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margin-top: .2em; margin-bottom: 0em; margin-left: 44%; margin-right: 44%;} +hr.r65 {width: 20%; margin-top: 1em; margin-bottom: 1em; margin-left: 40%; margin-right: 40%;} + +hr.r5t {width: 12%; margin-top: 2em; margin-bottom: 0em; margin-left: 44%; margin-right: 44%;} + +div.chapter {page-break-before: always;} +h2.nobreak {page-break-before: avoid;} + +ul.index { list-style-type: none; } +li.ifrst { + margin-top: 1em; + text-indent: -2em; + padding-left: 1em; +} +li.indx { + margin-top: .5em; + text-indent: -2em; + padding-left: 1em; +} +li.isub1 { + text-indent: -2em; + padding-left: 2em; +} + +table { + margin-left: auto; + margin-right: auto; +border-collapse: collapse; +} + +.tdl {text-align: left;} +.tdr {text-align: right;} +.tdc {text-align: center;} + +.pagenum { /* uncomment the next line for invisible page numbers */ + /* visibility: hidden; */ + position: absolute; + left: 92%; + font-size: small; + text-align: right; + font-style: normal; + font-weight: normal; + font-variant: normal; 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text-transform: lowercase;} + + +/* Images */ + +img { + max-width: 100%; + height: auto; +} +img.w100 {width: 100%;} + + +.figcenter { + margin: auto; + text-align: center; + page-break-inside: avoid; + max-width: 100%; +} + +.figleft { + float: left; + clear: left; + margin-left: 0; + margin-bottom: 1em; + margin-top: 1em; + margin-right: 1em; + padding: 0; + text-align: center; + page-break-inside: avoid; + max-width: 100%; +} +/* comment out next line and uncomment the following one for floating figleft on ebookmaker output */ +.x-ebookmaker .figleft {float: none; text-align: center; margin-right: 0;} +/* .x-ebookmaker .figleft {float: left;} */ + +.figright { + float: right; + clear: right; + margin-left: 1em; + margin-bottom: 1em; + margin-top: 1em; + margin-right: 0; + padding: 0; + text-align: center; + page-break-inside: avoid; + max-width: 100%; +} +/* comment out next line and uncomment the following one for floating figright on ebookmaker output */ +.x-ebookmaker .figright {float: none; text-align: center; margin-left: 0;} +/* .x-ebookmaker .figright {float: right;} */ + +/* Footnotes */ + +.footnote {margin-left: 10%; margin-right: 10%; font-size: 0.9em;} + +.footnote .label {position: absolute; right: 84%; text-align: right;} + +.fnanchor { + vertical-align: super; + font-size: .8em; + text-decoration: + none; +} + +/* Poetry */ +.poetry-container {display: flex; justify-content: center;} +.poetry-container {text-align: center;} +.poetry {text-align: left; margin-left: 5%; margin-right: 5%; font-size:90%;} +.poetry .stanza {margin: 1em auto;} +.poetry .verse {text-indent: -3em; padding-left: 3em;} + +/* Transcriber's notes */ +.transnote {background-color: #E6E6FA; + color: black; + font-size:small; + padding:0.5em; + margin-bottom:5em; + margin-top:3em; + font-family:sans-serif, serif; + border: .3em double gray; + padding: 1em; +} +.poetry .indent0 {text-indent: -3em;} + + </style> +</head> +<body> +<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 77004 ***</div> + +<div class="figcenter"> +<img src="images/cover.jpg" alt="cover"> +</div> + +<div class="figcenter1" id="f1"> +<img src="images/fig1.jpg" alt="hipparchus"> +<p class="caption"><span class="smcap">Hipparchus in the Observatory of Alexandria.</span></p> +</div> + +<h1> +<span class="up">THE STORY</span><br> + +<br> + +<span class="mid">OF THE</span><br> + +<br> + +<span class="xxlarge">SUN, MOON, AND STARS</span></h1> + +<p class="c">BY</p> + +<p class="c p2 xlarge">AGNES GIBERNE</p> + +<p class="c"><span class="smcap">Author of “The Starry Skies,” “The World’s Foundations,”<br> +“Radiant Suns,” Etc.</span></p> + +<div class="figcenter1"> +<img src="images/fig2.jpg" alt="decoration"> +</div> + + +<p class="c p2 x2large sp">WITH COPIOUS ADDITIONS</p> + +<hr class="r5t"> + +<hr class="r5"> + + +<p class="c oldeng large">Fully Illustrated</p> + +<hr class="r5"> + +<hr class="r5"> + +<p class="c p4">CINCINNATI</p> + +<p class="c sp large">NATIONAL BOOK COMPANY +</p> +<hr class="full x-ebookmaker-drop"> + + +<div class="chapter"> +<p class="c more"> +COPYRIGHT, 1898,</p> + +<p class="c more"> +<span class="smcap">By</span> J. T. JONES. +</p> +</div> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_5">[Pg 5]</span></p> + +<p class="ph2">INTRODUCTION.</p> +</div> + +<div class="figcenter"> +<img src="images/fig3.jpg" alt="decoration"> +</div> + +<p class="c large"><span class="smcap">By Charles Pritchard</span>, M. A., F. R. S.,</p> + +<p class="c"><span class="smcap">Professor of Astronomy in the University of Oxford</span>.</p> + +<hr class="r65"> + +<p><span class="smcap large">The</span> pages of this volume on a great subject were +submitted to my criticism while passing through the +press, with a request from a friend that I would make +any suggestions which might occur to me for its improvement. +Naturally, such a request was entertained, +in the first instance, with hesitation and misgiving. +But after a rapid perusal of the first sheet, I found my +interest awakened, and then gradually secured; for the +book seemed to me to possess certain features of no +ordinary character, and, in my judgment, held out the +promise of supplying an undoubted want, thus enabling +me to answer a question which I have been +often asked, and which had as often puzzled me, to +the effect, “Can you tell me of any book on astronomy +suited to beginners?” I think just such a book +is here presented to the reader; for the tale of the +stellar universe is therein told with great simplicity, +and perhaps with sufficient completeness, in an earnest +and pleasant style, equally free, I think, from inaccuracy<span class="pagenum" id="Page_6">[Pg 6]</span> +or unpardonable exaggeration. We have +here the outlines of elementary astronomy, not merely +detailed without mathematics, but to a very great extent +expressed in untechnical language. Success in +such an attempt I regard as a considerable feat, and +one of much practical utility.</p> + +<p>For the science of astronomy is essentially a science +of great magnitude and great difficulty. From the +time of Hipparchus, some century and a half before +the Christian era, down to the present day, the cultivation +of astronomy has severely taxed the minds of a +succession of men endowed with the rarest genius. +The facts and the truths of the science thus secured +have been of very slow accretion; but like all other +truths, when once secured and thoroughly understood, +they are found to admit of very simple verbal expression, +and to lie well within the general comprehension, +and, I may safely add, within the sympathies of all +educated men and women.</p> + +<p>Thus the great astronomers, the original discoverers +of the last twenty centuries, have labored, each in +his separate field of the vast universe of nature, and +other men, endowed with other gifts, have entered on +their labors, and by systematizing, correlating, and +simplifying the expression of their results, have +brought the whole within the grasp of cultivated +men engaged in other branches of the varied pursuits +of our complicated life. It is in this sort of order<span class="pagenum" id="Page_7">[Pg 7]</span> +that the amelioration and civilization of mankind +have proceeded, and at the present moment are, I +hope and believe, rapidly proceeding.</p> + +<p>It was, I suspect, under this point of view, though +half unconsciously so, that my attention was arrested +by the book now presented to the reader; for we +have here many of the chief results of the laborious +researches of such men as Ptolemy, Kepler, Newton, +Herschel, Fraunhofer, Janssen, Lockyer, Schiaparelli, +and others—no matter where accumulated or by +whom recorded—filtered through the mind of a +thoughtful and cultured lady, and here presented to +other minds in the very forms wherein they have been +assimilated and pictured in her own. And these forms +and pictures are true. It is in this way that the intellectual +“protoplasm” of the human mind is fostered +and practically disseminated.</p> + +<p>And, then, there is still another point of view from +which this general dissemination of great truths in a +simple style assumes an aspect of practical importance. +I allude to the influences of this process on +the imaginative or poetic side of our complex nature.</p> + +<p>Wordsworth, in one of his prefaces, has stated so +clearly the truth on this subject that I can not do better +than give his words. “If the time should ever +come,” he says, “when what is now science becomes +familiarized to men, then the remotest discoveries of +the chemist, the botanist, the mineralogist, will be as<span class="pagenum" id="Page_8">[Pg 8]</span> +proper objects of the poet’s art as any upon which it +can be employed. He will be ready to follow the +steps of the man of science; he will be at his side, +carrying sensation into the midst of the objects of +science itself. The poet will lend his divine spirit to +aid the transfiguration, and will welcome the being +thus produced as a dear and genuine inmate of the +household of man.”</p> + +<p>It is for reasons such as here stated that I heartily +commend this book to the attention of those who +take an interest in the advancement of the intellectual +progress and culture of society. The story of +the Kosmos is told by the authoress in her own language +and after her own method. I believe, as I have +said, the story is correct.</p> + +<p class="pad"><span class="smcap">Oxford University.</span></p> + + +<hr class="full x-ebookmaker-drop"> + +<p><span class="pagenum" id="Page_9">[Pg 9]</span></p> + +<div class="chapter"> +<p class="ph22">CONTENTS.</p> +</div> + +<div class="figcenter"> +<img src="images/fig3.jpg" alt="decoration"> +</div> + +<table> + +<tr> + <td class="tdr"><span class="smcap more">Chapter.</span></td> + <td class="tdl"></td> + <td class="tdr"><span class="smcap more">Page.</span></td></tr> + +<tr> + <td class="tdr"><a href="#c1">I.</a></td> + <td class="tdl"><span class="smcap">The Earth One of a Family</span>,</td> + <td class="tdr">13</td></tr> + +<tr> + <td class="tdr"><a href="#c2">II.</a></td> + <td class="tdl"><span class="smcap">The Head of Our Family</span>,</td> + <td class="tdr">24</td></tr> + +<tr> + <td class="tdr"><a href="#c3">III.</a></td> + <td class="tdl"><span class="smcap">What Binds the Family Together</span>,</td> + <td class="tdr">34</td></tr> + +<tr> + <td class="tdr"><a href="#c4">IV.</a></td> + <td class="tdl"><span class="smcap">The Leading Members of Our Family.—First +Group</span>,</td> + <td class="tdr">46</td></tr> + +<tr> + <td class="tdr"><a href="#c5">V.</a></td> + <td class="tdl"><span class="smcap">The Leading Members of Our Family.—Second +Group</span>,</td> + <td class="tdr">55</td></tr> + +<tr> + <td class="tdr"><a href="#c6">VI.</a></td> + <td class="tdl"><span class="smcap">The Moon</span>,</td> + <td class="tdr">62</td></tr> + +<tr> + <td class="tdr"><a href="#c7">VII.</a></td> + <td class="tdl"><span class="smcap">Visitors</span>,</td> + <td class="tdr">73</td></tr> + +<tr> + <td class="tdr"><a href="#c8">VIII.</a></td> + <td class="tdl"><span class="smcap">Little Servants</span>,</td> + <td class="tdr">83</td></tr> + +<tr> + <td class="tdr"><a href="#c9">IX.</a></td> + <td class="tdl"><span class="smcap">Neighboring Families</span>,</td> + <td class="tdr">95</td></tr> + +<tr> + <td class="tdr"><a href="#c10">X.</a></td> + <td class="tdl"><span class="smcap">Our Neighbors’ Movements</span>,</td> + <td class="tdr">106</td></tr> + +<tr> + <td class="tdr"><a href="#c11">XI.</a></td> + <td class="tdl"><span class="smcap">More About the Solar System</span>,</td> + <td class="tdr">122</td></tr> + +<tr> + <td class="tdr"><a href="#c12">XII.</a></td> + <td class="tdl"><span class="smcap">More About the Sun</span>,</td> + <td class="tdr">133</td></tr> + +<tr> + <td class="tdr"><a href="#c13">XIII.</a></td> + <td class="tdl"><span class="smcap">Yet More About the Sun</span>,</td> + <td class="tdr">148</td></tr> + +<tr> + <td class="tdr"><a href="#c14">XIV.</a></td> + <td class="tdl"><span class="smcap">More About the Moon</span>,</td> + <td class="tdr">157</td></tr> + +<tr> + <td class="tdr"><a href="#c15">XV.</a></td> + <td class="tdl"><span class="smcap">Yet More About the Moon</span>,</td> + <td class="tdr">164</td></tr> + +<tr> + <td class="tdr"><a href="#c16">XVI.</a></td> + <td class="tdl"><span class="smcap">Mercury, Venus, and Mars</span>,</td> + <td class="tdr">180</td></tr> + +<tr> + <td class="tdr"><a href="#c17">XVII.</a></td> + <td class="tdl"><span class="smcap">Jupiter</span>,</td> + <td class="tdr">199</td></tr> + +<tr> + <td class="tdr"><a href="#c18">XVIII.</a></td> + <td class="tdl"><span class="smcap">Saturn</span>,</td> + <td class="tdr">214</td></tr> + +<tr> + <td class="tdr"><a href="#c19">XIX.</a></td> + <td class="tdl"><span class="smcap">Uranus and Neptune</span>,</td> + <td class="tdr">225</td></tr> + +<tr> + <td class="tdr"><a href="#c20">XX.</a></td> + <td class="tdl"><span class="smcap">Comets and Meteorites</span>,</td> + <td class="tdr">240</td></tr> + +<tr> + <td class="tdr"><a href="#c21">XXI.</a></td> + <td class="tdl"><span class="smcap">More About Comets and Meteorites</span>,</td> + <td class="tdr">246</td></tr> + +<tr> + <td class="tdr"><a href="#c22">XXII.</a></td> + <td class="tdl"><span class="smcap">Many Suns</span>,</td> + <td class="tdr">267</td></tr> + +<tr> + <td class="tdr"><a href="#c23">XXIII.</a></td> + <td class="tdl"><span class="smcap">Some Particular Suns</span>,<span class="pagenum" id="Page_10">[Pg 10]</span></td> + <td class="tdr">278</td></tr> + +<tr> + <td class="tdr"><a href="#c24">XXIV.</a></td> + <td class="tdl"><span class="smcap">Different Kinds of Suns</span>,</td> + <td class="tdr">291</td></tr> + +<tr> + <td class="tdr"><a href="#c25">XXV.</a></td> + <td class="tdl"><span class="smcap">Groups and Clusters of Suns</span>,</td> + <td class="tdr">304</td></tr> + +<tr> + <td class="tdr"><a href="#c26">XXVI.</a></td> + <td class="tdl"><span class="smcap">The Problem of Sun and Star Distances</span>,</td> + <td class="tdr">310</td></tr> + +<tr> + <td class="tdr"><a href="#c27">XXVII.</a></td> + <td class="tdl"><span class="smcap">Measurement of Star Distances</span>,</td> + <td class="tdr">320</td></tr> + +<tr> + <td class="tdr"><a href="#c28">XXVIII.</a></td> + <td class="tdl"><span class="smcap">The Milky Way</span>,</td> + <td class="tdr">329</td></tr> + +<tr> + <td class="tdr"><a href="#c29">XXIX.</a></td> + <td class="tdl"><span class="smcap">A Whirling Universe</span>,</td> + <td class="tdr">337</td></tr> + +<tr> + <td class="tdr"><a href="#c30">XXX.</a></td> + <td class="tdl"><span class="smcap">Reading the Light</span>,</td> + <td class="tdr">344</td></tr> + +<tr> + <td class="tdr"><a href="#c31">XXXI.</a></td> + <td class="tdl"><span class="smcap">Stellar Photography</span>,</td> + <td class="tdr">355</td></tr> + +<tr> + <td class="tdr"><a href="#c32">XXXII.</a></td> + <td class="tdl"><span class="smcap">The Dawn of Astronomy</span>,</td> + <td class="tdr">363</td></tr> + +<tr> + <td class="tdr"><a href="#c33">XXXIII.</a></td> + <td class="tdl"><span class="smcap">Modern Astronomy</span>,</td> + <td class="tdr">375</td></tr> + +<tr> + <td class="tdr"><a href="#c34">XXXIV.</a></td> + <td class="tdl"><span class="smcap">Sir Isaac Newton</span>,</td> + <td class="tdr">382</td></tr> + +<tr> + <td class="tdr"><a href="#c35">XXXV.</a></td> + <td class="tdl"><span class="smcap">Later Astronomy</span>,</td> + <td class="tdr">393</td></tr> + +</table> + +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_11">[Pg 11]</span></p> + +<p class="ph22">LIST OF ILLUSTRATIONS.</p> +</div> + +<div class="figcenter"> +<img src="images/fig3.jpg" alt="decoration"> +</div> + +<table> + +<tr> + <td class="tdl"></td> + <td class="tdr"><span class="smcap more">Page.</span></td></tr> + +<tr> + <td class="tdl">Hipparchus in the Observatory at Alexandria</td> + <td class="tdr"><a href="#f1"><i>Frontispiece.</i></a></td></tr> + +<tr> + <td class="tdl">The Solar System</td> + <td class="tdr"><a href="#f4">15</a></td></tr> + +<tr> + <td class="tdl">The Pleiades</td> + <td class="tdr"><a href="#f5">19</a></td></tr> + +<tr> + <td class="tdl">Sun-spots</td> + <td class="tdr"><a href="#f6">29</a></td></tr> + +<tr> + <td class="tdl">Phases of Mercury before Inferior Conjunction—Evening Star</td> + <td class="tdr"><a href="#f7">50</a></td></tr> + +<tr> + <td class="tdl">Appearance of the Full Moon</td> + <td class="tdr"><a href="#f8">63</a></td></tr> + +<tr> + <td class="tdl">One Form of Lunar Crater</td> + <td class="tdr"><a href="#f9">69</a></td></tr> + +<tr> + <td class="tdl">The Earth as Seen from the Moon</td> + <td class="tdr"><a href="#f10">71</a></td></tr> + +<tr> + <td class="tdl">Passage of the Earth and the Moon through the Tail of a Comet</td> + <td class="tdr"><a href="#f11">76</a></td></tr> + +<tr> + <td class="tdl">Passage of the Comet of 1843 Close to the Sun</td> + <td class="tdr"><a href="#f12">79</a></td></tr> + +<tr> + <td class="tdl">Meteor Emerging from Behind a Cloud</td> + <td class="tdr"><a href="#f13">84</a></td></tr> + +<tr> + <td class="tdl">The Great Shower of Shooting-stars, November 27, 1872</td> + <td class="tdr"><a href="#f14">90</a></td></tr> + +<tr> + <td class="tdl">Constellation of the Great Bear</td> + <td class="tdr"><a href="#f15">108</a></td></tr> + +<tr> + <td class="tdl">The Great Bear 50,000 Years Ago</td> + <td class="tdr"><a href="#f16">109</a></td></tr> + +<tr> + <td class="tdl">The Great Bear 50,000 Years Hence</td> + <td class="tdr"><a href="#f17">109</a></td></tr> + +<tr> + <td class="tdl">Constellation of Orion as it Appears Now</td> + <td class="tdr"><a href="#f18">110</a></td></tr> + +<tr> + <td class="tdl">Constellation of Orion 50,000 Years Hence</td> + <td class="tdr"><a href="#f19">111</a></td></tr> + +<tr> + <td class="tdl">Position of Planets Inferior to Jupiter—Showing the Zone of the +Asteroids</td> + <td class="tdr"><a href="#f20">123</a></td></tr> + +<tr> + <td class="tdl">Comparative Size of the Planetary Worlds</td> + <td class="tdr"><a href="#f21">130</a></td></tr> + +<tr> + <td class="tdl">A Typical Sun-spot</td> + <td class="tdr"><a href="#f22">135</a></td></tr> + +<tr> + <td class="tdl">A Solar Eruption</td> + <td class="tdr"><a href="#f23">138</a></td></tr> + +<tr> + <td class="tdl">Sun-flames, May 3, 1892</td> + <td class="tdr"><a href="#f24">143</a></td></tr> + +<tr> + <td class="tdl">Solar Corona and Prominence</td> + <td class="tdr"><a href="#f25">152</a></td></tr> + +<tr> + <td class="tdl">Comparative Size of the Earth and Sun</td> + <td class="tdr"><a href="#f26">155</a></td></tr> + +<tr> + <td class="tdl">The Moon—an Expired Planet</td> + <td class="tdr"><a href="#f27">159</a></td></tr> + +<tr> + <td class="tdl">The Lunar Crater Copernicus</td> + <td class="tdr"><a href="#f28">170</a></td></tr> + +<tr> + <td class="tdl">Lunar Eruption—Brisk Action</td> + <td class="tdr"><a href="#f29">172</a></td></tr> + +<tr> + <td class="tdl">Lunar Eruption—Feeble Action</td> + <td class="tdr"><a href="#f30">173</a></td></tr> + +<tr> + <td class="tdl">Nicolaus Copernicus</td> + <td class="tdr"><a href="#f31">176</a></td></tr> + +<tr> + <td class="tdl">Phases of Venus</td> + <td class="tdr"><a href="#f32">186</a><span class="pagenum" id="Page_12">[Pg 12]</span></td></tr> + +<tr> + <td class="tdl">Mars and the Path of its Satellites</td> + <td class="tdr"><a href="#f33">191</a></td></tr> + +<tr> + <td class="tdl">General Aspect of Jupiter—Satellite and its Shadow</td> + <td class="tdr"><a href="#f34">200</a></td></tr> + +<tr> + <td class="tdl">Satellites of Jupiter Compared with the Earth and Moon</td> + <td class="tdr"><a href="#f35">206</a></td></tr> + +<tr> + <td class="tdl">The System of Jupiter</td> + <td class="tdr"><a href="#f36">208</a></td></tr> + +<tr> + <td class="tdl">Orbits of Nine Comets Captured by Jupiter</td> + <td class="tdr"><a href="#f37">213</a></td></tr> + +<tr> + <td class="tdl">Saturn and the Earth—Comparative Size</td> + <td class="tdr"><a href="#f38">215</a></td></tr> + +<tr> + <td class="tdl">Ideal View of Saturn’s Rings and Satellites from the Planet</td> + <td class="tdr"><a href="#f39">222</a></td></tr> + +<tr> + <td class="tdl">Great Astronomers of Earlier Times</td> + <td class="tdr"><a href="#f40">227</a></td></tr> + +<tr> + <td class="tdl">The Great Comet of 1811</td> + <td class="tdr"><a href="#f41">247</a></td></tr> + +<tr> + <td class="tdl">Donati’s Comet, 1858</td> + <td class="tdr"><a href="#f42">249</a></td></tr> + +<tr> + <td class="tdl">Great Comet of 1744</td> + <td class="tdr"><a href="#f43">254</a></td></tr> + +<tr> + <td class="tdl">The First Comet of 1888—June 4</td> + <td class="tdr"><a href="#f44">255</a></td></tr> + +<tr> + <td class="tdl">Great Comet of 1680</td> + <td class="tdr"><a href="#f45">260</a></td></tr> + +<tr> + <td class="tdl">Great Comet of 1769</td> + <td class="tdr"><a href="#f46">261</a></td></tr> + +<tr> + <td class="tdl">Baron Alexander Von Humboldt</td> + <td class="tdr"><a href="#f47">264</a></td></tr> + +<tr> + <td class="tdl">A Telescopic Field in the Milky Way</td> + <td class="tdr"><a href="#f48">270</a></td></tr> + +<tr> + <td class="tdl">Cygnus, Constellation of</td> + <td class="tdr"><a href="#f49">279</a></td></tr> + +<tr> + <td class="tdl">Stars whose Distances are Best Known</td> + <td class="tdr"><a href="#f50">281</a></td></tr> + +<tr> + <td class="tdl">Lyra, Constellation of</td> + <td class="tdr"><a href="#f51">297</a></td></tr> + +<tr> + <td class="tdl">Constellations in the Northern Hemisphere</td> + <td class="tdr"><a href="#f52">300</a></td></tr> + +<tr> + <td class="tdl">A Cluster of Stars in Centaurus</td> + <td class="tdr"><a href="#f53">305</a></td></tr> + +<tr> + <td class="tdl">The Great Nebula in Andromeda, Compared with Size of the Solar +System</td> + <td class="tdr"><a href="#f54">307</a></td></tr> + +<tr> + <td class="tdl">A Cluster of Stars in Perseus</td> + <td class="tdr"><a href="#f55">332</a></td></tr> + +<tr> + <td class="tdl">Hercules, Constellation of</td> + <td class="tdr"><a href="#f56">338</a></td></tr> + +<tr> + <td class="tdl">The Great Bear, Constellation of</td> + <td class="tdr"><a href="#f57">341</a></td></tr> + +<tr> + <td class="tdl">The Prism and Spectrum</td> + <td class="tdr"><a href="#f58">344</a></td></tr> + +<tr> + <td class="tdl">The Spectroscope</td> + <td class="tdr"><a href="#f59">345</a></td></tr> + +<tr> + <td class="tdl">Spectra, Showing the Dark Lines</td> + <td class="tdr"><a href="#f60">347</a></td></tr> + +<tr> + <td class="tdl">Great Astronomers of Later Times</td> + <td class="tdr"><a href="#f61">377</a></td></tr> + +<tr> + <td class="tdl">Sir Isaac Newton</td> + <td class="tdr"><a href="#f62">386</a></td></tr> + +<tr> + <td class="tdl">Eye-piece of Lick Telescope</td> + <td class="tdr"><a href="#f63">407</a></td></tr> + +<tr> + <td class="tdl">Lick Observatory</td> + <td class="tdr"><a href="#f64">409</a></td></tr> + +<tr> + <td class="tdl">Professor E. E. Barnard</td> + <td class="tdr"><a href="#f65">410</a></td></tr> + +</table> + +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_13">[Pg 13]</span></p> + +<p class="c up sp" id="c1">THE STORY</p> +</div> + +<p class="c less sp">OF THE</p> + +<p class="c up sp">SUN, MOON, AND STARS.</p> + +<hr class="r65"> + + +<h2>CHAPTER I.</h2> + +<p class="c sp">THE EARTH ONE OF A FAMILY.</p> + + +<p><span class="smcap large">What</span> is this earth of ours?</p> + +<p>Something very great—and yet something very +little. Something very great, compared with the +things upon the earth; something very little, compared +with the things outside the earth.</p> + +<p>And as our journeyings together are for a while to +be away from earth, we shall find ourselves obliged +to count her as something quite small in the great +universe, where so many larger and mightier things +are to be found,—if indeed they are mightier. Not +that we have to say good-bye altogether to our old +home. We must linger about her for a while before +starting, and afterwards it will be often needful to +come back, with speed swifter than the flight of light, +that we may compare notes on the sizes and conditions +of other places visited by us.</p> + +<p>But first of all: what <i>is</i> this earth of ours?</p> + +<p>It was rather a pleasant notion which men held in +olden days, that we—that great and important “We”<span class="pagenum" id="Page_14">[Pg 14]</span> +which loves to perch itself upon a height—stood firm +and fixed at the very center of everything. The earth +was supposed to be a vast flat plain, reaching nobody +could tell how far. The sun rose and set for us alone; +and the thousands of stars twinkled in the sky at night +for nobody’s good except ours; and the blue sky overhead +was a crystal covering for the men of our earth, +and nothing more. In fact, people seem to have +counted themselves not merely to have had a kind of +kingship over the lower animals of our earth, but to +have been kings over the whole universe. Sun, stars, +and sky, as well as earth, were made for man, and for +man only.</p> + +<p>This was the common belief, though even in those +olden days there were <i>some</i> who knew better. But the +world in general knows better now.</p> + +<p>Earth the center of the universe! Why, she is not +that of even the particular family in the heavens to +which she belongs. For we do not stand alone. The +earth is one of a family of worlds, and that family is +called <span class="smcap">The Solar System</span>. And so far is our earth +from being the head of the family, that she is not +even one of the more important members. She is +merely one of the little sisters, as it were.</p> + +<p>Men not only believed the earth, in past days, to +be at the center of the universe; but also they believed +her to remain there without change. Sun, moon, stars, +planets, sky, might move; but never the earth. The +solid ground beneath their feet, <i>that</i> at least was firm. +Every day the sun rose and set, and every night the +stars, in like manner, rose and set. But this was +easily explained. We on our great earth stood firm<span class="pagenum" id="Page_15">[Pg 15]</span> +and still, while sun, moon, stars, went circling round +us once in every twenty-four hours, just for our sole +and particular convenience. What an important personage +man must have felt himself then in God’s great +universe! Once again, we know better now!</p> + +<div class="figcenter" id="f4"> +<img src="images/fig4.jpg" alt="solar"> +<p class="caption">THE SOLAR SYSTEM.</p> +</div> + +<p><span class="pagenum" id="Page_16">[Pg 16]</span></p> + +<p>For it is the earth that moves, and not the sun; it +is the earth that moves, and not the stars. The daily +movements of sun and stars, rising in the east, traveling +over the sky, and setting in the west, are no more +real movements on their part than, when we travel in +a rail way-train, the seeming rush of hedges, telegraph +posts, houses, and fields is real. They are fixed and +we are moving; yet the movement appears to us to be +not ours but theirs.</p> + +<p>Still more strongly would this appear to be the case +if there were no noise, no shaking, no jarring and +trembling, to make us feel that we are not at rest. +Sometimes when a train begins to move gently out of +a station, from among other trains, it is at the first +moment quite impossible to say whether the movement +belongs to the train in which we are seated or to +a neighboring train. And in the motions of our earth +there is no noise, no shaking, no jarring—all are rapid, +silent, and even.</p> + +<p>If you were rising through the air in a balloon, you +would at first only know your own movement by seeing +the earth seem to drop away from beneath you. +And just so we can only know the earth’s movements +by seeing how worlds around us <i>seem</i> to move in consequence.</p> + +<p>When I speak of the Universe, I mean the whole of +God’s mighty creation as far as the stars reach. Sometimes +the word is used in this sense, and sometimes +it is used only for a particular part of creation nearer +to us than other parts. At present, however, we will +put aside all thought of the second narrower meaning.</p> + +<p>The wisest astronomer living can not tell us how<span class="pagenum" id="Page_17">[Pg 17]</span> +far the stars reach. We know now that there is no +firm crystal covering over our heads, dotted with +bright points here and there; but only the wide open +sky or heaven, containing millions of stars, some +nearer, some farther, some bright enough to be seen +by us all, some only visible through a telescope.</p> + +<p>People talk often of the stars being “set in space;” +and the meaning of “space” is simply “room.” Where +you are must be space, or you could not be there. +But it is when we get away from earth, and travel in +thought through the wide fields of space, where God +has placed his stars, that we begin to feel how vast it +is, and what specks we are ourselves—nay, what a +speck our very earth is, in this great and boundless +creation.</p> + +<p>For there is no getting to the borders of space. +As one telescope after another is made, each one +stronger in power and able to reach farther than the +last, still more and more stars are seen, and yet more +and more behind and beyond, in countless millions.</p> + +<p>It is the same all round the earth. The old notion +about our world being a flat plain has been long since +given up. We know her now to be a round globe, +not fixed, but floating like the stars in space.</p> + +<p>When you look <i>up</i> into the sky, you are looking +exactly in the opposite direction from where +you would be looking <i>up</i> if you were in Australia. +For Australia’s “up” is our “down,” and our “down” +is Australia’s “up.” Or, to put it more truly, “up” is +always in the direction straight away from this earth, +on whatever part of it you may be standing; and +“down” is always towards the center of the earth.</p> + +<p><span class="pagenum" id="Page_18">[Pg 18]</span></p> + +<p>All round the globe, in north, south, east, west, +whether you are in Europe, Asia, Africa, or America, +though you will see different stars in certain different +quarters of the earth, still overhead you will find shining +countless points of light.</p> + +<p>And now, what are these stars? This is a matter +on which people are often confused, and on which +it is well to be quite clear before going one step +farther.</p> + +<p>Some of the stars you have most likely often noticed. +The seven chief stars of the Great Bear are +known to a large number of people; and there are few +who have not admired the splendid constellation of +Orion. Perhaps you also know the W-shape of Cassiopeia, +and the brilliant shining of Sirius, and the +soft glimmer of the Pleiades.</p> + +<p>The different constellations or groups of principal +stars have been watched by men for long ages past. +They are called the fixed stars, for they do not change. +How many thousands of years ago they were first arranged +by men into these groups, and who first gave +them their names, we can not tell.</p> + +<p>True, night by night, through century after century, +they rise, and cross the sky, and set. But those +are only seeming movements. Precisely as the turning +round of the earth upon her axis, once in every +twenty-four hours, makes the sun appear to rise and +cross the sky and set, in the day-time; so also the +same turning of the earth makes the stars appear to +do the same in the night-time.</p> + +<p>There is another seeming movement among the +stars, which is only in seeming. Some come into<span class="pagenum" id="Page_19">[Pg 19]</span> +view in summer which can not be seen in winter; and +some come into view in winter which can not be seen +in summer. For the sun, moving on his pathway +through the sky, hides those stars which shine with +him in the day-time. The zodiac is an imaginary +belt in the heavens, sixteen or eighteen degrees wide, +containing the twelve constellations through which +the sun passes. And as he passes from point to point +of his pathway, he constantly conceals from us fresh +groups of stars by day, and allows fresh groups to appear +by night. +Speaking generally, +however, +the stars remain +the same year +after year, century +after century. +The groups +may still be seen +as of old, fixed +and unchanging.</p> + +<div class="figright" id="f5"> +<img src="images/fig5.jpg" alt="pleiades"> +<p class="caption">THE PLEIADES.</p> +</div> + +<p>What are these stars? Stars and planets have +both been spoken about. There is a great difference +between the two.</p> + +<p>Perhaps if you were asked whether the sun is most +like to a star or a planet, you would be rather at a loss; +and many who have admired the brilliant evening +star, Venus, often to be seen after sunset, would be +surprised to learn that the evening star is in reality no +star at all.</p> + +<p>A star is a sun. Our sun is nothing more nor less +than a star. Each one of the so-called “fixed stars,”<span class="pagenum" id="Page_20">[Pg 20]</span> +that you see shining at night in the sky, is a sun like +our sun; only some of the stars are larger suns and +some are smaller suns than ours.</p> + +<p>The main reason why our sun looks so much larger +and brighter than the stars is, that he is so very much +nearer to us. The stars are one and all at enormous +distances from the earth. By and by we will go more +closely into the matter of their distance, compared +with the distance of the sun.</p> + +<p>At present it is enough to say that if many of the +stars were placed just as near to us as our sun is +placed, they would look just as large and bright; +while there are some that would look a great deal +larger and brighter. And if our sun were to travel +away from us, to the distance of the very nearest +of the little twinkling stars, he would dwindle down +and down in size and brilliancy, till at last we should +not be able to tell him apart from the rest of the +stars.</p> + +<p>I have told you that the stars are called “fixed” +because they keep their places, and do not change from +age to age. Though the movement of the earth makes +them seem all to sweep past every night in company, +yet they do not travel in and out among one another, +or backwards and forwards, or from side to side. At +all events, if there be such changes, they are so slow +and so small as to be exceedingly difficult to find out. +Each group of stars keeps its own old shape, as for +hundreds of years back.</p> + +<p>But among these fixed stars there are certain stars +which do go to and fro, and backwards and forwards. +Now they are to be seen in the middle of one constellation,<span class="pagenum" id="Page_21">[Pg 21]</span> +and now in the middle of another. These restless +stars were long a great perplexity. Men named +them Planets or Wanderers.</p> + +<p>We know now that the planets are in reality not +stars at all, and also that they are not nearly so far +away from us as the fixed stars. In fact, they are +simply members of our own family—the Solar System. +They are worlds, more or less like the world we live +in; and they travel round and round the sun as we +do, each more or less near to him; and they depend +upon him for heat and light, in more or less the same +manner as ourselves.</p> + +<p>Therefore, just as our sun is a star, and stars are +suns, so our earth or world is a planet, and planets +are worlds. <span class="smcap">Earth</span> is the name we give to that particular +world or planet on which we live. Planets +may generally be known from stars by the fact that +they do not twinkle. But the great difference between +the two lies in the fact that a star shines by +its own radiant, burning light, whereas a planet shines +merely by light reflected or borrowed from the sun.</p> + +<p>But how were the earth and the other worlds made? +Let us imagine an immense gaseous mass placed in +space. Attraction is a force inherent in every atom of +matter. The denser portion of this mass will insensibly +attract towards it the other parts, and in the slow +fall of the more distant molecules towards this more +attractive region, a general motion is produced, incompletely +directed towards this center, and soon involving +the whole mass in the same motion of rotation. +The simplest form of all, even in virtue of this +law of attraction, is the spherical form. It is that<span class="pagenum" id="Page_22">[Pg 22]</span> +which a drop of water takes, and a drop of mercury +if left to itself.</p> + +<p>The laws of mechanics show that, as this gaseous +mass condenses and shrinks, the motion of rotation of +the nebula is accelerated. In turning, it becomes +flattened at the poles, and gradually takes the form of +an immense lens-shaped mass of gas. It has begun +to turn so quickly as to develop at its exterior circumference +a centrifugal force superior to the general +attraction of the mass, as when we whirl a sling. The +inevitable consequence of this excess is a rupture of +the equilibrium, which detaches an external ring. +This gaseous ring will continue to rotate in the same +time and with the same velocity; but the nebulous +mother will be henceforth detached, and will continue +to undergo progressive condensation and acceleration +of motion. The same feat will be reproduced as often +as the velocity of rotation surpasses that by which the +centrifugal force remains inferior to the attraction. It +may have happened also that secondary centers of +condensation would be formed even in the interior of +the nebula.</p> + +<p>In our system the rings of Saturn still subsist.</p> + +<p>The successive formation of the planets, their situation +near the plane of the solar equator, and their +motions of translation round the same center, are explained +by the theory which we are discussing. The +most distant known planet, Neptune, would be detached +from the nebula at the epoch when this nebula +extended as far as the planet, out to nearly three thousand +millions of miles, and would turn in a slow revolution +requiring a period of 165 years for its accomplishment.<span class="pagenum" id="Page_23">[Pg 23]</span> +The original ring could not remain in the +state of a ring unless it was perfectly homogeneous +and regular; but such a condition is, so to say, unrealizable, +and it did not delay in condensing itself into +a sphere. Successively, Uranus, Saturn, Jupiter, the +army of small planets, Mars, would thus be detached +or formed in the interior of this same nebula. Afterwards +came the earth, of which the birth goes back +to the epoch when the sun had arrived at the earth’s +present position. Venus and Mercury would be born +later. Will the sun give birth to a new world? This +is not probable.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_24">[Pg 24]</span></p> + +<h2 class="nobreak" id="c2">CHAPTER II</h2> +</div> + +<p class="c sp">THE HEAD OF OUR FAMILY.</p> + + +<p><span class="smcap large">People</span> began very early in the history of the +world to pay close attention to the sun. And no +wonder. We owe so much to his heat and light that +the marvel would be if men had not thought much +about him.</p> + +<p>Was the sun really any larger than he looked, and +if so, how much larger was he? And what was his +distance from the earth? These were two of the questions +which puzzled our ancestors the longest. If +once they could have settled exactly how far off the +sun really was, they could easily have calculated his +exact size; but this was just what they could not do.</p> + +<p>So one man supposed that the sun must be quite +near, and very little larger than he looked. Another +thought he might be seventy-five miles in diameter. +A third ventured to believe that he was larger than +the country of Greece. A fourth was so bold as to +imagine that he might even outweigh the earth +herself.</p> + +<p>After a while many attempts were made to measure +the distance of the sun; and a great many different +answers to this difficult question were given by different +men, most of them very wide of the mark. It is +only of late years that the matter has been clearly +settled. And, indeed, it was found quite lately that a +mistake of no less than three millions of miles had<span class="pagenum" id="Page_25">[Pg 25]</span> +been made, notwithstanding all the care and all the +attention given. But though three millions of miles +sounds a great deal, yet it is really very little—only a +tiny portion of the whole.</p> + +<p>For the distance of the sun from the earth is no +less than about <span class="allsmcap">NINETY-THREE MILLIONS OF MILES</span>. +Ninety-three millions of miles! Can you picture that +to yourself? Try to think what is meant by a thousand +miles. Our earth is eight thousand miles in +diameter. In other words, if you were to thrust a +gigantic knitting-needle through her body, from the +North Pole to the South Pole, it would have to be +about eight thousand miles long.</p> + +<p>To reach the thought of one million, you must picture +<i>one thousand times one thousand</i>. Our earth is +about twenty-five thousand miles round. If you were +to start from the mouth of the River Amazon, in South +America, and journey straight round the whole earth on +the equator, till you came back to the same point, you +would have traveled about twenty-five thousand miles. +But that would be a long way off from a million miles. +You would have gone only once round the earth. +Now a cord one million miles in length could be +wrapped, not once only, but <i>forty times</i>, round and +round the earth. And when you have managed to +reach up to the thought of one million miles, you have +then to remember that the sun’s distance is ninety-three +times as much again. So, to picture clearly to +ourselves the actual meaning of “ninety-three millions +of miles” is not so easy.</p> + +<p>Suppose it were possible to lay a railroad from here +to the sun. If you could journey thither in a perfectly<span class="pagenum" id="Page_26">[Pg 26]</span> +straight line, at the rate of thirty miles an hour, +never pausing for one single minute, night or day, you +would reach the sun in about three hundred and forty-six +years.</p> + +<p>Thirty miles an hour is a slow train. Suppose we +double the speed, and make it an express train, rushing +along at the pace of sixty miles an hour. Then +you might hope to reach the end of your journey in +one hundred and seventy-three years. If you had +quitted this earth early in the eighteenth century, +never stopping on your way, you would be, just about +now, near the end of the nineteenth, arriving at the sun.</p> + +<p>So much for the sun’s distance from us. Now as +to his size.</p> + +<p>I have already mentioned that our earth’s diameter—that +is, her <i>through measure</i>, as, for instance, the +line drawn straight from England through her center +to New Zealand—is about eight thousand miles. This +sounds a good deal. But what do you think of the +diameter of the sun being no less than <i>eight hundred +and fifty-eight thousand miles</i>? The one is eight thousand +miles, the other over eight hundred thousand!</p> + +<p>Suppose you had a long slender pole which would +pass through the middle of the earth, one end just +showing at the North Pole and the other at the South +Pole. You would need more than a hundred and +eight of such poles, all joined together, to show the +diameter of the sun.</p> + +<p>The sun seems not to be made of nearly such heavy +materials as the earth. He is what astronomers call +less “dense,” less close and compact in his make, just +as wood is less dense and heavy than iron. Still, his<span class="pagenum" id="Page_27">[Pg 27]</span> +size is so enormous, that if you could have a pair of +gigantic scales, and put the sun into one scale and +the earth with every one of her brother and sister +planets into the other, the sun’s side would go down +like lightning. He would be found to weigh seven +hundred and fifty times as much as all the rest put +together. And, it would take more than twelve hundred +thousand little earths like ours, rolled into one +huge ball, to make a globe as large as the sun.</p> + +<p>In the beginning of the seventeenth century a man +named Fabricius was startled by the sight of a certain +black spot upon the face of the sun. He watched till +too dazzled to look any longer, supposing it to be a +small cloud, yet anxious to learn more. Next day +the spot was there still, but it seemed to have moved +on a little way. Morning after morning this movement +was found to continue, and soon a second spot, and +then a third spot, were observed creeping in like manner +across the sun. After a while they vanished, one +at a time, round his edge, as it were; but after some +days of patient waiting on the part of the lookers-on, +they appeared again at the opposite edge, and once +more began their journey across.</p> + +<p>Fabricius seems to have been the first, but he was +not the last, to watch sun-spots. Many astronomers +have given close attention to them. Modern telescopes, +and the modern plan of looking at the sun +through darkened glass, have made this possible in a +way that was not possible two or three hundred years +ago.</p> + +<p>The first important discovery made through the +spots on the sun, was that the sun turns round upon<span class="pagenum" id="Page_28">[Pg 28]</span> +his axis, just in the same manner that the earth turns +round upon hers. Instead of doing so once in the +course of each twenty-four hours, like the earth, he +turns once in the course of about twenty-five days.</p> + +<p>It must not be supposed that the spots seen now +upon the sun are the same spots that Fabricius saw +so long ago. There is perpetual change going on; +new spots forming, old spots vanishing; one spot breaking +into two, two spots joining into one, and so on. +Even in a single hour great alterations are sometimes +seen to take place.</p> + +<p>Still, many of the spots do remain long enough and +keep their shapes closely enough to be watched from +day to day, and to be known again as old friends when +they reappear, after being about twelve days hidden +on the other side of the sun. So that the turning of +the sun upon his axis has become, after long and careful +examination, a certain known fact.</p> + +<p>For more than thirty years one astronomer kept +close watch over the spots on every day that it was +possible to see the sun. Much has been learned from +his resolute perseverance.</p> + +<p>Now what are these spots?</p> + +<p>One thing seems pretty sure, and that is that they +are caused by some kind of tremendous storms or +cyclones taking place on the surface of that huge ball +of fire.</p> + +<div class="figcenter" id="f6"> +<img src="images/fig6.jpg" alt="sun spots"> +<p class="caption">SUN SPOTS.</p> +</div> + +<p>The first attentive observer of the sun, Scheiner, +at first regarded the spots as satellites—an indefensible +opinion, which, however, some have attempted to +revive. Galileo attributed them to clouds or vapors +floating in the solar atmosphere; this was the best +<span class="pagenum" id="Page_29">[Pg 29]</span>conclusion which could be drawn from the observations +of that epoch. This opinion met for a long +time with general approval; it has even been renewed +in our day. Some astronomers, and among them +Lalande, believed, on the contrary, that they were +mountains, of which the flanks, more or less steep, +might produce the aspect of the penumbra—an opinion +irreconcilable with the proper motion which the +spots sometimes possess in a very marked manner. +It is not usual, in fact, to see mountains traveling.<span class="pagenum" id="Page_30">[Pg 30]</span> +Derham attributed them to the smoke issuing from +the volcanic craters of the sun, an opinion revived and +maintained in recent times by Chacornac. Several +<i>savants</i>, regarding the sun as a liquid and incandescent +mass, have also explained the spots by immense cinders +floating on this ocean of fire. But a century had +scarcely elapsed after the epoch when the spots were +observed for the first time, when an English astronomer, +Wilson, showed with certainty that the spots are +hollow.</p> + +<p>We do not know with any certainty whether the +sun is through and through one mass of glowing molten +heat, or whether he may have a solid and even +cool body within the blazing covering. Some have +thought the one, and some the other. We only know +that he is a mighty furnace of heat and flame, beyond +anything that we can possibly imagine on our quiet +little earth.</p> + +<p>It seems very sure that no such thing as “quietness” +is to be found on the surface of the sun. The wildest +and fiercest turmoil of rushing wind and roaring flame +there prevails. The cyclones or hurricanes which take +place are sometimes so rapid and so tremendous in +extent, tearing open the blazing envelope of the sun, +and showing glimpses of fiery though darker depths +below, that we, on our far-distant earth, can actually +watch their progress.</p> + +<p>Astronomers speak of the “quivering fringe of fire” +all around the edge of the sun, visible through telescopes. +But the sun is perpetually turning on his +axis, so that each hour fresh portions of his surface +thus pass the edge, showing the same appearance.<span class="pagenum" id="Page_31">[Pg 31]</span> +What conclusion can we come to but that the whole +enormous surface of the sun is one restless, billowy +sea of fire and flame?</p> + +<p>It sounds to us both grand and startling to hear of +the mighty outbreaks from Mount Vesuvius, or to read +of glowing lava from a volcano in Hawaii pouring in +one unbroken stream for miles.</p> + +<p>But what shall be thought of rosy flames mounting +to a height of fifty or a hundred thousand miles above +the edge of the sun? What shall be thought of a +tongue of fire long enough to fold three or four times +round our solid earth? What shall be thought of the +awful rush of burning gases, sometimes seen, borne +along at the rate of one or two or even three hundred +miles in a single second across the sun’s surface? +What shall be thought of the huge dark rents in this +raging fiery ocean, rents commonly from fifty to one +hundred thousand miles across, and not seldom more?</p> + +<p>Fifty thousand miles! A mere speck, scarcely +visible without a telescope; yet large enough to hold +seven earths like ours flung in together. The largest +spot measured was so enormous that eighteen earths +might have been arranged in a row across the breadth +of it, like huge boulders of rock in a mountain cavern; +and to have filled up the entire hole about one hundred +earths would have been needed.