="#Page_8">8</a>, <a href="#Page_22">22</a>, <a href="#Page_45">45</a>, <a href="#Page_66">66</a><br /> +<br /> +<span class="pagenum"><a name="Page_360" id="Page_360">[Pg 360]</a></span>Ashtoreth, <a href="#Page_260">260</a><br /> +<br /> +<i>Astra Borbonia</i>, <a href="#Page_4">4</a><br /> +<br /> +Astræa, <a href="#Page_263">263</a><br /> +<br /> +Astronomy, Laplace on, <a href="#Page_44">44</a><br /> +<br /> +<i>Astro Theology</i>, <a href="#Page_23">23</a><br /> +<br /> +Atarid, <a href="#Page_232">232</a>, <a href="#Page_233">233</a><br /> +<br /> +Atmosphere, height of, <a href="#Page_33">33</a><br /> +<br /> +Augean stables, <a href="#Page_269">269</a><br /> +<br /> +Augustus, <a href="#Page_262">262</a><br /> +<br /> +Auriga, <a href="#Page_245">245</a><br /> +<br /> +Aurora, <a href="#Page_33">33</a>, <a href="#Page_41">41</a>, <a href="#Page_42">42</a><br /> +<br /> +Auwers, <a href="#Page_206">206</a><br /> +<br /> +Axis of Mars, <a href="#Page_59">59</a><br /> +<br /> +<br /> +<span class="large">B</span><br /> +<br /> +Babilu, <a href="#Page_267">267</a><br /> +<br /> +Baily, <a href="#Page_137">137</a>, <a href="#Page_144">144</a><br /> +<br /> +Baker, <a href="#Page_183">183</a><br /> +<br /> +Ball, Sir Robert, <a href="#Page_6">6</a>, <a href="#Page_355">355</a><br /> +<br /> +Barnard, Prof., <a href="#Page_29">29</a>, <a href="#Page_54">54</a>, <a href="#Page_57">57</a>, <a href="#Page_79">79</a>, <a href="#Page_80">80</a>, <a href="#Page_81">81</a>, <a href="#Page_85">85</a>, <a href="#Page_86">86</a>, <a href="#Page_91">91</a>, <a href="#Page_93">93</a>, <a href="#Page_103">103</a>, <a href="#Page_104">104</a>, <a href="#Page_114">114</a>, <a href="#Page_130">130</a>, <a href="#Page_132">132</a>, <a href="#Page_139">139</a>, <a href="#Page_192">192</a>, <a href="#Page_213">213</a>, <a href="#Page_316">316</a>, <a href="#Page_317">317</a>, <a href="#Page_350">350</a><br /> +<br /> +Barnes, <a href="#Page_78">78</a>, <a href="#Page_79">79</a><br /> +<br /> +Bartlett, <a href="#Page_35">35</a>, <a href="#Page_36">36</a><br /> +<br /> +Bartschius, <a href="#Page_296">296</a>, <a href="#Page_298">298</a><br /> +<br /> +Bauschingen, <a href="#Page_69">69</a>, <a href="#Page_70">70</a><br /> +<br /> +Bayer, <a href="#Page_179">179</a>, <a href="#Page_221">221</a>, <a href="#Page_272">272</a>, <a href="#Page_284">284</a>, <a href="#Page_309">309</a>, <a href="#Page_310">310</a><br /> +<br /> +Bayeux Tapestry, <a href="#Page_105">105</a><br /> +<br /> +Becquerel, <a href="#Page_8">8</a><br /> +<br /> +“Beehive,” <a href="#Page_259">259</a><br /> +<br /> +Beer, <a href="#Page_20">20</a><br /> +<br /> +Bel, <a href="#Page_250">250</a><br /> +<br /> +Bellatrix, <a href="#Page_253">253</a><br /> +<br /> +Benoit, <a href="#Page_22">22</a><br /> +<br /> +Berenice, <a href="#Page_297">297</a><br /> +<br /> +Berry, <a href="#Page_25">25</a><br /> +<br /> +Bessel, <a href="#Page_339">339</a><br /> +<br /> +Betelgeuse, <a href="#Page_179">179</a>, <a href="#Page_222">222</a>, <a href="#Page_264">264</a><br /> +<br /> +Bianchini, <a href="#Page_21">21</a>, <a href="#Page_22">22</a>, <a href="#Page_77">77</a><br /> +<br /> +Biela’s comet, <a href="#Page_99">99</a><br /> +<br /> +Bifornis, <a href="#Page_268">268</a><br /> +<br /> +Binary stars, <a href="#Page_162">162</a><br /> +<br /> +Birmingham, <a href="#Page_5">5</a>, <a href="#Page_114">114</a><br /> +<br /> +“Black body,” <a href="#Page_3">3</a><br /> +<br /> +“Blackness” of sun-spots, <a href="#Page_6">6</a><br /> +<br /> +“Blaze star,” <a href="#Page_180">180</a>, <a href="#Page_184">184</a><br /> +<br /> +Bode, <a href="#Page_276">276</a><br /> +<br /> +Bohlin, <a href="#Page_199">199</a>, <a href="#Page_200">200</a><br /> +<br /> +Bond, <a href="#Page_85">85</a><br /> +<br /> +Bond (Jun.), <a href="#Page_74">74</a><br /> +<br /> +<i>Book of the Dead</i>, <a href="#Page_264">264</a>, <a href="#Page_274">274</a><br /> +<br /> +Borelly, <a href="#Page_103">103</a><br /> +<br /> +Boserup, <a href="#Page_28">28</a><br /> +<br /> +Boss, <a href="#Page_152">152</a><br /> +<br /> +Brahé, Tycho. <i>See</i> <a href="#tycho">Tycho Brahé</a><br /> +<br /> +Brauner, <a href="#Page_211">211</a><br /> +<br /> +Bravais, <a href="#Page_42">42</a><br /> +<br /> +Bredikhin, <a href="#Page_76">76</a><br /> +<br /> +Bremiker, <a href="#Page_94">94</a><br /> +<br /> +Brenner, Léo, <a href="#Page_13">13</a>, <a href="#Page_22">22</a>, <a href="#Page_87">87</a>, <a href="#Page_91">91</a>, <a href="#Page_133">133</a><br /> +<br /> +Brewster, <a href="#Page_356">356</a><br /> +<br /> +Brightness of Mercury, <a href="#Page_10">10-12</a><br /> +<br /> +<span style="margin-left: 2em;">"</span><span style="margin-left: 1.75em;">of nebulæ, <a href="#Page_193">193</a></span><br /> +<br /> +<span style="margin-left: 2em;">"</span><span style="margin-left: 1.75em;">of sun, <a href="#Page_1">1</a>, <a href="#Page_2">2</a>, <a href="#Page_3">3</a></span><br /> +<br /> +<span style="margin-left: 2em;">"</span><span style="margin-left: 1.75em;">of Venus, <a href="#Page_14">14</a>, <a href="#Page_17">17</a>, <a href="#Page_19">19</a>, <a href="#Page_31">31</a></span><br /> +<br /> +Bright clouds, <a href="#Page_33">33</a>, <a href="#Page_34">34</a><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1.25em;">night, <a href="#Page_45">45</a></span><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1.25em;">stars, <a href="#Page_278">278</a></span><br /> +<br /> +Brooks, <a href="#Page_118">118</a><br /> +<br /> +Brown, <a href="#Page_218">218</a>, <a href="#Page_219">219</a>, <a href="#Page_248">248</a>, <a href="#Page_255">255</a>, <a href="#Page_260">260</a>, <a href="#Page_267">267</a>, <a href="#Page_272">272</a>, <a href="#Page_279">279</a>, <a href="#Page_281">281</a>, <a href="#Page_291">291</a>, <a href="#Page_295">295</a><br /> +<br /> +Browning, <a href="#Page_25">25</a><br /> +<br /> +Brugsch, <a href="#Page_127">127</a><br /> +<br /> +Buddha, <a href="#Page_256">256</a><br /> +<br /> +Bull, Pope’s, <a href="#Page_107">107</a><br /> +<br /> +“Bull’s foot,” <a href="#Page_253">253</a><br /> +<br /> +Buonaparte, <a href="#Page_30">30</a><br /> +<br /> +Burnham, <a href="#Page_160">160</a>, <a href="#Page_165">165-167</a>, <a href="#Page_180">180</a>, <a href="#Page_184">184</a>, <a href="#Page_260">260</a>, <a href="#Page_350">350</a>, <a href="#Page_351">351</a><br /> +<br /> +Burns, <a href="#Page_130">130</a><br /> +<br /> +Buss, <a href="#Page_4">4</a><br /> +<br /> +<br /> +<span class="large">C</span><br /> +<br /> +Caaba, <a href="#Page_125">125</a><br /> +<br /> +Cacciatore, <a href="#Page_72">72</a><br /> +<br /> +Cælum, <a href="#Page_302">302</a><br /> +<br /> +Callimachus, <a href="#Page_297">297</a><br /> +<br /> +<span class="pagenum"><a name="Page_361" id="Page_361">[Pg 361]</a></span>Callixtus III., <a href="#Page_107">107</a><br /> +<br /> +Calvisius, <a href="#Page_53">53</a><br /> +<br /> +Camelopardalis, <a href="#Page_296">296</a><br /> +<br /> +Cameron, <a href="#Page_18">18</a><br /> +<br /> +Campbell, <a href="#Page_85">85</a>, <a href="#Page_153">153</a>, <a href="#Page_159">159</a>, <a href="#Page_178">178</a><br /> +<br /> +“Canals” on Mars, <a href="#Page_61">61-63</a><br /> +<br /> +Cancer, <a href="#Page_258">258</a>, <a href="#Page_259">259</a><br /> +<br /> +Canes Venatici, <a href="#Page_296">296</a><br /> +<br /> +Canicula, <a href="#Page_280">280</a><br /> +<br /> +Canis Major, <a href="#Page_279">279</a><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1em;">Minor, <a href="#Page_284">284</a></span><br /> +<br /> +Canopus, <a href="#Page_157">157</a>, <a href="#Page_286">286</a>, <a href="#Page_344">344</a><br /> +<br /> +Capella, <a href="#Page_156">156</a>, <a href="#Page_164">164</a>, <a href="#Page_189">189</a>, <a href="#Page_236">236</a>, <a href="#Page_245">245</a>, <a href="#Page_246">246</a><br /> +<br /> +Capricornus, <a href="#Page_267">267</a>, <a href="#Page_268">268</a><br /> +<br /> +“Capture” of satellites, <a href="#Page_58">58</a><br /> +<br /> +Carbonic acid, <a href="#Page_66">66</a><br /> +<br /> +Cassini, <a href="#Page_20">20</a>, <a href="#Page_22">22</a>, <a href="#Page_74">74</a>, <a href="#Page_78">78</a>, <a href="#Page_358">358</a><br /> +<br /> +Cassiopeia’s Chair, <a href="#Page_244">244</a><br /> +<br /> +Castor, <a href="#Page_160">160</a>, <a href="#Page_257">257</a><br /> +<br /> +Caswell, <a href="#Page_52">52</a><br /> +<br /> +Catullus, <a href="#Page_297">297</a><br /> +<br /> +Caussin, <a href="#Page_225">225</a><br /> +<br /> +Cecrops, <a href="#Page_268">268</a><br /> +<br /> +“Celestial Rivers,” <a href="#Page_308">308</a><br /> +<br /> +Celoria, <a href="#Page_324">324</a>, <a href="#Page_326">326</a><br /> +<br /> +Centaurus, <a href="#Page_292">292</a>, <a href="#Page_293">293</a><br /> +<br /> +Centre of gravity, <a href="#Page_8">8</a><br /> +<br /> +Cephalus, <a href="#Page_279">279</a><br /> +<br /> +Cepheid variables, <a href="#Page_187">187</a><br /> +<br /> +Ceraski, <a href="#Page_2">2</a>, <a href="#Page_176">176</a><br /> +<br /> +Cerberus, <a href="#Page_243">243</a>, <a href="#Page_257">257</a><br /> +<br /> +Ceres, <a href="#Page_260">260</a><br /> +<br /> +Cerulli, <a href="#Page_22">22</a>, <a href="#Page_62">62</a><br /> +<br /> +Cetus, <a href="#Page_272">272</a><br /> +<br /> +Chacornac, <a href="#Page_18">18</a>, <a href="#Page_84">84</a><br /> +<br /> +Chamælion, <a href="#Page_305">305</a><br /> +<br /> +Chamberlin, <a href="#Page_194">194</a><br /> +<br /> +Chambers, <a href="#Page_72">72</a><br /> +<br /> +“Charles’ Wain,” <a href="#Page_240">240</a><br /> +<br /> +Chinese Annals, <a href="#Page_19">19</a>, <a href="#Page_30">30</a>, <a href="#Page_105">105</a>, <a href="#Page_186">186</a>, <a href="#Page_223">223</a>, <a href="#Page_267">267</a>, <a href="#Page_330">330</a><br /> +<br /> +Childrey, <a href="#Page_128">128</a><br /> +<br /> +Chiron, <a href="#Page_295">295</a><br /> +<br /> +Christmann, <a href="#Page_281">281</a><br /> +<br /> +Chromosphere, sun’s, <a href="#Page_4">4</a><br /> +<br /> +Cicero, <a href="#Page_49">49</a>, <a href="#Page_262">262</a>, <a href="#Page_280">280</a>, <a href="#Page_355">355</a><br /> +<br /> +Circinus, <a href="#Page_307">307</a><br /> +<br /> +Clavius, <a href="#Page_334">334</a><br /> +<br /> +Climate, <a href="#Page_45">45</a><br /> +<br /> +“Coal Sack,” <a href="#Page_293">293</a>, <a href="#Page_320">320</a><br /> +<br /> +Cobham, <a href="#Page_88">88</a>, <a href="#Page_102">102</a><br /> +<br /> +Colbert, <a href="#Page_175">175</a><br /> +<br /> +Colours of stars, <a href="#Page_140">140</a>, <a href="#Page_141">141</a>, <a href="#Page_188">188-190</a><br /> +<br /> +Coma Berenices, <a href="#Page_297">297</a>, <a href="#Page_298">298</a><br /> +<br /> +Comets, number of, <a href="#Page_98">98</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.75em;">tails of, <a href="#Page_115">115</a>, <a href="#Page_116">116</a></span><br /> +<br /> +Comet years, <a href="#Page_104">104</a><br /> +<br /> +Comiers, <a href="#Page_99">99</a><br /> +<br /> +Comstock, <a href="#Page_90">90</a>, <a href="#Page_146">146</a><br /> +<br /> +Condamine, <a href="#Page_257">257</a><br /> +<br /> +Conon, <a href="#Page_297">297</a><br /> +<br /> +Coon Butte mountain, <a href="#Page_120">120</a>, <a href="#Page_121">121</a><br /> +<br /> +Cooper, <a href="#Page_3">3</a><br /> +<br /> +Copeland, <a href="#Page_76">76</a>, <a href="#Page_157">157</a><br /> +<br /> +Corona, sun’s, <a href="#Page_1">1</a>, <a href="#Page_334">334</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.75em;">round moon, <a href="#Page_35">35</a>, <a href="#Page_36">36</a></span><br /> +<br /> +Corona Australis, <a href="#Page_295">295</a><br /> +<br /> +Corvinus, <a href="#Page_292">292</a><br /> +<br /> +Corvus, <a href="#Page_292">292</a><br /> +<br /> +Cotsworth, <a href="#Page_46">46</a><br /> +<br /> +Cowell, <a href="#Page_105">105</a><br /> +<br /> +Crabtree, <a href="#Page_337">337</a><br /> +<br /> +Crater, <a href="#Page_291">291</a><br /> +<br /> +Craters on moon, <a href="#Page_55">55</a>, <a href="#Page_56">56</a><br /> +<br /> +Crawford, <a href="#Page_348">348</a><br /> +<br /> +Crecy, Battle of, <a href="#Page_333">333</a><br /> +<br /> +Crescent of Venus, <a href="#Page_19">19</a>, <a href="#Page_20">20</a><br /> +<br /> +Crommelin, <a href="#Page_105">105</a>, <a href="#Page_111">111</a><br /> +<br /> +Crucifixion, <a href="#Page_18">18</a><br /> +<br /> +Curtis, <a href="#Page_344">344</a><br /> +<br /> +Cusps of Venus, <a href="#Page_20">20</a><br /> +<br /> +Cygnus, (61), <a href="#Page_155">155</a><br /> +<br /> +Cynocephalus, <a href="#Page_222">222</a><br /> +<br /> +<br /> +<span class="large">D</span><br /> +<br /> +Dante, <a href="#Page_156">156</a>, <a href="#Page_258">258</a>, <a href="#Page_265">265</a><br /> +<br /> +Dark shade on moon, <a href="#Page_333">333</a><br /> +<br /> +D’Arrest, <a href="#Page_94">94</a><br /> +<br /> +Darwin, Sir George, <a href="#Page_158">158</a>, <a href="#Page_319">319</a><br /> +<br /> +“David’s Chariot,” <a href="#Page_241">241</a><br /> +<br /> +Davis, <a href="#Page_155">155</a><br /> +<br /> +Dawes, <a href="#Page_168">168</a><br /> +<br /> +<span class="pagenum"><a name="Page_362" id="Page_362">[Pg 362]</a></span>“Dawn proclaimer,” <a href="#Page_251">251</a><br /> +<br /> +Delambre, <a href="#Page_185">185</a><br /> +<br /> +Delauney, <a href="#Page_347">347</a><br /> +<br /> +Dembowski, <a href="#Page_190">190</a><br /> +<br /> +Demetrius, <a href="#Page_111">111</a><br /> +<br /> +Denning, <a href="#Page_11">11</a>, <a href="#Page_74">74</a>, <a href="#Page_77">77</a>, <a href="#Page_84">84</a>, <a href="#Page_86">86</a>, <a href="#Page_87">87</a>, <a href="#Page_89">89</a>, <a href="#Page_99">99</a>, <a href="#Page_118">118</a>, <a href="#Page_340">340</a><br /> +<br /> +Derham, <a href="#Page_21">21</a>, <a href="#Page_23">23</a><br /> +<br /> +Deucalion, <a href="#Page_268">268</a><br /> +<br /> +De Vico, <a href="#Page_21">21</a>, <a href="#Page_22">22</a><br /> +<br /> +Diamonds in meteorites, <a href="#Page_127">127</a><br /> +<br /> +Dilkur, <a href="#Page_251">251</a><br /> +<br /> +Diodorus Siculus, <a href="#Page_127">127</a><br /> +<br /> +Diogenes Laertius, <a href="#Page_41">41</a><br /> +<br /> +Diomed, <a href="#Page_272">272</a><br /> +<br /> +Dione, <a href="#Page_89">89</a><br /> +<br /> +“Dipper,” <a href="#Page_241">241</a><br /> +<br /> +Doberck, <a href="#Page_160">160</a><br /> +<br /> +Dollond, <a href="#Page_24">24</a><br /> +<br /> +Domitian, <a href="#Page_334">334</a><br /> +<br /> +Donati’s comet, <a href="#Page_100">100</a><br /> +<br /> +Dorado, <a href="#Page_304">304</a><br /> +<br /> +Dordona, <a href="#Page_256">256</a><br /> +<br /> +Dorn, <a href="#Page_245">245</a><br /> +<br /> +Douglass, <a href="#Page_81">81</a><br /> +<br /> +Dragon, <a href="#Page_242">242</a><br /> +<br /> +Draper, <a href="#Page_75">75</a><br /> +<br /> +Drayton, <a href="#Page_156">156</a><br /> +<br /> +Dreyer, <a href="#Page_115">115</a><br /> +<br /> +Drifting stars, <a href="#Page_152">152</a><br /> +<br /> +Dryden, <a href="#Page_242">242</a><br /> +<br /> +Duncan, <a href="#Page_187">187</a><br /> +<br /> +Dunlop, <a href="#Page_264">264</a><br /> +<br /> +Dupret, <a href="#Page_83">83</a><br /> +<br /> +Dupuis, <a href="#Page_245">245</a>, <a href="#Page_252">252</a>, <a href="#Page_257">257</a>, <a