</p> + +<p>It is well to grow familiar with certain names given +by astronomers to certain parts of the sun.</p> + +<p>The round shining disk or flat surface, seen by all +of us, is called the <i>photosphere</i>, or “light-sphere.” It +has a tolerably well-defined edge or “limb,” and dazzles +the eye with its intense brightness.</p> + +<p><span class="pagenum" id="Page_32">[Pg 32]</span></p> + +<p>Across the photosphere the spots move, sometimes +many, sometimes few, in number. Besides the dark +spots, there are spots of extreme brilliancy, standing +out on even that dazzling surface, which causes a piece +of white-hot iron to look black and cold by contrast. +These extra-radiant spots which come and go, and at +times change with great rapidity, are named <i>faculæ</i>—a +Latin word meaning “torches.”</p> + +<p>At the edge of the photosphere astronomers see +what has been already mentioned, that which is sometimes +called the <i>chromotosphere</i>, which one has named +“the <i>sierra</i>,” and which another has described as “a +quivering fringe of fire.” The waves of the sea, on a +stormy day, seen in the distance rising and breaking +the horizon-line, may serve as an illustration; only in +the sun the waves are of fire, not water. What must +their height be, to be thus visible at a distance of +ninety-three millions of miles?</p> + +<p>Outside the <i>sierra</i> are seen, at certain seasons, +bright, “rose-colored prominences” or flames of enormous +height. During an eclipse, when the dark body +of the moon comes between the sun and us, exactly +covering the photosphere, these red tips stand out +distinctly beyond the edge of sun and moon. Their +changes have been watched, and their height repeatedly +measured. Some are so lofty that ten little earths +such as ours might be heaped up, one upon another, +without reaching to their top. Whether they are in +character at all like the outbursts from our own volcanoes +it is hard to say. To compare the two would +be rather like comparing a small kitchen fire with +a mighty iron-smelting furnace. The faculæ, the<span class="pagenum" id="Page_33">[Pg 33]</span> +sierra, and the prominences are visible only through +a telescope.</p> + +<p>Outside these red flames or “prominences” is the +corona, commonly divided into the inner and outer +coronas.</p> + +<p>Many different explanations have been offered of +this beautiful crown of light round the sun, plainly +visible to the naked eye during an eclipse. But here +again we know little, and must be content to watch +and wait.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_34">[Pg 34]</span></p> + +<h2 class="nobreak" id="c3">CHAPTER III.</h2> +</div> + +<p class="c sp">WHAT BINDS THE FAMILY TOGETHER?</p> + + +<p><span class="smcap large">What</span> is it which binds together all the members +of the Solar System? Ah, what? Why should not +the sun at any moment rush away in one direction, +the earth in a second, the planets in half a dozen +others? What is there to hinder such a catastrophe? +Nothing—except that they are all held together by a +certain close family tie; or, more correctly, by the +powerful influence of the head of the family.</p> + +<p>This mysterious power which the sun has, and +which all the planets have also in their smaller degrees, +is called Attraction. Sometimes it is named +Gravitation or Gravity. When we speak, as we often +do, of the <i>law</i> of attraction or gravitation, we mean +simply this—that throughout the universe, in things +little and great, is found a certain wonderful <i>something</i>, +in constant action, which we call a “law.” +What the “something” may be, man can not tell; +for he knows it only by its effects. But these effects +are seen everywhere, on all sides, in the earth and in +the universe. It is well named in being called a +“law;” for we are compelled to obey it. None but +the Divine Lawgiver who made this law can for a single +moment suspend its working.</p> + +<p>What causes an apple to fall to the ground when +it drops from the branch? Why should it not, instead, +rise upwards? Because, of course, it is heavy, or has<span class="pagenum" id="Page_35">[Pg 35]</span> +weight. But what <i>is</i> weight? Simply this—that the +earth draws or drags everything downwards towards +herself by the power of attraction. Every substance, +great or small, light or heavy, is made up of tiny +atoms. Each one of these atoms attracts or draws +all the other atoms towards itself; and the closer +they are together, the more strongly they pull one +another.</p> + +<p>The atoms in a piece of iron are much closer than +the atoms in a piece of wood; therefore the iron is +called the “more <i>dense</i>” of the two, and its weight or +“mass” is greater. The more closely the atoms are +pressed together, the greater the number of them in +a small space, and the more strong the drawing towards +the earth; for the earth draws each one of these +atoms equally. That is only another way of saying +that a thing is “heavier.” If you drop a stone from +the top of a cliff, will it rise upwards or float in the +air? No, indeed. The pull of the earth’s attraction, +dragging and still dragging downward, makes it rush +through the air, with speed quickening each instant, +till it strikes the ground. Every single atom in every +single body <i>pulls</i> every other atom, whether far or +near. The nearer it is, the stronger always the +pulling.</p> + +<p>We do not always feel this, because the very much +greater attraction of the earth hides—or smothers, as +we may say—the lesser attraction of each small thing +for another. But though you and I might stand side +by side upon earth, and feel no mutual attraction, yet +if we could mount up a few thousands of miles, far +away from earth, and float in distant space, there we<span class="pagenum" id="Page_36">[Pg 36]</span> +should find ourselves drawn together, and unable to +remain apart.</p> + +<p>Now precisely as an apple falling from a tree and +a stone dropping from a cliff are dragged downward +to the earth, just so our earth and all the planets are +dragged downwards towards the sun and towards each +other. The law of the earth’s attraction of all objects +on its surface to itself was indistinctly suspected a +very long time ago; but it was the great Newton who +first discovered that this same law was to be found +working among the members of the whole Solar System. +The sun attracts the earth, and the earth attracts +the sun. But the enormous size of the sun +compared with our earth—like a great nine-foot globe +beside a tiny one-inch ball—makes our power of attraction +to be quite lost sight of in his, which is so +much greater.</p> + +<p>The principle of gravitation is of far wider scope +than we have yet indicated. We have spoken merely +of the attraction of the earth, and we have stated that +its attraction extends throughout space. But the law +of gravitation is not so limited. Not only does the +earth attract every other body, and every other body +attract the earth, but each of these bodies attracts +each other; so that, in its more complete shape, the +law of gravitation announces that “every body in the +universe attracts every other body with a force which +varies inversely as the square of the distance.” It is +impossible for us to overestimate the importance of +this law. It supplies the clue by which we can unravel +the complicated movements of the planets. It +has led to marvelous discoveries, in which the law of<span class="pagenum" id="Page_37">[Pg 37]</span> +gravitation has enabled us to anticipate the telescope, +and, indeed, actually to feel the existence of bodies +before those bodies have even been seen.</p> + +<p>We come now to another question. If the sun is +pulling with such power at the earth and all her sister +planets, why do they not fall down upon him? +What is to prevent their rolling some day into one of +those deep rents in his fiery envelope? Did you ever +tie a ball to a string, and swing it rapidly round and +round your head? If you did, you must have noticed +the steady outward pull of the ball. The heavier the +ball, and the more rapid its whirl, the stronger the pull +will be. Let the string slip, and the rush of the ball +through the air to the side of the room will make this +yet more plain. Did you ever carry a glass of water +quickly along, and then, on suddenly turning a corner, +find that the water has not turned with you? It has +gone on in its former direction, leaving the glass, and +spilling itself on the floor.</p> + +<p>The cause in both cases is the same. Here is another +“law of nature,” so-called. Though we can +neither explain nor understand why and how it is so, +we see it to be one of the fixed rules of God’s working +in every-day life throughout his universe. The law, +as we see it, seems to be this: Everything which is at +rest must remain at rest, until set moving by some +cause outside of, or independent of itself; and everything +which is once set moving, must continue moving +in a straight line until checked.</p> + +<p>According to this a cannon-ball lying on the ground +ought to remain there until it is set in motion; and, +once set in motion by being fired from a cannon, it ought<span class="pagenum" id="Page_38">[Pg 38]</span> +to go on forever. Exactly so—if nothing stops it. But +the earth’s attraction draws the cannon-ball downward, +and every time it strikes the ground it is partly +checked. Also each particle of air that touches it +helps to bring it to rest. If there were no earth +and no air in the question, the cannon-ball might rush +on in space for thousands of years.</p> + +<p>Why did the water get spilled? Because it necessarily +continued moving in a straight line. Your sudden +change of direction compelled the solid glass to +make the same change, but the liquid water was free to +go straight on in its former course; so it obeyed this +law, and <i>did</i> go on. Why did the ball pull hard at the +string as you swung it round? Because at each instant +it was striving to obey this same law, and to +rush onward in a straight line. The pull of the string +was every moment fighting against that inclination, +and forcing the ball to move in a circle.</p> + +<p>Just such is the earth’s movement in her yearly +journey round the sun. The string holding in the +ball pictures the sun’s attraction holding in the earth. +The pulling of the ball outward in order to continue +its course in a straight line, pictures the pulling of +our earth each moment to break loose from the sun’s +attraction and to flee away into distant space.</p> + +<p>For the earth is not at rest. Each tick of the clock +she has sped onward over more than eighteen miles +of her pathway through the sky. Every instant the +sun is dragging, with the tremendous force of his attraction, +to make her fall nearer to him. Every instant +the earth is dragging with the tremendous force +of her rapid rush, to get away from him. These two<span class="pagenum" id="Page_39">[Pg 39]</span> +pullings so far balance each other, or, more strictly, so +far combine together, that between the two she journeys +steadily round and round in her nearly circular +orbit.</p> + +<p>If the sun pulled a little harder she would need to +travel a little faster, or she would gradually go nearer +to him. If the earth went faster, and the sun’s attraction +remained the same as it is now, she would +gradually widen her distance. Indeed, it would only +be needful for the earth to quicken her pace to +about five-and-twenty miles a second, the sun’s power +to draw her being unchanged, and she would then +wander away from him for ever. Day by day we on +our earth should travel farther and farther away, leaving +behind us all light, all heat, all life, and finding +ourselves slowly lost in darkness, cold, and death.</p> + +<p>For what should we do without the sun? All our +light, all our warmth, come from him. Without the +sun, life could not exist on the earth. Plants, herbage, +trees, would wither; the waters of rivers, lakes, oceans, +would turn to masses of ice; animals and men would +die. Our earth would soon be one vast, cold, forsaken +tomb of darkness and desolation.</p> + +<p>We may not think so, but everything which moves, +circulates, and lives on our planet is the child of the +sun. The most nutritious foods come from the sun. +The wood which warms us in winter is, again, the sun +in fragments. Every cubic inch, every pound of wood, +is formed by the power of the sun. The mill which +turns under the impulse of wind or water, revolves +only by the sun. And in the black night, under the +rain or snow, the blind and noisy train, which darts<span class="pagenum" id="Page_40">[Pg 40]</span> +like a flying serpent through the fields, rushes along +above the valleys, is swallowed up under the mountains, +goes hissing past the stations, of which the pale eyes +strike silently through the mist,—in the midst of night +and cold, this modern animal, produced by human industry, +is still a child of the sun. The coal from the +earth which feeds its stomach is solar work, stored up +during millions of years in the geological strata of +the globe.</p> + +<p>As it is certain that the force which sets the watch +in motion is derived from the hand which has wound +it, so it is certain that all terrestrial power proceeds +from the sun. It is its heat which maintains the three +states of bodies—solid, liquid, and gaseous. The last +two would vanish, there would be nothing but solids; +water and air itself would be in massive blocks,—if +the solar heat did not maintain them in the fluid state. +It is the sun which blows in the air, which flows in +the water, which moans in the tempest, which sings +in the unwearied throat of the nightingale. It attaches +to the sides of the mountains the sources of the +rivers and glaciers, and consequently the cataracts and +the avalanches are precipitated with an energy which +they draw directly from him. Thunder and lightning +are in their turn a manifestation of his power. Every +fire which burns and every flame which shines has received +its life from the sun. And when two armies +are hurled together with a crash, each charge of cavalry, +each shock between two army corps, is nothing +else but the misuse of mechanical force from the same +star. The sun comes to us in the form of heat, he +leaves us in the form of heat; but between his arrival<span class="pagenum" id="Page_41">[Pg 41]</span> +and his departure, he has given birth to the +varied powers of our globe.</p> + +<p>I have spoken before about the old-world notion +that our earth was a fixed plain, with the sun circling +round her. When the truth dawned slowly upon +some great minds, anxious only to know what really +was the truth, others made a hard struggle for the +older and pleasanter mode of thinking. It went with +many sorely against the grain to give up all idea of +the earth being the chief place in the universe. Also +there was something bewildering and dizzying in the +notion that our solid world is never for one moment +still. But truth won the victory at last. Men consented +slowly to give up the past dream, and to learn +the new lesson put before them.</p> + +<p>We still talk of the sun rising and setting, and of +the stars doing the same. This is, however, merely a +common form of speech, which means just the opposite. +For instead of the sun and stars moving, it is +the earth which moves.</p> + +<p>The earth has two distinct movements. Indeed, I +ought to say that she has three; but we will leave all +thought of the third for the present. First, she turns +round upon her axis once in every twenty-four hours. +Secondly, she travels round the sun once in about every +three hundred and sixty-five days and a quarter. No +wonder our ancestors were startled to learn that the +world, which they had counted so immovable, was perpetually +spinning like a humming-top, and rushing +through space like an arrow.</p> + +<p>You may gain some clear notions as to the daily +rising and setting of our sun, with the help of an<span class="pagenum" id="Page_42">[Pg 42]</span> +orange. Pass a slender knitting-needle through the +orange, from end to end, and hold it about a yard distant +from a single candle in a room otherwise darkened. +Let the needle or axis slant somewhat, and turn the +orange slowly upon it.</p> + +<p>The candle does not move; but as the orange turns, +the candle-light falls in succession upon each portion +of the yellow rind. Half of the orange is always in +shade, and half is always in light; while at either side, +if a small fly were standing there, he would be passing +round out of shade into candle-light, or out of candle-light +into shade.</p> + +<p>Each spot on our earth moves round in turn into +half-light, full-light, half-light, and darkness; or, in +other words, has morning-dawn, midday-light, evening +twilight, and night. Each spot on our earth would +undergo regularly these changes every twenty-four +hours throughout the year, were it not for another +arrangement which so far affects this that the North +and South Poles are, by turns, cut off from the light +during many months together.</p> + +<p>Thus the sun is in the center of the Solar System, +turning slowly on his axis; and the earth and the +planets travel round him, each spinning like a teetotum, +so as to make the most of his bright warm rays. +But for this spinning movement of the earth, our day +and night, instead of being each a few hours long, +would each last six months.</p> + +<p>You may notice that, as you turn the orange steadily +round, the outside surface of the skin has to move +much more slowly in those parts close to the knitting-needle, +than in those parts which bulge out farthest<span class="pagenum" id="Page_43">[Pg 43]</span> +from it. Near the North and South Poles the surface +of our earth travels slowly round a very small circle in +the course of twenty-four hours. But at the equator +every piece of ground has to travel about twenty-five +thousand miles in the same time; so that it rushes along +at the rate of more than one thousand miles an hour. +A man standing on the earth at the equator is being +carried along at this great speed, not <i>through</i> the air, +for the whole atmosphere partakes of the same rapid +motion, but <i>with</i> the air, round and round the earth’s +axis.</p> + +<p>Now about the other movement of the earth—her +yearly journey round the sun. While she moves, the +sun, as seen from the earth, seems to change his place. +First he is observed against a background of one group +of stars, then against a second, then against a third. +Not that the stars are visible in the daytime when +the sun is shining, but their places are well known in +the heavens; and also they can be noted very soon +after he sets, or before he rises, so that the constellations +nearest to him may each day be easily found out.</p> + +<p>Of course, in old times the sun was thought to be +really taking this journey among the stars, and men +talked of “the sun’s path” in the heavens. This path +was named “the Ecliptic,” and we use the word still, +though we know well that the movements are not +really his, but ours.</p> + +<p>As the earth’s daily movement causes day and night, +so the earth’s yearly movement causes spring, summer, +autumn, and winter. A few pages back I mentioned, +in passing, one slight yet important fact which lies at +the root of this matter about the seasons. The earth,<span class="pagenum" id="Page_44">[Pg 44]</span> +journeying round the sun, travels with her axis <i>slanting</i>. +Put your candle in the middle of the table, and +stand at one end, holding your orange. Now let the +knitting-needle, with the orange upon it, so slant that +one end shall point straight over the candle, towards +the upper part of the wall at the farther end of the +room. Call the upper end so pointing the North Pole +of your orange. You will see that the candle-light +falls chiefly upon the upper half of the orange; and as +you turn it slowly, to picture day and night, you will +find that the North Pole has no night, and the South +Pole has no day. That is summer in the northern +hemisphere, and winter in the southern.</p> + +<p>Walk round next to one side of the table, towards +the right hand, taking care to let the knitting-needle +point steadily still in exactly the same direction, not +towards the same <i>spot</i>, for that would alter its direction +as you move, but towards the same <i>wall</i>. Stop, and +you will find the candle lighting up one-half of your +orange, from the North to the South Poles. Turn it +slowly, never altering the slope of the axis, and you +will see that every part of the orange comes by turns +under the light. This is the Autumnal Equinox, +when days and nights all over the world are equal in +length.</p> + +<p>Walk on to the other end of the table, still letting +the needle slope and point steadily as before. Now +the candle-light will shine upon the lower or South +Pole, and the North Pole will be entirely in the shade. +This is summer in the southern hemisphere, and +winter in the northern.</p> + +<p>Pass on to the fourth side of the table, and once<span class="pagenum" id="Page_45">[Pg 45]</span> +more you will find it, as at the second side, equal light +from North Pole to South Pole. This will be the +Spring Equinox.</p> + +<p>It is an illustration that may be easily practiced. +But everything depends upon keeping the slant of the +needle or axis unchanged throughout. If it be allowed +to point first to right, and then to left, first towards the +ceiling, and then towards the wall, the attempt will +prove a failure.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_46">[Pg 46]</span></p> + +<h2 class="nobreak" id="c4">CHAPTER IV.</h2> +</div> + +<p class="c sp">THE LEADING MEMBERS OF OUR FAMILY—FIRST<br> +GROUP.</p> + + +<p><span class="smcap large">The</span> chief distinction between stars and planets is, as +before said, that the stars shine entirely by their own +light, while the planets shine chiefly, if not entirely, +by reflected light. The stars are suns; mighty globes of +glowing flame. The planets simply receive the light +of the sun, and shine with a brightness not their own.</p> + +<p>A lamp shines by its own light; but a looking-glass, +set in the sun’s rays and flashing beams in all directions, +shines by reflected light. In a dark room it would +be dark. If there were no sun to shine upon Mars or +Venus, we should see no brightness in them. The +moon is like the planets in this. She has only borrowed +light to give, and none of her own.</p> + +<p>Any one of the planets removed to the distance of +the nearest fixed star, would be invisible to us. Reflected +light will not shine nearly so far as the direct +light of a burning body. There may be thousands or +millions of planets circling round the stars—those +great and distant suns—just as our brother-planets +circle round our sun. But it is impossible for us to +see them. The planets which we can see are close +neighbors, compared with the stars. I do not mean +that they are near in the sense in which we speak of +nearness upon earth. They are only near in comparison +with what is so very much farther away.</p> + +<p><span class="pagenum" id="Page_47">[Pg 47]</span></p> + +<p>For a while we must now leave alone all thought +of the distant stars, and try to gain a clear idea of the +chief members of our own Family Circle—that family +circle of which the sun is the head, the center, the +source of life and warmth and light. There are two +ways in which astronomers group the planets of the +Solar System. One way is to divide them into the +Inferior Planets, and the Superior Planets.</p> + +<p>As the earth travels in her pathway round the sun, +two planets travel on their pathways round the sun +nearer to him than ourselves. If the pathway or orbit +of our earth were pictured by a hoop laid upon the +table, with a ball in the center for the sun; then +those two planets would have two smaller hoops of +different sizes <i>within</i> ours; and the rest would have +larger hoops of different sizes <i>outside</i> ours. The two +within are called inferior planets, and the rest outside +are called superior planets.</p> + +<p>A round hoop would not make a good picture of +an orbit. For the yearly pathway of our earth is not +in shape perfectly round, but slightly oval; and the +sun is not exactly in the center, but a little to one side +of the center. This is more or less the case with the +orbits of all the planets.</p> + +<p>But the laying of the hoops upon the table would +give no bad idea of the way in which the orbits really +lie in the heavens. The orbits of all the chief planets +do not slope and slant round the sun in all manner of +directions. They are placed almost in the same <i>plane</i> +as it is called—or, as we might say, in the same <i>flat</i>. +In these orbits the planets all travel round in the same +direction. One may overtake a second on a neighboring<span class="pagenum" id="Page_48">[Pg 48]</span> +orbit, and get ahead of him, but one planet never +goes back to meet another.</p> + +<p>In speaking of the orbits, I do not mean that the +planets have visible marked pathways through the +heavens, any more than a swallow has a visible pathway +through the sky, or a ship a marked pathway +through the sea. Yet each planet has his own orbit, +and each planet so distinctly keeps to his own, that +astronomers can tell us precisely whereabouts in the +heavens any particular planet will be, at any particular +time, long years beforehand.</p> + +<p>There is also another mode of grouping the planets, +besides dividing them into superior and inferior planets. +By this other mode we find two principal groups +or quartets of planets, separated by a zone or belt of a +great many very small planets.</p> + +<table> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Mercury.</td></tr> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Venus.</td></tr> + +<tr> + <td class="tdl">First Group</td> + <td class="tdl">{ Earth.</td></tr> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Mars.</td></tr> + +<tr> + <td class="tdc" colspan="2">The Asteroids or Planetoids.</td> + </tr> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Jupiter.</td></tr> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Saturn.</td></tr> + +<tr> + <td class="tdl">Second Group</td> + <td class="tdl">{ Uranus.</td></tr> + +<tr> + <td class="tdl"></td> + <td class="tdl">{ Neptune.</td></tr> + + +</table> + +<p>The first four are small compared with the last +four, though much larger than any in the belt of tiny +Asteroids.</p> + +<p>It was believed at one time that a planet had been +discovered nearer to the sun than Mercury, and the +name Vulcan was given to it. But no more has been +seen of Vulcan, and his existence is so doubtful that +we must not count him as a member of the family +without further information.</p> + +<p><span class="pagenum" id="Page_49">[Pg 49]</span></p> + +<p>Mercury is very much smaller than our Earth. The +diameter of the earth is eight thousand miles, but the +diameter of Mercury is only about three thousand +miles—not even half that of the earth. Being so +much nearer to the sun than ourselves, the pulling of +his attraction is much greater, and this has to be balanced +by greater speed, or Mercury would soon fall down +upon the sun. Our distance from the sun is ninety-three +millions of miles. Mercury’s distance is only +about one-third of ours; and instead of traveling, like +the earth, at the rate of eighteen miles each second, +Mercury dashes headlong through space at the mad +pace of twenty-nine miles each second. It is a good +thing the earth does not follow his example, or she +would soon break loose from the sun’s control altogether.</p> + +<p>The earth takes more than three hundred and sixty-five +days, or twelve months, to journey round the sun +in her orbit. That is what we call “the length of our +year.” But Mercury’s year is only eighty-eight days, +or not quite three of our months. No wonder!—when +his pathway is so much shorter, and his speed so much +greater than ours. So Mercury has four years to one +year on earth; and a person who had lived on Mercury +as long as five earthly years, would then be +twenty years old. The increased number of birthdays +would scarcely be welcome in large families, supposing +we could pay a long visit there.</p> + +<p>The sun, as seen from Mercury, looks about four +and a half times as large as from here; the heat and +glare being increased in proportion. No moon has +ever been found, belonging to Mercury.</p> + +<p><span class="pagenum" id="Page_50">[Pg 50]</span></p> + +<p>The planet Mercury is, like the earth and the moon, +a globe of dark matter which only shines and is visible +by the illumination of the solar light. Its motion +round the central star, which brings it sometimes between +the sun and us, sometimes in an oblique direction, +sometimes at right angles, and shows us a part +incessantly variable, of its illuminated hemisphere, +produces in its aspect, as seen in a telescope, a succession +of phases similar to those which the moon +presents to us. The cut represent the apparent variations +of size and the succession of phases, visible in +the evening after sunset; when the planet attains its +most slender crescent, it is in the region of its orbit +nearest to the earth, and passes between the sun and +us; then, some weeks afterwards, it emerges from the +solar rays and passes again through the same series +of phases in inverse order, as we see them by reversing +the figure.</p> + +<div class="figcenter" id="f7"> +<img src="images/fig7.jpg" alt="mercury"> +<p class="caption">PHASES OF MERCURY BEFORE INFERIOR CONJUNCTION—EVENING<br> +STAR.</p> +</div> + +<p>Venus, the second inferior planet, is nearly the same +size as our earth. Seen from the earth, she is one of +the most brilliant and beautiful of all the planets.<span class="pagenum" id="Page_51">[Pg 51]</span> +Her speed is three miles a second faster than ours, +and her distance from the sun is about two-thirds that +of our own; so that the orbit of Venus lies half-way +between the orbit of Mercury and the orbit +of the earth. The day of Venus is about half an +hour shorter than ours. Her year is nearly two hundred +and twenty-five days, or seven and a half of our +months. One or two astronomers have fancied that +they caught glimpses of a moon near Venus; but this +is still quite doubtful, and indeed it is believed to have +been a mistake.</p> + +<p>Venus and Mercury are only visible as morning +and evening planets. Venus, being farther from the +sun, does not go before and follow after him quite so +closely as Mercury, and she is therefore the longer +within sight.</p> + +<p>When Venus, traveling on her orbit, comes just +between the sun and us, her dark side is turned towards +the earth, and we can catch no glimpse of her. +When she reaches that part of her orbit which is +farthest from us, quite on the other side of the sun, +her great distance from us makes her light seem less. +But about half-way round on either side, she shows +exceeding brilliancy, and that is the best view we can +get of her.</p> + +<p>Seen through a telescope, Venus undergoes phases +like those of Mercury, or of our moon. That is to +say, we really have “new Venus,” “quarter Venus,” +“half Venus,” “full Venus,” and so on.</p> + +<p>Of all the luminaries in the heavens, the sun and +moon excepted, the planet Venus is the most conspicuous +and splendid. She appears like a brilliant lamp<span class="pagenum" id="Page_52">[Pg 52]</span> +amid the lesser orbs of night, and alternately anticipates +the morning dawn, and ushers in the evening +twilight. When she is to the westward of the sun, in +winter, she cheers our mornings with her vivid light, +and is a prelude to the near approach of the break of +day and the rising sun. When she is eastward of that +luminary, her light bursts upon us after sunset, before +any of the other radiant orbs of heaven make their +appearance; and she discharges, in some measure, the +functions of the absent moon. The brilliancy of this +planet has been noticed in all ages, and has been frequently +the subject of description and admiration both +by shepherds and by poets. The Greek poets distinguished +it by the name of Phosphor, “light-bringer,” +when it rose before the sun, and Hesperus, “the west,” +when it appeared in the evening after the sun retired. +It is now generally distinguished by the name of the +Morning and Evening Star.</p> + +<p>Next to the orbit of Venus comes the orbit of our +own Earth, the third planet of the first group.</p> + +<p>Mars, the fourth of the inner quartet, but the first +of the superior planets, is a good deal smaller than +Venus or the earth. The name Mars, from the heathen +god of war, was given on account of his fiery reddish +color. Mars is better placed than Venus for being +observed from earth. When he is at the nearest point +of his orbit to us, we see him full in the blaze of sunlight; +whereas Venus, at her nearest point, turns her +bright face away.</p> + +<p>The length of the day of Mars—or, in other words, +the time he takes to turn upon his axis—is only forty +minutes longer than that of earth. Mars’ journey<span class="pagenum" id="Page_53">[Pg 53]</span> +round the sun is completed in the course of six hundred +and eighty-seven days, not much less than two +of our years. His distance from the sun is about one +hundred and forty millions of miles, and his speed is +fourteen miles a second. We shall find, with the increasing +distance of each planet, that the slower pace +balances the lessened amount of the sun’s attraction.</p> + +<p>Passing on from Mars, the last of the first group of +planets, we reach the belt of Asteroids, sometimes +called Planetoids, Minor Planets, or Telescopic Planets. +They are so tiny that Mercury is a giant compared +with the largest among them.</p> + +<p>The zone of space containing all these little planets +is more than a hundred millions of miles broad. Their +orbits do not lie flat in almost the same plane, but +slant about variously in a very entangled fashion. If +a neat model were made of this zone, with a slender +piece of wire to represent each orbit, it would be +found impossible to lift up one wire without pulling +up all the rest with it. Those asteroids lying nearest +to the sun take about three of our years to travel +round him, and those lying farthest take about six of +our years.</p> + +<p>New members of the group are very often found. +The number of asteroids now known amounts to +about three hundred and twenty. Ceres is estimated +by Professor Barnard, of the Yerkes Observatory, Chicago +University, to be six hundred miles in diameter. +Vesta is about two hundred and fifty miles in diameter. +Meta, on the other hand, is less than seventy-five +miles. There are some smaller ones that do not +measure twenty miles in diameter, and it is probable<span class="pagenum" id="Page_54">[Pg 54]</span> +that there are many which are so small as to be absolutely +invisible to the best telescopes, and which +measure only a few hundred rods in diameter. Twenty +thousand Vestas would be needed to make one globe +equal to our earth in size.</p> + +<p>Are they <i>worlds</i>? Why not? Is not a drop of +water, shown in the microscope, peopled with a multitude +of various beings? Does not a stone in a +meadow hide a world of swarming insects? Is not +the leaf of a plant a world for the species which inhabit +and prey upon it? Doubtless among the multitude +of small planets there are those which must +remain desert and sterile, because the conditions of +life (of any kind) are not found united. But we can +not doubt that on the majority the ever-active forces +of nature have produced, as in our world, creations +appropriate to these minute planets. Let us repeat, +moreover, that for nature there is neither great nor +little. And there is no necessity to flatter ourselves +with a supreme disdain for these little worlds; for in +reality the inhabitants of Jupiter would have more +right to despise us than we have to despise Vesta, +Ceres, Pallas, or Juno. The disparity is greater between +Jupiter and the earth than between the earth +and these planets. A world of two, three, or four +hundred miles in diameter is still a continent worthy +to satisfy the ambition of a Xerxes or a Tamerlane.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_55">[Pg 55]</span></p> + +<h2 class="nobreak" id="c5">CHAPTER V.</h2> +</div> + +<p class="c sp">THE LEADING MEMBERS OF OUR FAMILY—SECOND<br> +GROUP.</p> + + +<p><span class="smcap large">Leaving</span> behind us the busy zone of planetoids, +hurrying round and round the sun in company, we +cross a wide gap, and come upon a very different +sight.</p> + +<p>The distance from the sun which we have now +reached is little less than four hundred and fifty millions +of miles, or about five times as much as the +earth’s distance; and the sun in the heavens shows a +diameter only one-fifth of that which we are accustomed +to see. Slowly—yet not slowly—floating onwards +through space, in his far-off orbit, we find the +magnificent planet Jupiter.</p> + +<p>Is eight miles each second slow progress? Compared +with the wild whirl of little Mercury, or even +compared with the rate of our own earth’s advance, +we may count it so; but certainly not, compared with +our notions of speed upon earth. Eight miles each +second is five hundred times as fast as the swiftest express-train +ever made by man. No mean pace that +for so enormous a body. For Jupiter is the very +largest of all the members of the Solar System except +the sun himself—quite the eldest brother of the family. +His diameter is about eighty-five thousand miles, +his axis being nearly eleven times as long as that of +earth. Though in proportion to his great bulk not<span class="pagenum" id="Page_56">[Pg 56]</span> +nearly so heavy as our earth, yet his bulk is so vast +that more than twelve hundred earths would be needed +to make one Jupiter.</p> + +<p>It must not, however, be forgotten that there is a +certain amount of uncertainty about these measurements +of Jupiter. He seems to be so covered with a +dense atmosphere and heavy clouds that it is quite +impossible for us to learn the exact size of the solid +body within.</p> + +<p>Jupiter does not travel alone. Borne onwards with +him, and circling steadily around him, are five moons; +the smallest with a probable diameter of about one hundred +miles; one about the same size as our own moon, +and the others all larger. The nearest of the five, +though distant from the center of the planet over one +hundred and twelve thousand miles, revolves about +him in twelve hours; the second, though farther from +Jupiter than our moon from the earth, speeds round +him in less than two of our days. The most distant, +though over a million miles away, takes scarcely seventeen +days to accomplish its long journey. Jupiter and +his moons make a little system by themselves—a +family circle within a family circle.</p> + +<p>Like the smaller planets, Jupiter spins upon his +axis; and he does this so rapidly that, notwithstanding +his great size, his day lasts only ten hours, instead of +twenty-four hours like ours. But if Jupiter’s day is +short, his year is not. Nearly twelve of our years pass +by before Jupiter has traveled once completely round +the sun. So a native of earth who had just reached +his thirty-seventh year, would, on Jupiter, be only +three years old.</p> + +<p><span class="pagenum" id="Page_57">[Pg 57]</span></p> + +<p>Passing onward from Jupiter, ever farther and +farther from the sun, we leave behind us another vast +and empty space—empty as we count emptiness, +though it may be that there is in reality no such thing +as emptiness throughout the length and breadth of +the universe. The width of the gap which divides +the pathway of Jupiter from the pathway of his giant +brother-planet Saturn is nearly five times as much as +the width of the gap separating the earth from the +sun. The distance of Saturn from the sun is not +much less than double the distance of Jupiter.</p> + +<p>With this great space in our rear, we come upon +another large and radiant planet, the center, like Jupiter, +of another little system; though it can only be +called “little” in comparison with the much greater +Solar System of which it forms a part.</p> + +<p>Saturn’s diameter is less than that of Jupiter, but +the two come near enough to be naturally ranked together. +Nearly seven hundred earths would be needed +to make one globe as large as Saturn. But here again +the dense and cloudy envelope makes us very uncertain +about the planet’s actual size. Saturn is like Jupiter +in being made of lighter materials than our earth; +and also in his rapid whirl upon his axis, the length +of his “day” being only ten and a half of our hours.</p> + +<p>From Jupiter’s speed of eight miles each second, +we come down in the case of Saturn to only five miles +each second. And Jupiter’s long annual journey looks +almost short, seen beside Saturn’s long journey of +thirty earthly years. A man aged sixty, according to +our fashion of reckoning time, would on Saturn have +just kept his second birthday.</p> + +<p><span class="pagenum" id="Page_58">[Pg 58]</span></p> + +<p>The system or family of Saturn is yet more wonderful +than that of Jupiter. Not five only but eight +moons travel ceaselessly round Saturn, each in its own +orbit; and in addition to the eight moons, he has +revolving round him three magnificent rings. These +rings, as well as the moons, shine, not by their own +brilliancy, for they have none, but by borrowed sunlight. +The farthest of the moons wanders in his +lonely pathway about two millions of miles away from +Saturn. The largest of them is believed to be about +the same size as the planet Mars. Of the three rings +circling round Saturn, almost exactly over his equator, +the inside one is dusky, purplish, and transparent; the +one outside or over that is very brilliant; and the +third, outside the second, is rather grayish in hue.</p> + +<p>Another vast gap—more enormous than the last. +It is a wearisome journey. From the orbit of Jupiter +to the orbit of Saturn at their nearest points, was five +times as much as from the sun to the earth. But from +the orbit of Saturn to the orbit of Uranus, the next +member of the sun’s family, we have double even that +great space to cross.</p> + +<p>Still, obedient to the pulling of the sun’s attractive +power, Uranus wanders onward in his wide pathway +round the sun, at the rate of four miles a second. +Eighty-four of our years make one year of Uranus. +This planet has four moons, and thus forms a third +smaller system within the Solar System; but he may +have other satellites also, as yet undiscovered. In size +he is seventy-four times as large as our earth.</p> + +<p>One more mighty chasm of nine hundred millions +of miles, for the same distance which separates the<span class="pagenum" id="Page_59">[Pg 59]</span> +pathway of Saturn from the pathway of Uranus, separates +also the pathway of Uranus from the pathway +of Neptune. Cold, and dark, and dreary indeed seems +to us the orbit on which this banished member of our +family circle creeps round the sun, in the course of one +hundred and sixty-five years, at the sluggish rate of +three miles a second.</p> + +<p>On the planet Saturn, the quantity of light and +heat received from the sun is not much more than a +hundredth part of that which we are accustomed to +receive on earth. But by the time we reach Neptune, +the great sun has faded and shrunk in the distance +until to our eyes he looks only like an exceedingly +brilliant and dazzling star.</p> + +<p>We know little of this far-off brother, Neptune, +except that he is rather larger than Uranus, being one +hundred and five times as big as the earth; that he has +at least one moon; and also that, like Uranus, he is +made of materials lighter than those of earth, but +heavier than those of Jupiter or Saturn.</p> + +<p>After all, it is no easy matter to gain clear ideas as +to sizes and distances from mere statements of “so +many miles in diameter,” and “so many millions of +miles away.” A “million miles” carries to the mind +a very dim notion of the actual reality.</p> + +<p>Now if we can in imagination bring down all the +members of the Solar System to a small size, keeping +always the same proportions, we may find it a help. +“Keeping the same proportions” means that all must +be lessened alike, all must be altered in the same +degree. Whatever the supposed size of the earth may +be, Venus must be still about the same size as the<span class="pagenum" id="Page_60">[Pg 60]</span> +earth, Saturn seven hundred times as large, and so on. +Also, whatever the distance of the earth from the sun, +in miles, or yards, or inches, Mercury must still be one-third +as far, Jupiter still five times as far, and thus +with the rest.</p> + +<p>First, as to size alone. Suppose the earth is represented +by a small globe, exactly three inches in diameter. +It will be a very small globe. Not only men +and houses, but mountains, valleys, seas, will all have +to be reduced to so minute a size, as to be quite invisible +to the naked eye.</p> + +<p>Fairly to picture the other members of the Solar +System, in due proportion, you will have them as +follows:</p> + +<p>Mercury and Mars will be balls smaller than the +earth, and Venus nearly the same size of the earth. +Uranus and Neptune will be each somewhere about a +foot in diameter. Saturn will be twenty-eight inches +and Jupiter thirty-two inches in diameter. The sun +will be a huge dazzling globe, <i>twenty-six feet</i> in diameter. +No wonder he weighs seven hundred and +fifty times as much as all his planets put together.</p> + +<p>Next let us picture the system more exactly on +another and smaller scale. First, think of the sun as +a brilliant globe, about nine feet, or three yards, in +diameter, floating in space.</p> + +<p>About one hundred yards from the sun travels a +tiny ball, not half an inch in diameter, passing slowly +round the sun—slowly, because as sizes and distances +are lessened, speed must in due proportion be lessened +also. This is Mercury. About two hundred yards +from the sun travels another tiny ball, one inch in diameter.<span class="pagenum" id="Page_61">[Pg 61]</span> +This is Venus. Nearly a quarter of a mile +from the sun travels a third tiny ball, one inch again +in diameter; and at a distance of two feet and a half +from it a still smaller ball, one quarter of an inch in +diameter, journeys round it and with it. These are +the earth and the moon. About half as far again as +the last-named ball, travels another, over half an inch +in diameter. This is Mars.</p> + +<p>Then comes a wide blank space, followed by a large +number of minute objects, no bigger than grains of +powder, floating round the sun in company. These +are the Asteroids. Another wide blank space succeeds +the outermost of them.</p> + +<p>About one mile distant from the sun journeys a +globe, ten inches in diameter. Round him, as he +journeys, there travel five smaller balls, the largest of +which is about the third of an inch in diameter. Their +distances from the bigger globe vary from one and a +third to twelve and a half feet. These are Jupiter and +his moons.</p> + +<p>Nearly two miles distant from the sun journeys +another globe, about eight and a half inches in diameter. +Eight tiny balls and three delicate rings circle +round him as he moves. These are Saturn and his +belongings. About four miles distant from the sun +journeys another globe, four inches in diameter, with +four tiny balls accompanying him—Uranus and his +moons. Lastly, at a distance of six miles from the +sun, one more globe, not much larger than the last, +with one tiny companion, pursues his far-off pathway.</p> + +<p>These proportions as to size and distance will serve +to give a clear idea of the Solar System.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_62">[Pg 62]</span></p> + +<h2 class="nobreak" id="c6">CHAPTER VI.</h2> +</div> + +<p class="c sp">THE MOON.</p> + + +<p><span class="smcap large">Come</span>, and let us pay a visit to the moon. We +seem to feel a personal interest in her, just because +she is, in so peculiar a sense, our own friend and close +attendant. The sun shines for us; but, then, he shines +for all the members of the Solar System. And the +stars—so many as we can see of them—shine for us +too; but no doubt they shine far more brilliantly for +other and nearer worlds. The moon alone seems to +belong especially to ourselves.</p> + +<p>Indeed, we are quite in the habit of speaking about +her as “our moon.” Rather a cold and calm friend, +some may think her, sailing always serenely past, +whatever may be going on beneath her beams; yet +she has certainly proved herself constant and faithful +in her attachment.</p> + +<p>We have not very far to travel before reaching her,—merely +about two hundred and forty thousand miles. +That is nothing, compared with the weary millions of +miles which we have had to cross to visit some members +of our family. A rope two hundred and forty +thousand miles long would fold nearly ten times round +the earth at the equator. You know the earth’s diameter—about +eight thousand miles. If you had +thirty poles, each eight thousand miles long, and +could fasten them all together, end to end, one beyond +another, you would have a rod long enough to reach +from the earth to the moon.</p> + +<p><span class="pagenum" id="Page_63">[Pg 63]</span></p> + +<p>Let us take a good look at her before starting. She +is very beautiful. That soft silvery light, so unlike +sunlight or gaslight, or any other kind of light seen +upon earth, has made her the darling of poets and +the delight of all who love nature. Little children +like to watch her curious markings, and to make out +the old man with his bundle of sticks, or the eyes, +nose, and mouth of the moon—not dreaming what +those markings really are. And in moods of sadness, +how the pure calm moonlight seems to soothe the +feelings! Who would suppose that the moon’s beauty +is the beauty rather of death than of life?</p> + +<div class="figcenter" id="f8"> +<img src="images/fig8.jpg" alt="moon"> +<p class="caption">APPEARANCE OF THE FULL MOON.</p> +</div> + +<p>The stars have not much chance of shining through +her bright rays. It is well for astronomers that she is +not always at the full. But when she is, how large +she looks—quite as large as the sun, though in reality<span class="pagenum" id="Page_64">[Pg 64]</span> +her size, compared with his, is only as a very small +pin’s head compared with a school globe two feet in +diameter. Her diameter is little more than two thousand +miles, or one quarter that of our earth; and her +whole surface, spread out flat, would scarcely equal +North and South America, without any of the surrounding +islands.