href="#Page_258">258</a>, <a href="#Page_259">259</a>, <a href="#Page_266">266</a>, <a href="#Page_267">267</a>, <a href="#Page_268">268</a><br /> +<br /> +“Dusky star,” <a href="#Page_272">272</a><br /> +<br /> +<br /> +<span class="large">E</span><br /> +<br /> +“Earthen jar,” <a href="#Page_247">247</a><br /> +<br /> +Earth’s attraction on moon, <a href="#Page_55">55</a><br /> +<br /> +Earth’s motions, <a href="#Page_39">39</a><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1.75em;">rotation, <a href="#Page_46">46</a></span><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1.75em;">surface, <a href="#Page_32">32</a></span><br /> +<br /> +“Earthshine” on moon, <a href="#Page_51">51</a>, <a href="#Page_52">52</a>, <a href="#Page_56">56</a>, <a href="#Page_57">57</a><br /> +<br /> +Eastmann, <a href="#Page_316">316</a><br /> +<br /> +Easton, <a href="#Page_323">323</a>, <a href="#Page_324">324</a>, <a href="#Page_325">325</a><br /> +<br /> +Eclipses, ancient, <a href="#Page_52">52</a>, <a href="#Page_53">53</a>, <a href="#Page_57">57</a>, <a href="#Page_58">58</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.75em;">dark, of moon, <a href="#Page_53">53</a>, <a href="#Page_57">57</a>, <a href="#Page_58">58</a></span><br /> +<br /> +Ecliptic, obliquity of, <a href="#Page_47">47</a><br /> +<br /> +Eddington, <a href="#Page_357">357</a><br /> +<br /> +Electra, <a href="#Page_19">19</a><br /> +<br /> +Elster, <a href="#Page_39">39</a><br /> +<br /> +Emerson, <a href="#Page_353">353</a><br /> +<br /> +Enceladus, <a href="#Page_89">89</a><br /> +<br /> +Encke, <a href="#Page_113">113</a>, <a href="#Page_116">116</a>, <a href="#Page_240">240</a><br /> +<br /> +Ennis, <a href="#Page_189">189</a><br /> +<br /> +Eratosthenes, <a href="#Page_250">250</a>, <a href="#Page_297">297</a>, <a href="#Page_345">345</a><br /> +<br /> +Eridanus, <a href="#Page_274">274-278</a><br /> +<br /> +Eros, <a href="#Page_69">69</a>, <a href="#Page_70">70</a>, <a href="#Page_71">71</a><br /> +<br /> +Eta Argus, <a href="#Page_177">177</a>, <a href="#Page_287">287</a><br /> +<br /> +Eudemus, <a href="#Page_47">47</a><br /> +<br /> +Eudoxus, <a href="#Page_218">218</a>, <a href="#Page_219">219</a>, <a href="#Page_223">223</a><br /> +<br /> +Euler, <a href="#Page_56">56</a><br /> +<br /> +Eunomia, <a href="#Page_71">71</a><br /> +<br /> +Europa, <a href="#Page_252">252</a><br /> +<br /> +<br /> +<span class="large">F</span><br /> +<br /> +Fabritius, <a href="#Page_4">4</a>, <a href="#Page_101">101</a><br /> +<br /> +Fabry, <a href="#Page_1">1</a><br /> +<br /> +Faint stars in telescope, <a href="#Page_176">176</a><br /> +<br /> +“False Cross,” <a href="#Page_156">156</a><br /> +<br /> +“Famous stars,” <a href="#Page_246">246</a><br /> +<br /> +Fath, <a href="#Page_130">130</a>, <a href="#Page_213">213</a><br /> +<br /> +Faye, <a href="#Page_100">100</a><br /> +<br /> +February, Five Sundays in, <a href="#Page_36">36</a><br /> +<br /> +Fergani, <a href="#Page_189">189</a><br /> +<br /> +“Fisher Stars,” <a href="#Page_256">256</a><br /> +<br /> +“Fishes in Andromeda,” <a href="#Page_249">249</a><br /> +<br /> +Fitzgerald, <a href="#Page_127">127</a><br /> +<br /> +Flammarion, <a href="#Page_22">22</a>, <a href="#Page_26">26</a>, <a href="#Page_50">50</a>, <a href="#Page_138">138</a>, <a href="#Page_255">255</a>, <a href="#Page_265">265</a>, <a href="#Page_276">276</a><br /> +<br /> +Flamsteed, <a href="#Page_348">348</a><br /> +<br /> +“Flat earth” theory, <a href="#Page_32">32</a><br /> +<br /> +Fomalhaut, <a href="#Page_271">271</a>, <a href="#Page_309">309</a>, <a href="#Page_310">310</a><br /> +<br /> +Fontana, <a href="#Page_20">20</a><br /> +<br /> +Fontenelle, <a href="#Page_357">357</a><br /> +<br /> +Forbes, <a href="#Page_82">82</a>, <a href="#Page_95">95</a>, <a href="#Page_96">96</a><br /> +<br /> +Fornax, <a href="#Page_301">301</a><br /> +<br /> +<span class="pagenum"><a name="Page_363" id="Page_363">[Pg 363]</a></span>Fournier, <a href="#Page_87">87</a><br /> +<br /> +Fovea, <a href="#Page_284">284</a><br /> +<br /> +Freeman, <a href="#Page_88">88</a><br /> +<br /> +Fréret, <a href="#Page_222">222</a><br /> +<br /> +Frisby, <a href="#Page_101">101</a><br /> +<br /> +Fritsch, <a href="#Page_21">21</a><br /> +<br /> +Furner, <a href="#Page_163">163</a><br /> +<br /> +<br /> +<span class="large">G</span><br /> +<br /> +Gale, <a href="#Page_78">78</a><br /> +<br /> +Galileo, <a href="#Page_3">3</a>, <a href="#Page_4">4</a>, <a href="#Page_80">80</a>, <a href="#Page_82">82</a><br /> +<br /> +Galle, <a href="#Page_94">94</a>, <a href="#Page_341">341</a><br /> +<br /> +Ganymede, <a href="#Page_268">268</a><br /> +<br /> +Gaseous nebula, spectra of, <a href="#Page_195">195-198</a>, <a href="#Page_212">212</a><br /> +<br /> +Gassendi, <a href="#Page_14">14</a>, <a href="#Page_139">139</a><br /> +<br /> +Gathman, <a href="#Page_118">118</a><br /> +<br /> +Gaubil, <a href="#Page_99">99</a><br /> +<br /> +Gauthier, <a href="#Page_103">103</a><br /> +<br /> +Gegenschein, <a href="#Page_131">131</a><br /> +<br /> +Gemini, <a href="#Page_257">257</a>, <a href="#Page_258">258</a><br /> +<br /> +Geminid variables, <a href="#Page_187">187</a><br /> +<br /> +Gentil, Le, <a href="#Page_338">338</a>, <a href="#Page_339">339</a><br /> +<br /> +Gertel, <a href="#Page_39">39</a><br /> +<br /> +Ghizeh, Pyramids of, <a href="#Page_353">353</a><br /> +<br /> +Gibbous phase of Jupiter, <a href="#Page_75">75</a><br /> +<br /> +Gill, Sir David, <a href="#Page_118">118</a>, <a href="#Page_215">215</a>, <a href="#Page_216">216</a>, <a href="#Page_346">346</a><br /> +<br /> +Glacial epoch, <a href="#Page_42">42</a><br /> +<br /> +Gledhill, <a href="#Page_76">76</a><br /> +<br /> +Globular clusters, <a href="#Page_214">214</a>, <a href="#Page_215">215</a><br /> +<br /> +Goad, <a href="#Page_12">12</a><br /> +<br /> +Goatcher, <a href="#Page_179">179</a><br /> +<br /> +“Golden apples,” <a href="#Page_258">258</a><br /> +<br /> +Golius, <a href="#Page_281">281</a><br /> +<br /> +Gould, <a href="#Page_229">229</a>, <a href="#Page_278">278</a>, <a href="#Page_301">301</a>, <a href="#Page_304">304</a>, <a href="#Page_309">309</a>, <a href="#Page_310">310</a>, <a href="#Page_326">326</a><br /> +<br /> +Grant, <a href="#Page_82">82</a>, <a href="#Page_96">96</a>, <a href="#Page_345">345</a><br /> +<br /> +Gravitation, Law of, <a href="#Page_15">15</a>, <a href="#Page_40">40</a><br /> +<br /> +Greely, <a href="#Page_186">186</a><br /> +<br /> +Greisbach, <a href="#Page_80">80</a><br /> +<br /> +Groombridge 1830, <a href="#Page_159">159</a><br /> +<br /> +Grubb, Sir Howard, <a href="#Page_164">164</a><br /> +<br /> +Gruithuisen, <a href="#Page_21">21</a>, <a href="#Page_25">25</a>, <a href="#Page_26">26</a>, <a href="#Page_28">28</a><br /> +<br /> +Gruson, <a href="#Page_127">127</a><br /> +<br /> +Guillaume, <a href="#Page_331">331</a><br /> +<br /> +Guthrie, <a href="#Page_25">25</a><br /> +<br /> +<br /> +<span class="large">H</span><br /> +<br /> +Habitability of Mars, <a href="#Page_63">63-66</a><br /> +<br /> +<span style="margin-left: 2em;">"</span><span style="margin-left: 2.25em;">of planets, <a href="#Page_40">40</a></span><br /> +<br /> +Hadrian, <a href="#Page_248">248</a><br /> +<br /> +Halbert, <a href="#Page_78">78</a><br /> +<br /> +Hale, <a href="#Page_148">148</a>, <a href="#Page_150">150</a><br /> +<br /> +Hall, <a href="#Page_15">15</a>, <a href="#Page_131">131</a><br /> +<br /> +Halley, <a href="#Page_14">14</a>, <a href="#Page_17">17</a>, <a href="#Page_99">99</a>, <a href="#Page_105">105</a>, <a href="#Page_106">106</a>, <a href="#Page_108">108</a>, <a href="#Page_109">109</a>, <a href="#Page_116">116</a>, <a href="#Page_143">143</a>, <a href="#Page_145">145</a>, <a href="#Page_276">276</a><br /> +<br /> +Halm, <a href="#Page_122">122</a><br /> +<br /> +Halo, <a href="#Page_35">35</a>, <a href="#Page_36">36</a><br /> +<br /> +Hanouman, <a href="#Page_284">284</a><br /> +<br /> +Hansen, <a href="#Page_351">351</a><br /> +<br /> +Hansky, <a href="#Page_27">27</a><br /> +<br /> +Harding, <a href="#Page_25">25</a>, <a href="#Page_26">26</a>, <a href="#Page_94">94</a><br /> +<br /> +“Harris, Mrs.,” <a href="#Page_90">90</a><br /> +<br /> +Hartwig, <a href="#Page_88">88</a>, <a href="#Page_173">173</a><br /> +<br /> +Harvests, <a href="#Page_104">104</a><br /> +<br /> +Heat of sun, <a href="#Page_2">2</a>, <a href="#Page_3">3</a>, <a href="#Page_7">7</a><br /> +<br /> +Height of atmosphere, <a href="#Page_33">33</a><br /> +<br /> +Heis, <a href="#Page_132">132</a>, <a href="#Page_175">175</a>, <a href="#Page_189">189</a>, <a href="#Page_227">227</a>, <a href="#Page_229">229</a>, <a href="#Page_344">344</a><br /> +<br /> +Helium, <a href="#Page_4">4</a><br /> +<br /> +Hepidanus, <a href="#Page_267">267</a>, <a href="#Page_348">348</a><br /> +<br /> +Hercules, <a href="#Page_243">243</a>, <a href="#Page_259">259</a>, <a href="#Page_268">268</a><br /> +<br /> +Herod, <a href="#Page_18">18</a>, <a href="#Page_53">53</a><br /> +<br /> +Herschel, Miss Caroline, <a href="#Page_193">193</a>, <a href="#Page_194">194</a>, <a href="#Page_324">324</a>, <a href="#Page_357">357</a><br /> +<br /> +Herschel, Sir John, <a href="#Page_112">112</a>, <a href="#Page_177">177</a>, <a href="#Page_190">190</a>, <a href="#Page_207">207</a>, <a href="#Page_209">209</a>, <a href="#Page_210">210</a>, <a href="#Page_215">215</a>, <a href="#Page_289">289</a>, <a href="#Page_314">314</a>, <a href="#Page_346">346</a>, <a href="#Page_353">353</a><br /> +<br /> +Herschel, Sir Wm., <a href="#Page_3">3</a>, <a href="#Page_24">24</a>, <a href="#Page_80">80</a>, <a href="#Page_112">112</a>, <a href="#Page_114">114</a>, <a href="#Page_115">115</a>, <a href="#Page_116">116</a>, <a href="#Page_171">171</a>, <a href="#Page_178">178</a>, <a href="#Page_179">179</a>, <a href="#Page_190">190</a>, <a href="#Page_324">324</a>, <a href="#Page_325">325</a><br /> +<br /> +Hesiod, <a href="#Page_17">17</a>, <a href="#Page_220">220</a><br /> +<br /> +Hesperus, <a href="#Page_256">256</a><br /> +<br /> +Hevelius, <a href="#Page_99">99</a>, <a href="#Page_116">116</a>, <a href="#Page_221">221</a>, <a href="#Page_296">296</a>, <a href="#Page_299">299</a>, <a href="#Page_300">300</a><br /> +<br /> +Hill, <a href="#Page_87">87</a>, <a href="#Page_355">355</a><br /> +<br /> +Hind, <a href="#Page_19">19</a>, <a href="#Page_30">30</a>, <a href="#Page_54">54</a>, <a href="#Page_105">105</a>, <a href="#Page_111">111</a>, <a href="#Page_180">180</a><br /> +<br /> +Hipparchus, <a href="#Page_135">135</a>, <a href="#Page_221">221-223</a>, <a href="#Page_226">226</a>, <a href="#Page_250">250</a>, <a href="#Page_278">278</a>, <a href="#Page_281">281</a>, <a href="#Page_293">293</a>, <a href="#Page_329">329</a><br /> +<br /> +Hippocrates, <a href="#Page_258">258</a><br /> +<br /> +Hirst, <a href="#Page_333">333</a><br /> +<br /> +Holetschak, <a href="#Page_108">108</a><br /> +<br /> +Homer, <a href="#Page_17">17</a><br /> +<br /> +<span class="pagenum"><a name="Page_364" id="Page_364">[Pg 364]</a></span>Honorat, <a href="#Page_84">84</a><br /> +<br /> +Hooke, <a href="#Page_74">74</a>, <a href="#Page_128">128</a><br /> +<br /> +Horace, <a href="#Page_280">280</a><br /> +<br /> +Horologium, <a href="#Page_303">303</a><br /> +<br /> +Horus, <a href="#Page_145">145</a>, <a href="#Page_258">258</a><br /> +<br /> +Horrebow, <a href="#Page_29">29</a><br /> +<br /> +Horrocks, <a href="#Page_337">337</a><br /> +<br /> +Hortensus, Martinus, <a href="#Page_139">139</a><br /> +<br /> +Hough, <a href="#Page_76">76</a><br /> +<br /> +Houzeau, <a href="#Page_227">227</a>, <a href="#Page_229">229</a>, <a href="#Page_262">262</a>, <a href="#Page_274">274</a>, <a href="#Page_344">344</a><br /> +<br /> +Hovedin, Roger de, <a href="#Page_53">53</a><br /> +<br /> +Hubbard, <a href="#Page_100">100</a><br /> +<br /> +Huggins, Sir Wm., <a href="#Page_91">91</a>, <a href="#Page_148">148</a>, <a href="#Page_180">180</a><br /> +<br /> +Humboldt, <a href="#Page_30">30</a>, <a href="#Page_82">82</a>, <a href="#Page_83">83</a>, <a href="#Page_124">124</a>, <a href="#Page_128">128</a>, <a href="#Page_134">134</a>, <a href="#Page_154">154</a>, <a href="#Page_157">157</a>, <a href="#Page_342">342</a>, <a href="#Page_352">352</a>, <a href="#Page_357">357</a><br /> +<br /> +Hussey, <a href="#Page_88">88</a><br /> +<br /> +Hyades, <a href="#Page_157">157</a>, <a href="#Page_252">252</a>, <a href="#Page_253">253</a>, <a href="#Page_257">257</a><br /> +<br /> +Hydra, <a href="#Page_288">288</a><br /> +<br /> +Hydrus, <a href="#Page_303">303</a><br /> +<br /> +Hyperion, <a href="#Page_88">88</a>, <a href="#Page_90">90</a><br /> +<br /> +<br /> +<span class="large">I</span><br /> +<br /> +Ibn al-Aalam, <a href="#Page_225">225</a><br /> +<br /> +Ibn Alraqqa, <a href="#Page_281">281</a><br /> +<br /> +Icarus, <a href="#Page_284">284</a><br /> +<br /> +Indus, <a href="#Page_307">307</a><br /> +<br /> +Inhabited worlds, <a href="#Page_328">328</a>, <a href="#Page_357">357</a><br /> +<br /> +Innes, <a href="#Page_78">78</a>, <a href="#Page_168">168</a><br /> +<br /> +Intra-Mercurial planet, <a href="#Page_14">14</a>, <a href="#Page_15">15</a>, <a href="#Page_29">29</a><br /> +<br /> +Invention of telescope, <a href="#Page_342">342</a><br /> +<br /> +Io, <a href="#Page_252">252</a><br /> +<br /> +Ions, <a href="#Page_27">27</a><br /> +<br /> +Iris, <a href="#Page_71">71</a><br /> +<br /> +Isaiah, <a href="#Page_17">17</a>, <a href="#Page_356">356</a><br /> +<br /> +Isis, <a href="#Page_252">252</a>, <a href="#Page_261">261</a>, <a href="#Page_282">282</a>, <a href="#Page_283">283</a><br /> +<br /> +Istar, <a href="#Page_260">260</a><br /> +<br /> +<br /> +<span class="large">J</span><br /> +<br /> +Jansen, <a href="#Page_342">342</a><br /> +<br /> +Japetus, <a href="#Page_89">89</a>, <a href="#Page_90">90</a><br /> +<br /> +Jason, <a href="#Page_257">257</a>, <a href="#Page_285">285</a><br /> +<br /> +Johnson, Rev. S. J., <a href="#Page_19">19</a><br /> +<br /> +Jonckheere, <a href="#Page_15">15</a><br /> +<br /> +Jones, <a href="#Page_129">129</a><br /> +<br /> +Jordan, <a href="#Page_174">174</a><br /> +<br /> +Jupiter, <a href="#CHAPTER_VIII">chap. viii.</a><br /> +<br /> +<span style="margin-left: 1.25em;">"</span><span style="margin-left: 1.5em;">gibbous form of, <a href="#Page_75">75</a></span><br /> +<br /> +<span style="margin-left: 1.25em;">"</span><span style="margin-left: 1.5em;">and sun, <a href="#Page_8">8</a></span><br /> +<br /> +<br /> +<span class="large">K</span><br /> +<br /> +Kalevala, <a href="#Page_240">240</a><br /> +<br /> +Kapteyn, <a href="#Page_314">314</a>, <a href="#Page_316">316</a>, <a href="#Page_321">321</a>, <a href="#Page_322">322</a>, <a href="#Page_326">326</a>, <a href="#Page_357">357</a><br /> +<br /> +Kazemerski, <a href="#Page_244">244</a><br /> +<br /> +Keeler, <a href="#Page_86">86</a>, <a href="#Page_215">215</a><br /> +<br /> +Kelvin, Lord, <a href="#Page_206">206</a>, <a href="#Page_315">315</a>, <a href="#Page_316">316</a><br /> +<br /> +Kempf, <a href="#Page_174">174</a><br /> +<br /> +Kepler, <a href="#Page_52">52</a>, <a href="#Page_57">57</a>, <a href="#Page_298">298</a>, <a href="#Page_340">340</a>, <a href="#Page_341">341</a>, <a href="#Page_351">351</a><br /> +<br /> +Khayyam, Omar, <a href="#Page_127">127</a><br /> +<br /> +Kimah, <a href="#Page_255">255</a><br /> +<br /> +Kimball, <a href="#Page_51">51</a><br /> +<br /> +Kimta, <a href="#Page_255">255</a><br /> +<br /> +Kirch, <a href="#Page_23">23</a>, <a href="#Page_115">115</a><br /> +<br /> +Kirkwood, <a href="#Page_6">6</a><br /> +<br /> +Kleiber, <a href="#Page_123">123</a><br /> +<br /> +Klein, <a href="#Page_114">114</a>, <a href="#Page_183">183</a><br /> +<br /> +Knobel, <a href="#Page_238">238</a>, <a href="#Page_263">263</a><br /> +<br /> +Konkoly, <a href="#Page_183">183</a><br /> +<br /> +Koran, <a href="#Page_127">127</a>, <a href="#Page_270">270</a><br /> +<br /> +Kreusler, <a href="#Page_4">4</a><br /> +<br /> +Kreutz, <a href="#Page_101">101</a>, <a href="#Page_112">112</a><br /> +<br /> +<br /> +<span class="large">L</span><br /> +<br /> +Lacaille, <a href="#Page_294">294</a>, <a href="#Page_301">301</a>, <a href="#Page_302">302</a><br /> +<br /> +Lacerta, <a href="#Page_300">300</a><br /> +<br /> +Lagrange, <a href="#Page_345">345</a><br /> +<br /> +La Hire, <a href="#Page_20">20</a>, <a href="#Page_21">21</a><br /> +<br /> +Lalande, <a href="#Page_143">143</a>, <a href="#Page_144">144</a>, <a href="#Page_284">284</a><br /> +<br /> +Landerer, <a href="#Page_52">52</a><br /> +<br /> +Langdon, <a href="#Page_25">25</a><br /> +<br /> +Langley, Prof., <a href="#Page_3">3</a><br /> +<br /> +Laplace, <a href="#Page_43">43</a>, <a href="#Page_44">44</a>, <a href="#Page_98">98</a>, <a href="#Page_346">346</a>, <a href="#Page_351">351</a>, <a href="#Page_354">354</a><br /> +<br /> +Larkin, <a href="#Page_65">65</a><br /> +<br /> +Lassell, <a href="#Page_77">77</a>, <a href="#Page_128">128</a><br /> +<br /> +“Last in the River,” <a href="#Page_275">275-298</a><br /> +<br /> +Last year of century, <a href="#Page_37">37</a><br /> +<span class="pagenum"><a name="Page_365" id="Page_365">[Pg 365]</a></span><br /> +Lau, <a href="#Page_178">178</a>, <a href="#Page_183">183</a><br /> +<br /> +Leo, <a href="#Page_259">259</a><br /> +<br /> +Leo Minor, <a href="#Page_298">298</a><br /> +<br /> +Lepus, <a href="#Page_278">278</a>, <a href="#Page_279">279</a><br /> +<br /> +Lernæan marsh, <a href="#Page_258">258</a><br /> +<br /> +Leverrier, <a href="#Page_44">44</a>, <a href="#Page_347">347</a>, <a href="#Page_351">351</a><br /> +<br /> +Lewis, <a href="#Page_156">156</a>, <a href="#Page_162">162</a><br /> +<br /> +Lewis, Sir G. C., <a href="#Page_17">17</a><br /> +<br /> +Lexell’s comet, <a href="#Page_98">98</a><br /> +<br /> +Libra, <a href="#Page_262">262</a><br /> +<br /> +Life, possible, in Mars, <a href="#Page_63">63-65</a><br /> +<br /> +Light of full moon, <a href="#Page_1">1</a>, <a href="#Page_51">51</a><br /> +<br /> +Lippershey, <a href="#Page_342">342</a><br /> +<br /> +Littrow, <a href="#Page_339">339</a><br /> +<br /> +Lockyer, Sir Norman, <a href="#Page_144">144</a>, <a href="#Page_147">147</a><br /> +<br /> +Lodge, Sir Oliver, <a href="#Page_55">55</a><br /> +<br /> +Long, <a href="#Page_343">343</a>, <a href="#Page_357">357</a><br /> +<br /> +Longfellow, <a href="#Page_156">156</a>, <a href="#Page_273">273</a><br /> +<br /> +Lottin, <a href="#Page_42">42</a><br /> +<br /> +Lowell, <a href="#Page_22">22</a>, <a href="#Page_43">43</a>, <a href="#Page_59">59</a>, <a href="#Page_61">61</a>, <a href="#Page_64">64</a>, <a href="#Page_88">88</a><br /> +<br /> +Lucifer, <a href="#Page_17">17</a><br /> +<br /> +Lucretius, <a href="#Page_320">320</a><br /> +<br /> +“Luminous clouds,” <a href="#Page_33">33</a>, <a href="#Page_34">34</a><br /> +<br /> +Lunar craters, <a href="#Page_55">55</a>, <a href="#Page_56">56</a><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1em;">“mansions,” <a href="#Page_251">251</a></span><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1em;">mountains, <a href="#Page_58">58</a></span><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1em;">theory, <a href="#Page_56">56</a></span><br /> +<br /> +Lunt, <a href="#Page_179">179</a><br /> +<br /> +Lupus, <a href="#Page_294">294</a><br /> +<br /> +Lyman, <a href="#Page_25">25</a><br /> +<br /> +Lynn, <a href="#Page_37">37</a>, <a href="#Page_38">38</a>, <a href="#Page_96">96</a>, <a href="#Page_106">106</a>, <a href="#Page_179">179</a>, <a href="#Page_243">243</a>, <a href="#Page_244">244</a>, <a href="#Page_310">310</a><br /> +<br /> +Lynx, <a href="#Page_296">296</a><br /> +<br /> +Lyra, <a href="#Page_243">243</a>, <a href="#Page_244">244</a>, <a href="#Page_266">266</a><br /> +<br /> +<br /> +<span class="large">M</span><br /> +<br /> +Maclear, <a href="#Page_77">77</a><br /> +<br /> +Mädler, <a href="#Page_20">20</a>, <a href="#Page_22">22</a><br /> +<br /> +Mæstlin, <a href="#Page_341">341</a><br /> +<br /> +Magi, star of, <a href="#Page_1">1</a>, <a href="#Page_18">18</a>, <a href="#Page_145">145</a><br /> +<br /> +Magnitudes, star, <a href="#Page_311">311</a><br /> +<br /> +Maia, <a href="#Page_19">19</a>, <a href="#Page_256">256</a><br /> +<br /> +Mairan, <a href="#Page_357">357</a><br /> +<br /> +“Manger,” <a href="#Page_259">259</a><br /> +<br /> +Manilius, <a href="#Page_250">250</a>, <a href="#Page_259">259</a>, <a href="#Page_272">272</a><br /> +<br /> +Marius, Simon, <a href="#Page_82">82</a>, <a href="#Page_83">83</a>, <a href="#Page_231">231</a><br /> +<br /> +Markree Castle, <a href="#Page_3">3</a><br /> +<br /> +Marmol, <a href="#Page_76">76</a><br /> +<br /> +Mars, <a href="#CHAPTER_VI">chap. vi.</a>;<br /> +<span style="margin-left: 1em;">axis of <a href="#Page_59">59</a>;</span><br /> +<span style="margin-left: 1em;">red colour of, <a href="#Page_60">60</a>;</span><br /> +<span style="margin-left: 1em;">water vapour in, <a href="#Page_60">60</a>;</span><br /> +<span style="margin-left: 1em;">clouds in, <a href="#Page_61">61</a>;</span><br /> +<span style="margin-left: 1em;">“canals” in, <a href="#Page_61">61</a></span><br /> +<br /> +Martial, <a href="#Page_17">17</a><br /> +<br /> +Mascari, <a href="#Page_22">22</a><br /> +<br /> +Ma-tuan-lin, <a href="#Page_186">186</a>, <a href="#Page_267">267</a><br /> +<br /> +Mayer, <a href="#Page_24">24</a><br /> +<br /> +May transits of Mercury, <a href="#Page_15">15</a><br /> +<br /> +Maxwell, Clerk, <a href="#Page_86">86</a><br /> +<br /> +McHarg, <a href="#Page_16">16</a><br /> +<br /> +McKay, <a href="#Page_286">286</a><br /> +<br /> +Medusa, <a href="#Page_244">244</a><br /> +<br /> +Mee, <a href="#Page_88">88</a><br /> +<br /> +Melotte, <a href="#Page_82">82</a><br /> +<br /> +Mendelief, <a href="#Page_212">212</a><br /> +<br /> +Mensa, <a href="#Page_304">304</a><br /> +<br /> +Mercury, <a href="#CHAPTER_II">chap, ii.</a>, <a href="#Page_258">258</a><br /> +<br /> +Merrill, <a href="#Page_121">121</a><br /> +<br /> +Messier, <a href="#Page_114">114</a><br /> +<br /> +Meteoric stones, <a href="#Page_119">119</a><br /> +<br /> +Meteors, <a href="#Page_33">33</a><br /> +<br /> +Metius, <a href="#Page_342">342</a><br /> +<br /> +Microscopium, <a href="#Page_302">302</a><br /> +<br /> +Milky Way, <a href="#Page_320">320</a>, <a href="#Page_323">323</a>, <a href="#Page_325">325</a>, <a href="#Page_326">326</a>, <a href="#Page_328">328</a><br /> +<br /> +Milton, <a href="#Page_263">263</a><br /> +<br /> +Mimas, <a href="#Page_88">88</a>, <a href="#Page_89">89</a><br /> +<br /> +Minor planets, <a href="#CHAPTER_VII">chap. vii.</a><br /> +<br /> +Mira Ceti, <a href="#Page_178">178</a>, <a href="#Page_186">186</a>, <a href="#Page_272">272</a>, <a href="#Page_273">273</a><br /> +<br /> +Mitchell, <a href="#Page_4">4</a><br /> +<br /> +Mithridates, <a href="#Page_111">111</a><br /> +<br /> +Mitra, <a href="#Page_145">145</a><br /> +<br /> +Molyneux, <a href="#Page_80">80</a><br /> +<br /> +Monck, <a href="#Page_156">156</a>, <a href="#Page_181">181</a><br /> +<br /> +Monoceros, <a href="#Page_298">298</a><br /> +<br /> +Montanari, <a href="#Page_170">170</a>, <a href="#Page_171">171</a><br /> +<br /> +Montigny, <a href="#Page_34">34</a><br /> +<br /> +Moon, light of, <a href="#Page_1">1</a>, <a href="#Page_51">51</a><br /> +<br /> +<span style="margin-left: 1em;">"</span><span style="margin-left: 1.5em;">as seen through a telescope, <a href="#Page_50">50</a></span><br /> +<br /> +“Moon maiden,” <a href="#Page_52">52</a><br /> +<br /> +Moon mountains, <a href="#Page_58">58</a><br /> +<br /> +Morehouse, <a href="#Page_103">103</a>, <a href="#Page_110">110</a><br /> +<span class="pagenum"><a name="Page_366" id="Page_366">[Pg 366]</a></span><br /> +Motions of stars in line of sight, <a href="#Page_141">141</a>, <a href="#Page_142">142</a><br /> +<br /> +Moulton, <a href="#Page_133">133</a>, <a href="#Page_318">318</a><br /> +<br /> +Mountains, lunar, <a href="#Page_58">58</a><br /> +<br /> +Müller, <a href="#Page_174">174</a><br /> +<br /> +Musca, <a href="#Page_305">305</a><br /> +<br /> +Mycerinus, Pyramid of, <a href="#Page_353">353</a><br /> +<br /> +<br /> +<span class="large">N</span><br /> +<br /> +Nasmyth, <a href="#Page_11">11</a><br /> +<br /> +Nath, <a href="#Page_253">253</a><br /> +<br /> +Nautical Almanac, <a href="#Page_349">349</a><br /> +<br /> +Nebula in Andromeda, <a href="#Page_198">198-206</a>, <a href="#Page_231">231</a><br /> +<br /> +Nebulæ, gaseous, <a href="#Page_195">195-198</a>, <a href="#Page_212">212</a>, <a href="#Page_213">213</a><br /> +<br /> +Nebulæ, spiral, <a href="#Page_213">213</a><br /> +<br /> +Nebular hypothesis, <a href="#Page_354">354</a><br /> +<br /> +Nemælian lion, <a href="#Page_259">259</a><br /> +<br /> +Nemæus, <a href="#Page_259">259</a><br /> +<br /> +Neon in sun, <a href="#Page_4">4</a><br /> +<br /> +Nepthys, <a href="#Page_271">271</a><br /> +<br /> +Neptune, <a href="#Page_341">341</a><br /> +<br /> +Newcomb, <a href="#Page_13">13</a>, <a href="#Page_15">15</a>, <a href="#Page_33">33</a>, <a href="#Page_50">50</a>, <a href="#Page_65">65</a>, <a href="#Page_70">70</a>, <a href="#Page_129">129</a>, <a href="#Page_130">130</a>, <a href="#Page_153">153</a>, <a href="#Page_191">191</a>, <a href="#Page_203">203</a>, <a href="#Page_282">282</a>, <a href="#Page_339">339</a>, <a href="#Page_347">347</a>, <a href="#Page_349">349</a>, <a href="#Page_350">350</a>, <a href="#Page_355">355</a><br /> +<br /> +Newton, <a href="#Page_15">15</a>, <a href="#Page_351">351</a><br /> +<br /> +Nicephorus, <a href="#Page_127">127</a><br /> +<br /> +Nicholls, <a href="#Page_148">148</a>, <a href="#Page_154">154</a><br /> +<br /> +Nineveh tablets, <a href="#Page_17">17</a><br /> +<br /> +Noble, <a href="#Page_25">25</a><br /> +<br /> +Norma, <a href="#Page_302">302</a><br /> +<br /> +Novæ, <a href="#Page_180">180-182</a>, <a href="#Page_265">265</a>, <a href="#Page_267">267</a>, <a href="#Page_343">343</a><br /> +<br /> +Nova Persei, <a href="#Page_190">190</a><br /> +<br /> +November transits of Mercury, <a href="#Page_15">15</a><br /> +<br /> +Number of nebulæ, <a href="#Page_191">191</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.5em;">of stars, <a href="#Page_135">135</a>, <a href="#Page_136">136</a>, <a href="#Page_236">236</a>, <a href="#Page_237">237</a></span><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.5em;">of variable stars, <a href="#Page_182">182</a>, <a href="#Page_183">183</a></span><br /> +<br /> +<br /> +<span class="large">O</span><br /> +<br /> +Obliquity of ecliptic, <a href="#Page_47">47</a><br /> +<br /> +Occupations, <a href="#Page_14">14</a>, <a href="#Page_15">15</a>, <a href="#Page_54">54</a>, <a href="#Page_67">67</a>, <a href="#Page_80">80</a>, <a href="#Page_84">84</a>, <a href="#Page_85">85</a>, <a href="#Page_259">259</a>, <a href="#Page_340">340</a>, <a href="#Page_341">341</a><br /> +<br /> +Octans, <a href="#Page_303">303</a><br /> +<br /> +Odling, <a href="#Page_122">122</a><br /> +<br /> +Oeltzen, <a href="#Page_72">72</a><br /> +<br /> +Olbers, <a href="#Page_104">104</a>, <a href="#Page_124">124</a><br /> +<br /> +Old, <a href="#Page_340">340</a><br /> +<br /> +Orion, <a href="#Page_49">49</a>, <a href="#Page_146">146</a>, <a href="#Page_273">273</a>, <a href="#Page_274">274</a><br /> +<br /> +Osiris, <a href="#Page_145">145</a>, <a href="#Page_259">259</a>, <a href="#Page_261">261</a>, <a href="#Page_283">283</a><br /> +<br /> +“Ostriches,” <a href="#Page_266">266</a><br /> +<br /> +Otawa, <a href="#Page_240">240</a><br /> +<br /> +Ovid, <a href="#Page_242">242</a>, <a href="#Page_250">250</a>, <a href="#Page_255">255</a>, <a href="#Page_265">265</a>, <a href="#Page_288">288</a>, <a href="#Page_291">291</a>, <a href="#Page_322">322</a><br /> +<br /> +<br /> +<span class="large">P</span><br /> +<br /> +Palisa, <a href="#Page_71">71</a><br /> +<br /> +Palmer, <a href="#Page_182">182</a><br /> +<br /> +Parker, <a href="#Page_19">19</a><br /> +<br /> +Parkhurst, <a href="#Page_174">174</a><br /> +<br /> +Paschen, <a href="#Page_2">2</a><br /> +<br /> +Pastorff, <a href="#Page_25">25</a><br /> +<br /> +Pavo, <a href="#Page_307">307</a><br /> +<br /> +Payne, <a href="#Page_139">139</a><br /> +<br /> +Pearson, <a href="#Page_77">77</a><br /> +<br /> +Peary, <a href="#Page_119">119</a><br /> +<br /> +Peck, <a href="#Page_176">176</a><br /> +<br /> +Pegasus, <a href="#Page_248">248</a><br /> +<br /> +Pelion, <a href="#Page_282">282</a><br /> +<br /> +Peritheus, <a href="#Page_258">258</a><br /> +<br /> +Perrine, <a href="#Page_15">15</a>, <a href="#Page_76">76</a>, <a href="#Page_191">191</a>, <a href="#Page_192">192</a>, <a href="#Page_214">214</a><br /> +<br /> +Perrotin, <a href="#Page_351">351</a><br /> +<br /> +Perseus, <a href="#Page_244">244</a><br /> +<br /> +Petosiris, <a href="#Page_222">222</a><br /> +<br /> +Philostratus, <a href="#Page_334">334</a><br /> +<br /> +Phlegon, <a href="#Page_332">332</a><br /> +<br /> +Phœbe, <a href="#Page_90">90</a><br /> +<br /> +Phœnix, <a href="#Page_301">301</a><br /> +<br /> +Phosphorus, <a href="#Page_17">17</a><br /> +<br /> +Photographic nebula, <a href="#Page_192">192</a><br /> +<br /> +Pickering, E. C., <a href="#Page_125">125</a>, <a href="#Page_140">140</a>, <a href="#Page_144">144</a>, <a href="#Page_177">177</a><br /> +<br /> +Pickering, W. H., <a href="#Page_1">1</a>, <a href="#Page_12">12</a>, <a href="#Page_51">51</a>, <a href="#Page_61">61</a>, <a href="#Page_95">95</a>, <a href="#Page_102">102</a><br /> +<br /> +Pictor, <a href="#Page_304">304</a><br /> +<br /> +Pierce, <a href="#Page_228">228</a><br /> +<br /> +“Pilgrim Star,” <a href="#Page_180">180</a>, <a href="#Page_185">185</a>, <a href="#Page_186">186</a><br /> +<br /> +Pingré, <a href="#Page_54">54</a><br /> +<br /> +Pinzon, <a href="#Page_294">294</a><br /> +<span class="pagenum"><a name="Page_367" id="Page_367">[Pg 367]</a></span><br /> +Pisces, <a href="#Page_271">271</a><br /> +<br /> +Piscis Australis, <a href="#Page_295">295</a>, <a href="#Page_296">296</a><br /> +<br /> +Planetary nebulæ, <a href="#Page_213">213</a><br /> +<br /> +Platina, <a href="#Page_107">107</a><br /> +<br /> +Pleiades, <a href="#Page_19">19</a>, <a href="#Page_52">52</a>, <a href="#Page_137">137</a>, <a href="#Page_154">154</a>, <a href="#Page_157">157</a>, <a href="#Page_235">235</a>, <a href="#Page_254">254-257</a><br /> +<br /> +Pliny, <a href="#Page_17">17</a>, <a href="#Page_265">265</a>, <a href="#Page_280">280</a><br /> +<br /> +Plummer, W. E., <a href="#Page_180">180</a><br /> +<br /> +Plurality of worlds, <a href="#Page_328">328</a>, <a href="#Page_356">356</a>, <a href="#Page_357">357</a><br /> +<br /> +Pococke, <a href="#Page_271">271</a><br /> +<br /> +Pogson, <a href="#Page_317">317</a><br /> +<br /> +Polarization of moon’s surface, <a href="#Page_52">52</a><br /> +<br /> +Polarization on Mars, <a href="#Page_61">61</a><br /> +<br /> +Pole of cold, <a href="#Page_33">33</a><br /> +<br /> +<span style="margin-left: .75em;">"</span><span style="margin-left: 1em;">star, <a href="#Page_138">138</a>, <a href="#Page_239">239</a>, <a href="#Page_240">240</a></span><br /> +<br /> +Pollux, <a href="#Page_257">257</a><br /> +<br /> +Polydectus, <a href="#Page_244">244</a><br /> +<br /> +Poor, <a href="#Page_15">15</a> (footnote)<br /> +<br /> +Poynting, <a href="#Page_130">130</a><br /> +<br /> +Præsape, <a href="#Page_259">259</a><br /> +<br /> +Prince, <a href="#Page_25">25</a><br /> +<br /> +Proclus, <a href="#Page_221">221</a><br /> +<br /> +Proctor, <a href="#Page_7">7</a>, <a href="#Page_49">49</a>, <a href="#Page_59">59</a>, <a href="#Page_123">123</a>, <a href="#Page_285">285</a>, <a href="#Page_308">308</a>, <a href="#Page_323">323</a>, <a href="#Page_352">352</a><br /> +<br /> +Procyon, <a href="#Page_156">156</a>, <a href="#Page_157">157</a>, <a href="#Page_236">236</a>, <a href="#Page_284">284</a><br /> +<br /> +Ptolemy, <a href="#Page_189">189</a>, <a href="#Page_221">221-223</a>, <a href="#Page_224">224</a>, <a href="#Page_227">227</a>, <a href="#Page_230">230</a>, <a href="#Page_231">231</a>, <a href="#Page_234">234</a>, <a href="#Page_238">238</a>, <a href="#Page_244">244</a>, <a href="#Page_252">252</a>, <a href="#Page_253">253</a>, <a href="#Page_260">260</a>, <a href="#Page_263">263</a>, <a href="#Page_264">264</a>, <a href="#Page_267">267</a>, <a href="#Page_269">269</a>, <a href="#Page_275">275</a>, <a href="#Page_278">278</a>, <a href="#Page_281">281</a>, <a href="#Page_284">284</a>, <a href="#Page_293">293</a>, <a href="#Page_302">302</a>, <a href="#Page_330">330</a><br /> +<br /> +Pyramid, Great, <a href="#Page_46">46</a>, <a href="#Page_47">47</a>, <a href="#Page_308">308</a>, <a href="#Page_353">353</a><br /> +<br /> +Pytheas, <a href="#Page_46">46</a><br /> +<br /> +<br /> +<span class="large">Q</span><br /> +<br /> +Quadruple system, <a href="#Page_168">168</a><br /> +<br /> +Quénisset, <a href="#Page_21">21</a>, <a href="#Page_133">133</a><br /> +<br /> +<br /> +<span class="large">R</span><br /> +<br /> +Rabourdin, <a href="#Page_103">103</a><br /> +<br /> +Radium, <a href="#Page_7">7</a>, <a href="#Page_8">8</a>, <a href="#Page_38">38</a><br /> +<br /> +Râhu, <a href="#Page_93">93</a><br /> +<br /> +Rama, <a href="#Page_284">284</a>, <a href="#Page_340">340</a><br /> +<br /> +<i>Rational Almanac</i>, <a href="#Page_46">46</a><br /> +<br /> +“Red Bird,” <a href="#Page_290">290</a><br /> +<br /> +Red star, <a href="#Page_279">279</a>, <a href="#Page_292">292</a><br /> +<br /> +Regulus, <a href="#Page_30">30</a>, <a href="#Page_156">156</a>, <a href="#Page_235">235</a>, <a href="#Page_236">236</a>, <a href="#Page_260">260</a>, <a href="#Page_310">310</a>, <a href="#Page_340">340</a><br /> +<br /> +Remote galaxies, <a href="#Page_193">193</a>, <a href="#Page_204">204</a>, <a href="#Page_205">205</a><br /> +<br /> +Reticulum, <a href="#Page_304">304</a><br /> +<br /> +Rhea, <a href="#Page_89">89</a><br /> +<br /> +Rheita, De, <a href="#Page_144">144</a><br /> +<br /> +Riccioli, <a href="#Page_189">189</a><br /> +<br /> +Ricco, <a href="#Page_32">32</a><br /> +<br /> +Rigel, <a href="#Page_156">156</a>, <a href="#Page_157">157</a>, <a href="#Page_222">222</a><br /> +<br /> +Rigge, <a href="#Page_107">107</a><br /> +<br /> +Ring nebula in Lyra, <a href="#Page_211">211</a><br /> +<br /> +Rings of Saturn, <a href="#Page_85">85</a><br /> +<br /> +Rishis, <a href="#Page_240">240</a><br /> +<br /> +Ritter, <a href="#Page_76">76</a>, <a href="#Page_147">147</a><br /> +<br /> +“Rivers, celestial,” <a href="#Page_308">308</a><br /> +<br /> +Roberts, Dr. A. W., <a href="#Page_172">172</a>, <a href="#Page_173">173</a><br /> +<br /> +Roberts, Dr. I., <a href="#Page_95">95</a>, <a href="#Page_154">154</a>, <a href="#Page_200">200</a>, <a href="#Page_201">201</a>, <a href="#Page_203">203</a>, <a href="#Page_317">317</a><br /> +<br /> +Roberts, C., <a href="#Page_84">84</a><br /> +<br /> +Robigalia, <a href="#Page_280">280</a><br /> +<br /> +Robinson, <a href="#Page_342">342</a>, <a href="#Page_357">357</a><br /> +<br /> +Rœdeckœr, <a href="#Page_28">28</a><br /> +<br /> +Rogovsky, <a href="#Page_42">42</a>, <a href="#Page_43">43</a>, <a href="#Page_44">44</a>, <a href="#Page_75">75</a><br /> +<br /> +Rosse, Lord, <a href="#Page_76">76</a><br /> +<br /> +Roszel, <a href="#Page_70">70</a><br /> +<br /> +Rotation of Mercury, <a href="#Page_16">16</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.5em;">of Uranus, <a href="#Page_91">91</a></span><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.5em;">of Venus, <a href="#Page_22">22</a></span><br /> +<br /> +Rubáiyát, <a href="#Page_127">127</a><br /> +<br /> +Rudaux, <a href="#Page_80">80</a>, <a href="#Page_89">89</a><br /> +<br /> +Russell, H. C., <a href="#Page_21">21</a><br /> +<br /> +Russell, H. N., <a href="#Page_146">146</a><br /> +<br /> +Russell, J. C., <a href="#Page_333">333</a><br /> +<br /> +Rutherford, <a href="#Page_38">38</a><br /> +<br /> +<br /> +<span class="large">S</span><br /> +<br /> +Sadler, <a href="#Page_78">78</a>, <a href="#Page_299">299</a><br /> +<br /> +Safarik, <a href="#Page_24">24</a>, <a href="#Page_25">25</a><br /> +<br /> +Sagittarius, <a href="#Page_265">265-267</a><br /> +<span class="pagenum"><a name="Page_368" id="Page_368">[Pg 368]</a></span><br /> +<i>Sahu</i>, <a href="#Page_274">274</a><br /> +<br /> +Santini, <a href="#Page_357">357</a><br /> +<br /> +Satellite, eighth, of Jupiter, <a href="#Page_82">82</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.75em;">possible lunar, <a href="#Page_54">54</a></span><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.75em;">of Venus, <a href="#Page_28">28</a>, <a href="#Page_29">29</a></span><br /> +<br /> +Sawyer, <a href="#Page_186">186</a><br /> +<br /> +Sayce, <a href="#Page_218">218</a>, <a href="#Page_261">261</a><br /> +<br /> +Scaliger, <a href="#Page_299">299</a><br /> +<br /> +Schaeberle, <a href="#Page_93">93</a><br /> +<br /> +Schaer, <a href="#Page_88">88</a><br /> +<br /> +Scheiner, <a href="#Page_4">4</a>, <a href="#Page_150">150</a>, <a href="#Page_188">188</a>, <a href="#Page_195">195</a><br /> +<br /> +Scheuter, <a href="#Page_30">30</a><br /> +<br /> +Schiaparelli, <a href="#Page_22">22</a>, <a href="#Page_326">326</a><br /> +<br /> +Schjellerup, <a href="#Page_226">226</a>, <a href="#Page_228">228</a>, <a href="#Page_230">230</a>, <a href="#Page_231">231</a>, <a href="#Page_264">264</a>, <a href="#Page_277">277</a>, <a href="#Page_281">281</a>, <a href="#Page_340">340</a><br /> +<br /> +Schlesinger, <a href="#Page_183">183</a><br /> +<br /> +Schönfeld, <a href="#Page_287">287</a><br /> +<br /> +Schiraz, <a href="#Page_47">47</a><br /> +<br /> +Schmidt, <a href="#Page_51">51</a>, <a href="#Page_188">188</a>, <a href="#Page_220">220</a>, <a href="#Page_271">271</a><br /> +<br /> +Scholl, <a href="#Page_79">79</a><br /> +<br /> +Schröter, <a href="#Page_13">13</a>, <a href="#Page_20">20</a>, <a href="#Page_21">21</a>, <a href="#Page_22">22</a>, <a href="#Page_24">24</a>, <a href="#Page_26">26</a>, <a href="#Page_48">48</a><br /> +<br /> +Schuster, <a href="#Page_2">2</a>, <a href="#Page_148">148</a>, <a href="#Page_149">149</a>, <a href="#Page_150">150</a><br /> +<br /> +Schwabe, <a href="#Page_5">5</a><br /> +<br /> +Scorpio, <a href="#Page_263">263-265</a><br /> +<br /> +Sculptor, <a href="#Page_301">301</a><br /> +<br /> +Scutum, <a href="#Page_299">299</a><br /> +<br /> +Searle, <a href="#Page_132">132</a><br /> +<br /> +“Secondary light” of Venus, <a href="#Page_23">23-28</a><br /> +<br /> +See, Dr., <a href="#Page_12">12</a>, <a href="#Page_13">13</a>, <a href="#Page_33">33</a>, <a href="#Page_58">58</a>, <a href="#Page_96">96</a>, <a href="#Page_161">161</a>, <a href="#Page_164">164</a>, <a href="#Page_165">165</a>, <a href="#Page_210">210</a>, <a href="#Page_211">211</a>, <a href="#Page_281">281</a>, <a href="#Page_282">282</a>, <a href="#Page_354">354</a><br /> +<br /> +Seeliger, <a href="#Page_181">181</a>, <a href="#Page_206">206</a><br /> +<br /> +Seneca, <a href="#Page_218">218</a>, <a href="#Page_220">220</a><br /> +<br /> +Serapis, <a href="#Page_145">145</a><br /> +<br /> +Sestini, <a href="#Page_190">190</a><br /> +<br /> +“Seven Perfect Ones,” <a href="#Page_256">256</a><br /> +<br /> +Sextans, <a href="#Page_298">298</a><br /> +<br /> +Shaler, <a href="#Page_48">48</a><br /> +<br /> +Sharpe, <a href="#Page_357">357</a><br /> +<br /> +Shelley, <a href="#Page_356">356</a><br /> +<br /> +Shicor, <a href="#Page_274">274</a><br /> +<br /> +“Ship,” <a href="#Page_285">285</a><br /> +<br /> +“Sickle,” <a href="#Page_259">259</a><br /> +<br /> +Signalling to Mars, <a href="#Page_65">65</a><br /> +<br /> +Sihor, <a href="#Page_280">280</a><br /> +<br /> +Silkit, <a href="#Page_264">264</a><br /> +<br /> +Silvestria, <a href="#Page_124">124</a><br /> +<br /> +Simeon of Durham, <a href="#Page_53">53</a><br /> +<br /> +Simonides, <a href="#Page_255">255</a><br /> +<br /> +“Singing Maidens,” <a href="#Page_256">256</a><br /> +<br /> +Sirius, <a href="#Page_138">138</a>, <a href="#Page_156">156</a>, <a href="#Page_157">157</a>, <a href="#Page_160">160</a>, <a href="#Page_163">163</a>, <a href="#Page_236">236</a>, <a href="#Page_274">274</a>, <a href="#Page_280">280</a>, <a href="#Page_282">282</a>, <a href="#Page_283">283</a><br /> +<br /> +Slipher, <a href="#Page_60">60</a>, <a href="#Page_87">87</a>, <a href="#Page_161">161</a>, <a href="#Page_178">178</a><br /> +<br /> +Smart, <a href="#Page_109">109</a><br /> +<br /> +Smyth, Admiral, <a href="#Page_12">12</a>, <a href="#Page_72">72</a>, <a href="#Page_77">77</a>, <a href="#Page_107">107</a>, <a href="#Page_136">136</a>, <a href="#Page_140">140</a>, <a href="#Page_145">145</a>, <a href="#Page_170">170</a>, <a href="#Page_176">176</a>, <a href="#Page_190">190</a>, <a href="#Page_194">194</a>, <a href="#Page_253">253</a>, <a href="#Page_259">259</a>, <a href="#Page_351">351</a><br /> +<br /> +Snyder, Carl, <a href="#Page_8">8</a>, <a href="#Page_345">345</a><br /> +<br /> +Sobieski, <a href="#Page_299">299</a><br /> +<br /> +Sola, Comas, <a href="#Page_81">81</a>, <a href="#Page_87">87</a><br /> +<br /> +Somerville, Mrs., <a href="#Page_357">357</a><br /> +<br /> +Sothis, <a href="#Page_286">286</a><br /> +<br /> +Southern Cross, <a href="#Page_293">293</a>, <a href="#Page_344">344</a><br /> +<br /> +Spectra of double stars, <a href="#Page_162">162</a><br /> +<br /> +Spectrum of gaseous nebulæ, <a href="#Page_195">195-198</a>, <a href="#Page_212">212</a><br /> +<br /> +Spectrum of sun’s chromosphere, <a href="#Page_4">4</a><br /> +<br /> +Spencer, Herbert, <a href="#Page_193">193</a><br /> +<br /> +Sphinx, <a href="#Page_261">261</a><br /> +<br /> +Spica, <a href="#Page_156">156</a>, <a href="#Page_236">236</a><br /> +<br /> +Spiral nebulæ, <a href="#Page_213">213</a><br /> +<br /> +Star magnitudes, <a href="#Page_311">311</a><br /> +<br /> +“Star of Bethlehem,” <a href="#Page_17">17</a>, <a href="#Page_18">18</a><br /> +<br /> +Stars in daytime, <a href="#Page_158">158</a><br /> +<br /> +Stebbins, <a href="#Page_51">51</a><br /> +<br /> +Stockwell, <a href="#Page_18">18</a>, <a href="#Page_331">331</a><br /> +<br /> +“Stones from heaven,” <a href="#Page_125">125</a>, <a href="#Page_126">126</a><br /> +<br /> +Stoney, <a href="#Page_133">133</a><br /> +<br /> +Strabo, <a href="#Page_127">127</a><br /> +<br /> +Stratonoff, <a href="#Page_151">151</a>, <a href="#Page_320">320</a>, <a href="#Page_321">321</a><br /> +<br /> +Stromgen, <a href="#Page_88">88</a><br /> +<br /> +Strutt, <a href="#Page_7">7</a><br /> +<br /> +Struve, <a href="#Page_113">113</a>, <a href="#Page_240">240</a><br /> +<br /> +Struyck, <a href="#Page_54">54</a><br /> +<br /> +Succulæ, <a href="#Page_253">253</a><br /> +<br /> +Suhail, <a href="#Page_283">283</a>, <a href="#Page_286">286</a><br /> +<br /> +Sun darkenings, <a href="#Page_5">5</a>, <a href="#Page_335">335</a>, <a href="#Page_336">336</a><br /> +<br /> +Sun’s heat, <a href="#Page_7">7</a><br /> +<br /> +Sunlight, <a href="#Page_1">1</a>, <a href="#Page_2">2</a><br /> +<br /> +Sun-spots, <a href="#Page_5">5</a>, <a href="#Page_6">6</a><br /> +<br /> +Swift, <a href="#Page_102">102</a><br /> +<br /> +<i>Sydera Austricea</i>, <a href="#Page_5">5</a><br /> +<span class="pagenum"><a name="Page_369" id="Page_369">[Pg 369]</a></span><br /> +<br /> +<span class="large">T</span><br /> +<br /> +Tacchini, <a href="#Page_22">22</a><br /> +<br /> +Tamerlane, <a href="#Page_238">238</a><br /> +<br /> +Tammuz, <a href="#Page_261">261</a><br /> +<br /> +Tardé, <a href="#Page_4">4</a><br /> +<br /> +Taurus, <a href="#Page_251">251</a><br /> +<br /> +Taylor, <a href="#Page_40">40</a><br /> +<br /> +T Coronæ, <a href="#Page_184">184</a><br /> +<br /> +Tebbutt, <a href="#Page_183">183</a>, <a href="#Page_278">278</a><br /> +<br /> +Telescopium, <a href="#Page_302">302</a><br /> +<br /> +Temporary stars, <a href="#Page_180">180-182</a>, <a href="#Page_265">265</a>, <a href="#Page_267">267</a>, <a href="#Page_343">343</a><br /> +<br /> +Tennyson, <a href="#Page_40">40</a><br /> +<br /> +Terby, <a href="#Page_88">88</a><br /> +<br /> +Tethys, <a href="#Page_89">89</a><br /> +<br /> +Thales, <a href="#Page_357">357</a><br /> +<br /> +Thebes, <a href="#Page_271">271</a><br /> +<br /> +Themis, <a href="#Page_88">88-90</a><br /> +<br /> +Theogirus, <a href="#Page_279">279</a><br /> +<br /> +Theon, <a href="#Page_245">245</a><br /> +<br /> +Theseus, <a href="#Page_257">257</a><br /> +<br /> +Thome, <a href="#Page_101">101</a><br /> +<br /> +Thucydides, <a href="#Page_331">331</a><br /> +<br /> +Tibertinus, <a href="#Page_281">281</a><br /> +<br /> +Tibullus, <a href="#Page_282">282</a><br /> +<br /> +Tides, <a href="#Page_40">40</a><br /> +<br /> +Timocharis, <a href="#Page_340">340</a><br /> +<br /> +Tin, <a href="#Page_179">179</a><br /> +<br /> +Titan, <a href="#Page_85">85</a>, <a href="#Page_88">88</a>, <a href="#Page_89">89</a><br /> +<br /> +Titanium, <a href="#Page_179">179</a><br /> +<br /> +Toucan, <a href="#Page_308">308</a><br /> +<br /> +Transits of Mercury, <a href="#Page_14">14</a>, <a href="#Page_15">15</a><br /> +<br /> +<span style="margin-left: 1.5em;">"</span><span style="margin-left: 1.5em;">of Venus, <a href="#Page_337">337</a>, <a href="#Page_338">338</a>, <a href="#Page_339">339</a></span><br /> +<br /> +Triangulum, <a href="#Page_271">271</a><br /> +<br /> +<span style="margin-left: 2em;">"</span><span style="margin-left: 1.75em;">Australis, <a href="#Page_306">306</a></span><br /> +<br /> +Trio, <a href="#Page_220">220</a><br /> +<br /> +Triptolemus, <a href="#Page_257">257</a><br /> +<br /> +Triton, <a href="#Page_93">93</a><br /> +<br /> +Trouvelot, <a href="#Page_21">21</a>, <a href="#Page_22">22</a>, <a href="#Page_78">78</a>, <a href="#Page_211">211</a><br /> +<br /> +Tumlirz, <a href="#Page_46">46</a><br /> +<br /> +Turrinus, <a href="#Page_220">220</a><br /> +<br /><a name="tycho" id="tycho"></a> +Tycho Brahé, <a href="#Page_10">10</a>, <a href="#Page_30">30</a>, <a href="#Page_99">99</a>, <a href="#Page_145">145</a>, <a href="#Page_179">179</a>, <a href="#Page_298">298</a><br /> +<br /> +Typhon, <a href="#Page_263">263</a>, <a href="#Page_272">272</a><br /> +<br /> +<br /> +<span class="large">U</span><br /> +<br /> +Ulugh Beigh, <a href="#Page_238">238</a>, <a href="#Page_276">276</a>, <a href="#Page_278">278</a><br /> +<br /> +Underwood, <a href="#Page_85">85</a><br /> +<br /> +Uranus, <a href="#CHAPTER_X">chap. x.