</p> + +<p>The reason she looks the same size as the sun, is +that she is so very much nearer. The sun’s distance +from us is more than one-third as many <i>millions</i> of +miles as the moon’s distance is <i>thousands</i> of miles. +This makes an enormous difference.</p> + +<p>We call our friend a “moon,” and say that she +journeys round the earth, while the earth journeys +round the sun. This is true, but it is only part of the +truth. Just as certainly as the earth travels round +the sun, so the moon also travels round the sun. And +just as surely as the earth is a planet, so the moon also +is a planet. It is a common mode of expression to +talk about “the earth and her satellite.” A no less +correct, if not more correct, way would be to talk of +ourselves as “a pair of planets,” journeying round the +same sun, each pulled strongly towards him, and each +pulling the other with a greater or less attraction, according +to her size and weight. For the sun actually +does draw the moon with more force than that with +which the earth draws her. Only as he draws the +earth with the same sort of force, and nearly in the +same degree, he does not pull them apart.</p> + +<p>The moon, like the other planets, turns upon her +axis. She does this very slowly, however; and most +singularly she takes exactly the same time to turn<span class="pagenum" id="Page_65">[Pg 65]</span> +once upon her axis that she does to travel once round +the earth. The result of this is, that we only see one +face of the moon. If she turned upon her axis, +and journeyed round the earth in two different lengths +of time, or if she journeyed round us and did not turn +upon her axis at all, we should have views of her on +all sides, as of other planets. But as her two movements +so curiously agree, it happens that we always +have one side of the moon towards us, and never catch +a glimpse of the other side.</p> + +<p>And now we are ready to start on our journey of +two hundred and forty thousand miles. An express +train, moving ceaselessly onward night and day, at the +rate of sixty miles an hour, would take us there in +about five months and a half. But no line of rails has +ever yet been laid from the earth to the moon, and no +“Flying Dutchman” has ever yet plied its way to and +fro on that path through the heavens. Not on the +wings of steam, but on the wings of imagination, we +must rise aloft. Come—it will not take us long. We +shall pass no planets or stars on the road, for the moon +lies nearer to us than any other of the larger heavenly +bodies.</p> + +<p>Far, far behind us lies the earth, and beneath our +feet, as we descend, stretch the broad tracts of moonland. +For “downward” now means towards the +moon, and away from the distant earth.</p> + +<p>What a strange place we have reached! The weird, +ghastly stillness of all around, and the glaring, dazzling, +cloudless heat, strike us first and most forcibly. +Nothing like this heat have we ever felt on earth. For +the close of the moon’s long day—on this side of its<span class="pagenum" id="Page_66">[Pg 66]</span> +globe—is approaching, and during a whole fortnight +past the sun’s fierce rays have been beating down on +these shelterless plains. Talk of sweltering tropics on +earth! What do you call <i>this</i> heat? Look at the +thermometer: how the quicksilver is rising! Well, that +is not a common thermometer which we have brought +with us. The mercury has stopped—three hundred +degrees above boiling water!</p> + +<p>Not a cloud to be seen overhead; only a sky of inky +blackness, with a blazing sun, and thousands of brilliant +stars, and the dark body of our own earth, large +and motionless, and rimmed with light. Seen from +earth, sun and moon look much the same size; but +seen from the moon, the earth looks thirteen times as +large as our full moon. Not even a little mistiness in +the air to soften this fearful glare! Air! why, there +is no air; at least not enough for any human being to +breathe or feel. If there were air, the sky would be +blue, not black, and the stars would be invisible in +the daytime. It looks strange to see them now shining +beside the sun.</p> + +<p>And then, this deadly stillness! Not a sound, not +a voice, not a murmur of breeze or water. How could +there be? Sound can not be carried without air, and +of air there is none. As for breeze—wind is moving +air, and where we have no air we can have no wind. +As for water—if there ever was any water on the +moon, it has entirely disappeared. We shall walk to +and fro vainly in search of it now. No rivers, no rills, +no torrents in those stern mountain ramparts rising on +every side. All is craggy, motionless, desolate.</p> + +<p>How very, very slowly the sun creeps over the black<span class="pagenum" id="Page_67">[Pg 67]</span> +sky! And no marvel, since a fortnight of earth-time +is here but one day, answering to twelve hours upon +earth. Can not we find shelter somewhere from this +blazing heat? Yonder tall rock will do, casting a sharp +shadow of intense blackness. We never saw such +shadows upon earth. There the atmosphere so breaks +and bends and scatters about the light, that outlines +of shadows are soft and hazy, even the clearest and +darkest of them, compared with this.</p> + +<p>When will the sun go down? But he is well worth +looking at meanwhile. How magnificent he appears, +with his pure radiant photosphere, fringed by a sierra +of dazzling pink and white, orange and gold, purple +and blue. For here no atmosphere lies between to +blend all into yellow-white brightness. And how +plainly stand out those prominences or tongues of +tinted flame, not merely rose-colored, as seen from +earth, but matching the sierra in varying hues; while +beyond spreads a gorgeous belt of pink and green, +bounded by lines and streams of delicate white light, +reaching far and dying slowly out against the jet background. +The black spots on the face of the sun are +very distinct, and so also are the brilliant faculæ.</p> + +<p>We must take a look around us now at moonland, +and not only sit gazing at the sun, though such a sky +may well enchain attention. How unlike our earthly +landscapes! No sea, no rivers, no lakes, no streams, +no brooks, no trees, bushes, plants, grass, or flowers; +no wind or breeze; no cloud or mist or thought of possible +rain; no sound of bird or insect, of rustling +leaves or trickling water. Nothing but burning, steadfast, +changeless glare, contrasting with inky shadows;<span class="pagenum" id="Page_68">[Pg 68]</span> +sun and earth and stars in a black heaven above; +silent, desolate mountains and plains below.</p> + +<p>For though we stand here upon a rough plain, this +moon is a mountainous world. Ranges of rugged +hills stretch away in the distance, with valleys lying +between—not soft, green, sloping, earthly valleys, but +steep gorges and precipitous hollows, all white dazzle +and deep shade.</p> + +<p>But the mountains do not commonly lie in long +ranges, as on earth. The surface of the moon seems +to be dented with strange round pits, or craters, of +every imaginable size. We had a bird’s-eye view of +them as we descended at the end of our long journey +moonward. In many parts the ground appears to be +quite honeycombed with them. Here are small ones +near at hand, and larger ones in the distance. The +smaller craters are surrounded by steep ramparts of +rock, the larger ones by circular mountain-ranges. We +have nothing quite like them on earth.</p> + +<p>Are they volcanoes? So it would seem; only no +life, no fire, no action, remain now. All is dead, +motionless, still. Is this verily a blasted world? Has +it fallen under the breath of Almighty wrath, coming +out scorched and seared? Is it simply passing +through a certain burnt-out, chilled phase of existence, +through which other planets also pass, or will pass, at +some stage of their career? Who can tell?</p> + +<p>We will move onward, and look more closely at +that towering mass of rugged rocks, beyond which the +sun will by and by go down. Long jetty shadows lie +from them in this direction. No wonder astronomers +on earth can through their telescopes plainly see these<span class="pagenum" id="Page_69">[Pg 69]</span> +black shadows contrasting with the glaring brightness +on the other side.</p> + +<p>A “mass of rocks” I have said; but as, with our +powers of rapid movement, we draw near, we find a +range of craggy mountains sweeping round in a vast +circle. Such a height in Switzerland would demand +many hours of hard climbing. But on this small +globe attraction +is a very different +matter from +what it is on +earth; our weight +is so lessened +that we can leap +the height of a +tall house without +the smallest +difficulty. No +chamois ever +sprang from +peak to peak in +his native Switzerland with such amazing lightness as +that with which we now ascend these mighty rocks.</p> + +<div class="figright" id="f9"> +<img src="images/fig9.jpg" alt="crater"> +<p class="caption">ONE FORM OF LUNAR CRATER.</p> +</div> + +<p>Ha! what a depth on the other side! We stand +looking down into one of the monster craters of the +moon. A sheer descent of at least eleven thousand +feet would land us at the bottom. Why, Mont Blanc +itself is only about fifteen thousand feet in height. +And what a crater! Fifty-six miles across in a straight +line, from here to the other side, with these lofty +rugged battlements circling round, while from the +center of the rough plain below a sharp, cone-shaped<span class="pagenum" id="Page_70">[Pg 70]</span> +mountain rises to about a quarter of the height of the +surrounding range.</p> + +<p>It is a grand sight; peak piled upon peak, crag upon +crag, sharp rifts or valleys breaking here and there the +line of the narrow, uplifted ledge; all wrapped in silent +and desolate calm. There are many such craters as +this on the moon, and some much larger.</p> + +<p>The sun slowly nears his setting, and sinks behind +the opposite range. How we shiver! The last ray of +sunlight has gone and already the ground is pouring +out its heat into space, unchecked by the presence of +air or clouds. The change takes place with marvelous +quickness. A deadly chill creeps over all around. A +whole fortnight of earth-time must pass before the +sun’s rays will again touch this spot. Verily the contrasts +of climate in the moon, during the twelve long +days and nights which make up her year, are startling +to human notions.</p> + +<p>But though the sun is gone we are not in darkness. +The stars shine with dazzling brightness, and the huge +body of the earth, always seeming to hang motionless +at one fixed point in the sky, gives brilliant light, +though at present only half her face is lit up and half +is in shadow. Still her shape is plainly to be seen, +for she has ever round her a ring of light, caused by +the gathered shining of stars as they pass behind her +thick atmosphere. She covers a space on the sky +more than a dozen times as large as that covered by +the full moon in our sky.</p> + +<div class="figcenter" id="f10"> +<img src="images/fig10.jpg" alt="earth"> +<p class="caption">THE EARTH AS SEEN FROM THE MOON.</p> +</div> + +<p>It would be worth while to stay here and watch the +half-earth grow into magnificent full-earth. But the +cold is becoming fearful—too intense for even the +<span class="pagenum" id="Page_72">[Pg 72]</span>imagination to endure longer. What must be the state +of things on the other side of the moon, where there +is no bright earth-light to take the place of the sun’s +shining, during the long two weeks’ night of awful +chill and darkness?</p> + +<p>It seems probable that a building on the moon +would remain for century after century just as it was +left by the builders. There need be no glass in the +windows, for there is no wind and no rain to keep +out. There need not be fireplaces in the rooms, for +fuel can not burn without air. Dwellers in a city in +the moon would find that no dust can rise, no odors +be perceived, no sounds be heard. Man is a creature +adapted for life in circumstances which are very narrowly +limited. A few degrees of temperature, more +or less; a slight variation in the composition of air, +the precise suitability of food, make all the difference +between health and sickness, between life and death. +Looking beyond the moon, into the length and breadth +of the universe, we find countless celestial globes, with +every conceivable variety of temperature and of constitution. +Amid this vast number of worlds with +which space teems, are there any inhabited by living +beings? To this great question science can make no +response save this: We can not tell.</p> + +<p>Time for us to wend our way homewards from this +desolate hundred-fold arctic scene. We have more to +learn by and by about our friend and companion. +For the present—enough.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_73">[Pg 73]</span></p> + +<h2 class="nobreak" id="c7">CHAPTER VII.</h2> +</div> + +<p class="c sp">VISITORS.</p> + + +<p><span class="smcap large">We</span> come next to the very largest members of our +Solar System.</p> + +<p>From time to time in past days—and days not +very long past either—people were startled by the +sight of a long-tailed star, moving quickly across the +sky, called a comet. We see such long-tailed stars +still, now and then; but their appearance no longer +startles us.</p> + +<p>It is hardly surprising, however, that fears were +once felt. The great size and brilliancy of some of +these comets naturally caused large ideas to be held +as to their weight, and the general uncertainty about +their movements naturally added to the mysterious +notions afloat with respect to their power of doing +harm.</p> + +<p>A collision between the earth and a comet seemed +no unlikely event; and if it happened—what then? +Why, then, of course, the earth would be overpowered, +crushed, burnt up, destroyed. So convinced were +many on this point that the sight of a comet and the +dread of the coming “end of the world” were fast +bound together in their minds.</p> + +<p>Even when astronomers began to understand the +paths of some of the comets, and to foretell their return +at certain dates, the old fear was not quickly laid +to rest. So late as the beginning of the present century,<span class="pagenum" id="Page_74">[Pg 74]</span> +astronomers having told of an approaching +comet, other people added the tidings of an approaching +collision. “If a collision, then the end of the +world,” was the cry; and one worthy family, living +and keeping a shop in a well-known town on the +south coast of England, packed up and fled to America—doubtless +under full belief that the destruction +of the Old World would not include the destruction +of the New.</p> + +<p>The nature of these singular bodies is somewhat +better known in the present day; yet even now, among +all the members of the Solar System, they are perhaps +the ones about which we have most to learn. The +nucleus, or bright and star-like spot, which, with the +surrounding coma or “hair,” we sometimes call the +“head” of the comet, is the densest and heaviest part +of the whole. The comets are of immense size, sometimes +actually filling more space than the sun himself, +and their tails stream often for millions of miles +behind them; nevertheless, they appear to be among +the lightest of the members of the Solar System.</p> + +<p>This excessive lightness greatly lessens the comet’s +power of harm-doing. In the rebound from all the +old exaggerated fears, men laughed at the notion of +so light and delicate a substance working any injury +whatever, and even declared that a collision might +take place without people on earth being aware of +the fact. It is now felt that we really know too little +about the nature of the said substance to be able to +say what might or might not be the result of a collision. +A certain amount of injury to the surface of +the earth might possibly take place. But of the<span class="pagenum" id="Page_75">[Pg 75]</span> +“end of the world,” as likely to be brought about +by any comet in existence, we may safely banish +all idea.</p> + +<p>The word “comet” means “a hairy body,” the +name having been given from the hairy appearance +of the light around the nucleus. About seventeen +hundred different comets have been seen at different +times by men—some large, some small; some visible +to the naked eye, but most of them only visible through +telescopes. These hundreds are, there is no doubt, but +a very small number out of the myriads ranging through +the heavens.</p> + +<p>If you were seated in a little boat in mid-ocean, +counting the number of fishes which in one hour +passed near enough in the clear water for your sight +to reach them, you might fairly conclude, even if you +did not know the fact, that for every single fish which +you could see, there were tens of thousands which you +could not see.</p> + +<p>Reasoning thus about the comets, as we watch +them from our earth-boat in the ocean of space, we +feel little doubt that for each one which we can see, +millions pass to and fro beyond reach of our vision. +Indeed, so long ago as the days of Kepler, that great +astronomer gave it as his belief that the comets in +the Solar System, large and small, were as plentiful +as the fishes in the sea. And all that modern astronomers +can discover only tends to strengthen this +view.</p> + +<p>Why should the comets be called “visitors?” I +call them so simply because many of them <i>are</i> visitors. +Some, it is true, belong to the Solar System. But<span class="pagenum" id="Page_76">[Pg 76]</span> +even in their case, strong doubts are felt whether they +were not once visitors from a distance, caught in the +first instance by the attraction of one of the larger +planets, and retained thenceforward, for a time at least, +by the strong attraction of the sun.</p> + +<div class="figcenter" id="f11"> +<img src="images/fig11.jpg" alt="tail"> +<p class="caption">PASSAGE OF THE EARTH AND THE MOON THROUGH THE TAIL OF A<br> +COMET.</p> +</div> + +<p>Every comet, like every planet, has his own orbit +or pathway in the heavens, though the kind of orbit +varies with different comets. There are, first, those +comets which travel round and round the sun in +“closed orbits”—that is, in a ring with joined ends. +Only the ring is always oval, not round. There are, +secondly, those which travel in an orbit which <i>may</i> be +closed; but if so, the oval is so long and narrow, and +the farther closed end is at so great a distance, that +we can not speak certainly. There are, thirdly, those +which decidedly are mere visitors. They come from +the far-off star-depths, flash once with their brilliant +trains of light through our busy Solar System, causing<span class="pagenum" id="Page_77">[Pg 77]</span> +some little excitement by the way, and go off in another +direction, never to return.</p> + +<p>Only a small part of the orbits of these comets can +be seen from earth; but by careful attention astronomers +learn something of the shape of the curve in +which they travel. It is in that way possible to calculate, +sometimes certainly, and sometimes uncertainly, +whether a comet may be expected to return, or +whether we have seen him for the first and the last +time. By looking at <i>part</i> of a curve, the rest of +which is hidden from us, we are able to judge +whether that part belongs to a circle or an oval, or +whether the two ends pass away in different directions, +and do not join.</p> + +<p>The comets, whether members of our family circle +or visitors from a distance, are altogether very perplexing. +They are often extremely large, yet they are always +extremely light. They reflect the sun’s brightness +like a planet, yet in some measure they seem to +shine by their own light, like a star. They obey the +attraction of the sun, yet he appears to have a singular +power of driving the comets’ tails away from +himself.</p> + +<p>For, however rapidly the comet may be rushing +round the sun, and however long the tail may be, it is +almost always found to stream in an opposite direction +from the sun. An exception to this rule was seen in +the case of a certain comet with two tails, one of +which did actually point towards the sun; but the inner +tail may have been only a “jet” of unusual length, +like in kind to the smaller jets often thus poured out +from the nucleus.</p> + +<p><span class="pagenum" id="Page_78">[Pg 78]</span></p> + +<p>Very curious changes take place in comets as they +journey, especially as they come near the sun. One +was seen in the course of a few days to lose all his +hair, and also his tail. Another was seen to break +into two pieces, both of which pieces at last disappeared. +Sometimes the one tail divides into two tails.</p> + +<p>Traveling, as the comets do, from intense cold into +burning heat, they are very much affected by the violent +change of climate. For the paths of the comets +are such long ovals, or ellipses, that, while they approach +the sun very closely in one part of their “year,” +they travel to enormous distances in the other part.</p> + +<p>“Halley’s Comet,” which takes seventy-six of our +years to journey round the sun, comes nearer to him +than Venus, and goes farther away from him than +Neptune. As this comet draws gradually closer, he +has to make up for the added pull of the sun’s increasing +attraction by rushing onward with greater +and greater rapidity, till he whirls madly past the sun, +and then, with slowly slackening speed, journeys farther +and farther away, creeps at length lazily round +the farther end of his orbit in the chill, dark, neighborhood +of Neptune, and once more travels towards +the sun with growing haste.</p> + +<p>“Encke’s Comet” has a year of only three and a +half of our years, so he may be said to live quite in +our midst. But many comets travel much farther +away than the one named after Halley. It is calculated +of some that, if they ever return at all, it can not +be for many hundreds of years.</p> + +<div class="figcenter" id="f12"> +<img src="images/fig12.jpg" alt="comet"> +<p class="caption">PASSAGE OF THE COMET OF 1843 CLOSE TO THE SUN (FEBRUARY<br> +27TH, 10 HOURS, 29 MINUTES.)</p> +</div> + +<p>“Newton’s Comet,” seen about two centuries ago, +has a journey to perform of such length that he is<span class="pagenum" id="Page_79">[Pg 79]</span> +not expected again to appear for several thousand +years. Yet, at the nearest point in his orbit, he approached +the sun so closely, that the heat which he +endured was about two thousand times that of red-hot +iron. Changes were seen to be taking place in +his shape, as he drew near to the sun, and disappeared. +Four days he was hidden in the sun’s rays. He vanished, +with a tail streaming millions of miles behind<span class="pagenum" id="Page_80">[Pg 80]</span> +him. He made his appearance again with a tail +streaming millions of miles in front of him. But how +this wonderful movement took place is beyond man’s +power to explain.</p> + +<p>The comet of 1843 was one of the most attractive +seen during the present century. It was first observed +in March, and it appeared with a suddenness which had +quite a startling effect. It was an imposing object in +the southern regions. The comet was seen in Italy +on the 28th of February; at Washington, on the 6th +of March; at Oporto, on the 14th; but owing to unfavorable +weather, it was not visible in England, or any +of the northern countries of Europe, previous to the +17th. A little after sunset on that day the tail was +observed in the western sky, but the head had already +sunk below the horizon. The whole of the comet appeared +on the following evenings for a short time, for +it was traveling away from the sun with great velocity, +having doubled the solar orb before it became +visible; and about the beginning of April it finally +disappeared.</p> + +<p>The appearance of this startling stranger, as observed +at Washington, is thus described by Lieutenant +Maury, of the Hydrographical Office in that city: +“On Monday morning, March 6th, our attention was +called to a paragraph in the newspapers, stating that +a comet was visible near the sun at midday with the +naked eye. The sky was clear; but not being able to +discover any thing with the unassisted eye, recourse +was had to the telescope, but with no better success. +About sunset in the evening, the examination was renewed +with great diligence, but to no purpose. The<span class="pagenum" id="Page_81">[Pg 81]</span> +last faint streak of day gilded the west; beautiful +and delicate fleeces of cloud curtained the bed of +the sun; the upper sky was studded with stars, +and all hopes of seeing the comet that evening had +vanished. Soon after we had retired, the officer of +the watch announced its appearance in the west. The +phenomenon was sublime and beautiful. The needle +was greatly agitated, and a strongly marked pencil of +light was streaming up from the path of the sun in +an oblique direction to the southward and eastward; +its edges were parallel. It was 30° long. Stars +could be seen twinkling through it, and no doubt +was at first entertained that this was the tail of the +comet.”</p> + +<p>The tail, as seen in northerly countries, spread over +an arc of the heavens of about 40°; but in southern +latitudes it extended to from 60° to 70°. It had an absolute +length of two hundred millions of miles; so +that, had it been coiled around the earth like a serpent, +it would have girdled it eight thousand times at the +equator. This comet approached still nearer the sun +than that of Newton, and must therefore have been +exposed to a heat of greater intensity. Its center is +computed to have been within a hundred thousand +miles of the solar surface; and according to Sir John +Herschel’s calculations, it was then exposed to a heat +equal to that which would be received by an equal +portion of the earth’s surface, if it were subject to the +influence of forty-seven thousand suns, placed at the +common distance of the actual sun. It is difficult to +conceive how a flimsy substance in such circumstances +could escape being entirely dissipated. But such was<span class="pagenum" id="Page_82">[Pg 82]</span> +its velocity that it wheeled round the sun in less than +two hours.</p> + +<p>The general question of the probability and the +consequences of a collision with a comet may be legitimately +entertained. With reference to the first point, +it can not be denied that collision is possible; but, at +the same time, it is so extremely improbable that it +may be safely dismissed from apprehension. The fact +of such an event not having been experienced in the +known course of terrestrial history is surely some +guarantee against its occurrence. Another may be +found in the small volume of the earth and of comets +when compared with the immensity of space in which +they move. According to the well-understood principles +of probabilities, Arago has calculated that, upon +the appearance of a new comet, the odds are as 281,000,000 +to 1, that it will not strike against our globe. +But even supposing collision to occur, all that we +know of the constitution of comets justifies the conclusion +that the encounter would involve no terrestrial +convulsion, nor any result incompatible with full security +to life and happiness.</p> + +<p>So much for the largest members of our circle—largest, +though lightest; members some, visitors others. +Now we turn to the smallest.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_83">[Pg 83]</span></p> + +<h2 class="nobreak" id="c8">CHAPTER VIII.</h2> +</div> + +<p class="c sp">LITTLE SERVANTS.</p> + + +<p><span class="smcap large">If</span> you walk out any night after dark, and watch +the bright stars shining in a clear sky—shining as +they have done for ages past—you will probably see, +now and then, a bright point of light suddenly appear, +dart along a little distance, and as suddenly vanish. +That which you have seen was not the beginning of +a story, but in ninety-nine cases out of a hundred +it was the end of a story. The little shooting-star +was in existence long before you saw him, whirling +through space with millions of little companions. But +he has left them all, and dropped to earth. He is a +shooting-star no longer.</p> + +<p>If such a journey to the moon as the one described +two chapters back were indeed possible, the voyage +aloft would hardly be so easily and safely performed +as is there taken for granted. Putting aside the +thought of other difficulties, such as lack of conveyance +and lack of air, there would be the danger of +passing through a very considerable storm of missiles—a +kind of “celestial cannonade”—which, to say +the least, would prove very far from agreeable.</p> + +<p>These “starlets” and “meteor planets,” as they +have been called, are not visible in a normal condition, +because of their minuteness. But on entering our atmosphere +they are rendered luminous, owing to the +heat evolved by the sudden and violent compression<span class="pagenum" id="Page_84">[Pg 84]</span> +of the air in front of the moving body. According to +this view, shooting-stars, which simply dart across the +heavens, may be regarded as coming within the limits +of the atmosphere, and carried out of it again, by their +immense velocity, passing on in space. Meteoric +showers may result from an encounter with a group +of these bodies, while aërolites are those which come +so far within the sphere of the earth’s attraction as to +fall to its surface. More than two thousand years ago +the Greeks venerated a famous stone which fell from +the heavens on the river Ægos.</p> + +<div class="figcenter" id="f13"> +<img src="images/fig13.jpg" alt="meteor"> +<p class="caption">METEOR EMERGING FROM BEHIND A CLOUD (NOV. 23, 1877).</p> +</div> + +<p>It will scarcely be believed what numbers of these +shooting-stars or meteorites constantly fall to the earth. +As she travels on her orbit, hurrying along at the rate +of nineteen miles each second, she meets them by<span class="pagenum" id="Page_85">[Pg 85]</span> +tens of thousands. They too, like the earth, are journeying +round the great center of our family. But +they are so tiny, and the earth by comparison is so +immense, that her strong attraction overpowers one +after another, drags it from its pathway, and draws it +to herself.</p> + +<p>And then it falls, flashing like a bright star across +the sky, and the little meteorite has come to his end. +His myriads of companions, hastening still along their +heavenly track—for the meteorites seem to travel commonly +in vast flocks or companies—might, had they +sense, mourn in vain for the lost members of their +family.</p> + +<p>Any one taking the trouble to watch carefully some +portion of the sky after dark, may expect to see each +hour about four to eight of these shooting-stars—except +in the months of August and November, when +the number is much larger. About six in an hour +does not sound a great deal. But that merely means +that there have been six in one direction, and near +enough for you to see. Somebody else, watching, +may have seen six in another direction; and somebody +else, a few miles away, may have seen six more. +It is calculated that, in the course of every twenty-four +hours, about four hundred millions of meteorites +fall to earth, including those visible only through +telescopes.</p> + +<p>This is rather startling. What if you or I should +some day be struck by one of these solid, hard little +bodies, darting as they do towards earth with speed +swifter than that of a cannon-ball? True, they are +not really stars, neither are they really planets. But<span class="pagenum" id="Page_86">[Pg 86]</span> +they are, to say the least, often much larger than a +cannon-ball, and a cannon-ball can destroy life.</p> + +<p>Four hundred millions every twenty-four hours! +Does it not seem singular that we do not see them +constantly dropping to the ground? The truth is, we +<i>should</i> see them, and feel them too, and dire would +be the danger to human life, but for a certain protecting +something folded round this earth of ours to +ward off the peril. That “something” is the earth’s +atmosphere. But for the thick, soft, strong, elastic +air through which the meteorites have to pass, they +would fall with fearful violence, often doing terrible +mischief. As it is, we are guarded. The shooting-star, +drawn by the earth’s attraction, drops into her +atmosphere, darting with tremendous speed. In consequence +of this speed and the resistance of the air, +it catches fire. That is when we first see it. The +meteorites are believed to appear at a height of about +seventy miles, and to disappear at a height of about +fifty miles. So that, in one instant’s flash, the shooting-star +has traveled some twenty miles toward us. +Then the light goes out. The little meteorite is burnt. +It falls to earth still; but only as fine dust, sinking +harmlessly downward.</p> + +<p>The meteorites do not always vanish so quickly. +Now and then a larger one—too large to be rapidly +burnt—does actually reach the ground. If any man +were struck by such a stone he would undoubtedly be +killed.</p> + +<p>When meteorites thus fall to earth they are usually +called <i>aërolites</i>. Some are found no bigger than a +man’s fist, while others much exceed this size. There<span class="pagenum" id="Page_87">[Pg 87]</span> +is one, kept carefully in the British Museum, which +weighs three tons and a half; and we hear of another, +lying in South America, between seven and eight feet +in length. Such a sky-visitant would be very unwelcome +in any of our towns.</p> + +<p>We must remember that, whatever size an aërolite +may be when it reaches the earth, it must have been +far greater when journeying round the sun, since a +good part of it has been burnt away during its rush +downward through the earth’s atmosphere.</p> + +<p>Meteors, or bolides, or fireballs, are of much the +same nature as meteorites; but they are larger, longer +to be seen, and slower in movement. Also, it is not +uncommon for them to burst with a loud explosion. +Early in the present century such a meteor visited +Normandy. It exploded with a noise like the roll of +musketry, scattering thousands of hot stones over a +distance of several miles. A great number of them +were collected, still smoking. The largest of these +stones weighed no less than twenty pounds. Happily +no one seems to have been injured. Other such +falls have taken place from time to time. Sometimes +bright, slowly-moving meteors have been seen, looking +as large as the moon.</p> + +<p>A remarkable fireball appeared in England on +November 6, 1869. This fireball was extensively +seen from different parts of the island, and by combining +and comparing these observations, we obtain +accurate information as to the height of the object +and the velocity with which it traveled. It appears +that this meteor commenced to be visible at a point +ninety miles above Frome, in Somersetshire, and that<span class="pagenum" id="Page_88">[Pg 88]</span> +it disappeared at a point twenty-seven miles over the +sea, near St. Ives, in Cornwall. The whole length of +its course was about 170 miles, which was performed +in a period of five seconds, thus giving an average velocity +of thirty-four miles a second. A remarkable +feature in the appearance which this fireball presented +was the long, persistent streak of luminous +cloud, about fifty miles long and four miles wide, +which remained in sight for fully fifty minutes. We +have in this example an illustration of the chief features +of the phenomena of a shooting-star presented +on a very grand scale. It is, however, to be observed +that the persistent luminous streak is not a universal, +nor, indeed, a very common characteristic of a shooting-star.</p> + +<p>If we may liken comets to the <i>fishes</i> of the Solar +System—and in their number, their speed, their varying +sizes, their diverse motions, they may be fairly so +likened—we may perhaps speak of the meteorites as +the <i>animalcula</i> of the Solar System. For, in comparison +with the planets, they are, in the matter of +size, as the animalcula of our ponds in comparison +with human beings. In point of numbers they are +countless.</p> + +<p>Take a single drop of water from some long-stagnant +pond, and place it under a powerful microscope. +You will find it to be full of life, teeming with tiny animals, +darting briskly to and fro. The drop of water +is in itself a world of living creatures, though the +naked eye of man could never discover their existence. +So with the meteorites. There is good reason to believe +that the Solar System fairly teems with them.<span class="pagenum" id="Page_89">[Pg 89]</span> +We talk of “wide gaps of empty space,” between the +planets; but how do we know that there is any such +thing as empty space to be found throughout all the +sun’s domain?</p> + +<p>Not only are the meteorites themselves countless, a +matter easily realized, but the families or systems of +meteorites appear to be countless also. They, like +the systems of Jupiter and Saturn, are each a family +within a family—a part of the Solar System, and yet +a complete system by themselves. Each circles round +the sun, and each consists of millions of tiny meteorites. +When I say “tiny,” I mean it of course only by +comparison with other heavenly bodies. Many among +them may possibly be hundreds of feet and even more +in diameter, but the greater proportion appear to be +much smaller. It is not impossible that multitudes +beyond imagination exist, so small in size that it is +impossible we should ever see them, since their +dying flash in the upper regions of our atmosphere +would be too faint to reach our sight.</p> + +<p>The earth, traveling on her narrow orbit round the +sun, crosses the track of about one hundred of these +systems, or rings. Sometimes she merely touches the +edge of a ring, and sometimes she goes into the very +thick of a dense shower of meteorites. Twice every +year, for instance, on the 10th of August and the 11th +of November, the earth passes through such a ring, +and very many falling stars may be seen on those +nights. Numbers of little meteorites, dragged from +their orbits and entangled in the earth’s atmosphere, +like a fly caught in a spider’s web, give their dying +flash, and vanish. It used to be supposed that the<span class="pagenum" id="Page_90">[Pg 90]</span> +August and November meteorites belonged to one +single system; but now they are believed to be two +entirely distinct systems.</p> + +<div class="figcenter" id="f14"> +<img src="images/fig14.jpg" alt="shower"> +<p class="caption">THE GREAT SHOWER OF SHOOTING-STARS, NOVEMBER 27, 1872.</p> +</div> + +<p>The comet discovered on February 27, 1827, by +Biela, and ten days later at Marseilles by Gambart, +who recognized that it was the same as that of 1772 +and 1805, returned six and a half years later, in 1832. +In fact it crossed, as we have seen, the plane of the +terrestrial orbit at the respectable distance of fifty +millions of miles from the earth; but if there was +any danger in this meeting, it was rather for it than +for us; for it was certainly strongly disturbed in its +course. It returned in 1839, but under conditions +too unfavorable to enable it to be observed—in the +month of July, in the long days, and too near the +sun. It was seen again in 1845, on November<span class="pagenum" id="Page_91">[Pg 91]</span> +25th, near the place assigned to it by calculation, and +its course was duly followed. Everything went on to +the general satisfaction, when—unexpected spectacle!—on +January 13, 1846, <i>the comet split into two</i>! What +had passed in its bosom? Why this separation? What +was the cause of such a celestial cataclysm? We do +not know; but the fact is, that instead of one comet, +two were henceforth seen, which continued to move +in space like two twin-sisters—two veritable comets, +each having its nucleus, its head, its coma, and its +tail, slowly separating from each other. On February +10th there was already a hundred and fifty thousand +miles of space between the two. They would seem, +however, to have parted with regret, and during several +days a sort of bridge was seen thrown from one +to the other. The cometary couple, departing from +the earth, soon disappeared in the infinite night.</p> + +<p>They returned within view of the earth in the +month of September, 1852. On the 26th of this +month the twins reappeared, but much farther apart, +separated by an interval of twelve hundred and fifty +thousand miles.</p> + +<p>But this is not the strangest peculiarity which this +curious body presented to the attention of astronomers. +The catastrophe which was observed in 1846 was only +a presage of the fate which awaited it; for now its existence +is merely imagined, the truth being that <i>this +comet is lost</i>. Since 1852 all attempts to find it again +have been unavailing.</p> + +<p>To be lost is interesting, especially for a comet. +But this, doubtless, was not enough; for it reserved +for us a still more complete surprise. Its orbit intersects<span class="pagenum" id="Page_92">[Pg 92]</span> +the terrestrial orbit at a point which the earth +passes on November 27th. Well, nothing more was +thought about it—it was given up as hopeless, when, +on the evening of November 27, 1872, there fell from +the sky a veritable <i>rain of shooting stars</i>. The expression +is not exaggerated. They fell in great flakes. +Lines of fire glided almost vertically in swarms and +showers—here, with dazzling globes of light; there, +with silent explosions, recalling to mind those of rockets; +and this rain lasted from seven o’clock in the +evening till one o’clock next morning, the maximum +being attained about nine o’clock. At the observatory +of the Roman College, 13,892 were counted; at Montcalieri, +33,400; in England a single observer counted +10,579, etc. The total number seen was estimated at +<i>a hundred and sixty thousand</i>. They all came from the +same point of the sky, situated near the beautiful star +Gamma of Andromeda.</p> + +<p>On that evening I happened to be at Rome, in the +quarter of the Villa Medicis, and was favored with a +balcony looking towards the south. This wonderful +rain of stars fell almost before my eyes, so to say, and +I shall never cease regretting not having seen it. +Convalescent from a fever caught in the Pontine +Marshes, I was obliged to go into the house immediately +after the setting of the sun, which on that evening +appeared from the top of the Coliseum to sleep in +a bed of purple and gold. My readers will understand +what disappointment I felt next morning when, on going +to the observatory, Father Secchi informed me of +that event! How had he observed it himself? By +the most fortunate chance: A friend of his, seeing the<span class="pagenum" id="Page_93">[Pg 93]</span> +stars fall, went to him to ask an explanation of such a +phenomenon. It was then half-past seven. The spectacle +had commenced; but it was far from being finished, +and the illustrious astronomer was enabled to +view the marvelous shower of nearly <i>fourteen thousand</i> +meteors.</p> + +<p>This event made a considerable stir in Rome, and +the pope himself did not remain indifferent; for, some +days afterwards, having had the honor of being received +at the Vatican, the first words that Pius IX addressed +to me were these: “Have you seen the shower +of Danaë?” I had admired, some days before in +Rome, some admirable “Danaës,” painted by the +great masters of the Italian school in a manner which +left nothing to be desired; but I had not had the +privilege of finding myself under the cupola of the +sky during this new celestial shower, more beautiful +even than that of Jupiter.</p> + +<p>What was this shower of stars? Evidently—and +this is not doubtful—the encounter with the earth of +myriads of small particles of matter moving in space +along the orbit of Biela’s comet. The comet itself, +if it still existed, would have passed twelve weeks before. +It was not, then, to speak correctly, the comet +itself which we encountered, but perhaps a fraction +of its decomposed parts, which, since the breaking-up +of the comet in 1846, would be dispersed along its +orbit behind the head of the comet.<a id="FNanchor_1" href="#Footnote_1" class="fnanchor">[1]</a></p> + +<div class="footnote"> + +<p><a id="Footnote_1" href="#FNanchor_1" class="label">[1]</a> No doubt can remain of the identity of this swarm of shooting-stars +with the comet of Biela. On November 27, 1885, the +same encounter occurred. A magnificent shower of stars was observed +all over Europe just at the moment when the earth crossed +the comet’s orbit.</p> + +</div> + +<p><span class="pagenum" id="Page_94">[Pg 94]</span></p> + +<p>Once in every thirty-three years we have a grand +display of meteorites in November; tens of thousands +being visible in one single night. The meteorites in +that ring have their “year” of thirty-three earthly +years, and once in the course of that long year our +earth’s orbit carries her deep into their midst. In +this single November ring there are myriads upon +myriads of meteorites, spreading through millions of +miles of space.</p> + +<p>Yet this system is but one among many. There is +no reason whatever to suppose that the streams of meteorites +cluster more thickly about the orbit of the +earth, than in other parts of the Solar System. No +doubt the rest of the planets come across quite as +many. Indeed, the wonderful rings of Saturn are +probably formed entirely of meteorites—millions upon +millions of them whirling round the planet in a regular +orbit-belt, lit up by the rays of the sun. Also it is +believed that the meteorite families cluster more and +more closely in the near neighborhood of the sun, +rushing wildly round him, and falling by millions into +the ocean of flame upon his surface. It has even been +guessed that they may serve in part as fuel to keep up +his mighty furnace heat.</p> + +<p>There is a curious cone-shaped light seen sometimes +in the west after sunset. It is called the “Zodiacal +Light,” and men have often been much puzzled +to account for it. The shining is soft and dim, only +to be seen when the sky is clear, and only to be seen +in the neighborhood of the sun. This, too, <i>may</i> be +caused by reflected light from countless myriads of +meteorites gathering thickly round the sun.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_95">[Pg 95]</span></p> + +<h2 class="nobreak" id="c9">CHAPTER IX.</h2> +</div> + +<p class="c sp">NEIGHBORING FAMILIES.</p> + + +<p><span class="smcap large">We</span> have now to take flight in thought far, far beyond +the outskirts of our little Solar System. Yes, +our <i>great</i> Solar System, with its mighty sun, its +planets, its moons, its comets and meteorites, its +ceaseless motions, its vast distances,—even all this +sinks to littleness beside the wider reaches of space +which now have to be pictured to our minds. For +our sun, in all his greatness, is only a single star—only +one star among other stars—and not by any +means one of the largest of the stars.</p> + +<p>How many stars are there in the sky? Look overhead +some cloudless night, and try to count the brilliant +points of light. “Millions,” you would most +likely give as your idea of their number. Yet you +would be wrong; for you do not really perceive so +many. The stars visible to man’s naked eye have +been mapped and numbered. It is found that from +two to three thousand are, as a rule, the utmost ever +seen at once, even on a favorable night, and with particularly +good sight.</p> + +<p>But what is actually the full number of the stars? +Two or three thousand overhead. Five or six thousand +round the whole world. So much visible to +man’s unaided eyes. Ah, but take a telescope, and +see through it the opening fields of stars beyond stars. +Take a stronger telescope, and note how, as you pierce<span class="pagenum" id="Page_96">[Pg 96]</span> +deeper into space, fresh stars beyond fresh stars shine +faintly in the measureless distance. Take the most +powerful telescope ever made, and again it will be the +same story.</p> + +<p>There has been a chart or map drawn of known +stars in the northern hemisphere—including those +visible in telescopes down to a certain magnitude—containing +over three hundred thousand. But that is +only a part of even what man can see. Sir William +Herschel calculated roughly that the number of stars +within reach of his powerful telescope, round the +whole earth, amounted probably to something like +twenty millions.</p> + +<p>Twenty millions of suns! For that is what it really +means. Twenty millions of radiant, burning, heavenly +bodies—some the same size as our sun; some +larger, perhaps very much larger; some smaller, perhaps +very much smaller; but all <span class="allsmcap">SUNS</span>. And any +number of these suns may have, just like our own, +families of planets traveling round them, enjoying +their light and their heat.</p> + +<p>We talk about stars of the first, second, and other +magnitudes. Stars can be seen without a telescope +as low down as the sixth magnitude; after that they +become invisible to the naked eye. This word “magnitude” +is rather misleading. “Magnitude” means +size, and whatever the real size of the stars may be, +they have to our sight no seeming size at all. So +when we speak of different <i>magnitudes</i>, we really +mean different <i>brightnesses</i>. The brightest stars are +those of the first magnitude, the next brightest those +of the second magnitude, and so on. No doubt many<span class="pagenum" id="Page_97">[Pg 97]</span> +a star of the third or fourth magnitude is really much +larger than many a star of the first or second magnitude, +only being farther away it shines more dimly, or +the higher-magnitude star may in itself possess greater +natural brilliancy.</p> + +<p>Of first-magnitude stars there are altogether about +twenty; of second-magnitude stars about sixty-five; +of third-magnitude stars about two hundred; and so +the numbers increase till of the sixth-magnitude stars +we find more than three thousand. These are all that +can be commonly seen with the naked eye, amounting +to five or six thousand. With telescopes the numbers +rise rapidly to tens of thousands, hundreds of thousands, +and even millions.</p> + +<p>For a long while it was found quite impossible to +measure the distances of the stars. To this day the +distances of not over two dozen, among all those tens +of thousands, have been discovered. The difficulty of +finding out the distance of the sun was as nothing +compared with the difficulty of finding out the distances +of the stars.</p> + +<p>No base-line sufficient for the purpose could for +years be obtained. I must explain slightly what is +meant by a “base-line.” Suppose you were on the +brink of a wide river, which you had no means of +crossing, though you wished to discover its breadth. +Suppose there were on the opposite brink a small +tree, standing alone. As you stood, you would see +the tree seeming to lie against a certain part of the +country beyond. Then, if you moved along your +bank some fifty paces, the tree would seem to lie +against quite a different part of the country beyond.</p> + +<p><span class="pagenum" id="Page_98">[Pg 98]</span></p> + +<p>Now if you had a long piece of string to lay down +along the fifty paces you walked, and if two more +pieces of string were tied, one from each <i>end</i> of the +fifty paces, both meeting at the tree, then the three +pieces of string would make one large triangle, and +the “fifty paces” would be the “base” of your triangle.</p> + +<p>If you could not cross the river, you could not of +course tie strings to the tree. But having found your +<i>base-line</i>, and measured its exact length, and having +also found the shape of the two angles at its two ends, +by noting the seeming change of the tree’s position, +it would then be quite easy to find out the distance +of the tree. The exact manner in which this calculation +is made can hardly be understood without some +slight knowledge of a science called trigonometry. +The tree’s distance being found, the breadth of the river +would be known.</p> + +<p>This mode of measuring distance was found comparatively +easy in the case of the moon. But in the +case of the sun there was more difficulty, on account +of the sun’s greater distance. No base-line of ordinary +length would make the sun seem to change his position +in the sky in the slightest degree. Nor till the +very longest base-line on the earth was tried could the +difficulty be overcome. That base-line is no less than +eight thousand miles long. One man standing in +England looking at the sun, and another man standing +in Australia looking at the sun, have such a base-line +lying between them, straight through the center +of the earth.</p> + +<p>In the case of the stars this plan was found useless.<span class="pagenum" id="Page_99">[Pg 99]</span> +So closely has the sky been mapped out, and so exactly +is the place of each star known, that the tiniest +change would have been at once noticed. Not a star +showed the smallest movement. The eight thousand +miles of the earth’s diameter was a mere point with +regard to them.</p> + +<p>A bright idea came up. Here was our earth traveling +round the sun, in an orbit so wide that in the +middle of summer she is over one hundred and eighty +millions of miles away from where she is in the middle +of winter. Would not that make a magnificent +base-line? Why not observe a star in summer and +observe the same star again in winter, and then calculate +its distance.</p> + +<p>This, too, was done. For a long while in vain! +The stars showed no signs of change, beyond those due +to causes already known. Astronomers persevered, +however, and with close and earnest care and improved +instruments, success at last rewarded their efforts. +A few—only a few, but still a few—of those distant +suns have submitted to the little measuring-line of +earth, and their distance has been roughly calculated.</p> + +<p>Now, what is their distance? Alpha Centauri, the +second star which was attempted with success, is the +nearest of all whose distance we know. You have +heard how far the sun is from the earth. The distance +of Alpha Centauri is <i>two hundred and seventy-five +thousand times as much</i>. Can you picture to yourself +that vast reach of space—a line ninety-three millions +of miles long, repeated over and over again two hundred +and seventy-five thousand times?</p> + +<p>But Alpha Centauri is one of the very nearest.<span class="pagenum" id="Page_100">[Pg 100]</span> +The brilliant Sirius is at least twice as far away. +Others utterly refuse to show the smallest change +of position. It is with them, as had been said, much +the same as if a man were to look at a church-steeple, +twenty miles distant, out of one pane in a +window, and then were to look at it out of the next +pane. With the utmost attention he would find no +change of position in the steeple. And like the base-line +of two glass panes to that steeple, so is the base-line +formed by our whole yearly journey to thousands +of distant stars. We <i>might</i> measure how far away +they are, only the longest base-line within our reach +is too short for our purpose.</p> + +<p>The planet Neptune has a wider orbit than ours. +But even his orbit, seen from the greater number of +the stars, would shrink to a single point. After all, +how useless to talk of two hundred and seventy-five +thousand times ninety-three millions of miles! What +does it mean? We can not grasp the thought.</p> + +<p>Let us look at the matter from another view. Do +you know how fast light travels—this bright light +shining round us all day long? Light, so far as we +know, does not exist everywhere. It travels to and +fro, from the sun to his planets, from the planets to +one another; from the sun to the moon, from the +moon to the earth, and from the earth to the moon +again.</p> + +<p>Light takes time to travel. This sounds singular, +but it is true. Light can not pass from place to place +in no time. Light, journeying through space, is invisible. +Only when it strikes upon something, whether +a solid body or water or air, does it become visible to<span class="pagenum" id="Page_101">[Pg 101]</span> +our eyes. The shining all round us in the day-time +is caused by the sunlight being reflected, not only +from the ground, but from each separate particle of air. +If we had no atmosphere, we should see still the bright +rays falling on the ground, but the sky above would +be black. Yet that black sky would be full of millions +of light-rays, journeying hither and thither from +sun and stars, invisible except where they alight upon +something.</p> + +<p>The speed of light is far beyond that of an express +train, far beyond that of the swiftest planet. In one +tick of the clock, Mercury has rushed onward twenty-nine +miles. In one tick of the clock, storm-flames +upon the surface of the sun will sweep over two or +three hundred miles. But in one tick of the clock a +ray of light flashes through one hundred and eighty-six +thousand three hundred and thirty-seven miles.</p> + +<p>One hundred and eighty-six thousand miles! That +is the same as to say that, during one single instant, +a ray of light can journey a distance equal to about +eight times round and round our whole earth at the +Equator.</p> + +<p>By using this wonderful light-speed as a measurement, +we gain clearer ideas about the distances of the +stars. A ray of light takes more than eight minutes +to pass from the sun to the earth. Look at your watch, +and note the exact time. See the hand moving slowly +through the minutes, and imagine one single ray of +light, which has left the sun when first you looked, +flashing onward and onward through space, one hundred +and eighty-six thousand miles each second. Eight +minutes and a half are over. The ray falls upon your<span class="pagenum" id="Page_102">[Pg 102]</span> +hand. In those few minutes it has journeyed ninety-three +millions of miles.</p> + +<p>So much for the sun’s distance. How about the +stars? Alpha Centauri, a bright star seen in the +southern hemisphere, is one of our nearest neighbors. +Yet each light-gleam which reaches the eye of man +from that star, left Alpha Centauri four years and a +third before. During four years and a third, from the +moment when first it quitted the surface of the blazing +sun, it has flashed ceaselessly onward, one hundred +and eighty-six thousand miles each second, dwindling +down with its bright companion-rays from a glare of +brilliancy to a slender glimmer of light till it reaches +the eye of man. Four years and a third sounds much, +side by side with the eight minutes’ journey from the +sun. Sound would take more than three millions of +years to cross the same abyss. At the constant velocity +of thirty-seven miles an hour, an express-train +starting from the sun Alpha Centauri would not reach +the earth until after an uninterrupted course of nearly +seventy-five millions of years.</p> + +<p>This is our <i>neighbor</i> star. The second, the nearest +after it, is nearly double as far, and is found in +quite another region of space, in the constellation of +Cygnus, the Swan, always visible in our northern +hemisphere. If we wish to understand the relative +situation of our sun and the nearest two, let us take +a celestial globe, and draw a plane through the center +of the globe and through Alpha Centauri and 61 +Cygni. We shall thus have before us the relation +which exists between our position in infinitude and +those of these two suns. The angular distance which<span class="pagenum" id="Page_103">[Pg 103]</span> +separates them on the celestial sphere is 125°. Let +us make this drawing, and we shall discover certain +rather curious particulars. In the first place, these +two nearest stars are in the plane of the Milky Way, +so that we can also represent the Milky Way on our +drawing; again, this celestial river is divided into +two branches, precisely in the positions occupied by +these two nearest stars, the division remaining marked +along the whole interval which separates them. This +drawing shows us, further, that if we wish to trace the +curve of the Milky Way with reference to the distance +of our two stars, it will be nearer to us in the constellation +of the Centaur than in that of the Swan; +and, in fact, it is probable that the stars of that region +of the sky are nearer than those of the opposite region. +Another very curious fact is, that both the +nearest stars are double.</p> + +<p>But look at Sirius, that beautiful star so familiar to +us all. The light which reaches you to-night, left his +surface from nine to ten years ago. Look at the Little +Bear, with the Pole-star shining at the end of his tail. +That ray of soft light quitted the Pole-star some forty +years ago. Almost half a century it has been speeding +onward and ever onward, with ceaseless rapidity, +till its vast journey is so far accomplished that it has +reached the earth. Look at Capella, another fair star +of the first magnitude. The light which reaches you +from her has taken over thirty years to perform its +voyage. Ten, thirty, forty years—at the rate of +186,000 miles per second!</p> + +<p>These stars are among the few whose distance can +be roughly measured. Others lie at incalculable distances<span class="pagenum" id="Page_104">[Pg 104]</span> +beyond. There are stars whose light must, it +is believed, have started hundreds or even thousands +of years before the soft, faint ray at length reaches +the astronomer’s upturned eye through the telescope.</p> + +<p>Look at Capella, how gently and steadily she +shines! You see Capella, not as she is <i>now</i>, but as +she <i>was</i> thirty years ago. Capella may have ceased +to exist meantime. The fires of that mighty sun +may have gone out. If so, we shall by and by learn +the fact—more than thirty years after it happened. +Look at the Pole-star. Is there any Pole-star now? +I can not tell you. I only know there <i>was</i> one, forty +years ago, when that ray of light started on its long +journey. Stars have ceased to shine before now. +What may have happened in those forty years, who +can say? Look at that dim star, shining through a +powerful telescope with faint and glimmering light. +We are told that in all probability the tiny ray left its +home long before the time of Adam.</p> + +<p>There is a strange solemnity in the thought. Hundreds +of years ago—thousands of years ago—some say, +even tens or hundreds of thousands of years ago! It +carries us out of the little present into the unknown +ages of a past eternity.</p> + +<p>If the neighboring stars are placed at tens and +hundreds of trillions of miles from us, it is at quadrillions, +at quintillions of miles that most of the stars +lie which are visible in the sky in telescopic fields. +What suns! what splendors! Their light comes from +such distances! And it is these distant suns which +human pride would like to make revolve round our +atom; and it was for our eyes that ancient theology<span class="pagenum" id="Page_105">[Pg 105]</span> +declared these lights, invisible without a telescope, +were created! No contemplation expands the thought, +elevates the mind, and spreads the wings of the soul +like that of the sidereal immensities illuminated by +the suns of infinitude. We are already learning that +there is in the stellar world a diversity no less great +than that which we noticed in the planetary world. +As in our own Solar System the globes already studied +range from 6 miles in diameter (satellites of Mars) +up to 88,000 miles (Jupiter)—that is to say, in the +proportion of 1 to 14,000—so in the sidereal system +the suns present the most enormous differences of +volume and brightness: 61 Cygni, the stars numbered +2,398 in the catalogue of Lalande, and 9,352 in the +catalogue of Lacaille, and others of the eighth or ninth +magnitude, are incomparably smaller or less luminous +than Sirius, Arcturus, Capella, Canopus, Rigel, and +the other brilliants of the firmament.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_106">[Pg 106]</span></p> + +<h2 class="nobreak" id="c10">CHAPTER X.</h2> +</div> + +<p class="c sp">OUR NEIGHBORS’ MOVEMENTS.</p> + + +<p><span class="smcap large">How high</span>! how distant! how mighty! How little +we know about them, yet how overwhelming the little +we know, and how wonderful that we do know it!</p> + +<p>We have now to consider the movements of these +distant neighbors—first, their seeming movements; +secondly, their real movements.</p> + +<p>I have already spoken about the seeming motions +of the stars as a whole, once believed to be real, and +now known to be only caused by the motions of our +earth. For just as the turning of the earth upon her +axis makes the sun seem to rise every morning in the +east, and to set every evening in the west, so that +same continued turning makes the stars seem to rise +every evening in the east and to set every morning in +the west.</p> + +<p>When we speak of the stars as rising in the east, +we do not mean that they all rise at one point in the +east, but that all rise, more or less, in an easterly direction—northeast, +east, and southeast. So also with +respect to the west. It is to the east and west of the +earth as a whole that they rise and set—not merely to +the east and west of that particular spot on earth +where one man may be standing. All night long fresh +stars are rising, and others are setting, and if it were +not for the veil of light made by the sunshine in our +atmosphere, we should see the same going on all day +long as well.</p> + +<p><span class="pagenum" id="Page_107">[Pg 107]</span></p> + +<p>There are some constellations, or groups of stars, +always visible at night in our northern hemisphere; +and there are some constellations never visible to us, +but only seen by people living in the southern hemisphere—in +Australia, for instance. There are other +constellations which appear in summer and disappear +in winter, or which appear in winter and disappear in +summer. This change is caused by our earth’s journey +round the sun. It is not that the constellations +have altered their place in the heavens with respect +to the other constellations, it is merely that the earth +has so altered its position in the heavens that the +groups of stars which a short time ago were above the +horizon with the sun by day are now above the horizon +without him by night.</p> + +<p>Mention has been a good many times made of the +axis of the earth ending in the North and South Poles. +If this axis were carried straight onward through +space, a long, slender pole passing upwards into the +sky without any bend, from the North Pole in one +direction and from the South Pole in the other,—this +would be the pole of the heavens. The places of the +stars in the sky are counted as “so many degrees” +from the North and South Celestial Poles, just as the +places of towns on earth are counted as “so many +degrees” from the North and South Poles of earth. +There are atlases of the sky made as well as atlases of +the earth.</p> + +<p>The constellation of the Great Bear is known to all +who have ever used their eyes at all to watch the +heavens. Almost equally well known are the two +bright stars in this constellation named the Pointers,<span class="pagenum" id="Page_108">[Pg 108]</span> +because, taken together, they point in nearly a straight +line to a certain important star in the end of the Little +Bear’s tail, not very distant.</p> + +<p>This star, important less from its brightness than +from its position, lies close to that very spot in the +heavens where the celestial North Pole passes. It is +called the Pole-star. Night after night, through the +year, it there remains, all but motionless, never going +below the horizon for us in the northern hemisphere, +or northern half of the earth; never rising above the +horizon for those in the southern hemisphere. It +shines ever softly and steadily in its fixed position. +If you travel further south, the Pole-star sinks downward +towards the horizon. If you travel further +north, the Pole-star rises higher above the horizon. +If you were at the North Pole, you would see the Pole-star +exactly overhead.</p> + +<div class="figcenter" id="f15"> +<img src="images/fig15.jpg" alt="bear"> +<p class="caption">CONSTELLATION OF THE GREAT BEAR.</p> +</div> + +<p>Very near the Pole-star is the constellation of the +Great Bear, with Cassiopeia nearly opposite on the +other side of the Little Bear, and other groups between +the two, completing the circle. These constellations +do not, to us who live in the northern +hemisphere, rise or set; for they simply move in a<span class="pagenum" id="Page_109">[Pg 109]</span> +circle round and round the Pole-star, never going below +the horizon. All day and all night long this +circling movement continues, though only visible at +night. It is caused entirely by the earth’s own motion +on her axis.</p> + +<div class="figcenter" id="f16"> +<img src="images/fig16.jpg" alt="bear"> +<p class="caption">THE GREAT BEAR 50,000 YEARS AGO.</p> +</div> + +<div class="figcenter1" id="f17"> +<img src="images/fig17.jpg" alt="bear"> +<p class="caption">THE GREAT BEAR 50,000 YEARS HENCE.</p> +</div> + +<p>Lower down, or rather further off from the Pole-star, +comes another ring of constellations. These in +just the same manner appear to travel round and +round the Pole-star. But being further away, each +dips in turn below the horizon—or, as we call it, each +sets and rises again. And by the time we come to +yet another circle of leading constellations, we reach<span class="pagenum" id="Page_110">[Pg 110]</span> +those which are so far affected by the earth’s yearly +journey as to be only visible through certain months, +and to be hidden during other months.</p> + +<div class="figcenter" id="f18"> +<img src="images/fig18.jpg" alt="orion"> +<p class="caption">CONSTELLATION OF ORION, AS IT APPEARS NOW.</p> +</div> + +<p>If we could stand exactly at the North Pole, during +part of its six months’ night, we should see the Pole-star +just overhead, and all the constellations circling +round it once in every twenty-four hours. Those +nearest would move slowly, in a small ring. Those +furthest, and lowest down, would in the same length +of time sweep round the whole horizon. But the +stars would not there seem to rise or set. If we were +standing at the South Pole, we should see exactly the +same kind of seeming movement, only with altogether +a different set of stars. If we were standing on the +Equator at night, we should see the rising and setting +very plainly. The whole mass of stars would +appear to rise regularly and evenly in an easterly direction, +to pass steadily across the sky, each taking<span class="pagenum" id="Page_111">[Pg 111]</span> +its own straightforward path, and to set in a westerly +direction.</p> + +<p>We who are placed midway between the Pole and +the Equator, see a mixture of these two motions. Some +stars seem to circle round and round, as all would do +if we stood at the North Pole. Some stars seem to +rise and set, as all would do if we stood at the Equator. +So much for the seeming +movements of the stars.</p> + +<p>But now, about their +real movements. Are the +stars fixed, or are they not? +These seeming daily and +yearly motions do not affect +the question, being +merely caused by our own +motions. Trees and hedges +may appear to move as +we rush past them in a +train, yet they are really +fixed.</p> + +<div class="figright" id="f19"> +<img src="images/fig19.jpg" alt="orion"> +<p class="caption">CONSTELLATION OF ORION 50,000<br> +YEARS FROM NOW.</p> +</div> + +<p>During a long while, +after it was found out that +the quick, daily movements of all the stars in company +were merely apparent, men believed that they +really had no “proper motions”—that is, no movements +of their own. For century after century the +constellations remain the same. Hundreds of years +ago the seven chief stars of the Great Bear shone in +company as they shine now. Who could suppose that +each one of those seven stars is hurrying on its path +through space with a speed exceeding far that of the<span class="pagenum" id="Page_112">[Pg 112]</span> +swiftest express-train? Yet so it is. Hundreds of +years ago the grand group of Orion, with belt and +sword, gleamed brilliantly night by night as it gleams +in these days; and Cassiopeia had her W form, and +Hercules and Draco and Andromeda were shaped as +they are shaped still. Who would imagine that through +those hundreds of years each star of these different +constellations was hastening with more or less of speed +along its heavenly road? Yet so it is.</p> + +<p>Cases have been decisively ascertained of stars +changing their places among the other stars by a slow +and gradual motion. Three of the most conspicuous +of them—Sirius, Arcturus, and Aldebaran—have been +proved, by the comparison of modern with some ancient +observations, to have experienced a change of place +to the southward, to the extent of more than the breadth +of the moon in all the three. And during the period +of accurate modern measurement, other instances have +been ascertained of steady change of place by the +effect of proper motion.</p> + +<p>But if the stars are thus rapidly moving in all directions, +how is it that we do not <i>see</i> them move? How +is it that, night after night, year after year, century +after century, even thousand years after thousand +years, the shapes of the constellations remain unaltered?</p> + +<p>Suppose you and I were standing on the seashore +together, watching the movements of scores of +sea-craft, little boats and large boats, steamers, yachts, +and ships. Suppose we stood through a full quarter +of an hour looking on. Some might move, it is true, +very slowly; yet their movements in every case would<span class="pagenum" id="Page_113">[Pg 113]</span> +plainly be seen. There could be no possibility of +mistaking the fact, or of supposing them to be +“fixed.” Just so we see the nearer planets move. +Little danger of our supposing them to be “fixed +stars.”</p> + +<p>In the matter of the stars themselves, we must +carry our illustration further. Come with me up to +the top of that lofty hill on the border of the sea, and +let us look from the cliff. We see still the movements +among boats and smacks, yachts and steamers, +only the increased distance makes the movements +seem slower. But our view is widened. Look on the +far horizon and see three distant dots, which we know +to be ships—one and two close together, and a third a +little way off, making a small constellation of vessels. +Watch them steadily for a quarter of an hour. You +will detect no movement, no increased distance or +nearness between any two of the three. The group +remains unchanged.</p> + +<p>Are they really moving? Of course they are, more +or less rapidly, probably with differing speed and in +different directions. But at so great a distance, one +quarter of an hour is not long enough for their motions +to become visible to the naked eye. If we +could watch longer—say, for two or three hours—ah, +that would make all the difference! If only we could +watch longer! But the hundreds, and even thousands +of years during which men have watched the stars, +sink, at our vast distance, into no more than one quarter +of an hour spent in watching the far-off ships from +the high hilltop. The motions can not be detected. +In ten thousand years you might see something. In<span class="pagenum" id="Page_114">[Pg 114]</span> +fifty thousand years you might see much. But four +or five thousand years are not sufficient.</p> + +<p>One other mode there is, by means of which the +movements of the ships on the horizon might be made +plain. Suppose you had no more than the quarter of +an hour to spare, but suppose you had at your command +a powerful telescope. Then you may practically +bring the ships nearer, and by magnifying the small, +slow, distant motions, you may make them, as it were, +larger, quicker, more easy to see.</p> + +<p>Telescopes will do this for us, likewise, in the matter +of the stars. By means of telescopes, with the assistance +of careful watching and of close calculation it +has been found that the stars are really moving quickly, +each one in his own pathway. The very speed of +some of them has been measured.</p> + +<p>Arcturus is one of those stars, the motions of which +are most plainly to be seen. In the course of about +one thousand years he changes visibly his place in the +sky by a space equal to the apparent diameter of the +moon. The seeming movement of Arcturus in one +thousand years is the same as the seeming width of +the round moon that we see.</p> + +<p>But the actual speed with which Arcturus rushes +through space is said to be no less than fifty-four +miles each second, or not far from two hundred thousand +miles an hour. That is nearly three times as +fast as our own earth’s motion round the sun. How +enormous the distance must be which can shrink +such speed to such seeming slowness!</p> + +<p>Another beautiful star, Capella, is believed to travel +at the rate of thirty miles each second. The speed<span class="pagenum" id="Page_115">[Pg 115]</span> +of Sirius is slower, being only fourteen miles a second. +The Pole-star creeps along at the rate of only one +mile and a half each second.</p> + +<p>So also with the rest of the stars. There seems +good reason to believe that every star we see shining +in the heavens, every star visible in powerful telescopes, +is perpetually hastening onward. But hastening +whither? God knows! We do not.</p> + +<p>In all probability not one of the tens of millions +of stars which may be seen through telescopes is in +repose. This is a matter of conjecture, of reasoning +from analogy, and of reasoning also from the working +of known laws. We <i>know</i>, as a consequence of direct +observation, apart from the new spectroscopic method, +that at least hundreds are upon the wing. We <i>assume</i>, +as a matter of the greatest possible likelihood, that all +the millions besides, which can not be actually seen +to stir, are equally on the move. Knowing what we +do know of the laws by which the universe of stars is +governed, it seems to us an absolute impossibility that +any single star, amid the whole vast host, can be or +could be permanently at rest.</p> + +<p>If by any means a star were brought to repose—what +then would happen? It would inevitably start +off again, drawn by the attraction of other stars. +From whatever direction the strongest pull came, the +impulse would be given. Lengthened repose would be +out of the question. And this, it seems to us, must +be true, not of one star only, here or there, but of +every star in the enormous host of radiant suns which +make up the mighty Stellar System.</p> + +<p>Our forefathers, one thousand years ago, could not<span class="pagenum" id="Page_116">[Pg 116]</span> +measure the precise positions of individual stars, as +astronomers now are able to do. They had no modern +observatories, no telescopes, no spectroscopes, no photographic +appliances. These methods of observation +we shall explain in another chapter. Their measurements +at best were rough, their scientific knowledge +was crude. Had we any such accurate observations +handed down from one thousand years ago as are +made in these days, we should no doubt see clearly +many slight differences in the positions of many stars +which are not now apparent. But even then we +should see no changes sufficient in amount to affect +the general outlines of the leading constellations.</p> + +<p>A star, which in the course of a century makes +visible advance over a space in the sky equal to only +a small portion of the breadth of the full moon, is +looked upon as a fast voyager. One hundred times +this degree of movement, if it took place in a considerable +number of stars in our sky, would not in +centuries very materially change the face of our midnight +heavens.</p> + +<p>And all motions which would in the remotest degree +affect the shapes of constellations, must be sideway +motions. Those line-of-sight motions, of which +the spectroscope alone tells us, could never have been +discovered by simple observation of the sky. Until +the new method came to light we had no means +whatever of perceiving such movements among the +stars.</p> + +<p>Suppose you are looking at two men in the distance, +upon a wide, flat plain. One of the two is +walking very slowly <i>across</i> your line of vision. The<span class="pagenum" id="Page_117">[Pg 117]</span> +second man is moving very slowly straight <i>towards</i> +you. If you watch with care you may find out both +the movements. The sideway walking will be apparent +first and most easily, because, as the man +moves, he has constantly a fresh part of the horizon +behind him. But in time the advance of the second +man towards you will also become apparent; for although +he is seen still against precisely the same spot +on the horizon, he slowly occupies a larger spot on +the retina of your eye,—in other words, he seems to +grow bigger. And that, as you know from long experience, +can only mean increasing nearness.</p> + +<p>If a star seemed to grow larger as it drew nearer, +we should then be able to perceive that movement +also. But no star in the sky ever does seem to grow +any larger. Every star is to us but one point of light. +It may be rushing towards us at an enormous rate of +speed, yet still as a single point it remains, always at +the same point in our sky. Therefore we have no +chance of perceiving its movement; or rather, we <i>had</i> +no chance until the discovery of this new method. +In fact, the very nearest known star is at so enormous +a distance that, supposing it to be coming towards +us at the rate of one hundred miles each +second, it would still gain, in the course of a century, +only one-fortieth part more of brightness than it has +now. It would not increase at all in apparent size.</p> + +<p>When we leave behind us the thought of starry +motions, as we faintly detect them at this great distance, +and picture to ourselves the actual far-off whirl +of all those glorious suns, the effect upon the mind is +overwhelming. Stars are found to be rushing hither<span class="pagenum" id="Page_118">[Pg 118]</span> +and thither, at every degree of speed, in every imaginable +direction: stars to right, and stars to left; stars +towards us, and stars away from us; stars alone, and +stars in company,—all this, and more, deciphered out +of the tiny gleam of quivering light, which streams +through the vast abyss of space from each distant orb +to earth. So real star-motions were known—first, +through telescopic observation; secondly, through +spectroscopic observation; and now, lastly, photography +has stepped in, bringing with it much increase +of exactitude.</p> + +<p>But if all the stars are moving, what of our sun? +Our sun is a star. And our sun also is moving. He +is pressing onward, in a wide sweep through space, +bearing along with him his whole vast family—planets, +satellites, comets, meteorites—round or towards some +far distant center. For aught we know, every star in +the heavens may have a like family traveling with him.</p> + +<p>In infinite space the stars are strewn in immense +clusters, like archipelagoes of islands in the ocean +of the heavens. To go from one star to another in +the same archipelago light takes years; to pass from +one archipelago to another it takes thousands of years. +Each of these stars is a sun similar to ours, surrounded, +doubtless, at least for the most part, by +worlds gravitating in its light; each of these planets +possesses, sooner or later, a natural history adapted to +its constitution, and serves for many ages as the abode +of a multitude of living beings of different species. +Attempt to count the number of stars which people +the universe, the number of living beings who are +born and die in all these worlds, the pleasures and<span class="pagenum" id="Page_119">[Pg 119]</span> +pains, the smiles and tears, the virtues and vices! Imagination, +stop thy flight!</p> + +<p>The sun is not one of the most quickly-moving +stars. His rate of speed has not been found out with +any certainty, but it is believed to be about four or +five miles a second.</p> + +<p>And where are we going? This has been in +part discovered. If you and I were driving through a +forest of trees, we should see the trees on each side of +us seeming to move backward, while behind they +would close together, and in front they would open out.</p> + +<p>Astronomers—and first among them, William Herschel—reasoned +that if our Solar System were really +in motion, we ought to be able to see these changes +among the stars. And some such changes have become +visible through careful watching—not so much +those ahead and behind as those at the sides.</p> + +<p>It is not actually so simple a matter as looking at +the trees in a forest, because the trees would be at rest, +whereas each star has his own particular real motion, +as well as his seeming change of place caused by our +sun’s motion. It is more like moving in a small +steamer at sea, among hundreds of other craft, each +of which is going on its own way, at the same time +that all on either side seem to move backward because +we are moving forward.</p> + +<p>So each movement had to be noted, and the real +motions had to be separated from the seeming backward +drift of stars to the right and left of the sun’s +pathway. The result of all this is that the sun, with +his planets, is found to be hastening towards a certain +far-off constellation named Hercules.</p> + +<p><span class="pagenum" id="Page_120">[Pg 120]</span></p> + +<p>It is a strange and unexpected fact, but absolutely +true, that each sun of space is carried along with a +velocity so rapid that a cannon-ball represents rest in +comparison; it is at neither a hundred, nor three hundred, +nor five hundred yards per second that the +earth, the sun, Sirius, Vega, Arcturus, and all the +systems of infinitude travel: it is at ten, twenty, +thirty, a hundred thousand yards a second; all run, fly, +fall, roll, rush through the void—and still, seen as a +whole, all seems in repose.</p> + +<p>The immense distance which isolates us from all +the stars reduces them to the state of motionless lights +apparently fixed on the vault of the firmament. All +human eyes, since humanity freed its wings from the +animal chrysalis, all minds since minds have been, +have contemplated these distant stars lost in the ethereal +depths; our ancestors of Central Asia, the Chaldeans +of Babylon, the Egyptians of the Pyramids, the +Argonauts of the Golden Fleece, the Hebrews sung by +Job, the Greeks sung by Homer, the Romans sung by +Virgil,—all these earthly eyes, for so long dull and +closed, have been fixed, from age to age, on these eyes +of the sky, always open, animated, and living. Terrestrial +generations, nations and their glories, thrones +and altars have vanished: the sky of Homer is always +there. Is it astonishing that the heavens were contemplated, +loved, venerated, questioned, and admired, +even before anything was known of their true beauties +and their unfathomable grandeur?</p> + +<p>Better than the spectacle of the sea, calm or agitated, +grander than the spectacle of mountains adorned +with forests or crowned with perpetual snow, the spectacle<span class="pagenum" id="Page_121">[Pg 121]</span> +of the sky attracts us, envelops us, speaks to us +of the Infinite. “I have ascended into the heavens, +which receive most of His light, and I have seen +things which he who descends from on high knows +not, neither can repeat,” wrote Dante in the first canto +of his poem on “Paradise.” Let us, like him, rise towards +the celestial heights, no longer on the trembling +wings of faith, but on the stronger wings of science. +What the stars would teach us is incomparably more +beautiful, more marvelous, and more splendid than +anything we can dream of.</p> + +<p>How do such contemplations enlarge and transfigure +the vulgar idea which is generally entertained of the +world! Should not the knowledge of these truths +form the first basis of all instruction which aims at +being serious? Is it not strange to see the immense +majority of human beings living and dying without +suspecting these grandeurs, without thinking of learning +something of the magnificent reality which surrounds +them?</p> + +<p>Where the sun and his planets will journey in future +ages no living man can say. Indeed, though it +is a question which does not lack interest to a thoughtful +mind, yet there are numberless other questions +about centuries near at hand which concern man far +more nearly. The history of the Universe, and the +history of this Earth of ours, must have advanced +many broad stages before our sun and his attendant +planets can have traveled so far that any change will +be apparent in the shape of the star-constellations +which spangle our sky.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_122">[Pg 122]</span></p> + +<h2 class="nobreak" id="c11">CHAPTER XI.</h2> +</div> + +<p class="c sp">MORE ABOUT THE SOLAR SYSTEM.</p> + + +<p><span class="smcap large">We</span> have now reached a point where it ought not to +be difficult for us to picture to ourselves, with something +of vividness, the general outlines of the Solar System. +Awhile ago this Solar System was a very simple +matter in the eyes of astronomers. There was the +great sun fixed in the center, with seven planets circling +round him—seven of course, it was said, since +seven was the perfect number—and a few moons keeping +pace with some of the planets, and an occasional +comet, and a vast amount of black, empty space. But +astronomers now begin to understand better the wonderful +richness of the system as a whole; the immense +variety of the bodies contained in it; the perpetual +rush and stir and whirl of life in every part. Certainly +there is no such thing as dull stagnation +throughout the family.</p> + +<p>First, we have the great, blazing, central sun; not +a sun at rest, as regards the stars, but practically at +rest as regards his own system, of which he is always +head and center. Then come the four smaller planets, +rapidly whirling round him, all journeying in the +same direction, and all having their oval pathways lying +on nearly the same flat plane in space. Then the +broad belt of busy little planetoids. Then the four +giant planets,—Jupiter nearly five times as far as our +earth from the sun; Saturn nearly twice as far as Jupiter;<span class="pagenum" id="Page_123">[Pg 123]</span> +Uranus nearly twice as far as Saturn; Neptune +as far from Uranus as Uranus from Saturn,—all keeping +on very nearly the same level as the four inner planets.</p> + +<div class="figcenter" id="f20"> +<img src="images/fig20.jpg" alt="jupiter"> +<p class="caption">POSITION OF PLANETS INFERIOR TO JUPITER—SHOWING THE<br> +ZONE OF THE ASTEROIDS.</p> +</div> + +<p>And between and about these principal members of +the system, with their accompanying moons, we have +thousands of comets flashing hither and thither, with +long, radiant trains; and myriads of meteorites, gathered +often into dense, vast herds or families, but also scattered +thickly throughout every part of the system,<span class="pagenum" id="Page_124">[Pg 124]</span> +each tiny ball reflecting the sun’s rays with its little +glimmer of light.</p> + +<p>Broad reaches of black and empty space! Where +are they? Perhaps nowhere. We are very apt, in +our ignorance, to imagine that where we see nothing, +there must of necessity be nothing. But, for aught +we know, the whole Solar System, not to speak of +sky-depths lying beyond, may be bright with reflecting +bodies great and small, from the mighty Jupiter +down to the fine diamond-dust of countless meteorites. +In this earth of ours we find no emptiness. Closer +and closer examination with the microscope only +shows tinier and yet tinier wonders of form and life, +each perfect in finish. Not of form only, but of <i>life</i>. +How about that matter as regards the Solar System? Is +our little world the one only spot in God’s great universe +which teems with life? Are all other worlds +mere barren, empty wastes? Surely not. We may +safely conclude that life of one kind or another has +been, is, or will be, upon our brother and sister +worlds.</p> + +<p>The same reasoning may be used for the distant +stars—those millions of suns lying beyond reach of +man’s unassisted eyes. Are they formed in vain? +Do their beams pour uselessly into space, carrying +light, warmth, and life-giving power to nothing? +Surely around many of them, as around our sun, +must journey worlds; and not only worlds, but worlds +containing life.</p> + +<p>We shall have to speak of this matter again as we +go on. Whether men and women like ourselves could +live on the other planets is another question. In some<span class="pagenum" id="Page_125">[Pg 125]</span> +cases it looks doubtful, in some it would seem to be +impossible. But the endless variety of life on this +earth—life on land, life in the air, life in water, life +underground, life in tropical heat, life in arctic cold—forbids +us in anywise to be positive as to what may or +may not be.</p> + +<p>If no animals that we know could exist there, animals +that we do not know might be found instead. +Any one of the planets may, and very likely does, +abound with life. Nay, the very meteorites themselves, +before they catch fire and burn in our air, <i>may</i> +be the homes of tiny animalcula, altogether different +from anything we see on earth. We can not fancy +life without air, but neither could we fancy life in +water, if we had not seen and known it to be possible.</p> + +<p>I have spoken of the probable <i>brightness</i> of the +Solar System as a whole. We are so apt to think of +things merely as we see them with our short sight, +that it is well sometimes to try to realize them as +they actually are. Picture to yourself the great central +sun pouring out in every direction his burning +rays of light. A goodly abundance of them fall on +our earth, yet the whole amount of light and heat received +over the whole surface of this world is only the +two-thousand-millionth part of the enormous amount +which he lavishly pours into space. How much of +that whole is wasted? None, though God gives his +gifts with a kingly profusion which knows no bounds. +Each ray has its own work to do. Millions of rays +are needed for the lighting and nourishing and warming +of our companion-planets, while others are caught +up by passing comets, and myriads flash upon swift,<span class="pagenum" id="Page_126">[Pg 126]</span> +tiny meteorites. Of the rays not so used, many pass +onwards into the vast depths beyond our system, and +dwindle down into dim, starlike shining till they reach +the far-off brother-stars of our sun.</p> + +<p>Have they work to do there? We can not tell. +We do not know how far the sun’s influence reaches. +As head and center, he reigns only in his own system. +As a star among stars, a peer among his equals, +he may, for aught we can tell, have other work to do.</p> + +<p>In an early chapter, mention was made of the +earth’s three motions, two only being explained. +First, she spins ceaselessly upon her axis. So does +the sun, and so do the planets. Secondly, she travels +ceaselessly round and round the sun in her fixed orbit. +So does each one of the planets. Thirdly, she journeys +ceaselessly onward through space with the sun. +So also do the rest of the planets. These last two +movements, thought of together, make the earth’s +pathway rather perplexing at first sight. We talk of +her orbit being an ellipse or oval; but how can it be +an ellipse, if she is always advancing in one direction?</p> + +<p>The truth is, the earth’s orbit is and is not an +ellipse. As regards her yearly journey round the sun, +roughly speaking, we may call it an ellipse. As regards +her movement in space, it certainly is not an +ellipse.</p> + +<p>Think of the Solar System, with the orbits of all +the planets, as lying <i>nearly flat</i>—in the manner that +hoops might be laid upon a table, one within another. +The asteroids, comets, and meteorites do not keep to +the same level; but their light weight makes the matter +of small importance.</p> + +<p><span class="pagenum" id="Page_127">[Pg 127]</span></p> + +<p>Having imagined the sun thus in the center of a +large table—a small ball, with several tiny balls traveling +round him on the table at different distances—suppose +the sun to rise slowly upwards, not directly +up, but in a sharp slant, the whole body of planets +continuing to travel round, and at the same time rising +steadily with him.</p> + +<p>By carefully considering this double movement, +you will see that the real motion of the earth—as +also of each of the planets—is not a going round on +a flat surface to the same point from which she started, +but is a corkscrew-like winding round and round upwards +through space. Yet as regards the central sun, +the shape of the orbit comes very near being an ellipse, +if calculated simply by the earth’s distance from +him at each point in turn of her pathway through +the year.</p> + +<p>An illustration may help to explain this. On the +deck of a moving vessel, you see a little boy walking +steadily round and round the mast. Now is that +child moving in a circle, or is he not? Yes, he is. +No, he is not. He walks in a circle as regards the +position of the mast, which remains always the center +of his pathway. But his movement <i>in space</i> is never +a circle, since he constantly advances, and does not +once return to his starting-point. You see how the +two facts are possible side by side. Being carried +forward by the ship, with no effort of his own, the +forward motion does not interfere with the circling +motion. Each is performed independently of the +other.</p> + +<p>It is the same with the earth and the planets.<span class="pagenum" id="Page_128">[Pg 128]</span> +The sun, by force of his mighty attraction, bears +them along wherever he goes—no exertion on their +part, so to speak, being needed. That motion does +not in the least interfere with their steady circling +round the sun.</p> + +<p>Just as—to use another illustration—the earth, +turning on her axis, bears through space a man standing +on the Equator at the rate of one thousand miles +an hour. But this uniform movement, unfelt by himself, +does not prevent his walking backwards, or forwards, +or in circles, as much as he will.</p> + +<p>So, also, a bird in the air is unconsciously borne +along with the atmosphere, yet his freedom to wheel +in circles for any length of time is untouched.</p> + +<p>A few words about the orbits of the planets. I +have more than once remarked that these pathways +are, in shape, not circles, but ellipses. A circle is a +line drawn in the shape of a ring, every part of which +is at exactly the same distance from the center-point +or focus. But an ellipse, instead of being, like a circle, +perfectly round, is oval in shape; and instead of having +only one focus, it has two foci, neither being exactly +in the center. Foci is the plural word for focus. +If an ellipse is only slightly oval—or slightly <i>elliptical</i>—the +two foci are near together. The more oval or +<i>eccentric</i> the ellipse, the farther apart are the two foci.</p> + +<p>You may draw a circle in this manner. Lay a +sheet of white paper on a board, and fix a nail through +the paper into the board. Then pass a loop of thread—say +an inch or an inch and a half in length—round +the nail, and also round a pencil, which you hold. +Trace a line with the pencil, keeping the loop tight,<span class="pagenum" id="Page_129">[Pg 129]</span> +so that the distance of your line from the nail will be +always equal, and when it joins you have a circle. +The nail in the center is the focus of the circle.</p> + +<p>To draw an ellipse, you must fix <i>two</i> nails. Let +them be about half an inch apart; pass a loop over +both of them, and again placing a pencil point within +the loop, again trace a line carefully all round, keeping +the thread drawn tight. This time an oval instead +of a circle will appear. By putting the nails nearer +together or farther apart, you may vary as you will +the shape of the ellipse.</p> + +<p>In the orbits of the earth and the planets, all of +which are ellipses in shape, the sun is not placed in +the exact center, but in one of the two foci, the second +being empty. So at one time of the year the +planet is nearer to the sun than at another time. Our +earth is no less than three millions of miles nearer in +winter than she is in summer—speaking of the winter +and summer of the northern hemisphere. Three millions +of miles is so tiny a piece out of ninety-three +millions of miles, that it makes little or no difference +in our feelings of heat or cold.