</a>;<br /> +<span style="margin-left: 1em;">spectrum of, <a href="#Page_91">91</a>, <a href="#Page_92">92</a></span><br /> +<br /> +Urda, <a href="#Page_71">71</a><br /> +<br /> +<br /> +<span class="large">V</span><br /> +<br /> +Valz <a href="#Page_72">72</a><br /> +<br /> +“Vanishing star,” <a href="#Page_59">59</a><br /> +<br /> +Varvadjah, <a href="#Page_236">236</a><br /> +<br /> +Vega, <a href="#Page_148">148</a>, <a href="#Page_156">156</a>, <a href="#Page_244">244</a><br /> +<br /> +Vencontre, <a href="#Page_220">220</a><br /> +<br /> +Venus, <a href="#CHAPTER_III">chap. iii.</a>;<br /> +<span style="margin-left: 1em;">apparent motion of, <a href="#Page_28">28</a>;</span><br /> +<span style="margin-left: 1em;">supposed satellite of, <a href="#Page_28">28</a>, <a href="#Page_29">29</a>;</span><br /> +<span style="margin-left: 1em;">transit of, <a href="#Page_337">337-339</a></span><br /> +<br /> +Veronica, S, <a href="#Page_145">145</a><br /> +<br /> +Vesta, <a href="#Page_70">70</a><br /> +<br /> +Virgil, <a href="#Page_17">17</a>, <a href="#Page_218">218</a>, <a href="#Page_242">242</a>, <a href="#Page_262">262</a>, <a href="#Page_309">309</a><br /> +<br /> +Virgo, <a href="#Page_260">260</a><br /> +<br /> +Vogel, <a href="#Page_180">180</a><br /> +<br /> +Vogt, <a href="#Page_122">122</a><br /> +<br /> +Volans, <a href="#Page_304">304</a><br /> +<br /> +Voltaire, <a href="#Page_15">15</a><br /> +<br /> +Von Hahn, <a href="#Page_24">24</a><br /> +<br /> +Vulpecula, <a href="#Page_300">300</a><br /> +<br /> +<br /> +<span class="large">W</span><br /> +<br /> +Wallace, Dr., <a href="#Page_212">212</a>, <a href="#Page_357">357</a><br /> +<br /> +Wallis, <a href="#Page_80">80</a><br /> +<br /> +Ward, <a href="#Page_88">88</a><br /> +<br /> +Wargentin, <a href="#Page_178">178</a><br /> +<br /> +Watson, <a href="#Page_339">339</a><br /> +<br /> +Webb, <a href="#Page_24">24</a>, <a href="#Page_25">25</a>, <a href="#Page_77">77</a>, <a href="#Page_190">190</a>, <a href="#Page_286">286</a><br /> +<br /> +Weber, <a href="#Page_183">183</a><br /> +<br /> +Weinhand, <a href="#Page_122">122</a><br /> +<br /> +Wendell, <a href="#Page_71">71</a>, <a href="#Page_103">103</a>, <a href="#Page_109">109</a><br /> +<br /> +Werchojansk, <a href="#Page_33">33</a><br /> +<br /> +White spots on Jupiter’s satellites, <a href="#Page_81">81</a><br /> +<br /> +White spots on Venus, <a href="#Page_21">21</a><br /> +<br /> +Whitmell, <a href="#Page_50">50</a>, <a href="#Page_86">86</a><br /> +<br /> +Wiggins, <a href="#Page_333">333</a><br /> +<span class="pagenum"><a name="Page_370" id="Page_370">[Pg 370]</a></span><br /> +Wilczyniski, <a href="#Page_195">195</a><br /> +<br /> +Williams, Stanley, <a href="#Page_22">22</a>, <a href="#Page_277">277</a>, <a href="#Page_302">302</a><br /> +<br /> +Wilsing, <a href="#Page_155">155</a><br /> +<br /> +Wilson, H. C., <a href="#Page_137">137</a>, <a href="#Page_139">139</a><br /> +<br /> +Wilson, Dr. W. E., <a href="#Page_3">3</a>, <a href="#Page_148">148</a><br /> +<br /> +Winnecke, <a href="#Page_26">26</a>, <a href="#Page_188">188</a><br /> +<br /> +Winterhalter, <a href="#Page_351">351</a><br /> +<br /> +Wolf, Dr. Max, <a href="#Page_71">71</a>, <a href="#Page_72">72</a>, <a href="#Page_191">191</a>, <a href="#Page_211">211</a>, Note p. 537<br /> +<br /> +Wrangel, <a href="#Page_240">240</a><br /> +<br /> +<br /> +<span class="large">Y</span><br /> +<br /> +Young, Prof., <a href="#Page_4">4</a>, <a href="#Page_7">7</a>, <a href="#Page_9">9</a><br /> +<br /> +Young, Miss Anne S., <a href="#Page_79">79</a><br /> +<br /> +Yunis, Ibn, <a href="#Page_30">30</a><br /> +<br /> +<br /> +<span class="large">Z</span><br /> +<br /> +Zach, <a href="#Page_331">331</a><br /> +<br /> +Zenophon, <a href="#Page_127">127</a><br /> +<br /> +Zethas, <a href="#Page_257">257</a><br /> +<br /> +Zöllner, <a href="#Page_27">27</a><br /> +</p> + + +<p> </p> +<p class="center">THE END</p> +<p> </p> +<p class="center">PRINTED BY WILLIAM CLOWES AND SONS, LIMITED, LONDON AND BECCLES.</p> + +<p> </p> +<div class="figcenter"><img src="images/img3.jpg" alt="" /></div> + + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><strong>Footnotes:</strong></p> + +<p><a name='f_1' id='f_1' href='#fna_1'>[1]</a> <i>Comptes Rendus</i>, 1903, December 7.</p> + +<p><a name='f_2' id='f_2' href='#fna_2'>[2]</a> <i>Nature</i>, April 11, 1907.</p> + +<p><a name='f_3' id='f_3' href='#fna_3'>[3]</a> <i>Astrophysical Journal</i>, vol. 19 (1904), p. 39.</p> + +<p><a name='f_4' id='f_4' href='#fna_4'>[4]</a> <i>Astrophysical Journal</i>, vol. 21 (1905), p. 260.</p> + +<p><a name='f_5' id='f_5' href='#fna_5'>[5]</a> <i>Knowledge</i>, July, 1902, p. 132.</p> + +<p><a name='f_6' id='f_6' href='#fna_6'>[6]</a> <i>Nature</i>, April 30, 1903.</p> + +<p><a name='f_7' id='f_7' href='#fna_7'>[7]</a> <i>Ibid.</i>, May 18, 1905.</p> + +<p><a name='f_8' id='f_8' href='#fna_8'>[8]</a> <i>Ibid.</i>, May 18, 1905.</p> + +<p><a name='f_9' id='f_9' href='#fna_9'>[9]</a> <i>Nature</i>, June 29, 1871.</p> + +<p><a name='f_10' id='f_10' href='#fna_10'>[10]</a> <i>Nature</i>, October 15, 1903.</p> + +<p><a name='f_11' id='f_11' href='#fna_11'>[11]</a> <i>The Life of the Universe</i> (1909), vol. ii. p. 209.</p> + +<p><a name='f_12' id='f_12' href='#fna_12'>[12]</a> <i>The World Machine</i>, p. 234.</p> + +<p><a name='f_13' id='f_13' href='#fna_13'>[13]</a> Quoted in <i>The Observatory</i>, March 1908, p. 125.</p> + +<p><a name='f_14' id='f_14' href='#fna_14'>[14]</a> <i>The Observatory</i>, September, 1906.</p> + +<p><a name='f_15' id='f_15' href='#fna_15'>[15]</a> <i>Nature</i>, March 1, 1900.</p> + +<p><a name='f_16' id='f_16' href='#fna_16'>[16]</a> <i>Cycle of Celestial Objects</i>, p. 96.</p> + +<p><a name='f_17' id='f_17' href='#fna_17'>[17]</a> <i>Ast. Nach.</i> No. 3737.</p> + +<p><a name='f_18' id='f_18' href='#fna_18'>[18]</a> <i>Observatory</i>, September, 1906.</p> + +<p><a name='f_19' id='f_19' href='#fna_19'>[19]</a> <i>Nature</i>, November 29 and December 20, 1894.</p> + +<p><a name='f_20' id='f_20' href='#fna_20'>[20]</a> <i>Bulletin, Ast. Soc. de France</i>, July, 1898.</p> + +<p><a name='f_21' id='f_21' href='#fna_21'>[21]</a> <i>Observatory</i>, vol. 8 (1885), pp. 306-7.</p> + +<p><a name='f_22' id='f_22' href='#fna_22'>[22]</a> <i>Nature</i>, October 30, 1902.</p> + +<p><a name='f_23' id='f_23' href='#fna_23'>[23]</a> Charles Lane Poor, <i>The Solar System</i>, p. 170.</p> + +<p><a name='f_24' id='f_24' href='#fna_24'>[24]</a> Smyth, <i>Celestial Cycle</i>, p. 60.</p> + +<p><a name='f_25' id='f_25' href='#fna_25'>[25]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 225.</p> + +<p><a name='f_26' id='f_26' href='#fna_26'>[26]</a> <i>The Observatory</i>, 1894, p. 395.</p> + +<p><a name='f_27' id='f_27' href='#fna_27'>[27]</a> <i>Ast. Nach.</i> 4333, quoted in <i>Nature</i>, July 1, 1909, p. 20.</p> + +<p><a name='f_28' id='f_28' href='#fna_28'>[28]</a> <i>English Mechanic</i>, July 23, 1909.</p> + +<p><a name='f_29' id='f_29' href='#fna_29'>[29]</a> <i>Nature</i>, December 22, 1892.</p> + +<p><a name='f_30' id='f_30' href='#fna_30'>[30]</a> <i>Celestial Objects</i>, vol. i. p. 52, footnote.</p> + +<p><a name='f_31' id='f_31' href='#fna_31'>[31]</a> <i>Ibid.</i>, p. 54.</p> + +<p><a name='f_32' id='f_32' href='#fna_32'>[32]</a> <i>Astronomy and Astrophysics</i>, 1892, p. 618.</p> + +<p><a name='f_33' id='f_33' href='#fna_33'>[33]</a> <i>Nature</i>, August 7, 1879.</p> + +<p><a name='f_34' id='f_34' href='#fna_34'>[34]</a> <i>The World of Space</i>, p. 56.</p> + +<p><a name='f_35' id='f_35' href='#fna_35'>[35]</a> <i>Nature</i>, September 15, 1892.</p> + +<p><a name='f_36' id='f_36' href='#fna_36'>[36]</a> <i>Observatory</i>, 1880, p. 574.</p> + +<p><a name='f_37' id='f_37' href='#fna_37'>[37]</a> <i>Knowledge</i>, November 1, 1897, pp. 260, 261.</p> + +<p><a name='f_38' id='f_38' href='#fna_38'>[38]</a> <i>Worlds in the Making</i>, p. 61.</p> + +<p><a name='f_39' id='f_39' href='#fna_39'>[39]</a> <i>Ibid.</i>, p. 48.</p> + +<p><a name='f_40' id='f_40' href='#fna_40'>[40]</a> <i>Nature</i>, June 1, 1876.</p> + +<p><a name='f_41' id='f_41' href='#fna_41'>[41]</a> <i>Cel. Objects</i>, vol. i. p. 66 (5th Edition).</p> + +<p><a name='f_42' id='f_42' href='#fna_42'>[42]</a> <i>Celestial Objects</i>, vol. i. p. 65 (5th Edition).</p> + +<p><a name='f_43' id='f_43' href='#fna_43'>[43]</a> <i>Ast. Nach.</i> No. 1863.</p> + +<p><a name='f_44' id='f_44' href='#fna_44'>[44]</a> <i>Nature</i>, June 1, 1876.</p> + +<p><a name='f_45' id='f_45' href='#fna_45'>[45]</a> <i>Ibid.</i>, June 8, 1876.</p> + +<p><a name='f_46' id='f_46' href='#fna_46'>[46]</a> <i>Nature</i>, October 17, 1895.</p> + +<p><a name='f_47' id='f_47' href='#fna_47'>[47]</a> <i>Ibid.</i>, July 27, 1905.</p> + +<p><a name='f_48' id='f_48'>[48]</a> <i>Celestial Cycle</i>, p. 107.</p> + +<p><a name='f_49' id='f_49' href='#fna_49'>[49]</a> <i>Nature</i>, October 6, 1887.</p> + +<p><a name='f_50' id='f_50' href='#fna_50'>[50]</a> <i>Ast. Nach.</i>, No. 4106.</p> + +<p><a name='f_51' id='f_51' href='#fna_51'>[51]</a> <i>Copernicus</i>, vol. ii. p. 168.</p> + +<p><a name='f_52' id='f_52' href='#fna_52'>[52]</a> <i>Cosmos</i>, vol. iv. p. 476, footnote.</p> + +<p><a name='f_53' id='f_53' href='#fna_53'>[53]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 153.</p> + +<p><a name='f_54' id='f_54' href='#fna_54'>[54]</a> <i>Ibid.</i>, p. 154.</p> + +<p><a name='f_55' id='f_55' href='#fna_55'>[55]</a> <i>Nature</i>, July 13, 1876.</p> + +<p><a name='f_56' id='f_56' href='#fna_56'>[56]</a> P. M. Ryves in <i>Knowledge</i>, June 1, 1897, p. 144.</p> + +<p><a name='f_57' id='f_57' href='#fna_57'>[57]</a> <i>Bulletin, Ast. Soc. de France</i>, August, 1905.</p> + +<p><a name='f_58' id='f_58' href='#fna_58'>[58]</a> <i>Nature</i>, April 5, 1894.</p> + +<p><a name='f_59' id='f_59' href='#fna_59'>[59]</a> <i>Nature</i>, May 14, 1896. Some have attributed these “luminous clouds” +to light reflected from the dust of the Krakatoa eruption (1883).</p> + +<p><a name='f_60' id='f_60' href='#fna_60'>[60]</a> <i>The Observatory</i>, 1877, p. 90.</p> + +<p><a name='f_61' id='f_61' href='#fna_61'>[61]</a> <i>Popular Astronomy</i>, vol. 11 (1903), p. 293.</p> + +<p><a name='f_62' id='f_62' href='#fna_62'>[62]</a> <i>Popular Astronomy</i>, vol. 13 (1905), p. 226.</p> + +<p><a name='f_63' id='f_63' href='#fna_63'>[63]</a> <i>Nature</i>, July 25, 1901 (from Flammarion).</p> + +<p><a name='f_64' id='f_64' href='#fna_64'>[64]</a> <i>Popular Astronomy</i>, vol. 11 (1903), p. 496.</p> + +<p><a name='f_65' id='f_65' href='#fna_65'>[65]</a> <i>Kinetic Theories of Gravitation</i>, Washington, 1877.</p> + +<p><a name='f_66' id='f_66' href='#fna_66'>[66]</a> <i>The Observatory</i>, June, 1894, p. 208.</p> + +<p><a name='f_67' id='f_67' href='#fna_67'>[67]</a> <i>Nature</i>, June 8, 1899.</p> + +<p><a name='f_68' id='f_68' href='#fna_68'>[68]</a> <i>Astrophysical Journal</i>, vol. 14 (1901), p. 238, footnote.</p> + +<p><a name='f_69' id='f_69' href='#fna_69'>[69]</a> <i>Mars as the Abode of Life</i>, p. 52.</p> + +<p><a name='f_70' id='f_70' href='#fna_70'>[70]</a> Second Book of the Maccabees v. 1-4 (Revised Edition).</p> + +<p><a name='f_71' id='f_71' href='#fna_71'>[71]</a> Humboldt’s <i>Cosmos</i>, vol. i. p. 169 (Otté’s translation).</p> + +<p><a name='f_72' id='f_72' href='#fna_72'>[72]</a> Quoted by Grant in <i>History of Physical Astronomy</i>, p. 71.</p> + +<p><a name='f_73' id='f_73' href='#fna_73'>[73]</a> <i>Ibid.</i>, pp. 100, 101.</p> + +<p><a name='f_74' id='f_74' href='#fna_74'>[74]</a> <i>Exposition du Système du Monde</i>, quoted by Carl Snyder in <i>The World +Machine</i>, p. 226.</p> + +<p><a name='f_75' id='f_75' href='#fna_75'>[75]</a> <i>Worlds in the Making</i>, p. 63.</p> + +<p><a name='f_76' id='f_76' href='#fna_76'>[76]</a> <i>Cosmos</i>, vol. i. p. 131.</p> + +<p><a name='f_77' id='f_77' href='#fna_77'>[77]</a> <i>The Observatory</i>, June, 1909, p. 261.</p> + +<p><a name='f_78' id='f_78' href='#fna_78'>[78]</a> <i>Astronomical Essays</i>, pp. 61, 62.</p> + +<p><a name='f_79' id='f_79' href='#fna_79'>[79]</a> <i>Encyclopædia Britannica</i> (<i>Schiraz</i>).</p> + +<p><a name='f_80' id='f_80' href='#fna_80'>[80]</a> <i>Monthly Notices</i>, R.A.S., February, 1905.</p> + +<p><a name='f_81' id='f_81' href='#fna_81'>[81]</a> <i>Nature</i>, March 3, 1870.</p> + +<p><a name='f_82' id='f_82' href='#fna_82'>[82]</a> <i>Ibid.</i>, March 31, 1870, p. 557.</p> + +<p><a name='f_83' id='f_83' href='#fna_83'>[83]</a> Prof. W. H. Pickering found 12 times (see p. 1).</p> + +<p><a name='f_84' id='f_84' href='#fna_84'>[84]</a> <i>Nature</i>, January 30, 1908.</p> + +<p><a name='f_85' id='f_85' href='#fna_85'>[85]</a> <i>Nature</i>, September 5, 1901.</p> + +<p><a name='f_86' id='f_86' href='#fna_86'>[86]</a> <i>Ibid.</i>, July 31, 1890.</p> + +<p><a name='f_87' id='f_87' href='#fna_87'>[87]</a> <i>Nature</i>, October 16, 1884.</p> + +<p><a name='f_88' id='f_88' href='#fna_88'>[88]</a> <i>Nature</i>, February 19, 1885.</p> + +<p><a name='f_89' id='f_89' href='#fna_89'>[89]</a> <i>Nature</i>, January 14, 1909, p. 323.</p> + +<p><a name='f_90' id='f_90' href='#fna_90'>[90]</a> <i>Photographic Atlas of the Moon, Annals of Harvard Observatory</i>, vol. +li. pp. 14, 15.</p> + +<p><a name='f_91' id='f_91' href='#fna_91'>[91]</a> <i>Nature</i>, January 18, 1906.</p> + +<p><a name='f_92' id='f_92' href='#fna_92'>[92]</a> Humboldt’s <i>Cosmos</i>, vol. iv. p. 481.</p> + +<p><a name='f_93' id='f_93' href='#fna_93'>[93]</a> <i>Ibid.</i>, p. 482.</p> + +<p><a name='f_94' id='f_94' href='#fna_94'>[94]</a> <i>Monthly Notices</i>, R.A.S., June, 1895.</p> + +<p><a name='f_95' id='f_95' href='#fna_95'>[95]</a> Humboldt’s <i>Cosmos</i>, vol. iv. p. 483 (Otté’s translation).</p> + +<p><a name='f_96' id='f_96' href='#fna_96'>[96]</a> Grant, <i>History of Physical Astronomy</i>, p. 229.</p> + +<p><a name='f_97' id='f_97' href='#fna_97'>[97]</a> <i>Popular Astronomy</i>, vol. xvii. No. 6, p. 387 (June-July, 1909).</p> + +<p><a name='f_98' id='f_98' href='#fna_98'>[98]</a> <i>Nature</i>, October 7, 1875.</p> + +<p><a name='f_99' id='f_99' href='#fna_99'>[99]</a> <i>Mars as an Abode of Life</i> (1908), p. 281.</p> + +<p><a name='f_100' id='f_100' href='#fna_100'>[100]</a> <i>Knowledge</i>, May 2, 1886.</p> + +<p><a name='f_101' id='f_101' href='#fna_101'>[101]</a> <i>Nature</i>, March 12, 1908.</p> + +<p><a name='f_102' id='f_102' href='#fna_102'>[102]</a> <i>Bulletin, Ast. Soc. de France</i>, April, 1899.</p> + +<p><a name='f_103' id='f_103' href='#fna_103'>[103]</a> <i>Astronomy and Astrophysics</i> (1894), p. 649.</p> + +<p><a name='f_104' id='f_104' href='#fna_104'>[104]</a> <i>Nature</i>, April 20, 1905.</p> + +<p><a name='f_105' id='f_105' href='#fna_105'>[105]</a> <i>Astrophysical Journal</i>, vol. 14 (1901), p. 258.</p> + +<p><a name='f_106' id='f_106' href='#fna_106'>[106]</a> <i>Nature</i>, August 22, 1907.</p> + +<p><a name='f_107' id='f_107' href='#fna_107'>[107]</a> <i>Popular Astronomy</i>, vol. 12 (1904), p. 679.</p> + +<p><a name='f_108' id='f_108' href='#fna_108'>[108]</a> <i>Mars as an Abode of Life</i>, p. 69.</p> + +<p><a name='f_109' id='f_109' href='#fna_109'>[109]</a> <i>Ibid.</i>, p. 146.