</p> + +<p>The orbits of the comets are ellipses also, but ellipses +often so enormously lengthened out, that the two +foci are almost—if one may so speak—at the two <i>ends</i> +of the oval. To draw a good comet orbit, you must +fix the two nails on your paper some five or six +inches apart, with a loop of thread just large enough to +slip over them both, and to allow the pencil to pass +round them. When your ellipse is drawn, you must +picture the sun in the place of one of the two nails, +and you will see how, in their pathways, the comets<span class="pagenum" id="Page_130">[Pg 130]</span> +at one time pass very near the sun, and at another +time travel very far away from him.</p> + +<div class="figcenter" id="f21"> +<img src="images/fig21.jpg" alt="size"> +<p class="caption">COMPARATIVE SIZE OF THE PLANETARY WORLDS.</p> +</div> + +<p>It is generally found in families, not only that the +parent or head of the family has great influence over +all the members, but that each member has influence<span class="pagenum" id="Page_131">[Pg 131]</span> +over each other member. Brother influences brother, +and sister influences sister.</p> + +<p>This, too, we find in the Solar System. Not only +does the sun, by his powerful attraction, bind the +whole family together, but each member of the family +attracts each other member. True, the force of +the sun’s attraction is overpowering in amount compared +with others. The sun attracts the planets, and +the planets attract the sun; but their feeble pulling is +quite lost in the display of his tremendous strength.</p> + +<p>Among themselves we see the power more plainly. +The earth attracts the moon, keeping her in constant +close attendance; and the moon attracts the earth, causing +a slight movement on her part, and also causing the +tides of the sea. Each planet has more or less power +to hinder or help forward his nearest brother-planet. +For instance, when Jupiter on his orbit draws near +the slower Saturn on his orbit, Saturn’s attraction +pulls him on, and makes him move faster than usual; +but as soon as he gets ahead of Saturn then the same +attraction pulls him back, and makes him go more +slowly than usual. Jupiter has the same influence +over Saturn; and so also have Saturn and Uranus over +one another, or Uranus and Neptune.</p> + +<p>In early days astronomers were often greatly puzzled +by these quickened and slackened movements, +which could not be explained. Now the “perturbations” +of the planets, as they are called, are understood +and allowed for in all calculations. Indeed, it +is by means of this very attraction that Neptune was +discovered, and the planets have actually been weighed. +What a wonderful difference we find in this picture<span class="pagenum" id="Page_132">[Pg 132]</span> +of the Solar System, as we now know it to be, from +the old-world notion of our earth as the center of the +universe!</p> + +<p>When we think of all the planets, and of the magnificent +sun; when we pass onward in imagination +through space, and find our sun himself merely one +twinkling star amid the myriads of twinkling stars +scattered broadcast through the heavens, while planets +and comets have sunk to nothing in the far distance,—then +indeed we begin to realize the unutterable +might of God’s power! Why, our earth and all +that it contains may be regarded as but one grain of +dust in the wide universe.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_133">[Pg 133]</span></p> + +<h2 class="nobreak" id="c12">CHAPTER XII.</h2> +</div> + +<p class="c sp">MORE ABOUT THE SUN.</p> + + +<p><span class="smcap large">Not</span> among the least of the wondrous things of +creation are the tremendous disturbances taking place +upon the surface of the sun—that raging, roaring sea +of flame.</p> + +<p>A good many explanations have been from time to +time offered as to the dark spots seen to move across +the face of the sun. Some one or more of these explanations +may be true; but we know little about the +matter. A sun-spot does not commonly consist of +merely one black patch. There is the dark center, +called the <i>umbra</i>—plural, <i>umbræ</i>. There is the grayish +part surrounding the umbra, called the <i>penumbra</i>. +Also, in the center of the umbra there is sometimes +observable an intensely black spot, called the <i>nucleus</i>. +Sometimes a spot is made up of nucleus and umbra +alone, without any penumbra. Sometimes it is made +of penumbra alone, without any umbra. Sometimes +in one spot there are several umbræ, with the gray +penumbra round the whole, and gray bridges dividing +the umbræ.</p> + +<p>The enormous size of these spots has been already +described in an earlier chapter. Fifty thousand to +one hundred thousand miles across is nothing unusual. +In the year 1839 a spot was seen which measured no +less than one hundred and eighty-six thousand miles +in diameter.</p> + +<p><span class="pagenum" id="Page_134">[Pg 134]</span></p> + +<p>One explanation proposed was, that the sun might +be a cool body, covered over with different envelopes +or dense layers of cloudy form, one above another. +The inside envelope—or, as some say, the inside atmosphere—would +then be thick and dull-colored, +protecting the solid globe within and reflecting light, +but having none of its own. The next envelope +would be one mass of raging, burning gases—the +<i>photosphere</i>, in fact. The outer envelope would be a +transparent, surrounding atmosphere, lighted up by +the sea of fire within. A sun-spot would then consist +of the tearing open of one or more of these envelopes, +so as to give glimpses of the gray, inner atmosphere, +or even of the dark, cool globe at the center.</p> + +<p>There may be some truth in this explanation; but +the notion of a cool and dark body within is now +pretty well given up. The apparent blackness of a +spot-nucleus does not prove actual blackness or absence +of heat. A piece of white-hot iron, held up +against the sun, looks black; and it may be merely +the contrast of the glowing photosphere which makes +the nucleus seem so dark. It is even believed that +the blackest parts may be the most intensely hot +of all.</p> + +<p>Another proposed explanation was of dark clouds +floating in the sun’s atmosphere. There, again, are +found difficulties, particularly in the fact that, as the +spots move across the sun, the changes which regularly +take place in their appearance make it pretty +clear that their shape is not flat, but hollow and cave-like. +The changes here spoken of are seeming +changes of shape, caused by change of position.<span class="pagenum" id="Page_135">[Pg 135]</span> +There are also real changes constantly taking place. +Although the spots often keep their general outlines +long enough to be watched across the face of the sun, +and even to be known again after spending nearly a +fortnight hidden on the other side, still they are far +from being fixed in form.</p> + +<div class="figcenter" id="f22"> +<img src="images/fig22.jpg" alt="sun-spot"> +<p class="caption">A TYPICAL SUN-SPOT.</p> +</div> + +<p>The alterations are at times not only very great, +but very rapid. Sometimes in a single hour of watching, +an astronomer can see marked movement going<span class="pagenum" id="Page_136">[Pg 136]</span> +on—as you or I might in an hour observe movements +slowly taking place in a high layer of clouds. For +movement to show at all in one hour, at so immense +a distance, proves that the actual rate of motion must +be very great.</p> + +<p>The first great fact which was got from the study +of these spots was this, that this great sun is very +much like our own earth, in so far as it rotates on an +axis in exactly the same way that our earth does. Not +only do the spots change their position on the face of +the sun, in consequence of the sun’s rotation on its +axis, but they change very much from day to day, and +even from hour to hour; so that we have evidence not +only that the sun is rotating like our earth, but that +the atmosphere of the sun is subjected to most tremendous +storms—storms so tremendous, in fact, that +the fiercest cyclones on our own earth are not for one +moment to be compared with them. The fact that +the spots do really move with the sun, and are really +indentations, saucer-like hollows, in the photosphere, +is shown by the appearance, which is always presented +by a spot when it is near the edge of the sun. You +know if you take a dinner-plate, and look it full in +the face, it is round; but if you look at it edgeways, +it is not round. Take two different views of the same +spot: In one, you look the sun-spot straight in the face, +and you see into it and can learn all about it; but in +the other, when it has nearly gone round the corner, +and is disappearing on the sun’s edge, you see it in +the same way that you would see a plate looked at +edgeways.</p> + +<p>These sun-cyclones must indeed be of terrific force<span class="pagenum" id="Page_137">[Pg 137]</span> +and extent, compared with anything we see on earth. +It was calculated that the speed of movement perceived +in one spot was about three hundred and sixty-three +miles each second.</p> + +<p>And still all this is nothing, or almost nothing, in +comparison with the real power of the sun! The +liquid state of the ocean; the gaseous state of the atmosphere; +the currents of the sea; the raising of the +clouds, the rains, storms, streams, rivers; the calorific +value of all the forests of the globe and all the coal-mines +of the earth; the motion of all living beings; +the heat of all humanity; the stored-up power in +all human muscles, in all the manufactories, in all +the guns,—all that is almost nothing compared +with that of which the sun is capable. Do we +think that we have measured the solar power +by enumerating the effects which it produces on +the earth? Error! profound, tremendous, foolish +error! This would be to believe still that this star has +been created on purpose to illuminate terrestrial humanity. +In reality, what an infinitesimal fraction of +the sun’s total radiation the earth receives and utilizes! +In order to appreciate it, let us consider the distance +of ninety-three millions of miles which separates us +from the central star, and at this distance let us see +what effect our little globe produces, what heat it intercepts. +Let us imagine an immense sphere <i>traced at +this distance from the sun</i>, and entirely surrounding it. +Well, on this gigantic sphere, the spot intercepted by +our little earth is only equivalent to the fraction +<sup>1</sup>/<sub>2,138,000,000</sub>; that is to say, that the dazzling solar hearth +radiates all round it through immensity a quantity of<span class="pagenum" id="Page_138">[Pg 138]</span> +light and heat two thousand one hundred and thirty-eight +million times more than that which we receive, +and of which we have just now estimated the stupendous +effects. The earth only stops in its passage the +<i>two thousand millionth part of the total radiation</i>.</p> + +<p>Sometimes the storms or outbursts come in the +shape of a bright spot instead of a dark one.</p> + +<div class="figcenter" id="f23"> +<img src="images/fig23.jpg" alt="eruption"> +<p class="caption">A SOLAR ERUPTION.</p> +</div> + +<p>Two astronomers were one day watching the sun +from two different observatories, when they saw such +an event take place. An intense and dazzling spot of +light burst out upon the surface of the sun—so intense, +so dazzling, as to stand quite apart from the +radiant photosphere. To one astronomer it looked +like a single spot, while the other saw two spots close +together. In about a minute the light grew more +dim, and in five minutes all was over. But in those +five minutes the spot or spots had traveled a distance +of thirty-five thousand miles.</p> + +<p><span class="pagenum" id="Page_139">[Pg 139]</span></p> + +<p>It was a very remarkable thing that the <i>magnets</i> +on earth—those delicate little needles which point so +steadily yet perseveringly towards the North Pole—seemed +to be strongly agitated by the distant solar +outburst. This brings us to another interesting fact.</p> + +<p>The spots on the sun are not always the same in +number. Sometimes they are many, sometimes they +are few. Long and close watching has made it clear +that they pass through a regular <i>order</i> of changes: +some years of many spots being followed by other +years of less and less spots; then some years of very +few spots being followed by other years of more and +more spots,—decrease and increase being seemingly +regular and alternate.</p> + +<p>This turn or <i>cycle</i> of changes—from more to less, +and then from less to more again—is found to run its +course about once in every eleven years, with some +variations.</p> + +<p>Now, it has long been known that the magnetic-needle +goes through curious variations. Though we +speak of it as pointing always north, yet it does not +always so point exactly. Every day the needle is +found to make certain tiny, delicate motions, as if +faintly struggling to follow the daily movements of +the sun—just a little towards the east, or just a little +towards the west. These tiny motions, having been +long watched and measured, were found to go through +a regular course of changes—some years more, and +some years less, waxing and waning by turns. It was +discovered that the course of changes from more to +less, and from less to more again, took place in about +eleven years.</p> + +<p><span class="pagenum" id="Page_140">[Pg 140]</span></p> + +<p>These two things, you see, were quite independent +of one another. Those who watched the sun-spots +were not thinking of the magnets, and those who +watched the magnets were not thinking of the sun-spots. +But somebody did at last happen to think of +both together. He was laughed at, yet he took the +trouble carefully to compare the two. And, strange +to say, he found that these two periods in the main +agreed—the eleven years of alternate changes in the +number of sun-spots, and the eleven years of alternate +changes in the movements of the magnetic-needle. +When the spots are most, the needle moves most. +When the spots are least, the needle moves least. +So much we know. But to explain the why and the +wherefore is beyond our power.</p> + +<p>This study of the magnetism of our wandering +planet is very interesting, and one which is still very +little known. Here is a weak needle, a slip of magnetic +iron, which, with its restless and agitated finger, +incessantly seeks a region near the north. Carry this +needle in a balloon up to the higher aerial regions, where +human life begins to be extinguished; shut it up in a +tomb closely separated from the light of day; take it down +into the pit of a mine, to more than a thousand yards in +depth,—and incessantly, day and night, without fatigue +and without rest, it watches, trembles, throbs, seeks +the point which attracts it across the sky, through the +earth, and through the night. Now—and here is a +coincidence truly filled with notes of interrogation—the +years when the oscillation of this innocent little +steel wire is strongest are the years when there are +more spots, more eruptions, more tempests in the sun;<span class="pagenum" id="Page_141">[Pg 141]</span> +and the years when its daily fluctuations are weakest +are those when we see in the day-star neither spots, +eruptions, nor storms. Does there exist, then, a magnetic +bond between the immense solar globe and our +wandering abode? Is the sun magnetic? But the +magnetic currents disappear at the temperature of red-hot +iron, and the incandescent focus of light is at a +temperature incomparably higher still. Is it an electrical +influx which is transmitted from the sun to the +earth across a space of ninety-three millions of miles? +On September 1, 1859, two astronomers—Carrington +and Hodgson—were observing the sun, independently +of each other; the first on a screen which +received the image; the second directly through a telescope,—when, +in a moment, a dazzling flash blazed out +in the midst of a group of spots. This light sparkled +for five minutes above the spots without modifying +their form, as if it were completely independent, and +yet it must have been the effect of a terrible conflagration +occurring in the solar atmosphere. Each observer +ascertained the fact separately, and was for an +instant dazzled. Now, here is a surprising coincidence: +at the very moment when the sun appeared inflamed +in this region the magnetic instruments of the Kew +Observatory, near London, where they were observing, +manifested a strange agitation; the magnetic +needle jumped for more than an hour as if infatuated. +Moreover, a part of the world was on that day and +the following one enveloped in the fires of an aurora +borealis, in Europe as well as in America. It was +seen almost everywhere,—at Rome, at Calcutta, in +Cuba, in Australia, and in South America. Violent<span class="pagenum" id="Page_142">[Pg 142]</span> +magnetic perturbations were manifested, and at several +points the telegraph-lines ceased to act. Why +should these two curious events not be associated with +each other? A similar coincidence was observed on +August 3, 1872, by Professor Charles A. Young, of +Princeton, N. J.: a paroxysm in the solar chromosphere, +magnetic disturbances everywhere.</p> + +<p>There is a very singular appearance seen upon the +sun which must not be passed over without mention. +Some astronomers speak of the whole surface as being +<i>mottled</i> all over with a curious rough look when examined +through a powerful telescope. This “mottling” +is described by various observers in various ways. +One speaks of “luminous spots shaped like rice-grains.” +Another, of “luminous spots resembling +strokes made with a camel’s-hair pencil.” Another, +of “luminous objects or granules.” Others, of “multitudes +of leaves,” “nodules,” “crystalline shapes,” +“leaves or scales, crossing one another in all directions, +like what are called spills in the game of spillikens.” +They have also been pictured as “certain +luminous objects of an exceedingly definite shape and +general uniformity of size, whose form is that of the +oblong leaves of a willow-tree.” These cover the whole +disk of the sun, excepting the space occupied by the +spots, in countless millions, and lie crossing each other +in every imaginable direction.</p> + +<p>In size they are said to be about one thousand miles +long, by two or three hundred broad, but they vary a +good deal. Where there is a spot, the willow-leaves +at its edge are said to point pretty regularly towards +the center. Whether they are, as they seem to be,<span class="pagenum" id="Page_143">[Pg 143]</span> +solid in form; whether they are, as some suppose, the +chief source of the sun’s light and heat; whether they +lie on his surface or float in his atmosphere; what is +their real nature, and what is their real use,—about +these questions we are at present quite in the dark.</p> + +<p>We have next to +think a little more +about the edge or +limb of the sun, +and the stormy +flames and outburst +there seen. +Until quite lately +the only time for +observing such appearances +was during +a total eclipse +of the sun. Lately, +by means of the +new instrument +called the “spectroscope,” +it has been +found possible to +take observations when no eclipse is going on.</p> + +<div class="figright" id="f24"> +<img src="images/fig24.jpg" alt="sun-flames"> +<p class="caption">SUN-FLAMES, MAY 3, 1892.</p> +</div> + +<p>A few words of explanation as to eclipses of the +sun seem needful, before going further. An eclipse +of the sun is caused simply by the round body of the +moon passing exactly between the sun and the earth, +so as to hide the sun from us.</p> + +<p>Let there be a candle on the table, while you stand +near. The rays of light from the candle fall upon +your face. Now move slowly, to and fro, a round ball<span class="pagenum" id="Page_144">[Pg 144]</span> +between you and the candle. So long as it is not precisely +in the line between—so long as it is a little +higher, or a little lower, or a little to one side—then +you can still see the flame. Once you let the ball come +just between the light and your eyes, and you see it no +more. In other words the candle-flame is eclipsed—hidden, +veiled, cut off—by the ball.</p> + +<p>It may seem curious at first sight that the moon, +which is very small compared with the sun, should +have power to cover the sun. But remember the difference +of the distance. The sun is very far, and the +moon is very near. Any small object very near will +easily hide from your sight a large object at a considerable +distance. You may hold up a shilling-piece +at arm’s length, and make it cover from sight a man, +or even a house, if the latter be far enough away. +The sun at a distance of ninety-three millions of miles, +and the moon at a distance of two hundred and forty +thousand miles, have to our vision the same seeming +size. So, when the moon glides between, her round +face just about covers the sun’s round face.</p> + +<p>If the moon were traveling exactly in the same +plane as the plane of the earth’s orbit, an eclipse would +be a very common affair indeed. But the plane of the +moon’s orbit being not quite the same as the plane of +the earth’s orbit, she passes sometimes a little above, +and sometimes a little below, the exact spot where +she would hide the sun’s rays from us. Now and +then, at certain intervals, she goes just between. And +so well is the moon’s path in the heavens understood +that astronomers can tell us, long years beforehand, +the day and the hour an eclipse will take place.</p> + +<p><span class="pagenum" id="Page_145">[Pg 145]</span></p> + +<p>An eclipse of the sun is sometimes partial, sometimes +total, sometimes annular. In a partial eclipse, +the moon does indeed pass between, but only so as to +hide from us <i>part</i> of the sun. She is a little too low, +or a little too high, to cover his face. In a total +eclipse, the moon covers the sun completely, so that +for a few minutes the bright photosphere seems blotted +out from the heavens, a black round body, surrounded +by light, taking its place. In an annular +eclipse, the moon in like manner crosses the sun, but +does not succeed in covering him entirely, a rim of +bright photosphere showing round the black moon. +For in an annular eclipse, the moon, being a little +farther away from the earth than at the time of a +total eclipse, has too small a disk quite to hide the +sun’s disk.</p> + +<p>The blackness of the moon during an eclipse is +caused by the fact that her bright side is turned towards +the sun, and her dark side toward us. An +eclipse of the sun can take place only at new moon, +never at full moon. At her full, the moon is outside +the earth’s orbit, away from the sun, and can not by +any possibility pass between.</p> + +<p>Eclipses, like comets, have always been interpreted +as the indication of inevitable calamities. +Human vanity sees the finger of God making signs +to us on the least pretext, as if we were the end and +aim of universal creation. Let us mention, for example, +what passed even in France, with reference to +the announcement of an eclipse of the sun, on August +21, 1560. For one, it presaged a great overthrow of +States and the ruin of Rome; for another, it implied<span class="pagenum" id="Page_146">[Pg 146]</span> +another universal deluge; for a third, nothing less +would result than a conflagration of the globe; finally, +for the less excited, it would infect the air. The belief +in these terrible effects was so general that, by +the express order of the doctors, a multitude of frightened +people shut themselves up in very close cellars, +well heated and perfumed, in order to shelter themselves +from these evil influences. Petit relates that +the decisive moment approached, that the consternation +was at its height, and that a parish priest of the +country, being no longer able to confess his parishioners, +who believed their last hour had come, was +obliged to tell them in a sermon “not to be so much +hurried, seeing that, on account of the wealth of the +penitents, the eclipse had been postponed for a fortnight.” +These good parishioners found no more difficulty +in believing in the postponement of the eclipse +than they had in believing in its unlucky influence.</p> + +<p>History relates a crowd of memorable acts on which +eclipses have had the greatest influence. Alexander, +before the battle of Arbela, expected to see his army +routed by the appearance of a phenomenon of this +kind. The death of the Athenian general Nicias and +the ruin of his army in Sicily, with which the decline +of the Athenians commenced, had for their cause an +eclipse of the moon. We know how Christopher Columbus, +with his little army, threatened with death by +famine at Jamaica, found means of procuring provisions +from the natives by depriving them in the evening +of the light of the moon. The eclipse had scarcely +commenced when they supplied him with food. This +was the eclipse of March 1, 1504. We need not relate<span class="pagenum" id="Page_147">[Pg 147]</span> +other facts of this nature, in which history abounds, +and which are known to every one.</p> + +<p>Eclipses no longer cause terror to any one, since we +know that they are a natural and inevitable consequence +of the combined motions of the three great +celestial bodies—the sun, the earth, and the moon; +especially since we know that these motions are regular +and permanent, and that we can predict, by means +of calculation, the eclipses which will be produced in +the future as well as recognize those which have occurred +in the past.</p> + +<p>The following description of the total eclipse of +1860 will be found interesting. Mr. Lowe, who observed +it at Santander, Spain, thus writes:</p> + +<p>“Before totality commenced, the colors in the sky +and on the hills were magnificent beyond all description. +The clear sky in the north assumed a deep +indigo color, while in the west the horizon was first +black like night. In the east the clear sky was very +pale blue, with orange and red, like sunrise. On the +shadow creeping across, the deep blue in the north +changed, like magic, to pale, sunrise tints of orange +and red, while the sunrise appearance in the east had +changed to indigo. The darkness was great; the +countenances of men were of a livid pink. The +Spaniards lay down, and their children screamed with +fear; fowls hastened to roost, ducks clustered together, +pigeons dashed against the houses; flowers +closed; many butterflies flew as if drunk, and at last +disappeared. The air became very humid, so much +so that the grass felt to one of the observers as if recently +rained upon.”</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_148">[Pg 148]</span></p> + +<h2 class="nobreak" id="c13">CHAPTER XIII.</h2> +</div> + +<p class="c sp">YET MORE ABOUT THE SUN.</p> + + +<p><span class="smcap large">Having</span> seen something of storms taking place on +the sun’s photosphere, we must next give our attention +to storms taking place at his edge. But it should +be remembered that the said edge, far from being a +mere rim to a flat surface, is a kind of horizon-line—is, +in fact, just that part of the photosphere which is +passing out of or coming under our sight. The surface +there is, in kind, the same as the surface of the +broad disk facing us. In watching outbursts at the +edge of the sun, we have a side view instead of a +bird’s-eye view.</p> + +<p>In the year 1871, Professor Charles A. Young, of +Princeton, was looking at a large hydrogen cloud on +the edge of the sun. When I speak of a “cloud,” it +must not be supposed that anything like a damp, +foggy, earthly cloud is meant. This solar cloud was a +huge mass of red-hot gas, about one hundred thousand +miles long, rising to a height of fifty thousand +miles from the sun’s surface, and appearing to rest +on glowing pillars of fire.</p> + +<p>The professor, while watching, was called away for +half an hour. He came back, expecting to find things +much as he had left them. Instead of this, a startling +change had taken place. The whole mass of +glowing fire seemed to have been actually “blown to +shreds” by some tremendous outburst from below.<span class="pagenum" id="Page_149">[Pg 149]</span> +In place of the motionless cloud were masses of scattered +fire, each from about four thousand to fourteen +thousand miles long, and a thousand miles wide.</p> + +<p>As the professor gazed, these “bits” of broken +cloud rose rapidly upwards, away from the surface of +the sun. When I say “rapidly,” I mean that the real +movement, which the professor could calculate, was +rapid. The seeming movements were of course slow, +and over a small space. The actual motions were not +tardy, for in ten minutes these huge, fiery cloud-pieces +rushed upwards to a height of two hundred thousand +miles from the edge of the sun, moving at a rate of at +least one hundred and sixty-seven miles each second. +Gradually they faded away.</p> + +<p>But what caused this sudden change? Just before +the professor was interrupted, he had noticed a curious +little brilliant lump—a sort of suspicious thunder-cloud +appearance—below the quiet, bright cloud. And +after this tremendous shattering, the little bright lump +rose upwards into a huge mass of rolling flame, reaching +like a pyramid to a height of fifty thousand miles. +In the course of a few minutes these enormous flames +could be seen to move and bend, and to curl over their +gigantic tips. But they did not last long. At half-past +twelve the professor had been called away; by +half-past two the rolling flames completely vanished.</p> + +<p>Now, whatever may be the full explanation of this +sight, there is no doubt that on that day was observed +from earth a tremendous outburst, compared with +which our mightiest volcanoes are like the sputtering +of a farthing dip beside a roaring furnace. The awful +force and greatness of such a solar eruption are<span class="pagenum" id="Page_150">[Pg 150]</span> +more than we can possibly picture to ourselves. At +our distance we may catch a faint glimpse of what is +going on, and calculate speed of movement. But +vividly to realize the actual terrific grandeur of what +took place is past our power.</p> + +<p>Possibly this was much the same kind of outburst +as that seen by the two English astronomers; only +theirs was a bird’s-eye view, as it were, looking down +on the top of the sight, while the professor had a side-view, +certainly much the best for observation.</p> + +<p>It does not follow from what he saw that the eruption +must have taken place exactly at the “edge” of +the sun. Probably it happened near the edge. All +he could say, was that the flames rose fifty thousand +miles, and the pieces of cloud were carried two hundred +thousand miles, away from the edge. The eruption +may have begun on the other side of the sun, at +any distance from the horizon-edge where it first became +visible to earthly eyes.</p> + +<p>Also, while the professor found that the shattered +cloudlets moved at a rate of about one hundred and +sixty-seven miles each second, it is calculated that the +first fearful outburst must have caused movement, +near the surface of the sun, at a rate of at least three +hundred miles each second. Probably the hydrogen +cloud was borne upwards along with a vast mass of +fragments flung out from the sun. We are here upon +doubtful ground; but this tremendous power of eruption +in the sun, and of driving matter out of and away +from his surface, should not be forgotten.</p> + +<p>Though such a sun-storm as that just described is +not often to be seen, yet there are at all times certain<span class="pagenum" id="Page_151">[Pg 151]</span> +strange red prominences, or glowing flames, rising up +here and there from the sun’s “limb.” Doubtless they +rise also from other parts of the photosphere, though +they are only visible to us when near enough to the +edge to stand out beyond it.</p> + +<p>Seen during an eclipse, these prominences have +clear, sharp outlines, and are usually bright rose-red +in color. They are described as sometimes wide and +low, sometimes tall and slender; sometimes jagged, +sometimes regular; sometimes keeping long the same +shape, sometimes changing quickly in a few minutes. +They are said to be like flames, like mountains, like +the teeth of a saw, like icebergs, like floating cloudlets.</p> + +<p>As to their height, from fifty to eighty thousand +miles is nothing unusual. We must not speak of +Mont Blanc or Mount Everest here. Jupiter placed +bodily on the surface of the sun, beside such a fire-mountain, +would not far overtop it. The earth, Venus, +Mars, and Mercury, would lie like little toy-balls at its +foot. And these are common-sized sun-flames. One +was measured which reached to the enormous height +of two hundred thousand miles. The spectroscope +shows these solar prominences or jets to be made—at +least in part—of burning hydrogen gas.</p> + +<p>Beyond the sierra or chromatosphere—that border +of rippling, crimson flame-billows round the edge of +the sun, with red flame-mountains rising out of it +here and there—beyond these, stretches the corona. +The corona, as seen from earth, is a bright, far-reaching +glory of light, shining round the sun in a total +eclipse. The moon then comes between the sun and<span class="pagenum" id="Page_152">[Pg 152]</span> +the earth, her dark, round body creeping over the face +of the sun till the bright photosphere is completely +covered. But the sierra and the tall, red flames stand +out from behind the black moon, and the beautiful, +soft corona-light stretches far beyond.</p> + +<div class="figcenter" id="f25"> +<img src="images/fig25.jpg" alt="corona"> +<p class="caption">SOLAR CORONA AND PROMINENCE.</p> +</div> + +<p>It was long doubted whether the corona really belonged +to the sun or to the moon. There seems now +no doubt that it is a part of the sun.</p> + +<p>Various descriptions of the corona have been +given at different times, as observed during different<span class="pagenum" id="Page_153">[Pg 153]</span> +eclipses. It has been seen as a steady, beamy, white +cloud behind the moon, showing no flickering. It has +been seen marked with bright lines of light, and seeming +to move rapidly round and round. It has been +seen silvery white, sending off long streams of brightness. +It has been seen in the form of white light, +with bluish rays running over it. It has been seen +with entangled jets of light, like “a hank of thread in +disorder.” It has been seen silvery-white again, with +a faint tinge of greenish-violet about the outer edge. +It has been seen from a high mountain-top as a mass +of soft, bright light, “through which shot out, as if +from the circumference of the moon, straight, massive, +silvery rays, seeming distinct and separate from each +other, to a distance of two or three diameters of the +lunar disk, the whole spectacle showing as upon a +background of diffused, rose-colored light.”</p> + +<p>Majestic, indeed, are the proportions of some of +those mighty flames which leap from the surface of +the sun, yet these flames flicker, as do our terrestrial +flames, when we allow them time comparable to their +gigantic dimensions. Drawings of the same prominence +often show great changes in a few hours, or even +less. The magnitude of the changes could not be less +than many thousands of miles, and the actual velocity +with which such masses move is often not less than +one hundred miles a second. Still more violent are +the solar convulsions, which some observers have been +so fortunate as to behold, when from the sun’s surface, +as from a mighty furnace, vast incandescent masses +are projected upwards. All indications point to the +surface of the sun as the seat of the most frightful<span class="pagenum" id="Page_154">[Pg 154]</span> +storms and tempests, in which the winds sweep along +incandescent vapors.</p> + +<p>The corona consists of two parts—the inner and +brighter corona, the outer and fainter corona. The +shape of the whole seems to change much at different +times. The outer edge is usually blurred and indistinct, +fading gently away.</p> + +<p>Many explanations have been suggested. At one +time the corona was supposed to be a solar atmosphere, +reflecting light like our own atmosphere. Some +have thought the light might be caused by countless +myriads of meteorite systems, revolving in the close +neighborhood of the sun. Some suppose it may be +owing, in part at least, to solar eruptions, and the +pouring outward of burning gas and matter. But our +knowledge of the true nature of the corona is yet in +its infancy.</p> + +<p>A few closing words as to the size and weight of +the sun. In diameter, eight hundred and fifty-eight +thousand miles, and in bulk equal to one million two +hundred and eighty thousand earths, his weight is in +proportion less. Our earth is about four times as +dense as the sun. If her size were increased to the +sun’s size, her density being the same as now, she +would be very much heavier than the sun, and would +attract much more strongly. Still, though the sun is +of lighter materials than the earth, his immense size +gives him weight equal to seven hundred and fifty +times as much as all the planets put together.</p> + +<p>The attraction on the surface of the sun is also +very great—so great that we can hardly picture it to +ourselves. If life exists there at all—supposing it<span class="pagenum" id="Page_155">[Pg 155]</span> +possible that any kind of life can be in such a fiery +atmosphere—it must be life very different from any +known in this world. A man who on earth weighs +one hundred and sixty pounds, and walks lightly erect, +would, on the sun, lie helplessly bound to the ground, +crushed by his own overpowering weight. It is said +that a cannon-ball, reposing on the sun, if lifted one +inch and allowed to fall, would dash against the +ground with a speed three times greater than that of +our fastest express-trains. For weight on earth is +merely caused by the amount of force with which the +earth draws downward a body towards herself—a +force greater or less according to the density of that +body. So weight on the sun would be immensely +increased by his immensely greater power of attraction.</p> + +<div class="figcenter" id="f26"> +<img src="images/fig26.jpg" alt="size"> +<p class="caption">COMPARATIVE SIZE OF THE EARTH AND SUN.</p> +</div> + +<p><span class="pagenum" id="Page_156">[Pg 156]</span></p> + +<p>It is an interesting question how far the sun’s attractive +influence reaches effectually through space. +The nearer a body is to the sun, the greater the attraction +which he exercises over it. At the distance +of the planet Mercury, a speed of twenty-nine miles +each second is needful to overcome or balance it sufficiently +for the planet to remain in his orbit. At the +distance of the planet Neptune, about three miles +each second is enough. If a planet were journeying +at four times the distance of Neptune, the speed would +need to be not over two miles each second, lest the +planet should break loose and wander away. But +even two miles a second is no mean speed—more +than seven thousand miles an hour. If we come to +speak of that which we on earth call rapid motion, +we shall gain a clearer idea as to the extent of the +sun’s power.</p> + +<p>Suppose a planet were traveling through space at +the rate of one of our fastest express-trains—sixty +miles an hour. It has been calculated that, unless +the sun’s attraction were interfered with and overpowered +by some nearer sun, the said planet, though +placed at a distance ten or twelve times as great as +that of the far-off star Alpha Centauri, would still be +forced by the sun’s attraction to journey round him in +a closed orbit. At such a speed it would not be free +to wander off into the depths of space.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_157">[Pg 157]</span></p> + +<h2 class="nobreak" id="c14">CHAPTER XIV.</h2> +</div> + +<p class="c sp">MORE ABOUT THE MOON.</p> + + +<p><span class="smcap large">From</span> a globe all fire, all energy, all action, we +come to a globe silent, voiceless, changeless, lifeless. +So, at least, the moon seems to us. But it will not do +to speak too confidently.</p> + +<p>True, we can find no trace of an atmosphere in the +moon. If there is any atmosphere at all, it must be +so thin as to be less than that which we on earth +count as actually none. We pump away the air from +a glass inclosure in an air-pump, and say the glass +is empty. Only it is not quite empty. There is always +just a very little air remaining, though so little +that fire would not burn and animals could not live in +it. Some believe that air, up to that amount, may be +found in the moon. But this is much the same as to +say there is none at all. For, of course, with either +no air or so very little air, life can not possibly exist +on the moon. We can not imagine such a thing for a +moment. That is just how the matter stands. We +“can not imagine,” and therefore we conclude it to be +an impossibility. As if we knew a hundredth part of +the possibilities in any one corner of God’s great universe! +As if our being unable to picture a thing +proves that thing not to exist!</p> + +<p>Suppose we had always lived in tropical heat, and +had never seen, known, or heard of such a fact as life +in Arctic snows. Should we consider it a thing possible?<span class="pagenum" id="Page_158">[Pg 158]</span> +Suppose we had always lived on dry land, with +never a sight of sea or river or pond, and never a +proof that animal life could exist under water—aye, +and that some living animals may be suffocated by +air, just as other living animals are suffocated by +water. Should we not, in our wisdom, reason out +such a state of affairs to be utterly impossible?</p> + +<p>There <i>may</i> be no life on the moon. It <i>may</i> be that +she is now passing through a dead, cold, blasted stage, +either at the close of some past history, or in preparation +for some future history—or both. But, on the +other hand, it <i>may</i> be that the moon is no less full of +life than the earth; only the life must be different in +kind, must be something which we do not know any +thing at all about.</p> + +<p>The moon is very much smaller than the earth. +Her diameter is about two-sevenths of the earth’s diameter; +her entire surface is about two twenty-sevenths +of the earth’s surface; her size is about two +ninety-ninths of the earth’s size; and her whole weight +is about one-eightieth of the earth’s weight. Attraction +or gravitation on the surface of the moon is very +different from what it is on the earth. Her much +smaller bulk greatly lessens her power of attraction. +While a man from earth would, on the surface of +the sun—supposing he could exist there at all—lie +helpless, motionless, and crushed by his own weight, +he would on the moon find himself astonishingly light +and active. A leap over a tall house would be nothing +to him.</p> + +<div class="figcenter" id="f27"> +<img src="images/fig27.jpg" alt="moon"> +<p class="caption">THE MOON—AN EXPIRED PLANET.</p> +</div> + +<p>The moon, unlike the sun, has no light or heat of +her own to give out. She shines merely by reflected +<span class="pagenum" id="Page_159">[Pg 159]</span>light. Rays of sunlight falling upon her, rebound +thence, and find their way earthward. This giving of +reflected light is not a matter all on one side. We +yield to the moon a great deal more than she yields +to us. Full earth, seen from the moon, covers a<span class="pagenum" id="Page_160">[Pg 160]</span> +space thirteen times as large as full moon seen from +earth.</p> + +<p>Perhaps you may have noticed, soon after new +moon, when a delicate crescent of silver light shows +in the sky, that within the said crescent seems to lie +the body of a round, dark moon, only not perfectly +dark. It shows a faint glimmer. That glimmer is +called earth-shine. The bright crescent shines with +reflected sunlight. The dim portion shines with reflected +earth-light. What a journey those rays have +had! First, leaving the sun, flashing through ninety-three +millions of miles to earth, rebounding from earth +and flashing over two hundred and forty thousand +miles to the dark shaded part of the moon, then +once more rebounding and coming back, much wasted +and enfeebled, across the same two hundred and forty +thousand miles, to shine dimly in your eyes and mine. +The popular description of this particular view of the +moon is “the old moon in the arms of the new.”</p> + +<p>Now about the <i>phases</i> of the moon; that is, her +changes from “new” to “full,” and back again to +“new.” If the moon were a starlike body, shining +by her own light, she would always appear to be +round. But as she shines by reflected sunlight, and +as part of her bright side is often turned away from +us, the size and shape of the bright part seem to vary. +For, of course, only that half of the moon which is +turned directly towards the sun is bright. The other +half turned away is dark, and can give out no light at +all, unless it has a little earth-shine to reflect.</p> + +<p>As the moon travels round the earth, she changes +gradually from new to full moon, and then back to<span class="pagenum" id="Page_161">[Pg 161]</span> +new again. “New moon” is when the moon, in her +orbit, comes between the sun and the earth. The +half of her upon which the sun shines is turned away +from us, and only her dark side is towards us. So at +new moon she is quite invisible. It is at new moon +that an eclipse of the sun takes place, when the +moon’s orbit carries her in a line precisely between +sun and earth.</p> + +<p>Passing onwards round the earth, the moon, as we +get a little glimpse of her shining side, first shows a +slender sickle of light, which widens more and more +till she reaches her first quarter. She is then neither +between earth and sun, nor outside the earth away +from the sun, but just at one side of us, passing over +the earth’s own orbit. Still, as before, half her body +is lighted up by the sun. By this time <i>half</i> the bright +part and <i>half</i> the dark part are turned towards us; so +that, seeing the bright quarter, we name it the “first +quarter.”</p> + +<p>On and on round us moves the moon, showing +more light at every step. Now she passes quite outside +the earth’s orbit, away from the sun. Not the +slightest chance here of an eclipse of the sun, though +an eclipse of the moon herself is quite possible. But +more of that presently. As she reaches a point in a +line with earth and sun—only generally a little higher +or lower than the plane of the earth’s orbit—her +round, bright face, shining in the sun’s rays, is turned +exactly towards us. Then we have “full moon.”</p> + +<p>Still she goes on. Once more her light narrows +and wanes, as part of her bright half turns away. +Again at the “last quarter,” as at the first, she occupies<span class="pagenum" id="Page_162">[Pg 162]</span> +a “sideways” position, turning towards us half +her bright side and half her dark side. Then she +journeys on, with lessening rim of light, till it vanishes, +and once more we have the dark, invisible +“new moon.”</p> + +<p>It was these phases and aspects of the moon which +formerly gave birth to the custom of measuring time +by months, and by weeks of seven days, on account of +the return of the moon’s phases in a month, and because +the moon appears about every seven days, so to +say, under a new form. Such was the first measure of +time; there was not in the sky any signal of which +the differences, the alternations, and the epochs were +more remarkable. Families met together at a time +fixed by some lunar phase.</p> + +<p>The new moons served to regulate assemblies, sacrifices, +and public functions. The ancients counted +the moon from the day they first perceived it. In order +to discover it easily, they assembled at evening +upon the heights. The first appearance of the lunar +crescent was watched with care, reported by the high +priest, and announced to the people by the sound of +trumpets. The new moons which correspond with the +renewal of the four seasons were the most solemn; we +find here the origin of the “ember weeks” of the +Church, as we find that of most of our festivals in the +ceremonies of the ancients. The Orientals, the Chaldeans, +Egyptians, and Jews religiously observed this +custom.</p> + +<p>An eclipse of the sun has already been described. +An eclipse of the moon is an equally simple matter. +An eclipse of the sun is caused by the dark, solid<span class="pagenum" id="Page_163">[Pg 163]</span> +body of the moon passing just between earth and sun, +hiding the sun from us, and casting its shadow upon +the earth. An eclipse of the moon is also caused by +a shadow—the shadow of our own earth—falling upon +the moon.</p> + +<p>Here again, if the plane of the moon’s orbit were +the same as ours, eclipses of the moon would be very +common. As it is, her orbit carries her often just a +little too high or too low to be eclipsed, and it is only +now and then, at regular intervals, that she passes +through the shadow of the earth.</p> + +<p>If a large, solid ball is hung up in the air, with +bright sunlight shining on it, the sunlight will cast a +<i>cone of shadow</i> behind the ball. It will throw, in a +direction just away from the sun, a long, round shadow, +the same as the ball at first, but tapering gradually off +to a point. If the ball is near the ground, a round +shadow will rest there, almost as large as the ball. +The higher the ball is placed, the smaller will be the +round shadow, till at length, if the ball be taken far +enough upwards, the shadow will not reach the ground +at all. Our earth and all the planets cast just such +tapering cones of dark shadow behind them into space. +The cone always lies in a direction away from the sun.</p> + +<p>It is when the moon comes into this shadow that +an “eclipse of the moon” takes place. Sometimes +she only dips half-way into it, or just grazes along +the edge of it, and that is called a “partial eclipse.” +Sometimes she goes in altogether, straight through +the midst of the shadow, so that the whole of her +bright face for a short time grows quite dark. Then +we have a “total lunar eclipse.”</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_164">[Pg 164]</span></p> + +<h2 class="nobreak" id="c15">CHAPTER XV.</h2> +</div> + +<p class="c sp">YET MORE ABOUT THE MOON.</p> + + +<p><span class="smcap large">There</span> are two ways of thinking about the moon. +One way is to consider her as merely the earth’s +attendant satellite. The other way is to consider +her as our sister-planet, traveling with us round the +central sun.</p> + +<p>The first is the more common view; but the second +is just as true as the first.</p> + +<p>For the sun does actually pull the moon towards +himself, with a very much stronger pulling than that +of the earth. The attraction of the sun for the moon +is more than double the attraction of the earth for the +moon. If it were not that he pulls the earth quite as +hard as he pulls the moon, he would soon overpower +the earth’s attraction, and drag the moon away from +us altogether.</p> + +<p>People are often puzzled about the orbit or pathway +of the moon through the heavens. For in one +sense they have to think of her as traveling round +and round in a fixed orbit, with the earth in the +center. In another sense they have to think of her +as always journeying onwards with the earth in her +journey round the sun, and thus never returning to +the same point.</p> + +<p>There are two ways of meeting this difficulty. +First of all, remember that the one movement does +not interfere with the other. Just as in the case of<span class="pagenum" id="Page_165">[Pg 165]</span> +the earth traveling round the sun, and also traveling +onward with him through space; just as in the case +of a boy walking round and round a mast, and also +being borne onwards by the moving vessel,—so it is +here. The two movements are quite separate and +independent of each other. As regards the earth +alone, the moon journeys round and round perpetually, +not in a circle, but in a pathway which comes +near being an ellipse. As regards the actual <i>line</i> +which the moon’s movements may be supposed to +draw in space, it has nothing elliptical about it, since +no one point of it is ever reached a second time by +the moon.</p> + +<p>But according to this last view of the question, nobody +ever can or will walk in a circle or an oval. +Take a walk round your grass-plot, measuring your +distance carefully at all points from the center. Is +that a circle? All the while you moved, the surface +of the earth was rushing along and bearing you with +it, and the whole earth was hurrying round the sun, +and was being also carried by him in a third direction. +Whatever point in space you occupied when +you started, you can <i>never fill that particular part of +space again</i>. The two ends of your so-called circle +can never be joined.</p> + +<p>But then you may come back to the same point <i>on +the grass</i>, as that from which you started. And this +is all that really signifies. Practically you have +walked in a circle. Though not a circle as regards +space generally, it is a circle as regards the earth. +So also the moon comes back to the same point <i>in +her orbit round the earth</i>. Letting alone the question<span class="pagenum" id="Page_166">[Pg 166]</span> +of space, and considering only the earth, the moon +has—roughly speaking—journeyed in an ellipse. +You may, however, look at this matter in quite another +light. Forget about the moon being the earth’s +satellite, and think of earth and moon as two sister-planets +going round the sun in company.</p> + +<p>The earth, it is true, attracts the moon. So, also, +the moon attracts the earth; though the far greater +weight of the earth makes her attraction to be far +greater. If earth and moon were of the same size, +they would pull each other with equal force.</p> + +<p>But though the pull of the earth upon the moon is +strong, the pull of the sun upon the moon is more +than twice as strong. And greatly as the earth influences +the moon, yet the actual center of the moon’s +orbit is the sun, and not the earth. Just as the earth +travels round the sun, so also the moon travels round +the sun.</p> + +<p>The earth travels steadily in her path, being only +a little swayed and disturbed by the attraction of the +moon. The moon on the contrary, while traveling +in her orbit, is very much swayed and disturbed indeed +by the earth’s attraction. In fact, instead of +being able to journey straight onwards like the earth, +her orbit is made up of a succession of delicate curves +or scallops, passing alternately backwards and forwards +over the orbit of the earth. Now she is behind the +earth; now in front of the earth; now between earth +and sun; now outside the earth away from the sun. +The order of positions is not as here given, but each +is occupied by her in turn. Sometimes she moves +quickly, sometimes she moves slowly, just according<span class="pagenum" id="Page_167">[Pg 167]</span> +to whether the earth is pulling her on or holding her +back. Two hundred and forty thousand miles sounds a +good deal. That is the distance between earth and +moon. But it is, after all, a mere nothing, compared +with the ninety-three millions of miles which separate +the sun from the earth and moon.</p> + +<p>If we made a small model, with the sun in the +center, and the earth and moon traveling a few inches +off, only one slender piece of wire would be needed +to represent the path of earth and moon together. +For not only would the earth and the moon be so +small as to be quite invisible, but the whole of the +moon’s orbit would have disappeared into the thickness +of the single wire. This question of the moon’s +motions is in its nature intricate, and in its details +quite beyond the grasp of any beginner in astronomy. +But so much at least may be understood, that +though the earth’s attraction powerfully affects the +moon, and causes in her motions <i>perturbations</i>, such as +have been already spoken about as taking place among +the planets, yet that in reality the great controlling +power over the moon is the attraction of the sun.</p> + +<p>The tides of the ocean are chiefly brought about +by the moon’s attraction. The sun has something to +do with the matter, but the moon is the chief agent. +This action of the moon can best be seen in the southern +hemisphere, where there is less land. As the +moon travels slowly round the earth, her attraction +draws up the yielding waters of the ocean in a vast +wave which travels slowly along with her. The same +pulling which thus lifts a wave on the side of the +earth towards the moon, also pulls the earth gently<span class="pagenum" id="Page_168">[Pg 168]</span> +<i>away from</i> the water on the opposite side, and causes +a second wave there. The parts of the ocean between +these two huge waves are depressed, or lower in level. +These two waves on the opposite sides of the earth +sweep steadily onwards, following the moon’s movements,—not +real, but seeming movements, caused by +the turning of the earth upon her axis.</p> + +<p>Once in every twenty-four hours these wide waves +sweep round the whole earth in the southern ocean. +They can not do the same in the north, on account of +the large continents, but offshoots from the south +waves travel northwards, bringing high-tide into every +sea and ocean inlet. If there were only one wave, +there would be only one tide in each twenty-four +hours. As there are two waves, there are two tides, +one twelve hours after the other. In the space between +these two high-tides we have low-tide.</p> + +<p>Twice every month we have very high and very low +tides. Twice every month we have tides not so high +or so low. The highest are called “spring-tides,” and +the lowest “neap-tides.” When the moon is between +us and the sun, or when she is “new moon,” there are +spring-tides; for the pull or attraction of sun and +moon upon the ocean act exactly together. It is the +same at full moon, when once more the moon is in a +straight line with earth and sun. But at the first and +last quarters, when the moon has her <i>sideways</i> position, +and when the sun pulls in one direction and the +moon pulls in another, each undoes a little of the +other’s work. Then we only have neap-tides; for the +wave raised is smaller, and the water does not flow so +high upon our shores.</p> + +<p><span class="pagenum" id="Page_169">[Pg 169]</span></p> + +<p>In speaking of the surface of the moon, we are +able only to speak about one side. The other is +entirely hidden from us. This is caused by the +curious fact that the moon turns on her axis and +travels round the earth in exactly the same length of +time. One-half of the moon is thus always turned towards +us, though of that half we can only see so much +as is receiving the light of the sun. But the half +turned in our direction is always the same half. +One part of the moon—not quite so much as half, +though always the same portion—is turned away from +us. A small border on each side of that part becomes +now and then visible to us, owing to certain movements +of the earth and the moon.</p> + +<p>What sort of a landscape may lie in the unknown +district, it is idle to imagine. Many guesses have +been made. Some have supposed it possible that air +<i>might</i> be found there; that water <i>might</i> exist there; +that something like earthly animals <i>might</i> live there. +It is difficult to say what may not be, in a place about +which we know nothing whatever. But judging from +our earthly experience, nothing seems more unlikely +than that air, water, clouds, should be entirely banished +from over one-half of a globe, and collected together +in the space remaining.</p> + +<p>We are on safer ground when we speak about that +part of the moon which is turned towards us. For we +can say with confidence that if any atmosphere exist +there, it must be in thickness less than the two-thousandth +part of our earthly atmosphere. It seems +equally clear that water also must be entirely wanting. +The tremendous heat of the long lunar day would<span class="pagenum" id="Page_170">[Pg 170]</span> +raise clouds of vapor, which could not fail to be visible. +But no such mistiness ever disturbs the sharply-defined +outline of the moon, and no signs of water action are +seen in the craggy mountains and deep craters.</p> + +<div class="figcenter" id="f28"> +<img src="images/fig28.jpg" alt="crater"> +<p class="caption">THE LUNAR CRATER COPERNICUS.</p> +</div> + +<p>The craters which honeycomb the surface of the +moon are various in size. Many of the larger ones +are from fifty to a hundred miles in diameter. These +huge craters—or, as we may call them, deep circular +plains—are surrounded by mighty mountain ramparts, +rising to the height of thousands of feet. +Usually they have in their center a sugar-loaf or<span class="pagenum" id="Page_171">[Pg 171]</span> +cone-shape mountain, or even two or more such +mountains, somewhat lower in height than the surrounding +range. The sunset-lights upon certain of +these distant mountain-peaks were first watched by +Galileo through his telescope, and have since been +seen by many an observer—intense brightness contrasting +with intense blackness of shadow.</p> + +<p>In addition to her great craters, the moon seems +to be thickly covered with little ones, many of them +being as small as can be seen at all through a telescope. +Whether these are all volcano-craters remains to be +discovered. It is not supposed that any of them are +now active. From time to time, signs of faint changes +on the moon’s surface have been noticed, which it +was thought might be owing to volcanic outbursts. +Such an outburst as the worst eruptions of Mount +Vesuvius would be invisible at this distance. But the +said changes may be quite as well accounted for by +the startling fortnightly variations of climate which +the moon has to endure. The general belief now inclines +to the idea that the moon-volcanoes are extinct, +though no doubt there was in the past great volcanic +activity there.</p> + +<p>A description has been given earlier of the rain of +meteorites constantly falling to our earth, and only +prevented by the atmosphere from becoming serious. +But the moon has no such protecting atmosphere, and +the amount of cannonading which she has to endure +must be by no means small. Perhaps in past times, +when her slowly-cooling crust was yet soft, these celestial +missiles showering upon her may have occasionally +made deep round holes in her surface.</p> + +<p><span class="pagenum" id="Page_172">[Pg 172]</span></p> + +<p>This is another guess, which time may prove to be +true. Guesses at possible explanations of mysteries +do no harm, so long as we do not accept them for +truth without ample reason.</p> + +<div class="figcenter" id="f29"> +<img src="images/fig29.jpg" alt="brisk"> +<p class="caption">LUNAR ERUPTION—BRISK ACTION.</p> +</div> + +<p>The origin of the lunar craters must be referred +to some ancient epoch in the moon’s history. How +ancient that epoch is we have no means of knowing; +but in all probability the antiquity of the lunar craters +is enormously great. At the time when the moon +was sufficiently heated to have these vast volcanic +eruptions, of which the mighty craters are the survivals, +the earth must have been very much hotter +than it is at present. It is not, indeed, at all unreasonable +to believe that when the moon was hot enough +for its volcanoes to be active, the earth was so hot that +life was impossible on its surface. This supposition<span class="pagenum" id="Page_173">[Pg 173]</span> +would point to an antiquity for the moon’s craters far +too great to be estimated by the centuries and the +thousands of years which are adequate for the lapse +of time as recognized by the history of human events. +It seems not unlikely that millions of years may have +elapsed since the mighty craters of Plato or of Copernicus +consolidated into their present form.</p> + +<div class="figcenter" id="f30"> +<img src="images/fig30.jpg" alt="feeble"> +<p class="caption">LUNAR ERUPTION—FEEBLE ACTION.</p> +</div> + +<p>It will now be possible for us to attempt to account +for the formation of the lunar craters. The +most probable views on the subject are certainly those +adopted by Mr. Nasmyth, as represented in the cuts, +though it must be admitted that they are by no means +free from difficulty. We can explain the way in which +the rampart around the lunar crater is formed, and +the great mountain which so often adorns the center +of the plain. The first of these cuts contains an imaginary<span class="pagenum" id="Page_174">[Pg 174]</span> +sketch of a volcanic vent on the moon in the +days when the craters were active. The eruption is +here in the full flush of its energy, when the internal +forces are hurling forth a fountain of ashes or stones, +which fall at a considerable distance from the vent; and +these accumulations constitute the rampart surrounding +the crater. The second cut depicts the crater in +a later stage of its history. The prodigious explosive +power has now been exhausted, and perhaps has been +intermitted for some time. A feeble jet issues from +the vent, and deposits the materials close around the +orifice, and thus gradually raises a mountain in the +center.</p> + +<p>Besides the craters and their surrounding barriers, +there are ranges of mountains on the moon, and flat +plains which were once named “seas,” before it was +found that water did not exist there. Astronomers +also see bright ridges, or lines, or cracks of light, hard +to explain.</p> + +<p>One of the chief craters is called “Ptolemy,” and +in size it is roughly calculated to be no less than one +hundred and fourteen miles across. Another, “Copernicus,” +is about fifty-six miles; and another, +“Tycho,” about fifty-four miles. The central cone-mountain +of Tycho is five thousand feet high. The +crater of “Schickard” is supposed to be as much as +one hundred and thirty-three miles in diameter.</p> + +<p>Astronomers have agreed to name these craters +after the great discoverers who enlarged our knowledge +of the solar and sidereal systems. It is fitting +that these great names are suggested every time the +moon is seen through a telescope. To Ptolemy we<span class="pagenum" id="Page_175">[Pg 175]</span> +are indebted for what is known as “The Ptolemaic +System of the Universe,” which makes the earth the +center around which the sun, moon, planets, and stars +all revolve, and explains the apparently erratic movements +of the planets by supposing their orbits to be +epicycles; that is, curves returning upon themselves +and forming loops. Tycho Brahe was willing to allow, +with Copernicus, that the planets all revolved around +the sun; but he taught that both sun and planets +turned around the earth.</p> + +<p>The system known as “The Copernican” is now +known to be the only true one, and it is universally +accepted. It is so called after Nicolaus Copernicus, +who was born in Thorn, Prussia, February 19, 1473. +He was educated for the Church, and studied medicine, +but devoted himself especially to astronomy.</p> + +<p>Without being precisely a great genius, this quiet +and thoughtful monk seems to have been wise far +beyond the age in which he lived, and remarkable +for his independence of mind. He had a “profound +sagacity,” and a wide general grasp of scientific +subjects.</p> + +<p>The extremely complicated and cumbrous nature +of the Ptolemaic system appeared to his judgment +hardly compatible with the harmony and simplicity +elsewhere characteristic of nature. Moreover, he was +impressed and perplexed by the very marked changes +in the brilliancy of the planets at different seasons. +These changes <i>now</i> are no difficulty at all. Venus, +Mars, Jupiter, when on the same side of the sun as +ourselves, are comparatively near to us, and naturally +look much more bright in consequence of that nearness<span class="pagenum" id="Page_176">[Pg 176]</span> +than when they are on the opposite side of the +sun from ourselves. But under the Ptolemaic system, +each planet was supposed to revolve round our earth, +and to be always at about the same distance from us; +therefore, why such variations in their brilliancy?</p> + +<div class="figcenter" id="f31"> +<img src="images/fig31.jpg" alt="copernicus"> +<p class="caption">NICOLAUS COPERNICUS.</p> +</div> + +<p>During thirty-six long years he patiently worked +out this theory, and during part of those thirty-six +years he wrote the one great book of his lifetime, explaining +the newer view of the Solar System which<span class="pagenum" id="Page_177">[Pg 177]</span> +had taken hold of his reason and imagination. This +book, named <i>De Revolutionibus Orbium Cœlestium</i>, +or, “Concerning the Revolutions of the Celestial +Spheres,” which came out only a few hours before his +death, was dedicated to the Bishop of Rome—a little +touch of worldly wisdom which doubtless staved off +for a while the opposition of the Vatican.</p> + +<p>Copernicus was not the first who thought of interpreting +the celestial motions by the theory of the +earth’s motion. That immortal astronomer has taken +care to give, with rare sincerity, the passages in the +ancient writers from which he derived the first idea of +the probability of this motion—especially Cicero, who +attributed this opinion to Nicetas of Syracuse; Plutarch, +who puts forward the names of Philolaus, Heraclides +of Pontus, and Ecphantus the Pythagorean; +Martianus Capella, who adopted, with the Egyptians, +the motion of Mercury and Venus around the sun, etc. +Even a hundred years before the publication of the +work of Copernicus, Cardinal Nicolas of Cusa, in 1444, +in his great theological and scientific encyclopedia, +had also spoken in favor of the idea of the earth’s +motion and the plurality of worlds. From ancient +times to the age of Copernicus, the system of the +earth’s immobility had been doubted by clear-sighted +minds, and that of the earth’s motion was proposed +under different forms. But all these attempts still +leave to Copernicus the glory of establishing it definitely.</p> + +<p>Not content with merely admitting the idea of the +earth’s motion as a simple arbitrary hypothesis, which +several astronomers had done before him, he wished—and<span class="pagenum" id="Page_178">[Pg 178]</span> +this is his glory—to demonstrate it to himself by +acquiring the conviction by study, and wrote his book +to prove it. The true prophet of a creed, the apostle +of a doctrine, the author of a theory, is the man who, +by his works, demonstrates the theory, makes the +creed believed in, and spreads the doctrine. He is +not the creator. “There is nothing new under the +sun,” says an ancient proverb. We may rather say, +Nothing which succeeds is entirely new. The newborn +is unformed and incapable. The greatest things +are born from a state of germ, so to say, and increase +unperceived. Ideas fertilize each other. The sciences +help each other; progress marches. Men often feel a +truth, sympathize with an opinion, touch a discovery, +without knowing it. The day arrives when a synthetical +mind feels in some way an idea, almost ripe, +becoming incarnate in his brain. He becomes enamored +of it, he fondles it, he contemplates it. It grows +as he regards it. He sees, grouping round it, a multitude +of elements which help to support it. To him +the idea becomes a doctrine. Then, like the apostles +of good tidings, he becomes an evangelist, announces +the truth, proves it by his works, and all recognize in +him the author of the new contemplation of nature, +although all know perfectly well that he has not invented +the idea, and that many others before him have +foreseen its grandeur.</p> + +<p>Such is the position of Copernicus in the history of +astronomy. The hypothesis of the earth’s motion had +been suggested long before his birth on this planet. +This theory counted partisans in his time. But he—he +did his work. He examined it with the patience<span class="pagenum" id="Page_179">[Pg 179]</span> +of an astronomer, the rigor of a mathematician, the +sincerity of a sage, and the mind of a philosopher. +He demonstrated it in his works. Then he died without +seeing it understood, and it was not till a century +after his death that astronomy adopted it, and popularized +it by teaching it. However, Copernicus is really +the author of the true system of the world, and his +name will remain respected to the end of time.</p> + +<p>The so-called “seas” on the moon are those large +dark spots to be seen on its surface, in the shape of +“eyes, nose, and mouth,” or of the famous old man +with his bundle of sticks. The brighter parts are the +more mountainous parts.</p> + +<p>The chief ranges of lunar mountains have been +named by astronomers after mountains on earth, such +as the Apennines, the Alps, the Caucasian range, the +Carpathian and the Altai Mountains.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_180">[Pg 180]</span></p> + +<h2 class="nobreak" id="c16">CHAPTER XVI.</h2> +</div> + +<p class="c sp">MERCURY, VENUS, AND MARS.</p> + + +<p><span class="smcap large">Once</span> again we have to journey through the high-roads +of the Solar System, paying a brief visit to each +in turn of our seven chief brother-and-sister planets, +and learning a few more leading facts about them. +Having gone the same way before, it will not now seem +quite so far.</p> + +<p>Busy, hurrying Mercury! we must meet him first +in his wild rush through space. If he were to slacken +speed for a single instant, he would begin to fall with +fearful rapidity towards the sun. And if Mercury +were to drop into one of those huge black chasms of +rent furnace-flame on the sun’s surface, there would be +a speedy end to his life as a planet.</p> + +<p>Mercury’s day is about the same length as our day, +and his year is about one quarter the length of our +year. If Mercury has spring, summer, autumn, and +winter, each season must be extremely short; but this +depends upon whether Mercury’s axis slopes like the +earth’s axis—a matter difficult to find out. Mercury +is always so near to the sun, that it is by no means +easy to observe him well.</p> + +<p>We know more about his orbit than his axis. The +earth’s orbit, as before explained, is not a circle, but +an ellipse or oval. Mercury’s orbit is an ellipse also, +and a much longer—or, as it is called, a more eccentric—ellipse. +The earth is three millions of miles<span class="pagenum" id="Page_181">[Pg 181]</span> +nearer to the sun at one time of the year, than six +months before or after. Mercury is no less than fifteen +millions of miles nearer at one time than another, +which must make a marked difference in the amount +of heat received.</p> + +<p>Even when the distance is greatest, the sun as seen +from Mercury looks four and a half times as large as +the sun we see. What a blazing splendor of light! +It is not easy to imagine human beings living there, +in such heat and glare, and with either no changes of +season at all, or such very short seasons rapidly following +one another. Mercury may, and very likely +does, abound with living creatures, as much as the +earth abounds with them; only one fancies they must +be altogether a different kind of living creatures from +any ever seen on earth. And yet we do not know. Man +can so wonderfully adapt himself or be adapted to different +climates on earth, from extreme heat to extreme +cold, that we can not tell how far this adapting power +may reach.</p> + +<p>Both Mercury and Venus seem to be enfolded in +dense, cloud-laden atmospheres, rarely parting so as +to allow us to get even a glimpse of the real planets +within the thick, light-reflecting covering. Some +have thought that a heavy, moist, protecting atmosphere +may help to ward off the intense heat, and to +make Mercury a more habitable place. Our earthly +atmosphere is rather of a kind to store up heat, and +to make us warmer than we should be without it; but +there might be vapors differently constituted which +might act in some other way. At all events, we know +how easily God can have adapted either the planet<span class="pagenum" id="Page_182">[Pg 182]</span> +to the creatures he meant to place there, or the creatures +to the climate. “All things are possible” to +him. The how and the what are interesting questions +for us, but we must often be content to wait for an +answer.</p> + +<p>A thick, gray ring or belt has been noticed round +the small, black disk of Mercury, while it has passed +between us and the sun. The edge of Mercury, seen +against the bright photosphere beyond, would, if there +were no atmosphere, be sharp and clear as the edge of +the airless moon. This surrounding haze seems to +show that Mercury has an atmosphere. The sunlight +reflected from Mercury’s envelope of clouds shines at +least as brightly as if it were reflected from his solid +body.</p> + +<p>The small size of Mercury makes attraction on his +surface much less than on earth. A lump of iron +weighing on earth one pound, would weigh on Mercury +only about seven ounces, or less than half as +much. So a man would be a very light leaper indeed +there, and an elephant might be quite a frolicsome +animal. If there are star-gazers in Mercury, and if +the cloud-laden atmosphere allows many clear views +of the sky, the earth and Venus must both be beautiful +to look upon. Each of the two would shine far +more brightly than Jupiter, as seen at his best from +earth.</p> + +<p>Like Mercury, Venus, the next planet, has an orbit +lying inside our orbit. Mercury and Venus are always +nearer to the sun than we are; and if Mercury +and Venus traveled round the sun in orbits, the planes +of which were exactly the same as the plane of the<span class="pagenum" id="Page_183">[Pg 183]</span> +earth’s orbit, we should very often see them creeping +over the surface of the sun. Not that they really +“creep over” it; only, as they journey between the +sun and us, we can see them pass like little black dots +across the sun’s disk. This is the same thing as when +the moon passes across the sun’s disk and eclipses it. +But Mercury and Venus are too far away from us to +cause any eclipse of the sun’s light.</p> + +<p>Mercury has given more trouble to astronomers +than any other member of the system; for, owing to +his proximity to the sun, he is usually lost in the +solar glory, and is never seen in a dark part of the +heavens, even at the time of his greatest distance. +This circumstance, together with a small mass and an +immense velocity, renders it difficult to catch and watch +him. In high latitudes, where the twilight is strong +and lengthened, while mists often overhang the horizon, +the planet can seldom be seen with the naked eye. +Hence an old astro-meteorologist contemptuously describes +him as “a squirting lacquey of the sun, who +seldom shows his head in these parts, as if he was in +debt.” Copernicus lamented that he had never been +able to obtain a sight of Mercury; and the French astronomer +Delambre saw him not more than twice with +the naked eye.</p> + +<p>The most favorable times for making observations +are about an hour and three-quarters before sunrise in +autumn, and after sunset in spring; but very clear +weather and a good eye are required. At certain periods, +when between the earth and the sun, on a line +joining the centers of the two bodies, Mercury appears +projected on the solar disk as a small, round, dark<span class="pagenum" id="Page_184">[Pg 184]</span> +spot. This is called a <i>transit</i>, and would occur during +every revolution if the plane of his orbit coincided +with that of the orbit of the earth. But as one-half +of his orbit is a little above that of the earth, and the +other half a little below it, he passes above or below +the sun to the terrestrial spectator, except at those intervals, +when, being between us and the sun, he is +also at one of the two opposite points where the planes +of the respective orbits intersect each other. Then, +stripped of all luster, the planet passes over the face +of the great luminary as a black circular speck, affording +evidence of his shining by reflected light, and +of his spherical form.</p> + +<p>The first transit of Mercury recorded in history +was predicted by Kepler, and witnessed by Gassendi, +at Paris, on the morning of a cloudy day, the 7th of +November, 1631. It was toward nine o’clock when he +saw the planet; but owing to its extreme smallness, +he was at first inclined to think it was a minute solar +spot. It was then going off the sun; and made its +final egress toward half-past ten. The observed time +of the transit was nearly five hours in advance of the +computed time. This was a very satisfactory accordance +for that age between theory and observation; but +it was the effect of a fortuitous combination of circumstances, +rather than of computations founded upon +well-established data. “The crafty god,” wrote Gassendi, +in the peculiar style of his day, “had sought to +deceive astronomers by passing over the sun a little +earlier than was expected, and had drawn a veil of +dark clouds over the earth in order to make his escape +more effectual. But Apollo, knowing his knavish<span class="pagenum" id="Page_185">[Pg 185]</span> +tricks from his infancy, would not allow him to pass +altogether unnoticed. To be brief, I have been more +fortunate than those hunters after Mercury who have +sought the cunning god in the sun. I found him out, +and saw him where no one else had hitherto seen +him.” Since Gassendi’s time a number of transits +have been observed.</p> + +<p>These crossings of the sun’s face, or “transits,” as +they are called, have been important matters. The +transit of Venus especially was once eagerly looked +for by astronomers, since, by close observations of Venus’s +movements and positions, the distance of the +sun could at that time be better calculated than in any +other way. Other methods are now coming into vogue.</p> + +<p>The transits of Venus are rare. Two come near +together, separated by only eight years, and then for +more than one hundred years the little dark body of +Venus is never seen from earth to glide over the sun’s +photosphere. There was a transit of Venus in the +year 1761, and another in the year 1769. There was +a transit of Venus in 1874, and another in 1882. At +the last transits it was found that the sun, instead of +being ninety-five millions of miles away, as astronomers +thought, was only ninety-three millions of miles +away. The reason why these transits happen so +seldom, is that the orbits of Mercury and Venus lie in +rather a different plane or level from the earth’s orbit. +So, like the moon, though often passing between us +and the sun, they generally go just a little higher or +just a little lower than his bright face.</p> + +<p>Mercury and Venus show phases like the moon, although +they do not circle round the earth as the moon<span class="pagenum" id="Page_186">[Pg 186]</span> +does. These “phases,” or changes of shape, are probably +never visible except through a telescope. It will +be easier to think about the phases of Venus alone, +than to consider both together. Her orbit lies within +the earth’s orbit, and the earth and Venus travel round +the sun—as do all the planets—in the same direction. +But as Venus’s pathway is shorter than ours, and as +her speed is greater, she is much the quickest about +her yearly journey, and she overtakes us again and +again at different points of our orbit in turn.</p> + +<div class="figleft" id="f32"> +<img src="images/fig32.jpg" alt="venus"> +<p class="caption">PHASES OF VENUS.</p> +</div> + +<p>At one time +she comes between +us and +the sun. That +is her nearest +position to us, +and she is then +only about +twenty-five millions +of miles distant. +A beautiful sight she would be, but unfortunately +her bright side is entirely turned away, and +only her dark side is turned towards us. So then she +is “new Venus,” and is invisible.</p> + +<p>At another time she is completely beyond the sun, +and at her farthest position away from us. Her shining +is quite lost in the sun’s rays coming between. +And though we get a good view of her as “full Venus,” +at a little to one side or the other, yet so great +is her distance—as much as one hundred and fifty-seven +millions of miles—that her size and brightness +are very much lessened.</p> + +<p><span class="pagenum" id="Page_187">[Pg 187]</span></p> + +<p>Between these two nearest and farthest points, she +occupies two middle distances, one on each side of +the sun. Then, like the moon at her “quarters,” she +turns to us only half of her bright side. But this is +the best view of Venus that we have, as a brilliant, +untwinkling, starlike form,—the Evening Star of ancients +and of poets. Between these four leading positions +Venus is always traveling gradually from one to +another—always either waxing or waning in size and +in brightness. Mercury passes through the same +seeming changes.</p> + +<p>Inhabitants of Venus must have a glorious view of +the earth, with her attendant moon. For just at the +time when the two planets are nearest together, and +when she is only “new Venus” to us, a dark and invisible +body, the earth is “full earth” to Venus. The +very best sight we ever have of Venus can not come +near that sight. But if Mercury and Venus really are +so often covered with heavy clouds as astronomers believe, +this must greatly interfere with any habits of +star-gazing.</p> + +<p>Venus and the earth have often been called twin-sister +planets. There are many points of likeness between +them. In size they differ little, and in length +of day they are within an hour of being the same. +Earth certainly has a companion-moon, and Venus, it +is believed, has not. At one time several astronomers +were pretty certain that they had caught glimpses of a +moon; but the supposed moon has of late quite vanished, +and nobody can say whether it ever really existed. +Venus travels in an ellipse which comes nearer +to being a circle than the orbit of any other planet.</p> + +<p><span class="pagenum" id="Page_188">[Pg 188]</span></p> + +<p>Mountain-shadows have been watched through the +telescope, in Venus, as in the moon. Some astronomers +have believed that they saw signs of very lofty +mountains—as much as twenty-eight miles, or four +times the height of our highest earthly mountains, but +this requires confirmation.</p> + +<p>There is a good deal of uncertainty about the +climate of Venus. The heat there must greatly surpass +heat ever felt on earth—the sun being about +double the apparent size of our sun, and pouring out +nearly double the amount of light and heat that we +receive.</p> + +<p>This difference may be met, as already stated, by a +sheltering, cloudy atmosphere, or the inhabitants may +have frames and eyesight suited to the increased glare +and warmth.</p> + +<p>An atmosphere and water exist there as here. +From what we have seen above of the rapid and violent +seasons of this planet, we might think that the +agitations of the winds, the rains, and the storms +would surpass everything which we see and experience +here, and that its atmosphere and its seas would +be subject to a continual evaporation and precipitation +in torrential rains—an hypothesis confirmed by its +light, due, doubtless, to reflection from its upper +clouds, and to the multiplicity of the clouds themselves. +To judge by our own impressions, we should +be much less pleased with this country than with our +own, and it is even very probable that our physical +organization, accommodating and complaisant as it is, +could not become acclimatized to such variations of +temperature. But it is not necessary to conclude from<span class="pagenum" id="Page_189">[Pg 189]</span> +this that Venus is uninhabitable and uninhabited. +We may even suppose, without exaggeration, that its +inhabitants, organized to live in the midst of these +conditions, find themselves at their ease, like a fish in +water, and think that our earth is too monotonous and +too cold to serve as an abode for active and intelligent +beings.</p> + +<p>Of what nature are the inhabitants of Venus? Do +they resemble us in physical form? Are they endowed +with an intelligence analogous to ours? Do they pass +their life in pleasure, as Bernardin de St. Pierre said; +or, rather, are they so tormented by the inclemency of +their seasons that they have no delicate perception, +and are incapable of any scientific or artistic attention? +These are interesting questions, to which we +have no reply. All that we can say is, that organized +life on Venus must be little different from terrestrial +life, and that this world is one of those which resemble +ours most. It should, then, be inhabited by vegetable, +animal, and human races but little different from those +which people our planet. As to imagining it desert +or sterile—this is an hypothesis which could not arise +in the brain of any naturalist. The action of the divine +sun must be there, as in Mercury, still more fertile +than his terrestrial work, already so wonderful. +We may add that Venus and Mercury, having been +formed after the earth, are relatively younger than our +planet.</p> + +<p>It is believed also that the axis of Venus, instead +of being slanted only as much as the earth’s axis, is +tilted much more. Even if the tilting is less than +some have supposed, it is probably very considerable.<span class="pagenum" id="Page_190">[Pg 190]</span> +If Venus really does “lie over” in such a manner, +certain startling changes of climate on its surface—unpleasant +changes, according to our ideas—would +take place.</p> + +<p>Like earth, Venus would have her two arctic regions, +where a burning summer’s day would succeed +a bitter winter’s night, each half a year in length. +She would have also her tropical region—only in that +region intense cold would alternate with intense heat, +brief seasons of each in turn. And between the tropics +and the arctic regions would lie wide belts, by turns +entirely tropical and entirely arctic. The rapidity and +severity of these changes, following one another in a +year about as long as eight of our months, would +seem to be too much for any human frame to endure. +But it all rests upon an <i>if</i>. And we may be quite +sure that <i>if</i> there are any manner of human beings +in Venus, their frames are well suited to the climate +of their world.</p> + +<p>Though Mars is one of the inner group of four +small planets, divided by the zone of asteroids from +the outer group of four great planets, yet he belongs +to the outside set of Superior Planets. His orbit surrounds +ours, being at all points farther off from the +sun. Very slight “phases” have been seen in Mars. +He turns to us, from time to time, just enough of his +dark side to prove that he <i>has</i> a dark side, and that +he does not shine like a star by his own light. But +the phases on that planet are by no means marked as +they are with Venus.</p> + +<p>Until lately it was believed that Mars possessed no +moons. Two very small ones have, however, been<span class="pagenum" id="Page_191">[Pg 191]</span> +lately found circling round him.<a id="FNanchor_2" href="#Footnote_2" class="fnanchor">[2]</a> They have been +named Deimos and Phobos, after the “sons of Mars” +in Greek mythology. Deimos travels round Mars in +thirty-nine hours, while Phobos performs the same +journey in the astonishingly short period of seven +hours and a half!</p> + +<div class="footnote"> + +<p><a id="Footnote_2" href="#FNanchor_2" class="label">[2]</a> The discovery of the two moons is due to the agency of a +woman. Professor Asaph Hall, of Washington City, was searching +by the aid of the most powerful telescope which had yet been directed +to Mars, and at the very moment when the planet was in the +most favorable condition for observation. Having searched in +vain during several evenings in August, 1877, he was about to give +up, when Mrs. Hall begged him to search a little more. He did +so, and on the night of the 11th he discovered the first of the +satellites, and then on the 17th the second.</p> + +</div> + +<div class="figcenter" id="f33"> +<img src="images/fig33.jpg" alt="mars"> +<p class="caption">MARS AND THE PATH OF ITS SATELLITES.</p> +</div> + +<p>We have here, then, a system very different from +that of the earth and moon. But the most curious +point is the rapidity with which the inner satellite of +Mars revolves round its planet. This revolution is +performed in seven hours, thirty-nine minutes, fifteen +seconds, although the world of Mars rotates on itself +in twenty-four hours, thirty-seven minutes—that is to<span class="pagenum" id="Page_192">[Pg 192]</span> +say, this moon turns much more quickly than the +planet itself. This fact is inconsistent with all the +ideas we have had up to the present on the law of +formation of the celestial bodies. Thus, while the +sun appears to revolve in the Martian sky in a slow +journey of more than twenty-four hours, the inner +moon performs its entire revolution in a third of a +day. It follows that <i>it rises in the west</i> and <i>it sets in +the east</i>! It passes the second moon, eclipses it from +time to time, and goes through all its phases in eleven +hours, each quarter not lasting even three hours. +What a singular world!</p> + +<p>These satellites are quite small—they are the +smallest celestial bodies we know. The brightness +of the planet prevents us from measuring them exactly. +It seems, however, that the nearer is the +larger, and shows the brightness of a star of the tenth +magnitude, and that the second shines as a star of the +twelfth magnitude. According to the most trustworthy +photometric measures, the first satellite may +have a diameter of 7.45 miles, and the second a +diameter of 6.2 miles. <i>The larger of these two worlds +is scarcely larger than Paris.</i> Should we honor +them with the title of worlds? They are not even +terrestrial continents, nor empires, nor kingdoms, +nor provinces, nor departments. Alexander, Cæsar, +Charlemagne, or Napoleon, might care but little +to receive the scepter of such worlds. Gulliver might +juggle with them. Who knows, however? The vanity +of men being generally in the direct ratio of their +mediocrity, the microscopical reasoning mites which +doubtless swarm on their surface have also, perhaps,<span class="pagenum" id="Page_193">[Pg 193]</span> +permanent armies, which mutilate each other for the +possession of a grain of sand.</p> + +<p>These two little moons received from their discoverer +the names of <i>Deimos</i> (Terror) and <i>Phobos</i> +(Flight), suggested by the two verses of Homer’s +“Iliad” which represent Mars descending on the earth +to avenge the death of his son Ascalaphus:</p> + + +<div class="poetry-container"> +<div class="poetry"> + <div class="stanza"> + <div class="verse indent0">“He ordered Terror and Flight to yoke his steeds,</div> + <div class="verse indent0">And he himself put on his glittering arms.”</div> + </div> +</div> +</div> + + +<p><i>Phobos</i> is the name of the nearer satellite; <i>Deimos</i>, +that of the more distant.</p> + +<p>The existence of these little globes had already +been suspected from analogy, and thinkers had frequently +suggested that, since the earth has one satellite, +Mars should have two, Jupiter four, Saturn eight; +and this is indeed the fact—though as Jupiter is now +found to have <i>five</i> satellites, this arithmetical progression +is upset. But as we experience too often in +practice the insufficiency of these reasonings of purely +human logic, we can not give them more value than +they really possess. We might suppose in the same +way now that Uranus has sixteen satellites, and Neptune +thirty-two. This is possible; but we know nothing +of them, and have not even the right to consider +this proportion as probable. It is not the less curious +to read the following passage, written by Voltaire in +1750 in his masterpiece, the “Micromégas:”</p> + +<p>“On leaving Jupiter, our travelers crossed a space +of about a hundred millions of leagues, and reached +the planet Mars. They saw <i>two moons</i>, which wait on +this planet, and which have escaped the gaze of astronomers.<span class="pagenum" id="Page_194">[Pg 194]</span> +I know well that Father Castel wrote +against the existence of these two moons; but I agree +with those who reason from analogy. These good +philosophers know how difficult it would be for Mars, +which is so far from the sun, to get on with less than +two moons. However this may be, our people found +it so small that they feared they might not find anything +to lie upon, and went on their way.”</p> + +<p>Here we have unquestionably a very clear prophecy, +a rare quality in this kind of writing. The astronomico-philosophical +romance of “Micromégas” has +been considered as an imitation of Gulliver. Let us +open the masterpiece of Swift himself, composed about +1720, and we read, word for word, in Chapter III of +the “Voyage to Laputa:”</p> + +<p>“Certain astronomers ... spend the greatest +part of their lives in observing the celestial bodies, +which they do by the assistance of glasses far excelling +ours in goodness. For this advantage hath enabled +them to extend the discoveries much farther +than our astronomers in Europe; for they have made +a catalogue of ten thousand fixed stars, whereas the +largest of ours do not contain above one-third part of +that number. They have likewise discovered two +lesser stars, or satellites, which revolve about Mars, +whereof the innermost is distant from the center of +the primary planet exactly three of his diameters, and +the outermost five. The former revolves in the space +of ten hours, and the latter in twenty-one and a half; +so that the squares of their periodical times are very +near in the same proportion with the cubes of their +distance from the center of Mars, which evidently<span class="pagenum" id="Page_195">[Pg 195]</span> +shows them to be governed by the same law of gravitation +that influences the other heavenly bodies.”</p> + +<p>What are we to think of this double prediction of +the two satellites of Mars? Indeed, the prophecies +which have been made so much of in certain doctrinal +arguments have not always been as clear, nor +the coincidences so striking. However, it is evident +that no one had ever seen these satellites before 1877, +and that there was in this hit merely the capricious +work of chance. We may even remark that both the +English and French authors have only spoken ironically +against the mathematicians, and that in 1610, Kepler, +on receiving the news of the discovery of the satellites +of Jupiter, wrote to his friend Wachenfals that +“not only the existence of these satellites appeared to +him probable, but that doubtless there might yet be +found two to Mars, six or eight to Saturn, and perhaps +one to Venus and Mercury.” We can not, assuredly, +help noticing that reasoning from analogy is here +found on the right road. However this may be, this +discovery truly constitutes one of the most interesting +facts of contemporary astronomy.</p> + +<p>Mars is not only much smaller than the earth, but +a good deal less dense in his “make.” His material is +only about three-quarters as heavy as an equal amount +of the earth’s material. A very heavy man on earth +would be a most light and active individual on Mars. +Gold taken from earth to Mars would weigh there no +more than tin weighs upon earth.</p> + +<p>Mars has, it seems, an atmosphere, even as earth +has. Of all the planets Mars, is the only one whose +actual surface is discernible in the telescope. Mercury<span class="pagenum" id="Page_196">[Pg 196]</span> +and Venus are so hidden by dense envelopes of +clouds that the real planets within are only now and +then to be dimly caught sight of. Jupiter and Saturn +are so completely enwrapped in mighty masses of +vapor, that we can not even be certain whether there +are any solid bodies at all inside.</p> + +<p>But Mars can be studied. Here and there, it is +true, clouds sweep over the landscape, hiding from +view for a little while one continent or another, one +sea or another, growing, changing, melting away, as +do the clouds of earth. Still, though these clouds +come and go, there are other markings on the surface +of Mars which do not change. Or, rather, they only +change so much as the continents and oceans of earth +would seem to vary, if watched from another planet, +as the daily movement of earth carried them from +west to east, or as they might be hidden for a while +by cloud-layers coming between. It has been curiously +noted that these clouds over Mars form often in +the morning and evening, and are afterwards dispersed +by the heat of midday. Also there seems +every reason to believe that rainfalls take place in +Mars as upon earth.</p> + +<p>The red color of Mars is well known. This does +not vanish in the telescope, but it is found that parts +only have the red or orange hue, while other parts are +dark and greenish. These are the markings which +remain always the same, and they have been so +closely examined that more is known about the geography +of Mars than of any other world outside our +own.