</p> + +<p><a name='f_110' id='f_110' href='#fna_110'>[110]</a> <i>Worlds in the Making</i>, p. 49.</p> + +<p><a name='f_111' id='f_111' href='#fna_111'>[111]</a> <i>Worlds in the Making</i>, p. 53.</p> + +<p><a name='f_112' id='f_112' href='#fna_112'>[112]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 158.</p> + +<p><a name='f_113' id='f_113' href='#fna_113'>[113]</a> <i>Ibid.</i>, p. 166.</p> + +<p><a name='f_114' id='f_114' href='#fna_114'>[114]</a> <i>Nature</i>, July 13, 1876.</p> + +<p><a name='f_115' id='f_115' href='#fna_115'>[115]</a> <i>Nature</i>, May 2, 1907.</p> + +<p><a name='f_116' id='f_116' href='#fna_116'>[116]</a> <i>Nature</i>, May 30, 1907.</p> + +<p><a name='f_117' id='f_117' href='#fna_117'>[117]</a> <i>Publications of the Astronomical Society of the Pacific</i>, August, +1908.</p> + +<p><a name='f_118' id='f_118' href='#fna_118'>[118]</a> <i>Monthly Notices</i>, R.A.S., 1902, p. 291.</p> + +<p><a name='f_119' id='f_119' href='#fna_119'>[119]</a> <i>Monthly Notices</i>, R.A.S., February, 1902, p. 291.</p> + +<p><a name='f_120' id='f_120' href='#fna_120'>[120]</a> <i>Nature</i>, May 24, 1894.</p> + +<p><a name='f_121' id='f_121' href='#fna_121'>[121]</a> <i>Ibid.</i>, February 14, 1895.</p> + +<p><a name='f_122' id='f_122' href='#fna_122'>[122]</a> <i>Ibid.</i>, September 14, 1905.</p> + +<p><a name='f_123' id='f_123' href='#fna_123'>[123]</a> <i>Ibid.</i>, September 21, 1905.</p> + +<p><a name='f_124' id='f_124' href='#fna_124'>[124]</a> <i>Ibid.</i>, September 28, 1905.</p> + +<p><a name='f_125' id='f_125' href='#fna_125'>[125]</a> <i>Ibid.</i>, July 13, 1905.</p> + +<p><a name='f_126' id='f_126' href='#fna_126'>[126]</a> <i>Nature</i>, November 3, 1898.</p> + +<p><a name='f_127' id='f_127' href='#fna_127'>[127]</a> <i>Ibid.</i>, July 14, 1881, p. 235.</p> + +<p><a name='f_128' id='f_128' href='#fna_128'>[128]</a> Quoted in <i>The Observatory</i>, February, 1896, p. 104, from <i>Ast. +Nach.</i>, No. 3319.</p> + +<p><a name='f_129' id='f_129' href='#fna_129'>[129]</a> <i>Monthly Notices</i>, R.A.S., February, 1909.</p> + +<p><a name='f_130' id='f_130' href='#fna_130'>[130]</a> <i>Celestial Objects</i>, vol. i. p. 163.</p> + +<p><a name='f_131' id='f_131' href='#fna_131'>[131]</a> <i>Nature</i>, December 29, 1898.</p> + +<p><a name='f_132' id='f_132' href='#fna_132'>[132]</a> <i>Celestial Objects</i>, vol. i. p. 166.</p> + +<p><a name='f_133' id='f_133' href='#fna_133'>[133]</a> <i>Astrophysical Journal</i>, vol. 14 (1901), pp. 248-9.</p> + +<p><a name='f_134' id='f_134' href='#fna_134'>[134]</a> <i>Nature</i>, August 27, 1908.</p> + +<p><a name='f_135' id='f_135' href='#fna_135'>[135]</a> Webb’s <i>Celestial Objects</i>, vol. i. p. 177.</p> + +<p><a name='f_136' id='f_136' href='#fna_136'>[136]</a> <i>Ibid.</i>, vol. i. p. 187.</p> + +<p><a name='f_137' id='f_137' href='#fna_137'>[137]</a> <i>Celestial Objects</i>, vol. i. p. 186.</p> + +<p><a name='f_138' id='f_138' href='#fna_138'>[138]</a> <i>Astronomy and Astrophysics</i>, 1892, p. 87.</p> + +<p><a name='f_139' id='f_139' href='#fna_139'>[139]</a> <i>Ibid.</i>, 1892, pp. 94-5.</p> + +<p><a name='f_140' id='f_140' href='#fna_140'>[140]</a> <i>Observatory</i>, December, 1891.</p> + +<p><a name='f_141' id='f_141' href='#fna_141'>[141]</a> <i>Popular Astronomy</i>, vol. 11 (1903), p. 574.</p> + +<p><a name='f_142' id='f_142' href='#fna_142'>[142]</a> <i>Ibid.</i>, October, 1908.</p> + +<p><a name='f_143' id='f_143' href='#fna_143'>[143]</a> <i>Bulletin, Ast. Soc. de France</i>, August, 1907.</p> + +<p><a name='f_144' id='f_144' href='#fna_144'>[144]</a> <i>Nature</i>, August, 29 1907.</p> + +<p><a name='f_145' id='f_145' href='#fna_145'>[145]</a> <i>Ibid.</i>, March 7, 1907.</p> + +<p><a name='f_146' id='f_146' href='#fna_146'>[146]</a> <i>Bulletin, Ast. Soc. de France</i>, June, 1904.</p> + +<p><a name='f_147' id='f_147' href='#fna_147'>[147]</a> <i>The Observatory</i>, October, 1903, p. 392.</p> + +<p><a name='f_148' id='f_148' href='#fna_148'>[148]</a> <i>Astronomy and Astrophysics</i>, 1894, p. 277.</p> + +<p><a name='f_149' id='f_149' href='#fna_149'>[149]</a> <i>Nature</i>, November 18, 1897.</p> + +<p><a name='f_150' id='f_150' href='#fna_150'>[150]</a> <i>Journal</i>, B.A.A., January, 1907.</p> + +<p><a name='f_151' id='f_151' href='#fna_151'>[151]</a> <i>Journal</i>, B.A.A., February, 1909, p. 161.</p> + +<p><a name='f_152' id='f_152' href='#fna_152'>[152]</a> <i>Cosmos</i>, vol. ii. p. 703.</p> + +<p><a name='f_153' id='f_153' href='#fna_153'>[153]</a> <i>Ibid.</i></p> + +<p><a name='f_154' id='f_154' href='#fna_154'>[154]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 349.</p> + +<p><a name='f_155' id='f_155' href='#fna_155'>[155]</a> <i>Cosmos</i>, vol. iii. p. 75.</p> + +<p><a name='f_156' id='f_156' href='#fna_156'>[156]</a> <i>Journal</i>, B.A.A., June, 1896.</p> + +<p><a name='f_157' id='f_157' href='#fna_157'>[157]</a> <i>Celestial Objects</i>, vol. i. p. 191.</p> + +<p><a name='f_158' id='f_158' href='#fna_158'>[158]</a> <i>Nature</i>, May 30, 1901.</p> + +<p><a name='f_159' id='f_159' href='#fna_159'>[159]</a> <i>Bulletin, Ast. Soc. de France</i>, August, 1900.</p> + +<p><a name='f_160' id='f_160' href='#fna_160'>[160]</a> <i>Astronomy and Astrophysics</i>, 1892.</p> + +<p><a name='f_161' id='f_161' href='#fna_161'>[161]</a> <i>Astrophysical Journal</i>, January, 1908, p. 35.</p> + +<p><a name='f_162' id='f_162' href='#fna_162'>[162]</a> <i>Nature</i>, May 22, 1902.</p> + +<p><a name='f_163' id='f_163' href='#fna_163'>[163]</a> <i>Ibid.</i>, July 9, 1903.</p> + +<p><a name='f_164' id='f_164' href='#fna_164'>[164]</a> <i>Ibid.</i>, July 16, 1903.</p> + +<p><a name='f_165' id='f_165' href='#fna_165'>[165]</a> <i>Nature</i>, September 24, 1903.</p> + +<p><a name='f_166' id='f_166' href='#fna_166'>[166]</a> <i>Ibid.</i>, October 8, 1903.</p> + +<p><a name='f_167' id='f_167' href='#fna_167'>[167]</a> <i>Astrophysical Journal</i>, vol. 26 (1907), p. 60.</p> + +<p><a name='f_168' id='f_168' href='#fna_168'>[168]</a> <i>Nature</i>, January 30, 1908.</p> + +<p><a name='f_169' id='f_169' href='#fna_169'>[169]</a> <i>Ibid.</i>, October 15, 1908.</p> + +<p><a name='f_170' id='f_170' href='#fna_170'>[170]</a> <i>Ibid.</i>, October 29, 1908.</p> + +<p><a name='f_171' id='f_171' href='#fna_171'>[171]</a> <i>Journal</i>, B.A.A., March, 1908, and June 22, 1908.</p> + +<p><a name='f_172' id='f_172' href='#fna_172'>[172]</a> <i>Nature</i>, June 25, 1903.</p> + +<p><a name='f_173' id='f_173' href='#fna_173'>[173]</a> <i>Bulletin, Ast. Soc. de France</i>, June, 1904.</p> + +<p><a name='f_174' id='f_174' href='#fna_174'>[174]</a> <i>Pop. Ast.</i>, vol. 12, pp. 408-9.</p> + +<p><a name='f_175' id='f_175' href='#fna_175'>[175]</a> <i>Nature</i>, August 29, 1889.</p> + +<p><a name='f_176' id='f_176' href='#fna_176'>[176]</a> <i>Astrophysical Journal</i>, vol. 26 (1907), p. 62.</p> + +<p><a name='f_177' id='f_177' href='#fna_177'>[177]</a> <i>Bulletin, Ast. Soc. de France</i>, January, 1904.</p> + +<p><a name='f_178' id='f_178' href='#fna_178'>[178]</a> Humboldt’s <i>Cosmos</i>, vol. iv. p. 532.</p> + +<p><a name='f_179' id='f_179' href='#fna_179'>[179]</a> <i>Copernicus</i>, vol. ii. p. 64.</p> + +<p><a name='f_180' id='f_180' href='#fna_180'>[180]</a> <i>Knowledge</i>, May, 1909.</p> + +<p><a name='f_181' id='f_181' href='#fna_181'>[181]</a> <i>Journal</i>, British Astronomical Association, January, 1909, p. 132.</p> + +<p><a name='f_182' id='f_182' href='#fna_182'>[182]</a> <i>Ast. Nach.</i>, No. 4308.</p> + +<p><a name='f_183' id='f_183' href='#fna_183'>[183]</a> <i>History of Physical Astronomy</i>, p. 204.</p> + +<p><a name='f_184' id='f_184' href='#fna_184'>[184]</a> Smyth’s <i>Celestial Cycle</i>, pp. 210, 211.</p> + +<p><a name='f_185' id='f_185' href='#fna_185'>[185]</a> Poor, <i>The Solar System</i>, p. 274.</p> + +<p><a name='f_186' id='f_186' href='#fna_186'>[186]</a> <i>Celestial Cycle</i>, p. 246.</p> + +<p><a name='f_187' id='f_187' href='#fna_187'>[187]</a> <i>Nature</i>, October 2, 1879.</p> + +<p><a name='f_188' id='f_188' href='#fna_188'>[188]</a> <i>Ibid.</i>, May 6, 1880.</p> + +<p><a name='f_189' id='f_189' href='#fna_189'>[189]</a> <i>Ibid.</i>, February 19, 1880.</p> + +<p><a name='f_190' id='f_190' href='#fna_190'>[190]</a> <i>Nature</i>, September 30, 1897.</p> + +<p><a name='f_191' id='f_191' href='#fna_191'>[191]</a> <i>Nature</i>, August 5, 1875.</p> + +<p><a name='f_192' id='f_192' href='#fna_192'>[192]</a> <i>Ibid.</i>, October 12, 1882, and <i>Copernicus</i>, vol. iii. p. 85.</p> + +<p><a name='f_193' id='f_193' href='#fna_193'>[193]</a> <i>Nature</i>, May 8, 1884.</p> + +<p><a name='f_194' id='f_194' href='#fna_194'>[194]</a> <i>Ibid.</i>, June 16, 1887.</p> + +<p><a name='f_195' id='f_195' href='#fna_195'>[195]</a> <i>Journal</i>, B.A.A., December 13, 1901.</p> + +<p><a name='f_196' id='f_196' href='#fna_196'>[196]</a> <i>Nature</i>, September 20, 1900.</p> + +<p><a name='f_197' id='f_197' href='#fna_197'>[197]</a> <i>Ast. Nach.</i>, No. 3868, and <i>Nature</i>, March 12, 1903.</p> + +<p><a name='f_198' id='f_198' href='#fna_198'>[198]</a> <i>Nature</i>, November 13, 1908.</p> + +<p><a name='f_199' id='f_199' href='#fna_199'>[199]</a> <i>Nature</i>, December 7, 1905.</p> + +<p><a name='f_200' id='f_200' href='#fna_200'>[200]</a> <i>Celestial Cycle</i>, p. 259.</p> + +<p><a name='f_201' id='f_201' href='#fna_201'>[201]</a> <i>Celestial Cycle</i>, p. 260.</p> + +<p><a name='f_202' id='f_202' href='#fna_202'>[202]</a> <i>Journal</i>, B.A.A., April, 1907.</p> + +<p><a name='f_203' id='f_203' href='#fna_203'>[203]</a> <i>Monthly Notices</i>, R.A.S., March, 1908.</p> + +<p><a name='f_204' id='f_204' href='#fna_204'>[204]</a> <i>Celestial Cycle</i>, p. 231.</p> + +<p><a name='f_205' id='f_205' href='#fna_205'>[205]</a> <i>Journal</i>, B.A.A., July, 1908.</p> + +<p><a name='f_206' id='f_206' href='#fna_206'>[206]</a> <i>Popular Astronomy</i>, October, 1908.</p> + +<p><a name='f_207' id='f_207' href='#fna_207'>[207]</a> <i>Cape Obs.</i>, p. 401.</p> + +<p><a name='f_208' id='f_208' href='#fna_208'>[208]</a> <i>Nature</i>, July 2, 1908.</p> + +<p><a name='f_209' id='f_209' href='#fna_209'>[209]</a> <i>Journal</i>, B.A.A., January 20, 1909, pp. 123-4.</p> + +<p><a name='f_210' id='f_210' href='#fna_210'>[210]</a> Chambers’ <i>Handbook of Astronomy</i>, Catalogue of Comets.</p> + +<p><a name='f_211' id='f_211' href='#fna_211'>[211]</a> Seneca, quoted by Chambers, <i>Handbook</i>, vol. i. p. 554 (Fourth +Edition).</p> + +<p><a name='f_212' id='f_212' href='#fna_212'>[212]</a> <i>Ibid.</i></p> + +<p><a name='f_213' id='f_213' href='#fna_213'>[213]</a> <i>Ibid.</i></p> + +<p><a name='f_214' id='f_214' href='#fna_214'>[214]</a> <i>Ibid.</i>, p. 534.</p> + +<p><a name='f_215' id='f_215' href='#fna_215'>[215]</a> <i>Ibid.</i></p> + +<p><a name='f_216' id='f_216' href='#fna_216'>[216]</a> Ma-tuoan-lin, quoted by Chambers, <i>Handbook</i>, p. 570.</p> + +<p><a name='f_217' id='f_217' href='#fna_217'>[217]</a> <i>Astronomy and Astrophysics</i>, 1893, p. 798.</p> + +<p><a name='f_218' id='f_218' href='#fna_218'>[218]</a> <i>The Observatory</i>, October, 1898.</p> + +<p><a name='f_219' id='f_219' href='#fna_219'>[219]</a> Grant’s <i>History of Physical Astronomy</i>, p. 293.</p> + +<p><a name='f_220' id='f_220' href='#fna_220'>[220]</a> <i>Ibid.</i>, p. 294.</p> + +<p><a name='f_221' id='f_221' href='#fna_221'>[221]</a> Humboldt’s <i>Cosmos</i>, vol. i. pp. 89, 90 (Otté’s translation).</p> + +<p><a name='f_222' id='f_222' href='#fna_222'>[222]</a> <i>Celestial Objects</i>, vol. i. p. 211, footnote.</p> + +<p><a name='f_223' id='f_223' href='#fna_223'>[223]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 248.</p> + +<p><a name='f_224' id='f_224' href='#fna_224'>[224]</a> <i>Ibid.</i>, p. 248.</p> + +<p><a name='f_225' id='f_225' href='#fna_225'>[225]</a> <i>Ibid.</i>, p. 250.</p> + +<p><a name='f_226' id='f_226' href='#fna_226'>[226]</a> <i>Ibid.</i>, p. 231.</p> + +<p><a name='f_227' id='f_227' href='#fna_227'>[227]</a> Vol. iii. p. 106.</p> + +<p><a name='f_228' id='f_228' href='#fna_228'>[228]</a> Grant’s <i>History of Physical Astronomy</i>, p. 298.</p> + +<p><a name='f_229' id='f_229' href='#fna_229'>[229]</a> <i>Ibid.</i>, p. 305.</p> + +<p><a name='f_230' id='f_230' href='#fna_230'>[230]</a> Humboldt’s <i>Cosmos</i>, vol. i. p. 95.</p> + +<p><a name='f_231' id='f_231' href='#fna_231'>[231]</a> <i>Nature</i>, April 30, 1908.</p> + +<p><a name='f_232' id='f_232' href='#fna_232'>[232]</a> <i>Bulletin, Ast. Soc. de France</i>, May, 1906.</p> + +<p><a name='f_233' id='f_233' href='#fna_233'>[233]</a> <i>Nature</i>, November 24, 1904.</p> + +<p><a name='f_234' id='f_234' href='#fna_234'>[234]</a> <i>Ibid.</i>, September 10, 1896.</p> + +<p><a name='f_235' id='f_235' href='#fna_235'>[235]</a> <i>Ibid.</i>, June 29, 1893.</p> + +<p><a name='f_236' id='f_236' href='#fna_236'>[236]</a> <i>Journal</i>, B.A.A., May 22, 1903.</p> + +<p><a name='f_237' id='f_237' href='#fna_237'>[237]</a> <i>Nature</i>, December 13, 1906, p. 159.</p> + +<p><a name='f_238' id='f_238' href='#fna_238'>[238]</a> <i>Nature</i>, September 13, 1906.</p> + +<p><a name='f_239' id='f_239' href='#fna_239'>[239]</a> <i>Nature</i>, October 12, 1905, p. 596.</p> + +<p><a name='f_240' id='f_240' href='#fna_240'>[240]</a> <i>Knowledge</i>, January 13, 1882.</p> + +<p><a name='f_241' id='f_241' href='#fna_241'>[241]</a> <i>Ibid.</i>, January 20, 1882.</p> + +<p><a name='f_242' id='f_242' href='#fna_242'>[242]</a> <i>Popular Astronomy</i>, June-July, 1908, p. 345.</p> + +<p><a name='f_243' id='f_243' href='#fna_243'>[243]</a> <i>The Observatory</i>, March, 1896, p. 135.</p> + +<p><a name='f_244' id='f_244' href='#fna_244'>[244]</a> <i>The Observatory</i>, February, 1900, pp. 106-7.</p> + +<p><a name='f_245' id='f_245' href='#fna_245'>[245]</a> <i>Knowledge</i>, March, 1893, p. 51.</p> + +<p><a name='f_246' id='f_246' href='#fna_246'>[246]</a> <i>Ibid.</i>, July 3, 1885, p. 11.</p> + +<p><a name='f_247' id='f_247' href='#fna_247'>[247]</a> <i>Cosmos</i>, vol. i. p. 108 (Otté’s translation).</p> + +<p><a name='f_248' id='f_248' href='#fna_248'>[248]</a> <i>Ibid.</i>, vol. i. p. 124.</p> + +<p><a name='f_249' id='f_249' href='#fna_249'>[249]</a> <i>Ibid.</i>, vol. i. p. 119, footnote.</p> + +<p><a name='f_250' id='f_250' href='#fna_250'>[250]</a> <i>Copernicus</i>, vol. i. p. 72.</p> + +<p><a name='f_251' id='f_251' href='#fna_251'>[251]</a> <i>Ibid.</i></p> + +<p><a name='f_252' id='f_252' href='#fna_252'>[252]</a> <i>Astrophysical Journal</i>, June, 1909, pp. 378-9.</p> + +<p><a name='f_253' id='f_253' href='#fna_253'>[253]</a> <i>Knowledge</i>, July, 1909, p. 264.</p> + +<p><a name='f_254' id='f_254' href='#fna_254'>[254]</a> Quoted by Miss Irene E. T. Warner in <i>Knowledge</i>, July, 1909, p. +264.</p> + +<p><a name='f_255' id='f_255' href='#fna_255'>[255]</a> <i>The Observatory</i>, November, 1900.</p> + +<p><a name='f_256' id='f_256' href='#fna_256'>[256]</a> Or, “Before the phantom of false morning died” (4th edition); <i>The +Observatory</i>, September, 1905, p. 356.</p> + +<p><a name='f_257' id='f_257' href='#fna_257'>[257]</a> <i>The Observatory</i>, July, 1896, p. 274.</p> + +<p><a name='f_258' id='f_258' href='#fna_258'>[258]</a> <i>Journal</i>, B.A.A., January 24, 1906.</p> + +<p><a name='f_259' id='f_259' href='#fna_259'>[259]</a> <i>Ast. Soc. of the Pacific</i>, December, 1908, p. 280.</p> + +<p><a name='f_260' id='f_260' href='#fna_260'>[260]</a> <i>Nature</i>, November 1, 1906.