</p> + +<p>Mars, at his nearest point, does not draw closer to<span class="pagenum" id="Page_197">[Pg 197]</span> +us than forty millions of miles. At such a distance +one must not speak too confidently. There are, however, +many reasons for believing that the red portions +are continents and that the green portions are oceans.</p> + +<p>The spectroscope has lately shown us that water +does really exist in the atmosphere of Mars—unlike the +dreary, waterless moon. So we no longer doubt that +the cloudlike appearances are clouds, and that rain +sometimes falls on Mars. If there is rain, and if there +are clouds and vapor, there are probably oceans also.</p> + +<p>Two singular white spots are to be seen at the +north and south poles, which we believe to be polar +ice and snow. Somebody looking at our earth in like +manner from a distance, would doubtless perceive two +such white snow-spots. These two polar caps are +seen to vary with the seasons. When the north pole +of Mars is turned towards the sun, the white spot +there grows smaller; and at the same time, the south +pole of Mars being turned away from the sun, the +white spot there grows larger. Again, when the south +pole is towards the sun, and the north pole away from +the sun, the white spot at the south is seen to be the +smallest, and the white spot at the north is seen to +be the largest. This is exactly what takes place in +the summers and winters of our north and south poles.</p> + +<p>The markings of Mars have been so carefully studied, +that at last a map has been made of the planet—a +map of a world, never less than forty millions of +miles away! Names have been given to the continents +and oceans—such as Dawes Continent, Herschel +Continent, De La Rue Ocean, Airy Sea, Huggins +Inlet, and so on.</p> + +<p><span class="pagenum" id="Page_198">[Pg 198]</span></p> + +<p>Land and water seem to be very differently arranged +on Mars from what they are on earth. Here +we have about three times as much water as land, and +to get from one continent to another without crossing +the sea is in some cases impossible. But a traveler +there might go most conveniently to and fro, hither +and thither, to all parts of his world, either on land or +on water, without any change. If he preferred water, +he would never need to set foot on land; and if he +preferred land, he would never need to enter a boat. +The two are so curiously mingled together, narrow +necks of land running side by side with long, narrow +sea-inlets, that Atlantic and Pacific Oceans are unknown.</p> + +<p>Some have wondered whether the reddish color of +the land may be caused by grass and trees being red +instead of green. Very strange if so it were. But in +that case, no doubt the inhabitants of Mars would +find green just as trying to their eyesight, as we should +find red trying to ours.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_199">[Pg 199]</span></p> + +<h2 class="nobreak" id="c17">CHAPTER XVII.</h2> +</div> + +<p class="c sp">JUPITER.</p> + + +<p><span class="smcap large">Passing</span> at one leap over the belt of tiny asteroids, +about which we know little beyond their general movement, +and the size and weight of a few among them, +we reach at once the giant planet Jupiter: Mighty +Jupiter, hurrying ever onward, with a speed, not indeed +equal to that of Mercury or of our earth, yet eighty +times as rapid as the speed of a cannon-ball! Think +of a huge body, equal in bulk to twelve hundred +earths, equal in weight to three hundred earths, rushing +ceaselessly through space, at the rate of seven +hundred thousand miles a day!</p> + +<p>Jupiter’s shape is greatly flattened at the poles. +He spins rapidly on his axis, once in nearly ten hours, +and has therefore a five hours’ day and a five hours’ +night. As the slope of his axis is exceedingly slight, +he can boast little or no changes of season. The climate +near the poles has never much of the sun’s heat. +In fact, all the year round the sun must shine upon +Jupiter much as he shines on the earth at the equinoxes.</p> + +<p>But the amount of light and heat received by Jupiter +from the sun is only about one twenty-fifth part +of that which we receive on earth; and the sun, as +seen from Jupiter, can have but a small, round surface, +not even one-quarter the diameter of the sun we see +in the sky.</p> + +<p><span class="pagenum" id="Page_200">[Pg 200]</span></p> + +<p>When looked at with magnifying power, the bright, +starlike Jupiter grows into a broad, softly-shining disk +or plate, with flattened top and bottom, and five tiny, +bright moons close at hand. Sometimes one moon is +on one side, and four are on the other; sometimes +two are one side and three on the other; sometimes +one or more are either hidden behind Jupiter or passing +in front of him. Jupiter has also curious markings +on his surface, visible through a telescope. These +markings often undergo changes; for Jupiter is no +chill, fixed, dead world, such as the moon seems to be.</p> + +<div class="figcenter" id="f34"> +<img src="images/fig34.jpg" alt="jupiter"> +<p class="caption">GENERAL ASPECT OF JUPITER—SATELLITE AND ITS SHADOW.</p> +</div> + +<p>There are dark belts and bright belts, usually running +in a line with the equator, from east to west.<span class="pagenum" id="Page_201">[Pg 201]</span> +Across the regions of the equator lies commonly a +band of pearly white, with a dark band on either side +of “coppery, ruddy, or even purplish” hue. Light +and dark belts follow one after another, up to the +north pole and down to the south pole.</p> + +<p>When we talk of “north and south poles” in the +other planets, we merely mean those poles which +point towards those portions of the starry heavens +which we have chosen to call “northern” and “southern.” +You know that all the chief planets travel +round the sun in very nearly the same <i>plane</i> or flat +surface that we do ourselves. That plane is called +the “plane of the ecliptic.” Suppose that you had an +enormous sheet of cardboard, and that in the middle +of this cardboard the sun were fixed, half his body +being above and half below. At a little distance, fixed +in like manner in the card, would be the small body +of the earth, half above and half below, her axis being +in a slanting position. The piece of cardboard represents +what is called in the heavens the <i>plane of the +ecliptic</i>—an imaginary flat surface, cutting exactly +through the middle of the sun and of the earth.</p> + +<p>If the planets all traveled in the same precise plane, +they would all be fixed in the cardboard just like the +earth, half the body of each above and half below. +As they do not so travel, some would have to be placed +a little higher, some a little lower, according to what +part of their orbits they were on. This supposed +cardboard “plane of the ecliptic” would divide the +heavens into two halves. One half, containing the +constellations of the Great Bear, the Little Bear, Cepheus, +Draco, and others, would be called the Northern<span class="pagenum" id="Page_202">[Pg 202]</span> +Heavens. One end of the earth’s axis, pointing just +now nearly to the Polar Star, we name the North +Pole; and all poles of planets pointing towards this +northern half of the heavens, are in like manner +named by us their north poles.</p> + +<p>With regard to west and east, lay in imagination +upon this cardboard plane a watch, with its face upwards; +remembering that all the planets and nearly +all the moons of the Solar System are said both to +spin on their axes, and to travel in their orbits round +the sun, <i>from west to east</i>. Note how the hands of +your watch would move in such a position. The +“west to east” motions of planets and moons would +be in exactly the opposite direction from what the motions +of the watch-hands would be.</p> + +<p>To return to Jupiter. It is believed that these +bands of color are owing to a heavy, dense atmosphere, +loaded with vast masses of cloudy vapor. By +the “size” of Jupiter, we really mean the size of this +outside envelope of clouds. How large the solid body +within may be, or whether there is any such solid +body at all, we do not know. The extreme lightness +of Jupiter, as compared with his great size, has caused +strong doubts on this head.</p> + +<p>The white belts are supposed to be the outer side +of cloud-masses shining in the sunlight. Travelers +in the Alps have seen such cloud-masses, spreading +over the whole country beneath their feet, white as +driven snow, and shining in the sunbeams which they +were hiding from villages below; or looking like soft +masses of cotton-wool, from which the mountain-peaks +rose sharply here and there.</p> + +<p><span class="pagenum" id="Page_203">[Pg 203]</span></p> + +<p>The dark spaces between seem to be rifts or breaks +in the clouds. Whether, when we look at those dark +spaces, we are looking at the body of Jupiter, or only +at lower layers of clouds, is not known. But sometimes +blacker spots show upon the dark cloud-belts, +and this seems rather as if they were only lower layers +of clouds, the black spots giving us peeps down +into still lower and deeper layers, or else perhaps to +the planet itself. These appearances remind one +strongly of the sun-spots, each with its penumbra, +umbra, and nucleus. Occasionally bright white spots +show, instead of dark ones. It is thought that they +may be caused by a violent upward rush of dense +clouds of white vapor. The white spots again recall +the sun and his <i>faculæ</i>.</p> + +<p>Jupiter’s bands are not fixed. Great changes go +on constantly among them. Sometimes a white band +will turn dark-colored, or a dark band will turn white. +Sometimes few and sometimes many belts are to be +seen. Sometimes a dark belt will lie slanting across +the others, nearly from north to south. Once, in a +single hour, an entirely new belt was seen to come +into shape. Another time, two whole belts vanished +in one day. The bands, in which such rapid movements +are seen, are often thousands of miles in breadth. +Sometimes these wide zones of clouds will remain for +weeks the same. At another time a break or rift in +them will be seen to journey swiftly over the surface +of the planet.</p> + +<p>The winds on earth are often destructive. A hurricane, +moving at the rate of ninety miles an hour, +will carry away whole buildings and level entire plantations.<span class="pagenum" id="Page_204">[Pg 204]</span> +Such hurricanes rarely, if ever, last more +than a few hours. But winds in Jupiter, judging from +the movements of the clouds, often travel at the rate +of one hundred and fifty miles an hour; and that, not +for hours only, but for many weeks together. What +manner of living beings could stand such weather +may well be questioned.</p> + +<p>Another difficulty which arises is as to the cause +of these tremendous disturbances on Jupiter. Our +earthly storms are brought about by the heat of the +sun acting on our atmosphere. But the sun-heat +which reaches Jupiter seems very far from enough to +raise such vast clouds of vapor, and to bring about +such prolonged and tremendous hurricanes of wind.</p> + +<p>What if there is another cause? What if Jupiter +is <i>not</i> a cooled body like our earth, but a liquid, seething, +bubbling mass of fiery heat—just as we believe +our earth was once upon a time, in long past ages, before +her outside crust became cold enough for men and +animals to live thereon? <i>Then</i>, indeed, we could understand +how, instead of oceans lying on his surface, +all the water of Jupiter would be driven aloft to hang +in masses of steam or be condensed into vast cloud-layers. +<i>Then</i> we could understand why a perpetual +stir of rushing winds should disturb the planet’s atmosphere.</p> + +<p>In that case would Jupiter be a planet at all? Certainly—in +the sense of obeying the sun’s control. Our +earth was once, we believe, a globe of melted matter, +glowing with heat—and farther back still, possibly, a +globe of gas. Some people are very positive about +these past changes; but it is wise not to be over-positive<span class="pagenum" id="Page_205">[Pg 205]</span> +where we can not know to a certainty what +has taken place. However, Jupiter <i>may</i> have cooled +down only to the liquid state, and if he goes on cooling +he may, by and by, gain a solid crust like the earth.</p> + +<p>This idea about Jupiter’s hot and molten state belongs +quite to late years. Certain other matters seem +to bear it out, though of actual proof we have none. +It is thought, for instance, that the dull, coppery red +light, showing often in the dark bands, may be a red +glow from the heated body within. Also it has been +calculated that Jupiter gives out much more light than +our earth would do, if increased to his size and moved +to his place—more, in fact, than we could reasonably +expect him to give out. If so, whence does he obtain +the extra brightness? If he does not shine by reflected +light alone, he probably shines also in some +additional degree by his own light.</p> + +<p>But what about Jupiter being inhabited? Would +it in such a case be quite impossible? “Impossible” +is not a word for us to use about matters where we are +ignorant. We can only say that it is impossible for +us to <i>imagine</i> any kind of living creatures finding a +home there, if our present notions about the present +state of Jupiter are correct. Then is the chief planet +of the Solar System a huge, useless monument of +God’s power to create? Not so fast. Even as merely +such a monument, he could not be useless. And +even if he were put to no present use at all, it might +be merely because this is a time of preparation for +the future. God has his times of long and slow +preparation, alike with worlds, with nations, and +with individuals.</p> + +<p><span class="pagenum" id="Page_206">[Pg 206]</span></p> + +<p>But now as to the five moons circling round Jupiter. +There used to be some very pretty ideas afloat +about the wonderful beauty of the moons, as seen +from Jupiter, their united brilliancy so far surpassing +the shining of our one poor satellite, and making up +for the dim light of Jupiter’s sun.</p> + +<p>A certain little difficulty was not quite enough considered. +If anybody were living on the surface of Jupiter, +he would have, one is inclined to think, small +chance of often seeing the moons through the cloud-laden +atmosphere.</p> + +<div class="figcenter" id="f35"> +<img src="images/fig35.jpg" alt="satellites"> +<p class="caption">SATELLITES OF JUPITER COMPARED WITH THE EARTH AND MOON.</p> +</div> + +<p>The nearest of the four larger moons to Jupiter +would, it is true, appear—when visible at all—rather +bigger than ours does to us; while the two next would +be almost half as large, and the farthest about a quarter +as large—supposing inhabitants of Jupiter to have +our powers of vision.</p> + +<p>All taken together they would cover a considerably +larger space in the sky than does our moon. But it +must be remembered that Jupiter’s moons, like ours, +shine merely by reflected sunlight. And so dim is the<span class="pagenum" id="Page_207">[Pg 207]</span> +sunshine at that distance compared with what it is +at our distance, that all the five moons together, even +if full at the same time, could only give about one-sixteenth +part of the light which we obtain from our +one full moon.</p> + +<p>Besides, they never are full together, seen from any +one part of Jupiter. The four inner moons are never +to be seen “full” at all; for just when they might be +so, they are eclipsed or shaded by Jupiter’s shadow. +The fourth sometimes escapes this eclipse, from being +so much farther away.</p> + +<p>A thought has been lately put forward, which may +or may not have truth in it. What if—instead of +Jupiter being a world, inhabited by animals and people, +as is often supposed, with a small distant sun and +five dim moons to give them light—what if Jupiter is +himself in some sort a second sun to his moons, and +what if those “moons” are really inhabited planets? +It may be so. That is all we can say. The idea is +not an impossible one.</p> + +<p>The so-called “moons” are certainly small. But +they are by no means too small for such a purpose. +Jupiter would in that case, with his five moons circling +round him, enjoying his light and warmth, be a small +picture of the sun, with his four inner planets and the +asteroids circling round him, basking in a more lavish +amount of the same.</p> + +<p>Picturing the moons as giving light to Jupiter, we +find them seemingly dim and weak for such a purpose—though, +of course, we may here make a grand +mistake in supposing the eyesight of living creatures +in Jupiter to be no better than our own eyesight.<span class="pagenum" id="Page_208">[Pg 208]</span> +Even upon earth a cat can see plainly where a man +has to grope his way in darkness.</p> + +<p>But by picturing the moons as inhabited, and +Jupiter as giving out some measure of heat and light +to make up for the lessened amount of light and heat +received from the sun, the matter becomes more easy +to our understanding.</p> + +<div class="figcenter" id="f36"> +<img src="images/fig36.jpg" alt="system"> +<p class="caption">THE SYSTEM OF JUPITER.</p> +</div> + +<p>The nearest moon has indeed a magnificent view +of Jupiter as a huge bright disk in its sky, no less<span class="pagenum" id="Page_209">[Pg 209]</span> +than three thousand times as large as our moon appears +to us, shining brightly with reflected sunlight, +and it may be glowing with a red light of his own in +addition. Even the farthest off of the five sees him +with a face sixty-five times the size of our moon. +And the varying colors and stormy changes in the +cloud-belts, viewed thus near at hand, must afford +marvelously beautiful effects.</p> + +<p>Just as Mercury, Venus, Earth, and Mars travel +round the sun, at different distances, nearly in the +same plane, so Jupiter’s five moons travel round him, +at different distances, nearly in the same plane. +Jupiter’s moons are always to be seen in a line, not +one high and another low, one near his pole and another +near his equator.</p> + +<p>The moon nearest to Jupiter, discovered in September, +1892, by Professor Barnard, now of the Yerkes +Observatory of the Chicago University, has a probable +diameter of one hundred miles, and revolves round its +primary in about twelve hours. The second satellite, +named Io, is said to be over two thousand miles in +diameter, travels round Jupiter in less than two of our +days, and is eclipsed by Jupiter’s shadow once in every +forty-two hours.</p> + +<p>The third moon, Europa, is rather smaller, takes +over three days to its journey, and suffers eclipse once +in every eighty-five hours.</p> + +<p>The fourth moon, Ganymede, is believed to be considerably +larger than Mercury, journeys round Jupiter +once a week, and is eclipsed once every hundred and +seventy-one hours.</p> + +<p>The fifth moon, Callisto, is also said to be slightly<span class="pagenum" id="Page_210">[Pg 210]</span> +larger than Mercury, performs its journey in something +more than sixteen days, and from its greater +distance suffers eclipse less often than the other four.</p> + +<p>The distance of the nearest is more than one hundred +thousand miles from Jupiter; that of the farthest, +more than one million miles.</p> + +<p>The following table presents more minutely the +results of the latest discoveries concerning these satellites:</p> + +<table> + +<tr> + <td class="tdc bl bt bb">SATELLITES.</td> + <td class="tdc bl bt bb">DISTANCE FROM<br>CENTER OF<br>JUPITER.</td> + <td class="tdc bl bt bb">DIAMETER.</td> + <td class="tdc bl bt br bb">PERIOD OF<br>REVOLUTION.</td></tr> + +<tr> + <td class="tdl bl br"></td> + <td class="tdl br"></td> + <td class="tdl br"></td> + <td class="tdr br">D. H. M. S.</td></tr> + +<tr> + <td class="tdl bl br">1. Barnard’s Satellite,</td> + <td class="tdl br">112,500 miles.</td> + <td class="tdl br">100 miles.</td> + <td class="tdr br">11 57 23</td></tr> + +<tr> + <td class="tdl bl br">2. Io,</td> + <td class="tdl br">266,000 ”</td> + <td class="tdl br">2,356 ”</td> + <td class="tdr br">1 18 27 33</td></tr> + +<tr> + <td class="tdl bl br">3. Europa,</td> + <td class="tdl br">424,000 ”</td> + <td class="tdl br">2,046 ”</td> + <td class="tdr br">3 13 13 42</td></tr> + +<tr> + <td class="tdl bl br">4. Ganymede,</td> + <td class="tdl br">676,000 ”</td> + <td class="tdl br">3,596 ”</td> + <td class="tdr br">7   3 42 33</td></tr> + +<tr> + <td class="tdl bl br bb">5. Callisto,</td> + <td class="tdl br bb">1,189,000 ”</td> + <td class="tdl br bb">2,728 ”</td> + <td class="tdr br bb">16 15 32 11</td></tr> + + +</table> + + +<p>The fact of these eclipses, and of the shadow +thrown by Jupiter’s body, shows plainly that though +he may give out some measure of light, as has been +suggested, yet that light can not be strong, or it +would prevent any shadow from being thrown by the +sunlight. Also, the dense masses of cloud around +him, though reflecting sunlight brightly, would shut +in much of his own light. Possibly it is chiefly as +heat-giver and as sunlight-reflector that Jupiter serves +his five satellites.</p> + +<p>As with our own moon, so with Jupiter’s moons, +the real center of their orbit is the sun, and not +Jupiter. They accompany Jupiter in his journey, +controlled by the sun, and immensely influenced by +Jupiter.</p> + +<p><span class="pagenum" id="Page_211">[Pg 211]</span></p> + +<p>At night the spectacle of the sky seen from Jupiter +is, with reference to the constellations, the same +as that which we see from the earth. There, as here, +shine Orion, the Great Bear, Pegasus, Andromeda, +Gemini, and all the other constellations, as well as the +diamonds of our sky: Sirius, Vega, Capella, Procyon, +Rigel, and their rivals. The 390,000,000 of miles +which separate us from Jupiter <i>in no way</i> alter the +celestial perspectives. But the most curious character +of this sky is unquestionably the spectacle of the +five moons, each of which shows a different motion. +The second moves in the firmament with an enormous +velocity, and Barnard’s satellite still faster, and +produce almost every day total eclipses of the sun in +the equatorial regions. The four inner moons are +eclipsed at each revolution, just at the hours when they +are at their “full.” The fifth alone attains the full +phase.</p> + +<p>Contrary to the generally received opinion, these +bodies do not give to Jupiter all the light which is +supposed. We might think, in fact, as has been so +often stated, that these five moons illuminate the +nights five times better relatively than our single +moon does in this respect, and that they supplement in +some measure the feebleness of the light received +from the sun. This result would be, assuredly, very +agreeable, but nature has not so arranged it. The +five satellites cover, it is true, an area of the sky +greater than our moon, but they reflect the light of a +sun twenty-seven times smaller than ours; indeed, the +total light reflected is only equal to a sixteenth of +that of our full moon, even supposing the soil of these<span class="pagenum" id="Page_212">[Pg 212]</span> +satellites to be as white as it appears to be, especially +the fifth satellite.</p> + +<p>Jupiter appears to be a world still in process of +formation, which lately—some thousands of centuries +ago—served as a sun to his own system of five or +perhaps more worlds. If the central body is not at +present inhabited, his satellites may be. In this case, +the magnificence of the spectacle presented by Jupiter +himself to the inhabitants of the satellites is worthy +of our attention. Seen from Barnard’s satellite, Jupiter’s +disk has a diameter of 47°, or more than half +the distance from the horizon to the zenith. Seen +from the second satellite, the Jovian globe presents an +immense disk of twenty degrees in diameter, or 1,400 +times larger than the full moon! What a body! +What a picture, with its belts, its cloud motions, and +its glowing coloration, seen from so near! What a +nocturnal sun!—still warm, perhaps. Add to this the +aspect of the satellites themselves seen from each other, +and you have a spectacle of which no terrestrial night +can give an idea.</p> + +<p>Such is the world of Jupiter from the double point +of view of its vital organization and of the spectacle +of external nature, seen from this immense observatory.</p> + +<p>The attraction of the planets has always played an +important part in the motion of comets and the form +of their orbits. The enormous size of Jupiter gives +it more influence than any other planet, and we are +not surprised that it should have seriously interfered +with some of the comets that belong to the Solar +System. We have already seen that Biela’s comet<span class="pagenum" id="Page_213">[Pg 213]</span> +was captured by Jupiter, and that it was probably dissolved +into meteoric dust. We show in the cut the +orbits of eight others that circle around the sun, but +retreat no farther away than Jupiter. These are the +orbits as now determined, but they vary from age to +age on account of disturbances of other planets. But +it is not likely that the comets themselves will ever +escape from the control of Jupiter.</p> + +<div class="figcenter" id="f37"> +<img src="images/fig37.jpg" alt="comets"> +<p class="caption">ORBITS OF NINE COMETS CAPTURED BY JUPITER.</p> +</div> + +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_214">[Pg 214]</span></p> + +<h2 class="nobreak" id="c18">CHAPTER XVIII.</h2> +</div> + +<p class="c sp">SATURN.</p> + + +<p><span class="smcap large">The</span> system of Jupiter is a simple system compared +with that of Saturn, next in order. For whereas +Jupiter has only five moons, Saturn has eight, and, +in addition to these, he has three wonderful rings. +Neither rings nor moons can be seen without a telescope, +on account of Saturn’s great distance from us—more +than three thousand times the distance of the +moon, or upwards of eight hundred millions of miles. +Saturn’s mean distance from the sun is eight hundred +and seventy-six million seven hundred and sixty-seven +thousand miles.</p> + +<p>Saturn does not equal his mighty brother Jupiter +in size, though he comes near enough in this respect +to be called often his “twin”—just as that small pair +of worlds, Venus and Earth, are called “twins.” +While Jupiter is equal in size to over one thousand +two hundred earths, Saturn is equal to about seven +hundred earths. And while Jupiter is equal in weight +to three hundred earths, Saturn is only equal in weight +to ninety earths. He appears to be made of very light +materials—not more than three-quarters as dense as +water. This would show the present state of Saturn +to be very different from the present state of the earth. +We are under the same uncertainty in speaking of +Saturn as in speaking of Jupiter. Like Jupiter, Saturn +is covered with dense masses of varying clouds, occasionally<span class="pagenum" id="Page_215">[Pg 215]</span> +opening and allowing the astronomer peeps +into lower cloud-levels; but rarely or never permitting +the actual body of the planet to be seen.</p> + +<p>The same perplexities also come in here, to be answered +much in the same manner. We should certainly +expect that in a vast globe like Saturn the +strong force of attraction would bind the whole into a +dense solid mass; instead of which, Saturn is about +the least solid of all the planets. He seems to be +made up of a light, watery substance, surrounded by +vapor.</p> + +<div class="figcenter" id="f38"> +<img src="images/fig38.jpg" alt="saturn"> +<p class="caption">SATURN AND THE EARTH—COMPARATIVE SIZE.</p> +</div> + +<p>One explanation can be offered. What if the globe +of Saturn be still in a red-hot, molten state, keeping +such water as would otherwise lie in oceans on his +surface, floating aloft in masses of steam, the outer +parts of which condense into clouds?</p> + +<p>No one supposes that Jupiter and Saturn are in the +same condition of fierce and tempestuous heat as the<span class="pagenum" id="Page_216">[Pg 216]</span> +sun. They may have been so once, but they must +now have cooled down very many stages from that +condition. Though no longer, however, a mass of +far-reaching flames and fiery cyclones, the body of +each may have only so far cooled as to have reached a +stage of glowing molten red-heat, keeping all water in +the form of vapor, and sending up strong rushes of +burning air to cause the hurricanes which sweep to +and fro the vast cloud-masses overhead.</p> + +<p>And if this be the case, then, with Saturn as with +Jupiter, comes the question, Can Saturn be inhabited? +And if—though we may not say it is impossible, yet +we feel it to be utterly unlikely—then again follows +the question, What if Saturn’s <i>moons</i> are inhabited?</p> + +<p>Telescopic observations tempt us to believe that +there is on this planet a quantity of heat greater than +that which results from its distance from the sun; for +the day-star as seen from Saturn is, as we have said, +ninety times smaller in surface, and its heat and light +are reduced in the same proportion. Water could +only exist in the solid state of ice, and the vapor of +water could not be produced so as to form clouds +similar to ours. Now, meteorological variations are +observed similar to those which we have noticed on +Jupiter, but less intense. Facts, then, combine with +theory to show us that the world of Saturn is at a +temperature at least as high as ours, if not higher.</p> + +<p>But the strangest feature of the Saturnian calendar +is, unquestionably, its being complicated, not only +with the fabulous number of 25,060 days in a year, +but, further, with eight different kinds of months, of +which the length varies from 22 hours to 79 days—that<span class="pagenum" id="Page_217">[Pg 217]</span> +is to say, from about two Saturnian days to 167. +It is as if we had here <i>eight moons revolving in eight +different periods</i>.</p> + +<p>The inhabitants of such a world must assuredly +differ strangely from us from all points of view. +The specific lightness of the Saturnian substances +and the density of the atmosphere will have conducted +the vital organization in an extra-terrestrial +direction, and the manifestations of life will be produced +and developed under unimaginable forms. To +suppose that there is nothing fixed, that the planet itself +is but a skeleton, that the surface is liquid, that +the living beings are gelatinous—in a word, that all is +unstable—would be to surpass the limits of scientific +induction.</p> + +<p>The diameter of the largest moon is about half the +diameter of the earth, or much larger than Mercury. +The four inner satellites are all nearer to Saturn than +our moon to us, though the most distant of the eight +is ten times as far away. The inner moon takes less +than twenty-three hours to travel round Saturn, and +the outer one over seventy-nine days.</p> + +<p>A great many charming descriptions have been +worked up, with Saturn as with Jupiter, respecting +the magnificent appearance of the eight radiant +moons, joined to the glorious shining of the rings, +as quite making up for the diminished light and heat +of the sun. But here again comes in the doubt, +whether really it is the moons who make up to Saturn +for lack of light, or whether it is Saturn who makes +up to the moons for lack of light.</p> + +<p>Certainly, Saturn’s cloudy covering would a little<span class="pagenum" id="Page_218">[Pg 218]</span> +interfere with observations of the moons by any inhabitants +of the solid body within—supposing there +be any solid body at all. And though it sounds very +wonderful to have eight moons instead of one moon, +yet all the eight together give Saturn only a very +small part of the light which we receive from our +one full moon—so much more dimly does the sun light +them up at that enormous distance.</p> + +<p>The same thing has been noticed with Saturn as +with Jupiter—that he seems to shine more brightly +than is to be expected in his position, from mere reflection +of the sun’s rays. A glowing body within, +sending a certain amount of added light through or +between the masses of clouds, would explain away +this difficulty.</p> + +<p>One more possible proof of Saturn’s half-liquid +state is to be found in his occasional very odd changes +of shape. Astronomers have been startled by a peculiar +bulging out on one side, taking off from his +roundness, and giving a square-shouldered aspect. +We may not say it is quite impossible that a solid +globe should undergo such tremendous upheavals and +outbursts as to raise a great portion of its surface five +or six hundred miles above the usual level—the +change being visible at a distance of eight hundred +millions of miles. But it would be easier to understand +the possibility of such an event, in the case +of a liquid, seething mass, than in the case of a +solid ball.</p> + +<p>On the other hand this alteration of outline may +be caused simply by a great upheaval not of the planet’s +surface, but of the overhanging layers of clouds.<span class="pagenum" id="Page_219">[Pg 219]</span> +Some such changes, only much slighter, have been +remarked in Jupiter.</p> + +<p>And now as to the rings. Nothing like them is to +be seen elsewhere in the Solar System. They are believed +to be three in number; though some would +divide them into more than three. Passing completely +round the whole body of Saturn, they rise, one +beyond another, to a height of many thousands of miles.</p> + +<p>The inner edge of the inner ring—an edge perhaps +one hundred miles in thickness—is more than ten +thousand miles from the surface of Saturn or more +strictly speaking, from the outer surface of Saturn’s +cloudy envelope. A man standing exactly on +the equator and looking up, even if no clouds came +between, would scarcely be able to see such a slender +dark line at such a height.</p> + +<p>This dark, transparent ring, described sometimes +as dusky, sometimes as richly purple, rises upwards +to a height or breadth of nine thousand miles. Closely +following it is a ring more brilliant than Saturn himself, +over eighteen thousand miles in breadth. When astronomers +talk of the “breadth” of these rings, it +must be understood that they mean the width of the +band measured <i>upwards</i>, in a direction away from the +planet.</p> + +<p>Beyond the broad, bright ring is a gap of about +one thousand seven hundred miles. Then follows the +third ring, ten thousand miles in breadth; its outermost +edge being at a height of more than forty-eight +thousand miles from Saturn. The color of the third +ring is grayish, much like the gray markings often +seen on Saturn.</p> + +<p><span class="pagenum" id="Page_220">[Pg 220]</span></p> + +<p>What would not be our admiration, our astonishment, +our stupor perhaps, if it were granted us to be +transported there alive, and, among all these extra-terrestrial +spectacles, to contemplate the strange aspect +of the rings, which stretch across the sky like a +bridge suspended in the heights of the firmament! +Suppose we lived on the Saturnian equator itself, +these rings would appear to us as a thin line drawn +across the sky above our heads, and passing exactly +through the zenith, rising from the east and increasing +in width, then descending to the west and diminishing +according to perspective. Only there have we +the rings precisely in the zenith. The traveler who +journeys from the equator towards either pole leaves +the plane of the rings, and these sink imperceptibly, +at the same time that the two extremities cease to appear +diametrically opposite, and by degrees approach +each other. What an amazing effect would be produced +by this gigantic arch, which springs from the +horizon and spans the sky! The celestial arch diminishes +in height as we approach the pole. When we +reach the sixty-third degree of latitude the summit of +the arch has descended to the level of our horizon and +the marvelous system disappears from the sky; so that +the inhabitants of those regions know nothing of it, +and find themselves in a less favorable position to +study their own world than we, who are nearly 800,000,000 +miles distant.</p> + +<p>During one-half of the Saturnian year the rings +afford an admirable moonlight on one hemisphere of +the planet, and during the other half they illuminate +the other hemisphere; but there is always a half-year<span class="pagenum" id="Page_221">[Pg 221]</span> +without “ringlight,” since the sun illuminates but one +face at a time. Notwithstanding their volume and +number, the satellites do not give as much nocturnal +light as might be supposed; for they receive, on an +equal surface, only the ninetieth part of the solar +light which our moon receives. All the Saturnian satellites +which can be at the same time above the horizon +and as near as possible to the full phase do not +afford more than the hundredth part of our lunar light. +But the result may be nearly the same, for the optic +nerve of the Saturnians may be ninety times more +sensitive than ours.</p> + +<p>But there are further strange features in this system. +The rings are so wide that their shadow extends over +the greater part of the mean latitudes. During fifteen +years the sun is to the south of the rings, and for fifteen +years it is to the north. The countries of Saturn’s +world which have the latitude of Paris endure +this shadow for more than five years. At the equator +the eclipse is shorter, and is only renewed every fifteen +years; but there are every night, so to say, eclipses +of the Saturnian moons by the rings and by themselves. +In the circumpolar regions the day-star is +never eclipsed by the rings; but the satellites revolve +in a spiral, describing fantastic rounds, and the sun +himself disappears at the pole during a long night of +fifteen years.</p> + +<p>At one time it was supposed that the rings were +solid, but they are now believed to consist of countless +myriads of meteorites, each whirling in its own appointed +pathway round the monster planet.</p> + +<div class="figcenter" id="f39"> +<img src="images/fig39.jpg" alt="saturn"> +<p class="caption">IDEAL VIEW OF SATURN’S RINGS AND SATELLITES FROM THE<br> +PLANET.</p> +</div> + +<p>As already said—leaving out of the question the +<span class="pagenum" id="Page_222">[Pg 222]</span>cloudy atmosphere—a man standing on the equator +would see nothing of the rings. A man standing at +the north pole or the south pole of Saturn could see +nothing either, since the rings would all lie below his +horizon. But if he traveled southward from the north +pole, or northward from the south pole, towards the +equator, he would in time see the ringed arch appearing +above the horizon, rising higher and growing +wider with every mile of his journey; and when he +was in a position to view the whole broad expanse, the +transparent half-dark belt below, the wide radiant band<span class="pagenum" id="Page_223">[Pg 223]</span> +rising upwards over that, and the grayish border surmounting +all, he would truly have a magnificent spectacle +before him.</p> + +<p>This magnificent spectacle is, however, by no means +always visible, even from those parts of Saturn where +alone it ever can be seen. The rings shine merely +by reflected sunlight. Necessarily, therefore, while +the sunbeams make one side bright the other side is +dark; and not only this, but the rings throw broad and +heavy shadows upon Saturn in the direction away +from the sunlight.</p> + +<p>In the daytime they probably give out a faint shining, +something like our own moon when seen in sunlight. +During the summer nights they shine, no +doubt, very beautifully. During the winter nights it +so happens that their bright side is turned away; and +not only that, but during the winter days the rings, +while giving no light themselves to the wintry hemisphere +of Saturn, completely hide the sun.</p> + +<p>When it is remembered that Saturn’s winter—that +is, the winter of each hemisphere in turn—lasts during +fifteen of our years; and when we hear of total +eclipses of the sun lasting unbroken through eight +years of such a winter, with not even bright rings to +make up for his absence, we can not think of Saturn +as a tempting residence. The sun gives Saturn +at his best only about one-ninetieth of the heat and +light that he gives to our earth; but to be deprived of +even that little for eight years at a time, does indeed +sound somewhat melancholy.</p> + +<p>Looking now at the other side of the question, the +possible inhabitants of the moons, especially those<span class="pagenum" id="Page_224">[Pg 224]</span> +near at hand, would have splendid views of Saturn +and his rings in all their varying phases. For Saturn +is a beautiful globe, wrapped in his changeful envelope +of clouds, which, seen through a telescope, are lit +up often with rainbow tints of blue and gold; a creamy +white belt lying usually on the equator; while around +extend the purple and shining and gray rings, sometimes +rivaling in bright colors Saturn himself.</p> + +<p>We are compelled to assume that the continuous +appearance of the rings is not due to real continuity +of substance, but that they are composed of flights of +disconnected satellites, so small and so closely packed +that, at the immense distance to which Saturn is removed, +they appear to form a continuous mass. There +are analogous instances in the Solar System. In the +zone of asteroids we have an undoubted instance +of a flight of disconnected bodies traveling in a ring +about a central attracting mass. The existence of +zones of meteorites traveling around the sun has long +been accepted as the only probable explanation of the +periodic returns of meteoric showers. Again, the singular +phenomenon called the Zodiacal Light is, in all +probability, caused by a ring of minute cosmical bodies +surrounding the sun. In the Milky Way and in the +ring-nebulæ we have other illustrations of similar arrangements +in nature, belonging, however, to orders +immeasurably vaster than any within the Solar System.</p> + +<p>The moons of Saturn do not, like those of Jupiter, +travel in one plane.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_225">[Pg 225]</span></p> + +<h2 class="nobreak" id="c19">CHAPTER XIX.</h2> +</div> + +<p class="c sp">URANUS AND NEPTUNE.</p> + + +<p><span class="smcap large">Till</span> the year 1781, Saturn was believed to be the +outermost planet of the Solar System, and nobody +suspected the fact of two great, lonely brother-planets +wandering around the same sun at vast distances beyond,—Uranus, +nine hundred millions of miles from +Saturn; Neptune, nine hundred millions of miles +from Uranus. No wonder they remained long undiscovered.</p> + +<p>Uranus can sometimes be seen by the unaided eye +as a dim star of the sixth magnitude. And when he +was known for a planet, it was found that he <i>had</i> +been often so seen and noted. Again and again he +had been taken for a fixed star, and as he moved on, +disappearing from that particular spot, it was supposed +that the star had vanished.</p> + +<p>One night, March 13, 1781, when William Herschel +was busily exploring the heavens with a powerful +telescope, he noticed something which he took for a +comet without a tail. He saw it was no mere point of +light like the stars, but had a tiny round disk or face, +which could be magnified. So he watched it carefully, +and found in the course of a few nights that it +moved—very slowly, certainly; but still it did move. +Further watching and calculation made it clear that, +though the newly-found heavenly body was at a very +great distance from the sun, yet it was moving slowly<span class="pagenum" id="Page_226">[Pg 226]</span> +in an orbit <i>round</i> the sun. Then it was known to be +a planet, and another member of the Solar System.</p> + +<p>From that day the reputation of Herschel rapidly +increased. King George III, who loved the sciences +and patronized them, had the astronomer presented +to him; charmed with the simple and modest account +of his efforts and his labors, he secured him a life +pension and a residence at Slough, in the neighborhood +of Windsor Castle. His sister Caroline assisted +him as secretary, copied all his observations, and +made all his calculations; the king gave him the title +and salary of assistant astronomer. Before long the +observatory at Slough surpassed in celebrity the principal +observatories of Europe; we may say that, in +the whole world, this is the place where the most discoveries +have been made.</p> + +<p>Astronomers soon applied themselves to the observation +of the new body. They supposed that this +“comet” would describe, as usually happens, a very +elongated ellipse, and that it would approach considerably +to the sun at its perihelion. But all the calculations +made on this supposition had to be constantly +recommenced. They could never succeed in representing +all its positions, although the star moved very +slowly: the observations of one month would utterly +upset the calculations of the preceding month.</p> + +<p>Several months elapsed without a suspicion that a +veritable planet was under observation, and it was not +till after recognizing that all the imaginary orbits for +the supposed comet were contradicted by the observations, +and that it had probably a circular orbit much +farther from the sun than Saturn, till then the frontier +<span class="pagenum" id="Page_228">[Pg 228]</span>of the system, that astronomers came to consider +it as a planet. Still, this was at first but a provisional +consent.</p> + +<div class="figcenter" id="f40"> +<img src="images/fig40.jpg" alt="astronomers"> +<p class="caption"><span class="smcap">Prominent Astronomers of Former Times.</span></p> +<p class="caption">Tycho Brahe, Hipparchos, Galilei, Newton,<br>Kepler, Kant, Kopernikus, Laplace.</p> +</div> + +<p>It was, in fact, more difficult than we may think to +increase without scruple the family of the sun. Indeed, +for reasons of expediency this idea was opposed. +Ancient ideas are tyrannical. Men had so +long been accustomed to consider old Saturn as the +guardian of the frontiers, that it required a rare boldness +of spirit to decide on extending these frontiers +and marking them by a new world.</p> + +<p>William Herschel proposed the name of <i>Georgium +Sidus</i> “the Star of George,” just as Galileo had given +the name of “Medicean stars” to the satellites of Jupiter +discovered by him, and as Horace had said <i>Julium +Sidus</i>. Others proposed the name of <i>Neptune</i>, in +order to maintain the mythological character, and to +give to the new body the trident of the English maritime +power; others, <i>Uranus</i>, the most ancient deity of +all, and the father of Saturn, to whom reparation was +due for so many centuries of neglect. Lalande proposed +the name of <i>Herschel</i>, to immortalize the name +of its discoverer. These last two denominations prevailed. +For a long time the planet bore the name of +Herschel; but custom has since declared for the mythological +appellation, and Jupiter, Saturn, and Uranus +succeed each other in order of descent—son, father, +and grandfather.</p> + +<p>The discovery of Uranus extended the radius of +the Solar System from 885,000,000 to 1,765,000,000 +of miles.</p> + +<p>The apparent brightness of this planet is that of<span class="pagenum" id="Page_229">[Pg 229]</span> +a star of the sixth magnitude; observers whose sight +is very piercing may succeed in recognizing it with +the naked eye when they know where to look for it. +Uranus moves slowly from west to east, and takes no +less than eighty-four years to make the complete circuit +of the sky. In its annual motion round the sun +the earth passes between the sun and Uranus every +369 days—that is to say, once in a year and four days. +It is at these times that this planet crosses the meridian +at midnight. We can observe it in the evening +sky for about six months of every year.</p> + +<p>Everybody supposed that now, at least, the outermost +member of all was discovered. But a very +strange and remarkable thing happened.</p> + +<p>Astronomers know with great exactness the paths +of the planets in the heavens. They can tell, years +beforehand, precisely what spot in space will be filled +at any particular time by any particular planet. I am +speaking now of their movements round the sun and +in the Solar System—not of the movements of the +whole family with the sun, about which little is yet +known.</p> + +<p>Each planet has its own particular pathway; its +own particular distance from the sun, varying at each +part of its pathway; its own particular speed in traveling +round the sun, changing constantly from faster +to slower or slower to faster, according to its distance +from the sun, and according to the pull backwards or +forwards of our neighboring planets in front or in rear. +For as the orbits of all the planets are ovals, with the +sun not in the middle, but somewhat to one side of the +middle, it follows that all the planets, in the course of<span class="pagenum" id="Page_230">[Pg 230]</span> +their years, are sometimes nearer to and sometimes +farther from the sun.</p> + +<p>The astronomers of the present day understand +this well, and can describe with exactness the pathway +of each planet. This knowledge does not come +merely from watching one year how the planets travel, +and remembering for another year, but is much more +a matter of close and difficult calculation. Many +things have to be considered, such as the planet’s +distance from the sun, the sun’s power of attraction, +the planet’s speed, the nearness and weight of other +neighboring planets.</p> + +<p>All these questions were gone into, and astronomers +sketched out the pathway in the heavens which they +expected Uranus to follow. He would move in such +and such an orbit, at such and such distances from the +sun, and at such and such rates of speed.</p> + +<p>But Uranus would not keep to these rules. He +quite discomfited the astronomers. Sometimes he +went fast, when, according to their notions, he ought +to have gone more slowly; and sometimes he went +slowly, when they would have looked for him to go +more fast, and the line of his orbit was quite outside +the line of the orbit which they had laid down. He +was altogether a perplexing acquaintance, and difficult +to understand. However, astronomers felt sure +of their rules and modes of calculation, often before +tested, and not found to fail. They made a guess at +an explanation. What if there were yet another +planet beyond Uranus, disturbing his motions—now +drawing him on, now dragging him back, now so far +balancing the sun’s attraction by pulling in the opposite<span class="pagenum" id="Page_231">[Pg 231]</span> +direction as to increase the distance of Uranus +from the sun?