</p> + +<p><a name='f_261' id='f_261' href='#fna_261'>[261]</a> <i>Ibid.</i>, November 22, 1906, p. 93.</p> + +<p><a name='f_262' id='f_262' href='#fna_262'>[262]</a> <i>Nature</i>, August 30, 1906.</p> + +<p><a name='f_263' id='f_263' href='#fna_263'>[263]</a> <i>Cosmos</i>, vol. i. p. 131, footnote.</p> + +<p><a name='f_264' id='f_264' href='#fna_264'>[264]</a> <i>Nature</i>, December 16, 1875.</p> + +<p><a name='f_265' id='f_265' href='#fna_265'>[265]</a> <i>Ibid.</i>, July 23, 1891.</p> + +<p><a name='f_266' id='f_266' href='#fna_266'>[266]</a> <i>Bulletin, Ast. Soc. de France</i>, April, 1903.</p> + +<p><a name='f_267' id='f_267' href='#fna_267'>[267]</a> <i>Bulletin, Ast. Soc. de France</i>, April, 1903.</p> + +<p><a name='f_268' id='f_268' href='#fna_268'>[268]</a> <i>The Observatory</i>, May, 1896. The italics are Brenner’s.</p> + +<p><a name='f_269' id='f_269' href='#fna_269'>[269]</a> <i>Cosmos</i>, vol. iv. p. 563.</p> + +<p><a name='f_270' id='f_270' href='#fna_270'>[270]</a> For details of this enumeration, see <i>Astronomical Essays</i>, p. 222.</p> + +<p><a name='f_271' id='f_271' href='#fna_271'>[271]</a> <i>Nature</i>, June 11, 1908.</p> + +<p><a name='f_272' id='f_272' href='#fna_272'>[272]</a> <i>Popular Astronomy</i>, vol. 14 (1906), p. 510.</p> + +<p><a name='f_273' id='f_273' href='#fna_273'>[273]</a> <i>Bedford Catalogue</i>, p. 532.</p> + +<p><a name='f_274' id='f_274' href='#fna_274'>[274]</a> <i>Popular Astronomy</i>, vol. 15 (1907), p. 194.</p> + +<p><a name='f_275' id='f_275' href='#fna_275'>[275]</a> <i>Popular Astronomy</i>, vol. 15 (1907), p. 195.</p> + +<p><a name='f_276' id='f_276' href='#fna_276'>[276]</a> <i>Bulletin, Ast. Soc. de France</i>, February, 1903.</p> + +<p><a name='f_277' id='f_277' href='#fna_277'>[277]</a> Here χ is probably 17 Cygni, χ being the famous +variable near it.</p> + +<p><a name='f_278' id='f_278' href='#fna_278'>[278]</a> <i>Popular Astronomy</i>, vol. 13 (1904), p. 509.</p> + +<p><a name='f_279' id='f_279' href='#fna_279'>[279]</a> <i>Astrophysical Journal</i>, December, 1895.</p> + +<p><a name='f_280' id='f_280' href='#fna_280'>[280]</a> <i>The Observatory</i>, July, 1895, p. 290.</p> + +<p><a name='f_281' id='f_281' href='#fna_281'>[281]</a> <i>Celestial Cycle</i>, p. 302.</p> + +<p><a name='f_282' id='f_282' href='#fna_282'>[282]</a> <i>Nature</i>, December 13, 1894.</p> + +<p><a name='f_283' id='f_283' href='#fna_283'>[283]</a> <i>Histoire Celeste</i>, p. 211.</p> + +<p><a name='f_284' id='f_284' href='#fna_284'>[284]</a> <i>Nature</i>, October, 1887.</p> + +<p><a name='f_285' id='f_285' href='#fna_285'>[285]</a> <i>Ibid.</i>, August 29, 1889.</p> + +<p><a name='f_286' id='f_286' href='#fna_286'>[286]</a> <i>Science Abstracts</i>, February 25, 1908, pp. 82, 83.</p> + +<p><a name='f_287' id='f_287' href='#fna_287'>[287]</a> <i>Bedford Catalogue</i>, pp. 227-8.</p> + +<p><a name='f_288' id='f_288' href='#fna_288'>[288]</a> <i>Knowledge</i>, February 1, 1888.</p> + +<p><a name='f_289' id='f_289' href='#fna_289'>[289]</a> <i>Celestial Cycle</i>, p. 280.</p> + +<p><a name='f_290' id='f_290' href='#fna_290'>[290]</a> <i>Popular Astronomy</i>, February, 1904.</p> + +<p><a name='f_291' id='f_291' href='#fna_291'>[291]</a> <i>Ibid.</i>, vol. 15 (1907), p. 444.</p> + +<p><a name='f_292' id='f_292' href='#fna_292'>[292]</a> <i>Journal</i>, B.A.A., June, 1899.</p> + +<p><a name='f_293' id='f_293' href='#fna_293'>[293]</a> <i>Astrophysical Journal</i>, vol. 8 (1898), p. 314.</p> + +<p><a name='f_294' id='f_294' href='#fna_294'>[294]</a> <i>Astrophysical Journal</i>, vol. 8, p. 213.</p> + +<p><a name='f_295' id='f_295' href='#fna_295'>[295]</a> <i>Ibid.</i>, vol. 17, January to June, 1902.</p> + +<p><a name='f_296' id='f_296' href='#fna_296'>[296]</a> <i>Astronomy and Astrophysics</i>, 1894, pp. 569-70.</p> + +<p><a name='f_297' id='f_297' href='#fna_297'>[297]</a> <i>The Study of Stellar Evolution</i> (1908), p. 171.</p> + +<p><a name='f_298' id='f_298' href='#fna_298'>[298]</a> <i>Astrophysical Journal</i>, January, 1905.</p> + +<p><a name='f_299' id='f_299' href='#fna_299'>[299]</a> <i>Journal</i>, B.A.A., June, 1901.</p> + +<p><a name='f_300' id='f_300' href='#fna_300'>[300]</a> <i>Ast. Soc. of the Pacific</i>, December, 1908.</p> + +<p><a name='f_301' id='f_301' href='#fna_301'>[301]</a> <i>The Observatory</i>, November, 1902, p. 391.</p> + +<p><a name='f_302' id='f_302' href='#fna_302'>[302]</a> <i>Cosmos</i>, vol. iv. p. 567 (Otté’s translation).</p> + +<p><a name='f_303' id='f_303' href='#fna_303'>[303]</a> <i>Journal</i>, B.A.A., February, 1898.</p> + +<p><a name='f_304' id='f_304' href='#fna_304'>[304]</a> <i>The Observatory</i>, April, 1887.</p> + +<p><a name='f_305' id='f_305' href='#fna_305'>[305]</a> <i>Evangeline</i>, Part the Second, III.</p> + +<p><a name='f_306' id='f_306' href='#fna_306'>[306]</a> <i>Legend of Robert, Duke of Normandy.</i></p> + +<p><a name='f_307' id='f_307' href='#fna_307'>[307]</a> <i>Copernicus</i>, vol. iii. p. 231.</p> + +<p><a name='f_308' id='f_308' href='#fna_308'>[308]</a> <i>Ibid.</i>, p. 61.</p> + +<p><a name='f_309' id='f_309' href='#fna_309'>[309]</a> <i>Cosmos</i>, vol. i. p. 142.</p> + +<p><a name='f_310' id='f_310' href='#fna_310'>[310]</a> These apertures are computed from the formula, minimum visible = 9 + +5 log. aperture.</p> + +<p><a name='f_311' id='f_311' href='#fna_311'>[311]</a> <i>Cosmos</i>, vol. iii. p. 73.</p> + +<p><a name='f_312' id='f_312' href='#fna_312'>[312]</a> <i>Darwin and Modern Science</i>, p. 563.</p> + +<p><a name='f_313' id='f_313' href='#fna_313'>[313]</a> <i>Journal</i>, B.A.A., October, 1895.</p> + +<p><a name='f_314' id='f_314' href='#fna_314'>[314]</a> Burnham’s <i>General Catalogue of Double Stars</i>, p. 494.</p> + +<p><a name='f_315' id='f_315' href='#fna_315'>[315]</a> <i>Journal</i>, B.A.A., November 18, 1896.</p> + +<p><a name='f_316' id='f_316' href='#fna_316'>[316]</a> <i>Ibid.</i>, B.A.A., January, 1907.</p> + +<p><a name='f_317' id='f_317' href='#fna_317'>[317]</a> <i>Studies in Astronomy</i>, p. 185.</p> + +<p><a name='f_318' id='f_318' href='#fna_318'>[318]</a> <i>Knowledge</i>, June, 1891.</p> + +<p><a name='f_319' id='f_319' href='#fna_319'>[319]</a> Seen by Drs. Ludendorff and Eberhard, <i>The Observatory</i>, April, +1906, p. 166, quoted from <i>Ast. Nach.</i>, No. 4067.</p> + +<p><a name='f_320' id='f_320' href='#fna_320'>[320]</a> <i>The Observatory</i>, January, 1907, p. 61.</p> + +<p><a name='f_321' id='f_321' href='#fna_321'>[321]</a> <i>Astronomy and Astrophysics</i>, 1894.</p> + +<p><a name='f_322' id='f_322' href='#fna_322'>[322]</a> Smyth’s <i>Celestial Cycle</i>, p. 223.</p> + +<p><a name='f_323' id='f_323' href='#fna_323'>[323]</a> <i>Nature</i>, February 7, 1907.</p> + +<p><a name='f_324' id='f_324' href='#fna_324'>[324]</a> <i>Ibid.</i>, March 19, 1908.</p> + +<p><a name='f_325' id='f_325' href='#fna_325'>[325]</a> <i>Popular Astronomy</i>, vol. 15 (1907), p. 9.</p> + +<p><a name='f_326' id='f_326' href='#fna_326'>[326]</a> <i>Astrophysical Journal</i>, June, 1907, p. 330.</p> + +<p><a name='f_327' id='f_327' href='#fna_327'>[327]</a> <i>Ibid.</i>, vol. 22, p. 172.</p> + +<p><a name='f_328' id='f_328' href='#fna_328'>[328]</a> <i>Nature</i>, November 18, 1886.</p> + +<p><a name='f_329' id='f_329' href='#fna_329'>[329]</a> <i>Astrophysical Journal</i>, vol. 17 (1903), p. 282.</p> + +<p><a name='f_330' id='f_330' href='#fna_330'>[330]</a> <i>Astrophysical Journal</i>, vol. 12 (1900), p. 54.</p> + +<p><a name='f_331' id='f_331' href='#fna_331'>[331]</a> <i>Nature</i>, March 21, 1878.</p> + +<p><a name='f_332' id='f_332' href='#fna_332'>[332]</a> <i>Bulletin, Ast. Soc. de France</i>, June, 1904.</p> + +<p><a name='f_333' id='f_333' href='#fna_333'>[333]</a> <i>Journal</i>, B.A.A., vol. 17 (1903), p. 282.</p> + +<p><a name='f_334' id='f_334' href='#fna_334'>[334]</a> <i>Nature</i>, June 20, 1909.</p> + +<p><a name='f_335' id='f_335' href='#fna_335'>[335]</a> <i>The Observatory</i>, vol. 7 (1884), p. 17.</p> + +<p><a name='f_336' id='f_336' href='#fna_336'>[336]</a> <i>The Observatory</i>, vol. 14 (1891), p. 69.</p> + +<p><a name='f_337' id='f_337' href='#fna_337'>[337]</a> <i>Astronomy and Astrophysics</i>, 1896, p. 54</p> + +<p><a name='f_338' id='f_338' href='#fna_338'>[338]</a> <i>Nature</i>, August 28, 1902.</p> + +<p><a name='f_339' id='f_339' href='#fna_339'>[339]</a> <i>Astrophysical Journal</i>, October, 1903.</p> + +<p><a name='f_340' id='f_340' href='#fna_340'>[340]</a> <i>Nature</i>, May 30, 1907.</p> + +<p><a name='f_341' id='f_341' href='#fna_341'>[341]</a> <i>Popular Astronomy</i>, February, 1909, p. 125.</p> + +<p><a name='f_342' id='f_342' href='#fna_342'>[342]</a> <i>The Observatory</i>, May, 1907, p. 216.</p> + +<p><a name='f_343' id='f_343' href='#fna_343'>[343]</a> <i>Astrophysical Journal</i>, May, 1907.</p> + +<p><a name='f_344' id='f_344' href='#fna_344'>[344]</a> <i>Histoire de l’Astronomie Moderne</i>, vol. i. pp. 185-6.</p> + +<p><a name='f_345' id='f_345' href='#fna_345'>[345]</a> Humboldt’s <i>Cosmos</i>, vol. iii. p. 210 (Otté’s translation).</p> + +<p><a name='f_346' id='f_346' href='#fna_346'>[346]</a> <i>Ibid.</i>, vol. iii. pp. 213-14.</p> + +<p><a name='f_347' id='f_347' href='#fna_347'>[347]</a> J. C. Duncan, <i>Lick Observatory Bulletin</i>, No. 151.</p> + +<p><a name='f_348' id='f_348' href='#fna_348'>[348]</a> <i>Astrophysical Journal</i>, vol. 17, p. 283.</p> + +<p><a name='f_349' id='f_349' href='#fna_349'>[349]</a> <i>The Origin of the Stars</i>, p. 143.</p> + +<p><a name='f_350' id='f_350' href='#fna_350'>[350]</a> <i>Ibid.</i>, p. 135.</p> + +<p><a name='f_351' id='f_351' href='#fna_351'>[351]</a> Quoted by Ennis in <i>The Origin of the Stars</i>, p. 133.</p> + +<p><a name='f_352' id='f_352' href='#fna_352'>[352]</a> <i>Astrophysical Journal</i>, vol. 20 (1904), p. 357.</p> + +<p><a name='f_353' id='f_353' href='#fna_353'>[353]</a> <i>Nature</i>, March 8, 1906.</p> + +<p><a name='f_354' id='f_354' href='#fna_354'>[354]</a> <i>Astronomical Society of the Pacific</i>, August, 1908.</p> + +<p><a name='f_355' id='f_355' href='#fna_355'>[355]</a> <i>Astronomy and Astrophysics</i>, 1894, p. 812.</p> + +<p><a name='f_356' id='f_356' href='#fna_356'>[356]</a> <i>The Observatory</i>, May, 1905.</p> + +<p><a name='f_357' id='f_357' href='#fna_357'>[357]</a> This is a misquotation. See my <i>Astronomical Essays</i>, p. 135.</p> + +<p><a name='f_358' id='f_358' href='#fna_358'>[358]</a> <i>Nature</i>, February 3, 1870.</p> + +<p><a name='f_359' id='f_359' href='#fna_359'>[359]</a> <i>Bedford Catalogue</i>, p. 14.</p> + +<p><a name='f_360' id='f_360' href='#fna_360'>[360]</a> <i>Ibid.</i>, p. 307.</p> + +<p><a name='f_361' id='f_361' href='#fna_361'>[361]</a> <i>Astrophysical Journal</i>, vol. 14, p. 37.</p> + +<p><a name='f_362' id='f_362' href='#fna_362'>[362]</a> <i>Ibid.</i>, vol. 9, p. 149.</p> + +<p><a name='f_363' id='f_363' href='#fna_363'>[363]</a> <i>Nature</i>, July 20, 1899.</p> + +<p><a name='f_364' id='f_364' href='#fna_364'>[364]</a> <i>Ast. Nach.</i>, No. 3476.</p> + +<p><a name='f_365' id='f_365' href='#fna_365'>[365]</a> <i>Astronomische Nachrichten</i>, No. 4213.</p> + +<p><a name='f_366' id='f_366' href='#fna_366'>[366]</a> <i>Astrophysical Journal</i>, vol. 9, p. 149.</p> + +<p><a name='f_367' id='f_367' href='#fna_367'>[367]</a> <i>Cape Observations</i>, p. 61.</p> + +<p><a name='f_368' id='f_368' href='#fna_368'>[368]</a> <i>Ibid.</i>, p. 85.</p> + +<p><a name='f_369' id='f_369' href='#fna_369'>[369]</a> <i>Cape Observations</i>, p. 98.</p> + +<p><a name='f_370' id='f_370' href='#fna_370'>[370]</a> <i>Transactions</i>, Royal Dublin Society, vol. 2.</p> + +<p><a name='f_371' id='f_371' href='#fna_371'>[371]</a> <i>Ast. Nach.</i>, 3628, quoted in <i>The Observatory</i>, April, 1900.</p> + +<p><a name='f_372' id='f_372' href='#fna_372'>[372]</a> <i>Nature</i>, April 8, 1909.</p> + +<p><a name='f_373' id='f_373' href='#fna_373'>[373]</a> <i>Problems in Astrophysics</i>, p. 477.</p> + +<p><a name='f_374' id='f_374' href='#fna_374'>[374]</a> <i>Ibid.</i>, p. 499.</p> + +<p><a name='f_375' id='f_375' href='#fna_375'>[375]</a> <i>Copernicus</i>, vol. iii. p. 55.</p> + +<p><a name='f_376' id='f_376' href='#fna_376'>[376]</a> <i>Lick Observatory Bulletin</i>, No. 149.</p> + +<p><a name='f_377' id='f_377' href='#fna_377'>[377]</a> <i>Ibid.</i></p> + +<p><a name='f_378' id='f_378' href='#fna_378'>[378]</a> <i>Ibid.</i></p> + +<p><a name='f_379' id='f_379' href='#fna_379'>[379]</a> <i>Monthly Notices</i>, R.A.S., April, 1908, pp. 465-481.</p> + +<p><a name='f_380' id='f_380' href='#fna_380'>[380]</a> <i>Lick Observatory Bulletin</i>, No. 155 (February, 1909).</p> + +<p><a name='f_381' id='f_381' href='#fna_381'>[381]</a> <i>Outlines of Astronomy</i>, par. 870 (Edition of 1875).</p> + +<p><a name='f_382' id='f_382' href='#fna_382'>[382]</a> <i>Georgics</i>, i. II. 217-18.</p> + +<p><a name='f_383' id='f_383' href='#fna_383'>[383]</a> See paper by Mr. and Mrs. Maunder in <i>Monthly Notices</i>, R.A.S., +March, 1904, p. 506.</p> + +<p><a name='f_384' id='f_384' href='#fna_384'>[384]</a> <i>Primitive Constellations</i>, vol. ii. p. 143.</p> + +<p><a name='f_385' id='f_385' href='#fna_385'>[385]</a> <i>Recherches sur l’Histoire de l’Astronomie Ancienne</i>, by Paul +Tannery (1893), p. 298.</p> + +<p><a name='f_386' id='f_386' href='#fna_386'>[386]</a> <i>Primitive Constellations</i>, vol. ii. p. 225.</p> + +<p><a name='f_387' id='f_387' href='#fna_387'>[387]</a> <i>Nature</i>, October 2, 1890.</p> + +<p><a name='f_388' id='f_388' href='#fna_388'>[388]</a> Lalande’s <i>Astronomie</i>, vol. i. pp. 243-4.</p> + +<p><a name='f_389' id='f_389' href='#fna_389'>[389]</a> Lalande’s <i>Astronomie</i>, vol. i. pp. 242-3.</p> + +<p><a name='f_390' id='f_390' href='#fna_390'>[390]</a> There are three copies of Al-Sufi’s work in the Imperial Library at +Paris, but these are inaccurate. There is also one in the British Museum +Library, and another in the India Office Library; but these are imperfect, +considerable portions of the original work being missing.</p> + +<p><a name='f_391' id='f_391' href='#fna_391'>[391]</a> <i>Harvard Annals</i>, vol. ix. p. 51.</p> + +<p><a name='f_392' id='f_392' href='#fna_392'>[392]</a> The science of the risings and settings of the stars was called <i>ilm +el-anwa</i> (Caussin, <i>Notices et Extraits des Manuscrits de la Bibliothèque +due Roi</i>, tome xii. p. 237).</p> + +<p><a name='f_393' id='f_393' href='#fna_393'>[393]</a> See Mr. E. B. Knobel’s papers on this subject in the <i>Monthly +Notices</i>, R.A.S., for 1879 and 1884.</p> + +<p><a name='f_394' id='f_394' href='#fna_394'>[394]</a> In reading this chapter the reader is recommended to have a Star +Atlas beside him for reference; Proctor’s smaller Star Atlas will be found +very convenient for this purpose. On the title-page of this useful work +the author quotes Carlyle’s words, “Why did not somebody teach me the +constellations and make me at home in the starry heavens which are always +overhead, and which I don’t half know to this day?”</p> + +<p><a name='f_395' id='f_395' href='#fna_395'>[395]</a> <i>Bedford Catalogue</i>, p. 29.</p> + +<p><a name='f_396' id='f_396' href='#fna_396'>[396]</a> <i>Cosmos</i>, vol. iii. p. 87.</p> + +<p><a name='f_397' id='f_397' href='#fna_397'>[397]</a> <i>Heavenly Display</i>, 579-85.</p> + +<p><a name='f_398' id='f_398' href='#fna_398'>[398]</a> <i>Bedford Catalogue</i>, p. 385.</p> + +<p><a name='f_399' id='f_399' href='#fna_399'>[399]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 529.</p> + +<p><a name='f_400' id='f_400' href='#fna_400'>[400]</a> Lalande’s <i>Astronomie</i>, vol. i. pp. 268-9.</p> + +<p><a name='f_401' id='f_401' href='#fna_401'>[401]</a> <i>Primitive Constellations</i>, vol. i. p. 48.</p> + +<p><a name='f_402' id='f_402' href='#fna_402'>[402]</a> <i>Bedford Catalogue</i>, pp. 27, 28.</p> + +<p><a name='f_403' id='f_403' href='#fna_403'>[403]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 492.</p> + +<p><a name='f_404' id='f_404' href='#fna_404'>[404]</a> <i>Bedford Catalogue</i>, p. 120.</p> + +<p><a name='f_405' id='f_405' href='#fna_405'>[405]</a> <i>Primitive Constellations</i>, vol. i. p. 143.</p> + +<p><a name='f_406' id='f_406' href='#fna_406'>[406]</a> Perseus.</p> + +<p><a name='f_407' id='f_407' href='#fna_407'>[407]</a> <i>Heavenly Display</i>, 254-8, 261-5, quoted by Brown in <i>Primitive +Constellations</i>, vol. i. p. 274.</p> + +<p><a name='f_408' id='f_408' href='#fna_408'>[408]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 493.</p> + +<p><a name='f_409' id='f_409' href='#fna_409'>[409]</a> <i>Primitive Constellations</i>, vol. i. p. 292.</p> + +<p><a name='f_410' id='f_410' href='#fna_410'>[410]</a> <i>Paradiso</i>, xxii. 111.</p> + +<p><a name='f_411' id='f_411' href='#fna_411'>[411]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 493.</p> + +<p><a name='f_412' id='f_412' href='#fna_412'>[412]</a> <i>Bedford Catalogue</i>, p. 225.</p> + +<p><a name='f_413' id='f_413' href='#fna_413'>[413]</a> <i>Nature</i>, April 6, 1882.</p> + +<p><a name='f_414' id='f_414' href='#fna_414'>[414]</a> <i>Primitive Constellations</i>, vol. i. p. 68.</p> + +<p><a name='f_415' id='f_415' href='#fna_415'>[415]</a> <i>Ibid.</i>, vol. i. p. 71.</p> + +<p><a name='f_416' id='f_416' href='#fna_416'>[416]</a> <i>Bibliographie Gènèrale de l’Astronomie</i>, vol. i. Introduction, pp. +131, 132.</p> + +<p><a name='f_417' id='f_417' href='#fna_417'>[417]</a> Lalande’s <i>Astronomie</i>, vol. i. p. 296.</p> + +<p><a name='f_418' id='f_418' href='#fna_418'>[418]</a> <i>Primitive Constellations</i>, vol. i. p. 74.</p> + +<p><a name='f_419' id='f_419' href='#fna_419'>[419]</a> <i>Cape Observations</i>, p. 116.</p> + +<p><a name='f_420' id='f_420' href='#fna_420'>[420]</a> <i>Metamorphoses</i>, xv. 371.</p> + +<p><a name='f_421' id='f_421' href='#fna_421'>[421]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 487.</p> + +<p><a name='f_422' id='f_422' href='#fna_422'>[422]</a> <i>Monthly Notices</i>, R.A.S., April 14, 1848.</p> + +<p><a name='f_423' id='f_423' href='#fna_423'>[423]</a> <i>Prim. Const.</i>, vol. ii. p. 45.</p> + +<p><a name='f_424' id='f_424' href='#fna_424'>[424]</a> Lalande’s <i>Astronomie</i>, pp. 472-3.</p> + +<p><a name='f_425' id='f_425' href='#fna_425'>[425]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 485.</p> + +<p><a name='f_426' id='f_426' href='#fna_426'>[426]</a> This star is not shown in Proctor’s small Atlas, but it lies between +μ and ν, nearer to μ.</p> + +<p><a name='f_427' id='f_427' href='#fna_427'>[427]</a> Lalande’s <i>Astronomie</i>, vol. i. p. 247.</p> + +<p><a name='f_428' id='f_428' href='#fna_428'>[428]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 489.</p> + +<p><a name='f_429' id='f_429' href='#fna_429'>[429]</a> <i>Primitive Constellations</i>, vol. i. p. 91.</p> + +<p><a name='f_430' id='f_430' href='#fna_430'>[430]</a> <i>Memoirs</i>, R.A.S., vol. xiii. 61.</p> + +<p><a name='f_431' id='f_431' href='#fna_431'>[431]</a> <i>Monthly Notices</i>, R.A.S., June, 1895.</p> + +<p><a name='f_432' id='f_432' href='#fna_432'>[432]</a> Lalande’s <i>Astronomie</i>, vol. i. p. 274.</p> + +<p><a name='f_433' id='f_433' href='#fna_433'>[433]</a> <i>Primitive Constellations</i>, vol. i. p. 143.</p> + +<p><a name='f_434' id='f_434' href='#fna_434'>[434]</a> <i>Primitive Constellations</i>, vol. i. p. 278.</p> + +<p><a name='f_435' id='f_435' href='#fna_435'>[435]</a> Lalande’s <i>Astronomie</i>, vol. iv. p. 468.</p> + +<p><a name='f_436' id='f_436' href='#fna_436'>[436]</a> <i>Quæst. Nat.</i>, Lib. 1, Cap. I. § 6; quoted by Dr. See. “Canicula” is +Sirius, and “Nartis,” Mars.</p> + +<p><a name='f_437' id='f_437' href='#fna_437'>[437]</a> <i>Astronomy and Astrophysics</i>, vol. 11, 1892.</p> + +<p><a name='f_438' id='f_438' href='#fna_438'>[438]</a> <i>The Observatory</i>, April, 1906, p. 175.</p> + +<p><a name='f_439' id='f_439' href='#fna_439'>[439]</a> Houzeau, <i>Bibliographie Gènèrale de l’Astronomie</i>, vol. i., +Introduction, p. 129.</p> + +<p><a name='f_440' id='f_440' href='#fna_440'>[440]</a> <i>English Mechanic</i>, March 25, 1904, p. 145.</p> + +<p><a name='f_441' id='f_441' href='#fna_441'>[441]</a> Humboldt’s <i>Cosmos</i>, vol. iii. p. 185, footnote (Otté’s +translation).</p> + +<p><a name='f_442' id='f_442' href='#fna_442'>[442]</a> Lalande’s <i>Astronomie</i>, vol, i. p. 277.</p> + +<p><a name='f_443' id='f_443' href='#fna_443'>[443]</a> This was pointed out by Flammarion in his work <i>Les Étoiles</i>, page +532; but his identifications do not agree exactly with mine.</p> + +<p><a name='f_444' id='f_444' href='#fna_444'>[444]</a> See Proctor’s Map 7, now x.</p> + +<p><a name='f_445' id='f_445' href='#fna_445'>[445]</a> <i>Primitive Constellations</i>, vol. i. p. 106.</p> + +<p><a name='f_446' id='f_446' href='#fna_446'>[446]</a> Lalande’s <i>Astronomie</i>, vol. i. p. 278.</p> + +<p><a name='f_447' id='f_447' href='#fna_447'>[447]</a> Lalande’s <i>Astronomie</i>, vol. iv.</p> + +<p><a name='f_448' id='f_448'>[448]</a> <i>Primitive Constellations</i>, vol. i. p. 112.</p> + +<p><a name='f_449' id='f_449' href='#fna_449'>[449]</a> <i>Ibid.</i>, vol. i. p. 113.</p> + +<p><a name='f_450' id='f_450' href='#fna_450'>[450]</a> Lalande’s <i>Astronomie</i>, vol. i.</p> + +<p><a name='f_451' id='f_451' href='#fna_451'>[451]</a> W. T. Lynn in <i>The Observatory</i>, vol. 22, p. 236.</p> + +<p><a name='f_452' id='f_452' href='#fna_452'>[452]</a> <i>Knowledge</i>, May 1, 1889. Sir John Herschel, however, gives 3970 +<span class="smcaplc">B.C.</span></p> + +<p><a name='f_453' id='f_453' href='#fna_453'>[453]</a> <i>The Observatory</i>, November 1907, p. 412.</p> + +<p><a name='f_454' id='f_454' href='#fna_454'>[454]</a> This is not, however, <i>invariably</i> the case, as pointed out by Mr. +Denning in <i>The Observatory</i>, 1885, p. 340.</p> + +<p><a name='f_455' id='f_455' href='#fna_455'>[455]</a> <i>The Observatory</i>, vol. 8 (1885), pp. 246-7.</p> + +<p><a name='f_456' id='f_456' href='#fna_456'>[456]</a> <i>Harvard College Observatory Annals</i>, vol. xlviii. No. 5.</p> + +<p><a name='f_457' id='f_457' href='#fna_457'>[457]</a> <i>Popular Astronomy</i>, vol. 15 (1907), p. 529.</p> + +<p><a name='f_458' id='f_458' href='#fna_458'>[458]</a> <i>Cape Observations</i>, p. 77.</p> + +<p><a name='f_459' id='f_459' href='#fna_459'>[459]</a> <i>Monthly Notices</i>, R.A.S., March, 1899.</p> + +<p><a name='f_460' id='f_460' href='#fna_460'>[460]</a> <i>Nature</i>, February 13, 1890.</p> + +<p><a name='f_461' id='f_461' href='#fna_461'>[461]</a> <i>Popular Astronomy</i>, vol. 15 (1907), p. 530.</p> + +<p><a name='f_462' id='f_462' href='#fna_462'>[462]</a> <i>Photographs of Star-Clusters and Nebulæ</i>, vol. ii. p. 17.</p> + +<p><a name='f_463' id='f_463' href='#fna_463'>[463]</a> <i>Monthly Notices</i>, R.A.S., May 9, 1856.</p> + +<p><a name='f_464' id='f_464' href='#fna_464'>[464]</a> <i>Astrophysical Journal</i>, vol. 25 (1907), p. 219.</p> + +<p><a name='f_465' id='f_465' href='#fna_465'>[465]</a> <i>Popular Astronomy</i>, vol. 11 (1903), p. 293.</p> + +<p><a name='f_466' id='f_466' href='#fna_466'>[466]</a> Translated by W. H. Mallock, <i>Nature</i>, February 8, 1900, p. 352.</p> + +<p><a name='f_467' id='f_467' href='#fna_467'>[467]</a> Howard Payn, <i>Nature</i>, May 16, 1901, p. 56.</p> + +<p><a name='f_468' id='f_468' href='#fna_468'>[468]</a> Howard Payn, <i>Nature</i>, May 16, 1901, p. 56.</p> + +<p><a name='f_469' id='f_469' href='#fna_469'>[469]</a> <i>Contributions from the Mount Wilson Solar Observatory</i>, No. 31.</p> + +<p><a name='f_470' id='f_470' href='#fna_470'>[470]</a> Quoted by Denning in <i>Telescopic Work for Starlight Evenings</i>, p. +297.</p> + +<p><a name='f_471' id='f_471' href='#fna_471'>[471]</a> <i>Astrophysical Journal</i>, March, 1895.</p> + +<p><a name='f_472' id='f_472' href='#fna_472'>[472]</a> <i>Outlines of Astronomy</i>, Tenth Edition, p. 571.</p> + +<p><a name='f_473' id='f_473' href='#fna_473'>[473]</a> <i>Astrophysical Journal</i>, vol. 12, p. 136.</p> + +<p><a name='f_474' id='f_474' href='#fna_474'>[474]</a> <i>De Placitis.</i> Quoted by Carl Snyder in <i>The World Machine</i> p. 354.</p> + +<p><a name='f_475' id='f_475' href='#fna_475'>[475]</a> <i>Popular Astronomy</i>, vol. 14 (1906), p. 638.</p> + +<p><a name='f_476' id='f_476' href='#fna_476'>[476]</a> Article on “The Greek Anthology,” <i>Nineteenth Century</i>, April, 1907, +quoted in <i>The Observatory</i>, May, 1907.</p> + +<p><a name='f_477' id='f_477' href='#fna_477'>[477]</a> <i>Popular Astronomy</i>, vol. 13 (1905), p. 346.</p> + +<p><a name='f_478' id='f_478' href='#fna_478'>[478]</a> <i>Bulletin de la Soc. Ast. de France</i>, April, 1908.</p> + +<p><a name='f_479' id='f_479' href='#fna_479'>[479]</a> <i>The Observatory</i>, vol. 11, p. 375.</p> + +<p><a name='f_480' id='f_480' href='#fna_480'>[480]</a> Grant, <i>History of Physical Astronomy</i>, p. 364.</p> + +<p><a name='f_481' id='f_481' href='#fna_481'>[481]</a> <i>Ibid.</i>, p. 377.</p> + +<p><a name='f_482' id='f_482' href='#fna_482'>[482]</a> <i>Ibid.</i>, p. 366.</p> + +<p><a name='f_483' id='f_483' href='#fna_483'>[483]</a> <i>Ibid.</i>, p. 367.</p> + +<p><a name='f_484' id='f_484' href='#fna_484'>[484]</a> Grant, <i>History of Physical Astronomy</i>, p. 370.</p> + +<p><a name='f_485' id='f_485' href='#fna_485'>[485]</a> <i>Nature</i>, July 25, 1889.</p> + +<p><a name='f_486' id='f_486' href='#fna_486'>[486]</a> <i>Cosmos</i>, vol. iv. p. 381.</p> + +<p><a name='f_487' id='f_487' href='#fna_487'>[487]</a> <i>Cosmos</i>, vol. iv. pp. 381-6.</p> + +<p><a name='f_488' id='f_488' href='#fna_488'>[488]</a> <i>Ibid.</i>, vol. i. p. 121.</p> + +<p><a name='f_489' id='f_489' href='#fna_489'>[489]</a> <i>The Observatory</i>, vol. 6 (1883), pp. 327-8.</p> + +<p><a name='f_490' id='f_490' href='#fna_490'>[490]</a> <i>Nature</i>, June 25, 1874.</p> + +<p><a name='f_491' id='f_491' href='#fna_491'>[491]</a> <i>Popular Astronomy</i>, May, 1895, “Reflectors or Refractors.”</p> + +<p><a name='f_492' id='f_492' href='#fna_492'>[492]</a> Denning, <i>Telescopic Work for Starlight Evenings</i>, p. 225.</p> + +<p><a name='f_493' id='f_493' href='#fna_493'>[493]</a> <i>Nature</i>, November 2, 1893.</p> + +<p><a name='f_494' id='f_494' href='#fna_494'>[494]</a> <i>Telescopic Work</i>, p. 226.</p> + +<p><a name='f_495' id='f_495' href='#fna_495'>[495]</a> <i>Copernicus</i>, vol. i. p. 229.</p> + +<p><a name='f_496' id='f_496' href='#fna_496'>[496]</a> Grant, <i>History of Physical Astronomy</i>, p. 433.</p> + +<p><a name='f_497' id='f_497' href='#fna_497'>[497]</a> <i>Cosmos</i>, vol. ii. p. 699.</p> + +<p><a name='f_498' id='f_498' href='#fna_498'>[498]</a> Grant, <i>History of Physical Astronomy</i>, p. 536, footnote.</p> + +<p><a name='f_499' id='f_499' href='#fna_499'>[499]</a> <i>Bedford Catalogue</i>, p. 179.</p> + +<p><a name='f_500' id='f_500' href='#fna_500'>[500]</a> <i>The Observatory</i>, July, 1891.</p> + +<p><a name='f_501' id='f_501' href='#fna_501'>[501]</a> <i>Nature</i>, September 3, 1903.</p> + +<p><a name='f_502' id='f_502' href='#fna_502'>[502]</a> <i>Cosmos</i>, vol. ii. p. 669.</p> + +<p><a name='f_503' id='f_503' href='#fna_503'>[503]</a> <i>The World Machine</i>, p. 80.</p> + +<p><a name='f_504' id='f_504' href='#fna_504'>[504]</a> <i>Ibid.</i>, p. 89.</p> + +<p><a name='f_505' id='f_505' href='#fna_505'>[505]</a> Grant, <i>History of Physical Astronomy</i>, p. 107.</p> + +<p><a name='f_506' id='f_506' href='#fna_506'>[506]</a> Grant, <i>History of Physical Astronomy</i>, p. 113.</p> + +<p><a name='f_507' id='f_507' href='#fna_507'>[507]</a> <i>Nature</i>, August 11, 1898.</p> + +<p><a name='f_508' id='f_508' href='#fna_508'>[508]</a> <i>Ibid.</i>, August 18, 1898.</p> + +<p><a name='f_509' id='f_509' href='#fna_509'>[509]</a> <i>Ibid.</i>, October 20, 1898.</p> + +<p><a name='f_510' id='f_510' href='#fna_510'>[510]</a> <i>The Observatory</i>, vol. iv. (1881), p. 234.</p> + +<p><a name='f_511' id='f_511' href='#fna_511'>[511]</a> W. T. Lynn, <i>The Observatory</i>, July, 1909, p. 291.</p> + +<p><a name='f_512' id='f_512' href='#fna_512'>[512]</a> Quoted in <i>The Observatory</i>, July, 1902, p. 281.</p> + +<p><a name='f_513' id='f_513' href='#fna_513'>[513]</a> <i>Astrophysical Journal</i>, vol. 6, 1897, p. 304.</p> + +<p><a name='f_514' id='f_514' href='#fna_514'>[514]</a> <i>Celestial Cycle</i>, p. 367.</p> + +<p><a name='f_515' id='f_515' href='#fna_515'>[515]</a> <i>The Observatory</i>, vol. 5 (1882), p. 251.</p> + +<p><a name='f_516' id='f_516' href='#fna_516'>[516]</a> Quoted by Humboldt in <i>Cosmos</i>, vol. ii. p. 696, footnote.</p> + +<p><a name='f_517' id='f_517' href='#fna_517'>[517]</a> Quoted by Denning in <i>Telescopic Work</i>, p. 347.</p> + +<p><a name='f_518' id='f_518' href='#fna_518'>[518]</a> <i>Knowledge</i>, February 20, 1885, p. 149.</p> + +<p><a name='f_519' id='f_519' href='#fna_519'>[519]</a> Humboldt’s <i>Cosmos</i>, vol. i. p. 123.</p> + +<p><a name='f_520' id='f_520' href='#fna_520'>[520]</a> <i>Outlines of Astronomy</i>, par. 319; edition of 1875.</p> + +<p><a name='f_521' id='f_521' href='#fna_521'>[521]</a> <i>Bulletin de la Soc. Ast. de France</i>, March, 1908, p. 146.</p> + +<p><a name='f_522' id='f_522' href='#fna_522'>[522]</a> An “astronomical unit” is the sun’s mean distance from the earth.</p> + +<p><a name='f_523' id='f_523' href='#fna_523'>[523]</a> This is on the American and French system of notation, but on the +English system, 10<sup>66</sup> = 10<sup>60</sup> × 10<sup>6</sup> would be a million decillion.</p> + +<p><a name='f_524' id='f_524' href='#fna_524'>[524]</a> <i>Astronomical Society of the Pacific</i>, April, 1909 (No. 125), and +<i>Popular Astronomy</i>, May, 1909.</p> + +<p><a name='f_525' id='f_525' href='#fna_525'>[525]</a> <i>Nature</i>, July 22, 1909.</p> + +<p><a name='f_526' id='f_526' href='#fna_526'>[526]</a> <i>Ibid.</i></p> + +<p><a name='f_527' id='f_527' href='#fna_527'>[527]</a> <i>The Observatory</i>, vol. 9 (December, 1886), p. 389.</p> + +<p><a name='f_528' id='f_528' href='#fna_528'>[528]</a> <i>De Nat. Deorum</i>, quoted in Smyth’s <i>Cycle</i>, p. 19.</p> + +<p><a name='f_529' id='f_529' href='#fna_529'>[529]</a> <i>The Observatory</i>, May, 1907.</p> + +<p><a name='f_530' id='f_530' href='#fna_530'>[530]</a> <i>More Worlds than Ours</i>, p. 17.</p> + +<p><a name='f_531' id='f_531' href='#fna_531'>[531]</a> <i>Man’s Place in Nature.</i></p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><strong>Transcriber’s Notes:</strong></p> + +<p>Foonote <a href='#f_48'>48</a> appears on <a href="#Page_28">page 28</a> of the text, but there is no corresponding marker on the page.</p> + +<p>Foonote <a href='#f_448'>448</a> appears on <a href="#Page_295">page 295</a> of the text, but there is no corresponding marker on the page.</p> + + + + + + + + + +<pre> + + + + + +End of Project Gutenberg's Astronomical Curiosities, by J. 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