</p> + +<p>It might be so. But who could prove it? Hundreds +of years might pass before any astronomer, in +his star-gazing, should happen to light upon such a +dim and distant world. Nay, the supposed planet +might be, like Uranus, actually seen, and only be mistaken +for a “variable star,” shining but to disappear.</p> + +<p>There the matter seemed likely to rest. There the +matter probably would have rested for a good while, +had not two men set themselves to conquer the difficulty. +One was a young Englishman, a student of +Cambridge, John Couch Adams; the other, a young +Frenchman, Urbain Jean Joseph Leverrier,—both being +astronomers.</p> + +<p>Each worked independently of the other, neither +knowing of the other’s toil. The task which they +had undertaken was no light one—that of reaching +out into the unknown depths of space to find an unknown +planet.</p> + +<p>Each of these silent searchers into the sky-depths +calculated what the orbit and speed of Uranus would +be, without the presence of another disturbing planet +beyond. Each examined what the amount of disturbance +was, and considered the degree of attraction +needful to produce that disturbance, together with +the direction from which it had come. Each, in +short, gradually worked his way through calculations +far too deep and difficult for ordinary minds to grasp, +till he had found just that spot in the heavens where a +planet <i>ought</i> to be, to cause, according to known laws, +just such an effect upon Uranus as had been observed.</p> + +<p><span class="pagenum" id="Page_232">[Pg 232]</span></p> + +<p>Adams finished his calculation first, and sent the +result to two different observatories. Unfortunately, +his report was not eagerly taken up. It was, in fact, +hardly believed. Leverrier finished his calculation +also, and sent the result to the Berlin Observatory. +The planet was actually seen in England first, but the +discovery was actually made known from Berlin first. +The young Englishman had been beforehand, but the +young Frenchman gained foremost honor.</p> + +<p>It was on the 23d of September, 1846, that Leverrier’s +letter reached the Berlin astronomers. The +sky that night was clear, and we can easily understand +with what anxiety Dr. Galle directed his telescope to +the heavens. The instrument was pointed in accordance +with Leverrier’s instructions. The field of view +showed, as does every part of the heavens, a multitude +of stars. One of these was really the planet. +The new chart—prepared by the Berlin Academy of +Sciences, upon which the place of every star, down +even to those of the tenth magnitude, was engraved—was +unrolled, and, star by star, the heavens were compared +with the chart. As the process of identification +went on, one object after another was found in the +heavens as engraved on the chart, and was of course +rejected. At length a star of the eighth magnitude—a +brilliant object—was brought into review. The +map was examined, but there was no star there. +This object could not have been in its present place +when the map was formed. The object was therefore +a wanderer—a planet. Yet it is necessary to be +excessively cautious in such a matter.</p> + +<p>Many possibilities had to be guarded against. It<span class="pagenum" id="Page_233">[Pg 233]</span> +was, for instance, possible that the object was really a +star which, by some mischance, eluded the careful eye +of the astronomer who constructed the map. It was +even possible that the star might be one of the large +class of variables which alternate in brightness, and +it might have been conceivable that it was too faint +to be seen when the chart was made. Even if neither +of these explanations would answer, it was still necessary +to show that the object was now moving, and +moving with that particular velocity and in that particular +direction which the theory of Leverrier indicated. +The lapse of a single day was sufficient to +dissipate all doubts. The next night the object was +again observed. It had moved, and when its motion +was measured it was found to accord precisely with +what Leverrier had foretold. Indeed, as if no circumstance +in the confirmation should be wanting, it was +ascertained that the diameter of the planet, as measured +by the micrometers at Berlin, was practically coincident +with that anticipated by Leverrier.</p> + +<p>The world speedily rang with the news of this +splendid achievement. Instantly the name of Leverrier +rose to a pinnacle hardly surpassed by that of any +astronomer of any age or country. For a moment it +seemed as if the French nation were to enjoy the undivided +honor of this splendid triumph. But in the +midst of the pæans of triumph with which the enthusiastic +French nation hailed the discovery of Leverrier, +there appeared a letter from Sir John Herschel +in the <i>Athenæum</i> for 3d October, 1846, in which he +announced the researches made by Adams, and claimed +for him a participation in the glory of the discovery.<span class="pagenum" id="Page_234">[Pg 234]</span> +Subsequent inquiry has shown that this claim was a +just one, and it is now universally admitted by all independent +authorities.</p> + +<p>This, however, was of slight comparative importance. +The truly wonderful part of the matter was, +that these two men could have so reasoned that, from +the movements of one lately-discovered planet, they +could point out the exact spot where a yet more distant +planet ought to be, and that close to this very +spot the planet was found. For when, both in England +and in Germany, powerful telescopes were pointed +in the direction named—<i>there the planet was</i>. No +doubt about the matter. Not a star, but a real new +planet in the far distance, wandering slowly round +the sun.</p> + +<p>Here we have the discovery of Neptune in its simple +grandeur. This discovery is splendid, and of the +highest order from a philosophical point of view, for +it proves the security and the precision of the data of +modern astronomy. Considered from the point of +view of practical astronomy, it was but a simple exercise +of calculation, and the most eminent astronomers +saw in it nothing else! It was only after its verification, +its public demonstration—it was only after the +visual discovery of Neptune—that they had their eyes +opened, and felt for a moment the dizziness of the infinite +in view of the horizon revealed by the Neptunian +perspective. The author of the calculation himself, +the transcendent mathematician, did not even +give himself the trouble to take a telescope and look +at the sky to see whether a planet was really there! +I even believe that he never saw it. For him, however,<span class="pagenum" id="Page_235">[Pg 235]</span> +then and always, to the end of his life, astronomy +was entirely inclosed in formulæ—the stars were but +centers of force.</p> + +<p>Very often I submitted to him the doubts of an +anxious mind on the great problems of infinitude: I +asked him if he thought that the other planets might +be inhabited like ours, what might be especially the +strange vital conditions of a world separated from the +sun by the distance of Neptune, what might be the +retinue of innumerable suns scattered in immensity, +what astonishing colored lights the double stars should +shed on the unknown planets which gravitate in these +distant systems. His replies always showed me that +these questions had no interest for him, and that, in +his opinion, the essential knowledge of the universe +consisted in equations, formulæ, and logarithmic series +having for their object the mathematical theory of velocities +and forces.</p> + +<p>But it is not the less surprising that he had not +the <i>curiosity</i> to verify the position of his planet, which +would have been easy, since it shows a planetary disk; +and, besides, he might have had the aid of a chart, +because he had only to ask for these charts from the +Berlin Observatory, where they had just been finished +and <i>published</i>. It is not the less surprising that Arago, +who was more of a physicist than a mathematician, +more of a naturalist than a calculator, and whose +mind had so remarkable a synthetical character, had +not himself directed one of the telescopes of the observatory +towards this point of the sky, and that no +other French astronomer had this idea. But what surprises +us still more is to know that <i>nearly a year before<span class="pagenum" id="Page_236">[Pg 236]</span></i>, +in October, 1845, a young student of the University +of Cambridge, Mr. Adams, had sought the +solution of the <i>same</i> problem, obtained the same results, +and communicated these results to the director +of the Greenwich Observatory, and that the astronomer +to whom these results were confided had said +nothing, and had not himself searched in the sky +for the optical verification of his compatriot’s solution!</p> + +<p>This was indeed a triumph of human intellect. +Yet it is no matter for human pride, but rather of +thankfulness to God, who gave to man this marvelous +reasoning power. And the very delight we have in +such a success may humble us in the recollection of +the vast amount lying beyond of the utterly unknown. +But while the rare mind of a Newton could meekly +realize the littleness of all he knew, lesser minds are +very apt to be puffed up with the thought of what the +human intellect can accomplish.</p> + +<p>Perhaps the chief feeling of lawful satisfaction in +this particular discovery arises from the fact that it +gives marked and strong proof of the truth of our +present astronomical system and beliefs. Many mistakes +may be made, and much has often to be unlearned. +Nevertheless, if the general principles of +modern astronomy were wrong, if the commonly-received +facts were a delusion, such complete success +could not have attended so delicate and difficult a +calculation.</p> + +<p>We do not know much about these two outer planets, +owing to their enormous distance from us. Uranus +is in size equal to seventy-four earths, and Neptune is<span class="pagenum" id="Page_237">[Pg 237]</span> +in size equal to one hundred and five earths. Both +these planets are formed of somewhat heavier materials +than Saturn, being about as dense as water.</p> + +<p>The size of the sun as seen from Uranus is about +one three-hundred-and-ninetieth part of the size of +the sun we see. To Neptune he shows a disk only +one nine-hundredth part of the size of that visible to +us—no disk at all, in fact, but only starlike brilliancy.</p> + +<p>The Uranian year lasts about eighty-four of our +years; and this, with a very sloping axis, must cause +most long and dreary winters, the tiny sun being hidden +from parts of the planet during half an earthly +life-time.</p> + +<p>Uranus has at least four moons, traveling in very +different planes from the plane of the ecliptic. Once +it was thought that he had eight, but astronomers have +since searched in vain for the other four, believed for +a while to exist. Neptune has one moon, and may +possess others not yet discovered.</p> + +<p>Sir Henry Holland, the celebrated physician, and +a devoted student of astronomy, has left on record an +incident of his life connected with the planet Neptune +of singular interest. I give it here, and in his own +words, because it is scarcely likely otherwise to fall +under the notice of astronomical readers. After stating +that his interest in astronomy had led him to take advantage +of all opportunities of visiting foreign observatories, +he says:</p> + +<p>“Some of these opportunities, indeed, arising out +of my visits to observatories both in Europe and +America, have been remarkable enough to warrant a +more particular mention of them. That which most<span class="pagenum" id="Page_238">[Pg 238]</span> +strongly clings to my memory is an evening I passed +with Encke and Galle in the observatory at Berlin, +some ten or twelve days after the discovery of the +planet Neptune on this very spot; and when every +night’s observations of its motions had still an especial +value in denoting the elements of its orbit. I +had casually heard of the discovery at Bremen, and +lost no time in hurrying on to Berlin. The night in +question was one of floating clouds, gradually growing +into cumuli; and hour after hour passed away +without sight of the planet which had just come to +our knowledge by so wonderful a method of predictive +research. Frustrated in this main point, it was +some compensation to stay and converse with Encke +in his own observatory, one signalized by so many +discoveries, the stillness and darkness of the place +broken only by the solemn ticking of the astronomical +clock, which, as the unfailing interpreter of the +celestial times and motions, has a sort of living existence +to the astronomer. Among other things discussed, +while thus sitting together in a sort of tremulous +impatience, was the name to be given to the new +planet. Encke told me he had thought of ‘Vulcan,’ +but deemed it right to remit the choice to Leverrier, +then supposed to be the sole indicator of the planet and +its place in the heavens; adding that he expected Leverrier’s +answer by the first post. Not an hour had +elapsed before a knock at the door of the observatory +announced the letter expected. Encke read it aloud; +and, coming to the passage where Leverrier proposed +the name of ‘Neptune,’ exclaimed, ‘<i>So lass den Namen +Neptun sein.</i>’</p> + +<p><span class="pagenum" id="Page_239">[Pg 239]</span></p> + +<p>It was a midnight scene not easily to be forgotten. +A royal baptism, with its long array of titles, would +ill compare with this simple naming of the remote +and solitary planet thus wonderfully discovered. There +is no place, indeed, where the grandeur and wild ambitions +of the world are so thoroughly rebuked and +dwarfed into littleness as in the astronomical observatory. +As a practical illustration of this remark, +I would add that my own knowledge of astronomers—those +who have worked themselves with the telescope—has +shown them to be generally men of tranquil +temperament, and less disturbed than others by +worldly affairs, or by the quarrels incident even to +scientific research.”</p> + +<p>The same reasoning which has been used in reference +to Jupiter and his moons, and to Saturn and his +moons, might perhaps be applied also to Uranus and +Neptune and their moons.</p> + +<p>We know too little yet of their condition to venture +far in such speculations. Still, taking the matter as +a whole, there seem many reasons to incline us to the +idea that each of the four greater outside planets may +be a kind of secondary half-cooled sun to his satellites, +helping to make up to them for the small amount +of light and heat which they can obtain from the far-off +sun.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_240">[Pg 240]</span></p> + +<h2 class="nobreak" id="c20">CHAPTER XX.</h2> +</div> + +<p class="c sp">COMETS AND METEORITES.</p> + + +<p><span class="smcap large">A curious</span> discovery has been lately made. It is +that some sort of mysterious tie seems to exist between +comets and meteorites. For a long while this +was never suspected. How should it be? The comets, +so large, so airy, so light; the meteorites, so small, so +solid, so heavy,—how could it possibly be supposed +that the one had anything to do with the other? But +supposings often have to give in to facts. Astronomers +are gradually becoming convinced that there certainly +is a connection between the two.</p> + +<p>Strange to say, comets and meteorites occupy—sometimes, +at least—the very same pathways in the +heavens, the very same orbits round the sun. A certain +number of meteorite systems are now pretty well +known to astronomers as regularly met by our earth +at certain points in her yearly journey. Some of +these systems or rings have each a comet belonging +to it—not merely journeying near, but actually in its +midst, on the same orbit.</p> + +<p>Perhaps it would be more correct to say that the +meteorites belong to the comet, than that the comet +belongs to the meteorites. We tread here on uncertain +ground; for whether the meteorites spring from +the comet, or whether the comet springs from the +meteorites, or whether each has been brought into<span class="pagenum" id="Page_241">[Pg 241]</span> +existence independently of the other, no one can at +present say.</p> + +<p>Though it is out of our power to explain the kind +of connection, yet a connection there plainly is. So +many instances are now known of a comet and a +meteorite ring traveling together that it is doubtful +whether any such ring could be found without a +comet in its midst. By and by the doubt may spring +up whether there ever exists a comet without a train +of meteorites following him.</p> + +<p>Among the many different meteorite rings which +are known, two of the most important are the so-called +August and November systems. Of these two, +the November system must claim our chief attention. +Not that we are at all sure of these being the most +important meteorite rings in the Solar System. On +the contrary, as regards the November ring, we have +some reason to think that matters may lie just the +other way.</p> + +<p>The comet belonging to the November system is +a small one—quite an insignificant little comet—only +visible through a telescope. We do not, of course, +know positively that larger comets and greater meteorite +systems generally go together, but, to say the least, +it seems likely. And if the greatness of a ring can +at all be judged of by the size of its comet, then the +November system must be a third-rate specimen of +its kind. It is of particular importance to us, merely +because it happens to be the one into which our +earth plunges most deeply, and which we therefore +see and know the best. The August ring is, on the +contrary, connected with a magnificent comet, and<span class="pagenum" id="Page_242">[Pg 242]</span> +may be a far grander system. But our pathway does +not lead us into the midst of the August meteors as +into those of November. We pass, seemingly, through +its outskirts.</p> + +<p>The meteorites of the November system are very +small. They are believed to weigh commonly only +a few grains each. If they were larger and heavier, +some of them would fall to earth as aerolites, not +more than half-burnt in their rush through the atmosphere. +But this they are never found to do.</p> + +<p>There are known meteorite systems, which our +earth merely touches or grazes in passing, from which +drop aerolites of a very different description—large, +heavy, solid masses. It is well for us that we do not +plunge into the midst of any such ring, or we might +find our air, after all, a poor protection.</p> + +<p>The last grand display of the November system of +meteorites took place in the years 1866 to 1869, being +continued more or less during three or four Novembers +following. The next grand display will occur +in the year 1899.</p> + +<p>For this system—Leonides, as it is called, because +the falling-stars in this display seem all to shoot towards +us from a spot in the constellation Leo—seems +to have a “time” or “year” of thirty-three and a +quarter earthly years. The shape of its orbit is a +very long ellipse, near one end of which is the sun, +while the other end is believed to reach farther away +than the orbit of Uranus.</p> + +<p>A great deal of curiosity has been felt about the +actual length and breadth and depth of the stream of +meteorites through which our solid earth has so often<span class="pagenum" id="Page_243">[Pg 243]</span> +plowed her way. During many hours at a time, +lookers-on have watched the magnificent display of +heavenly fireworks,—not a mere shooting-star here +and there, as on common nights, but radiant meteors, +flashing and dying by thousands through the sky. +In 1866 no less than eight thousand meteors, in two +hours and a quarter, were counted from the Greenwich +Observatory in England. A natural wonder +sprang up in many minds as to the extent of the ring +from which they fell.</p> + +<p>For not in one night only, but in several nights +during three or four years, and that not once only but +once in every thirty-three years, thousands and tens +of thousands appear to have been stolen by our earth +from the meteorite-ring, never again to be restored. +Yet each time we touch the ring, we find the abundance +of little meteorites in nowise seemingly lessened.</p> + +<p>When speaking of a “ring” of meteorites, it must +not be supposed that necessarily the meteorites form +a whole unbroken ring all round the long oval orbit. +There may be no breaks. There may be a more or +less thin scattering throughout the entire length of +the pathway. But the meteorites certainly seem to +cluster far more densely in some parts of the orbit +than in other parts, and it was about the size of the +densest cluster that so much curiosity was felt.</p> + +<p>Little can be positively known, though it is very +certain that the cluster must be enormous in extent. +Three or four years running, as our earth, after journeying +the whole way round the sun, came again to +that point in her orbit where she passes through the<span class="pagenum" id="Page_244">[Pg 244]</span> +orbit of the Leonides, she found the thick stream of +meteorites still pouring on, though each year lessening +in amount. Taking into account this fact, and +also the numbers that were seen to fall night after +night, and also the speed of our earth, a “rough estimate” +was formed.</p> + +<p>The length of this dense cluster is supposed to +reach to many hundreds of millions of miles. The +thickness or depth of the stream is calculated to be +in parts over five hundred thousand miles, and the +breadth about ten times as much as the depth. Each +meteorite is probably at a considerable distance from +his neighbor; but the whole mass of them, when in +the near neighborhood of the sun, must form a magnificent +sight.</p> + +<p>And if this be only a third-rate system, what must +a first-rate system be like? And how many such systems +are there throughout the sun’s wide domains? +The most powerful telescope gives us no hint of the +existence of these rings till we find ourselves in their +midst.</p> + +<p>It may be that they are numbered by thousands, +even by millions. The whole of the Solar System—nay, +the very depths of space beyond—may, for aught +we know, be crowded with meteorite systems. Every +comet may have his stream of meteorites following +him. But though the comet is visible to us, the meteorites +are not. Billions upon billions of them may +be ever rushing round our sun, entirely beyond our +ken, till one or another straggler touches our atmosphere +to flash and die as a “shooting star” in our sight.</p> + +<p>We have, and with our present powers we can<span class="pagenum" id="Page_245">[Pg 245]</span> +have, no certainty as to all this. But I may quote +here the illustration of a well-known astronomical +writer on the subject.</p> + +<p>Suppose a blind man were walking out of doors +along a high road, and during the course of a few +miles were to feel rain falling constantly upon him. +Would it be reasonable on his part, if he concluded +that a small shower of rain had accompanied him along +the road as he moved, but that fine weather certainly +existed on either side of the road? On the contrary, +he might be sure that the drops which he felt, were +but a few among millions falling all together.</p> + +<p>Or, look at the raindrops on your window some +dull day at home. Count how many there are? Could +you, with any show of common sense, decide that +those raindrops, and those alone, had fallen that day? +So, when we find these showers of meteorites falling +to earth, we may safely conclude that, for every one +which touches our atmosphere, myriads rush elsewhere +in space, never coming near us.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_246">[Pg 246]</span></p> + +<h2 class="nobreak" id="c21">CHAPTER XXI.</h2> +</div> + +<p class="c sp">MORE ABOUT COMETS AND METEORITES.</p> + + +<p><span class="smcap large">The</span> three prominent features of comets—a head, +nucleus, and tail—are seen only in particular instances. +The great majority appear as faint globular +masses of vapor, with little or no central condensation, +and without tails. On the other hand, some +have a strongly-defined nucleus, which shines with a +light as vivacious as that of the planets, so as to be +even visible in the daytime. This was the case with +one seen at Rome soon after the assassination of Julius +Cæsar, believed by the populace to be the soul of +the dictator translated to the skies. The first comet +of the year 1442 was also so brilliant, that the light of +the sun at noon, at the end of March, did not prevent +it from being seen; and the second, which appeared +in the summer, was visible for a considerable time +before sunset. In 1532, the people of Milan were +alarmed by the appearance of a star in the broad daylight; +and as Venus was not then in a position to be +visible, the object is inferred to have been a comet. +Tycho Brahe discovered the comet of 1577, from his +observatory in the isle of Huene, in the sound, before +sunset; and Chizeaux saw the comet of 1744, at one +o’clock in the afternoon, without a telescope.</p> + +<p>The comet of 1843, already referred to in a previous +chapter, was distinctly seen at noon by many persons +in the streets of Bologna without the aid of glasses.<span class="pagenum" id="Page_247">[Pg 247]</span> +The nucleus is generally of small size, but the surrounding +nebulosity, which forms the head, is often of +immense extent; and the hazy envelope, the “horrid +hair” of poetry, is sometimes seen separated from it +by a dark space, encircling it like a ring. This was +the aspect of the comet of 1811. The entire diameter of +the head measured 1,250,000 miles, and hence its bulk +was nearly three times that of the sun, and four million +times that of the earth. But such extraordinary +dimensions are quite exceptional.</p> + +<div class="figcenter" id="f41"> +<img src="images/fig41.jpg" alt="1811"> +<p class="caption">THE GREAT COMET OF 1811.</p> +</div> + +<p>Popular impressions respecting the supposed terrestrial +effects of the comet of 1811—a fine object in +the autumn of that year, long remembered by many—are +on record. It was gravely noted, that wasps<span class="pagenum" id="Page_248">[Pg 248]</span> +were very few in number; that flies became blind, +and disappeared early; and that twins were born more +frequently than usual. The season was remarkable +for its bountiful harvest and abundant vintage. Grapes, +figs, melons, and other fruits, were not only produced +in extraordinary quantity, but of delicious flavor, so +that “comet wines” had distinct bins allotted to them +in the cellars of merchants, and were sold at high +prices. There is, however, no fact better attested, by +a comparison of observations, than that comets have +no influence whatever in heightening or depressing +the temperature of the seasons. The fine fruits and +ample harvest of the year in question were, therefore, +coincidences merely with the celestial phenomenon, +without the slightest physical connection with it.</p> + +<p>Though the advanced civilization of recent times +has led to juster views of cometary apparitions than +to regard them as divinely-appointed omens of terrestrial +calamity, yet society is apt to be nervous respecting +these bodies, as likely to cause some great natural +convulsion by collision with our globe.</p> + +<p>The great comet, which in 1682 received first the +name of Halley’s comet, appeared last in 1835, his +return having been foretold within three days of its +actually taking place. For Halley’s comet is a member +of the Solar System, having a yearly journey of +seventy-six earthly years. He journeys nearer the +sun than Venus, and travels farther away than +Neptune.</p> + +<p>In the years 1858, 1861, and 1862, three more +comets appeared, all visible without the help of a +telescope. Of these three, Donati’s comet, in 1858,<span class="pagenum" id="Page_249">[Pg 249]</span> +was far superior to the rest. This fine object was +first discovered on the 2d of June by Dr. Donati, at +Florence. It appeared at first as a faint nebulous +patch of light, without any remarkable condensation; +and as its motion towards the sun at that time was +slow, it was not till the beginning of September that +it became visible to the naked eye. A short tail was +then seen on the side opposite to the sun.</p> + +<div class="figcenter" id="f42"> +<img src="images/fig42.jpg" alt="1858"> +<p class="caption">DONATI’S COMET, 1858.</p> +</div> + +<p>The development was afterwards rapid, and the +comet became equally interesting to the professional +astronomer and to the unlearned gazer. In the first +week of October the tail attained its greatest length, +36°. At this time the tail was sensibly curved, and<span class="pagenum" id="Page_250">[Pg 250]</span> +had the appearance of a large ostrich-feather when +waved gently in the hand. At the latter end of October +the comet was lost in the evening twilight. Its +nearest approach to the earth was about equal to half +the distance of the earth from the sun, and the nearest +approach to Venus was about one-ninth part of that +distance. An elliptical orbit, with a periodic time of +more than 2,000 years, has been assigned to our late +visitor.</p> + +<p>It was a singular fact about this comet that at one +time the star Arcturus could be seen shining through +the densest portion of the tail, close to the nucleus. +Now, although the faintest cloud-wreath of earth +would dim, if not hide, this star, yet the tail of the +great comet was of so transparent a nature that Arcturus +shone undimmed, as if no veil had come between. +The exceedingly slight and airy texture of a +comet’s tail could hardly be more plainly shown. It +was this gauzy appendage to a little nucleus which +men once thought could destroy our solid earth at a +single blow!</p> + +<p>These cometary trains generally appear straight, +or at least, by the effect of perspective, they seem to +be directed along the arcs of great circles of the celestial +sphere. Some are recorded, however, which presented +a different appearance. Thus, in 1689, a comet +was seen whose tail, according to the historians, was +curved like a Turkish saber. This tail had a total +length of 68°. It was the same with the beautiful +comet of Donati, which we admired in 1858, and of +which the tail had a very decided curvature.</p> + +<p>A comet can only be observed in the sky for a<span class="pagenum" id="Page_251">[Pg 251]</span> +limited time. We perceive it at first in a region +where nothing was visible on preceding days. The +next day, the third day, we see it again; but it has +changed its place considerably among the constellations. +We can thus follow it in the sky for a certain +number of days, often during several months; then we +cease to perceive it. Often the comet is lost to view +because it approaches the sun, and the vivid light of +that body hides it completely; but soon we observe it +again on the other side of the sun, and it is not till +some time afterwards that it definitely disappears. +Some have been visible at noonday, quite near the +sun, like that of 1882, on September 17th.</p> + +<p>Yet, while taking care not to overrate, we must not +underrate. True, the comets are delicate and slight +in structure. One comet, in 1770, wandered into the +very midst of Jupiter’s moons, and so small was its +weight that it had no power whatever, so far as has +been detected, to disturb the said moons in their orbits. +Jupiter and his moons did very seriously disturb +the comet, however; and when he came out +from their midst, though none the worse for his adventure, +he was forced to travel in an entirely new +orbit, and never managed to get back to his old pathway +again.</p> + +<p>But there are comets <i>and</i> comets, some being +heavier than others. The comet named after Donati, +albeit too transparent to hide a star, was yet so immense +in size that his weight was calculated by one +astronomer to amount to as much as a mass of water +forty thousand miles square and one hundred and nine +yards deep.</p> + +<p><span class="pagenum" id="Page_252">[Pg 252]</span></p> + +<p>When first noticed, Donati’s comet had, like all +large comets, a bright envelope of light round the +nucleus. After a while the one envelope grew into +three envelopes, and a new tail formed beside the +principal tail, which for a time was seen to bend +gracefully into a curve, like a splendid plume. A +third, but much fainter tail, also made its appearance, +and many angry-looking jets were poured out from +the nucleus. These changes took place while the +comet was passing through the great heat of near +neighborhood to the sun. Afterwards, as he passed +away, he seemed gradually to cool down and grow +quiet. The singular changes in the appearance of Newton’s +comet have been earlier noticed. No marvel +that he did undergo some alterations. The tremendous +glare and burning heat which that comet had to +endure in his rush past the sun, were more than +twenty-five thousand times as much as the glare and +heat of the fiercest tropical noonday ever known upon +earth. Can we wonder that he should have shown +“signs of great excitement,” that his head should have +grown larger and his tail longer?</p> + +<p>It certainly was amazing, and past comprehension, +that the said tail, over ninety millions of miles in +length, should in four days have seemingly swept +round in a tremendous half-circle, so as first to point +in one direction, and then to point in just the opposite +direction.</p> + +<p>We are much in the habit of speaking about +comets as traveling through the heavens with their +tails streaming behind them. But though this is +sometimes the case, it is by no means always.</p> + +<p><span class="pagenum" id="Page_253">[Pg 253]</span></p> + +<p>The tails of comets always stream <i>away from the +sun</i>—whether before or behind the comet’s head seeming +to be a matter of indifference. As the comet comes +hurrying along his orbit, with ever-increasing speed, +towards the sun, the head journeys first, and the long +tail follows after. But as the comet rounds the loop +of his orbit near the sun—the point nearest of all +being called his <i>perihelion</i>—the head always remains +towards the sun, while the tail swings, or seems to +swing, in a magnificent sweep round, pointing always +in the direction just away from the sun.</p> + +<p>Then, as the comet journeys with slackening speed, +on the other side of his orbit, towards the distant +<i>aphelion</i>, or farthest point from the sun, he still keeps +his head towards the sun. So, at this part of his +passage, in place of the head going first and the tail +following after, the tail goes first and the head follows +after. The comet thus appears to be moving backwards; +or, like an engine pushing instead of drawing +a train, the head seems to be driving the tail +before it.</p> + +<div class="figcenter" id="f43"> +<img src="images/fig43.jpg" alt="1744"> +<p class="caption">GREAT COMET OF 1744.</p> +</div> + +<div class="figcenter1" id="f44"> +<img src="images/fig44.jpg" alt="1888"> +<p class="caption">THE FIRST COMET OF 1888—JUNE 4.</p> +</div> + +<p>The sun, then, acts on these bodies when they approach +him, produces in them important physical and +chemical transformations, and exercises on their developed +atmosphere a repulsive force, the nature of +which is still unknown to us, but the effects of which +coincide with the formation and development of the +tails. The tails are thus, in the extension of the +cometary atmosphere, driven back, either by the solar +heat, by the light, by electricity, or by other forces; +and this extension is rather a motion in the ether than +a real transport of matter, at least in the great comets +<span class="pagenum" id="Page_254">[Pg 254]</span>which approach very near the sun, and in their immense +luminous appendages. The effects produced +and observed are not the same in all comets, which +proves that they differ from each other in several respects. +The tails have sometimes been seen to diminish +before the perihelion passage, as in 1835. +<span class="pagenum" id="Page_255">[Pg 255]</span>Luminous envelopes have also been seen succeeding +each other round the head, concentrating themselves +on the side opposite to the sun, and leaving the central +line of the tail darker than the two sides. This +is what happened in the Donati comet and in that of +1861. Sometimes a secondary tail has been seen projected +towards the sun, as in 1824, 1850, 1851, and +1880. Comets have been seen with the head enveloped +in phosphorescence, surrounding them with a +sort of luminous atmosphere. Comets have also been +seen with three, four, five, and <i>six tails</i>, like that of +1744, for example, which appeared like a splendid +aurora borealis rising majestically in the sky, until, +the celestial fan being raised to its full height, it was +perceived that the six jets of light all proceeded from +the same point, which was nothing else but the nucleus +of a comet. On the other hand, the nuclei +themselves show great variations—some appear simply +nebulous, and permit the faintest stars to be visible<span class="pagenum" id="Page_256">[Pg 256]</span> +through them; others seem to be formed of one +or more solid masses surrounded by an enormous atmosphere; +in others, again, a nucleus does not exist, +as in the Southern comet of 1887. One of the comets +of 1888 showed a triple nucleus and a bristling coma, +as may be seen in the cut. We may, then, consider +that the wandering bodies collected under the name +of comets are of several origins and <i>several different +species</i>.</p> + +<p><i>Why</i> the tails of comets should so persistently +avoid the sun it is impossible to say. We do not +even know whether the cause lies actually in the sun +or in the comet. Astronomers speak of the “repulsive +energy” with which the sun “sweeps away” from his +neighborhood the light vapory matter of which the +tails are made. But the how and the wherefore of +this strange seeming repulsion they can not explain. +For at the selfsame time the sun appears to be attracting +the comet towards himself, and driving the comet’s +tail away from himself.</p> + +<p>A few of the more well-known comets have been +mentioned; but a year rarely passes in which at least +one comet is not discovered, though often only a small +specimen, sometimes even tailless and hairless. No +doubt many others pass unseen. The large and grand +ones only come to view now and then.</p> + +<p>What are comets and meteorites made of? Respecting +comets, a good many ideas are put forth, and +a good many guesses are made, as to “burning gas,” +“luminous vapor,” “beams of light,” and so on. But +in truth, little is known about the matter. Respecting +meteorites, we can speak more certainly. A good<span class="pagenum" id="Page_257">[Pg 257]</span> +many meteorites have fallen to earth as aerolites, and +have been carefully examined. They are found to +contain nickel, cobalt, iron, phosphorus, and sometimes +at least, a large supply of hydrogen gas.</p> + +<p>Not only do solid aerolites fall half-burnt to the +ground, but even when the meteorites are quite consumed +in the air, the fine dust remaining still sinks +earthward. This fine dust has been found upon +mountain-tops, and has been proved by close examination +to be precisely the same as the material of the +solid aerolites.</p> + +<p>A luminous body of sensible dimensions rapidly +traverses space, diffusing on all sides a vivid light—like +a globe of fire of which the apparent size is often +comparable with that of the moon. This body usually +leaves behind it a perceptible luminous train. On or +immediately after its appearance it often produces an +explosion, and sometimes even several successive explosions, +which are heard at great distances. These +explosions are also often accompanied by the division +of the globe of fire into luminous fragments, more or +less numerous, which seem to be projected in different +directions. This phenomenon constitutes what is +called a <i>meteor</i>, properly speaking, or a <i>bolide</i>. It is +produced during the day as well as the night. The +light which it causes in the former case is greatly enfeebled +by the presence of the solar light, and it is +only when it is developed with sufficient intensity that +it can be perceived.</p> + +<p>In the British Museum there is a superb collection +of meteorites. They have been brought together from +all parts of the earth, and vary in size from bodies not<span class="pagenum" id="Page_258">[Pg 258]</span> +much larger than a pin’s-head up to vast masses +weighing many hundred pounds. There are also +many models of celebrated meteorites, of which the +originals are dispersed through various other museums.</p> + +<p>Many of these objects have nothing very remarkable +in their external appearance. If they were met +with on the sea-beach, they would be passed by without +more notice than would be given to any other +stone. Yet what a history such a stone might tell us +if we could only manage to obtain it! It fell; it was +seen to fall from the sky; but what was its course anterior +to that movement? Where was it one hundred +years ago, one thousand years ago? Through what +regions of space has it wandered? Why did it never +fall before? Why has it actually now fallen? Such +are some of the questions which crowd upon us as we +ponder over these most interesting bodies. Some of +these objects are composed of very characteristic materials. +Take, for example, one of the more recent meteorites, +known as the Rowton siderite. This body differs +very much from the more ordinary kind of stony meteorite. +It is an object which even a casual passer-by +would hardly pass without notice. Its great weight +would also attract attention, while if it be scratched +or rubbed with a file, it would be found that it was +not in any sense a stone, but that it was a mass of +nearly pure iron. We know the circumstances under +which that piece of iron fell to the earth. It was on +the 20th of April, 1876, about 3.40 P. M., that a strange +rumbling noise, followed by a startling explosion, was +heard over an area of several miles in extent among +the villages in Shropshire. About an hour after this<span class="pagenum" id="Page_259">[Pg 259]</span> +occurrence, a farmer noticed the ground in one of his +grass-fields to have been disturbed, and he probed the +hole which the meteorite had made, and found it, still +warm, about eighteen inches below the surface. Some +men working at no great distance had actually heard +the noise of its descent, but without being able to indicate +the exact locality. This remarkable object +weighs 7¾ pounds. It is an irregular angular mass +of iron, though all its edges seem to have been rounded +by fusion in its transit through the air, and it is covered +with a thick black film of the magnetic oxide of +iron, except at the point where it first struck the +ground.</p> + +<p>This siderite is specially interesting on account of +its distinctly metallic character. Falls of the siderites, +as they are called, are not so common as those of the +stony meteorites; in fact, there are only a few known +instances of meteoric irons having been actually seen +to fall, while the falls of stony meteorites are to be +counted in scores or in hundreds. The inference is +that the iron meteorites are much less frequent than +the stony ones.</p> + +<p>It is a wonderful thought that we should really have +these visitants from the sky, solid metal or showers of +dust, coming to us from distant space.</p> + +<p>If the dust of thousands of meteorites is always +thus falling earthward, one would imagine that it +must in time add something to the weight of the +earth. And this actually is the case. During the last +three thousand years, no less than one million tons of +meteorite-dust must, according to calculation, have +fallen to earth out of the sky. A million tons is of<span class="pagenum" id="Page_260">[Pg 260]</span> +course a mere nothing compared +with the size of the world. Still, +the fact is curious and interesting.</p> + +<p>It has been suggested that, <i>perhaps</i> +the flames of the sun are +partly fed by vast showers of falling +meteorites. It has even been +suggested that <i>perhaps</i>, in long +past ages, the earth and the planets +grew to their present size under +a tremendous downpour of +meteorites; the numbers which +now drop to earth being merely +the thin remains of what once +existed. But for this guess there +is no real foundation.</p> + +<p>Whether suns and worlds full-grown, +created as in an instant; +whether tiny meteorites in countless +myriads to be used as stones +in “building;” whether vast +masses of flaming gas, to be gradually +cooled and “framed” into +shape—which ever may have +come first, and whichever may +have been the order of God’s +working—still that “first” was +made by him; still he throughout +was the Master-builder.</p> + +<div class="figleft" id="f45"> +<img src="images/fig45.jpg" alt="1680"> +<p class="caption">GREAT COMET OF 1680.</p> +</div> + +<p>A few words more about +“comet-visitors.” Many comets, +as already stated, belong to our<span class="pagenum" id="Page_261">[Pg 261]</span> +Solar System, though +whether they have always +so belonged is another +question. It is +not impossible that they +may once upon a time +have wandered hence +from a vast distance, +and, being caught prisoner +by the powerful attraction +of Jupiter or +one of his three great +brother-planets, have +been compelled thenceforth +to travel in a closed +pathway round the sun.</p> + +<div class="figright" id="f46"> +<img src="images/fig46.jpg" alt="1769"> +<p class="caption">GREAT COMET OF 1769.</p> +</div> + +<p>There are also many +comets which come once +only to our system, flashing +round past the sun, +and rushing away in +quite another direction, +never to return. Where +do these comets come +from? And where do +they go? From other +suns—brother suns to +ours? It may be. One +is almost disposed to +think that it must be so.</p> + +<p>Do we ever think +what an immense voyage<span class="pagenum" id="Page_262">[Pg 262]</span> +they must have made to come from there to here? Do +we imagine for how many years they must have flown +through the dark immensity to plunge themselves into +the fires of our sun? If we take into account the directions +from which certain comets come to us, and if +we assign to the stars situated in that region the least +distances consistent with known facts, we find that +these comets certainly left their last star more than +<i>twenty millions of years ago</i>.</p> + +<p>In thus putting to us from the height of their celestial +apparitions so many notes of interrogation on +the grandest problems of creation, comets assume to +our eyes an interest incomparably greater than that +with which superstition blindly surrounded them in +past ages. When we reflect for a moment that a certain +comet which shines before us in the sky came +originally from the depths of the heavens, that it has +traveled during millions of years to arrive here, and +that consequently it is by millions of years that we +must reckon its age if we wish to form any idea of it, +we can not refrain from respecting this strange visitor +as a witness of vanished eras, as an echo of the past, +as the most ancient testimony which we have of the +existence of matter. But what do we say? These +bodies are neither old nor young. There is nothing +old, nothing new—all is present. The ages of the +past contemplate the ages of the future, which all +work, all gravitate, all circulate, in the eternal plan. +Musing, you look at the river which flows so gently +at your feet, and you believe you see again the river +of your childhood; but the water of to-day is not that +of yesterday, it is not the same substance which you<span class="pagenum" id="Page_263">[Pg 263]</span> +have before your eyes, and never, never shall this +union of molecules, which you behold at this moment, +come back there—never till the consummation of +the ages!</p> + +<p>If the appearance of comets forebodes absolutely +nothing as to the microscopical events of our ephemeral +human history, it is not the same with the effects +which might be produced by their encounter with our +wandering planet. In such an encounter there is +nothing impossible. No law of celestial mechanics +forbids that two bodies should come into collision in +their course, be broken up, pulverized, and mutually +reduced to vapor.</p> + +<p>I have before described some of the tremendous +outbursts seen on the surface of our sun. It is believed +that in these outbursts matter is expelled, or +driven forth, with such fearful violence as to send it +whirling through space, never to fall back to the sun.</p> + +<p>Some meteorites may have their births thus. So +also may some comets. And if all the stars are suns—huge +fiery globes like our sun, and subject like him +to tremendous eruptions—they too, probably, send out +comets and meteorites to wander through space. +Whether or no comets come into existence in any such +manner, one thing seems pretty certain. Those comets +which come to us from outside our system must +come from some other system. And the nearest systems +known are those of the stars.</p> + +<p>The nearest star of all, whose distance has been +measured, is Alpha Centauri. It has been roughly +calculated that a comet, passing direct from Alpha +Centauri to our sun, would take about twenty millions<span class="pagenum" id="Page_264">[Pg 264]</span> +of years for his journey. But here we tread upon +very doubtful ground. Many matters, at present unknown +to us, might greatly affect the result of such a +calculation. Also it is by no means impossible that +other stars lie really much nearer to us than Alpha +Centauri, whose distance astronomers have not yet +attempted to measure.</p> + +<div class="figcenter" id="f47"> +<img src="images/fig47.jpg" alt="humboldt"> +<p class="caption">BARON ALEXANDER VON HUMBOLDT.</p> +</div> + +<p>“In order to complete our view,” says Alexander<span class="pagenum" id="Page_265">[Pg 265]</span> +Von Humboldt, “of all that we have learned to consider +as appertaining to our Solar System, which now, +since the discovery of the small planets, of the interior +comets of short revolutions, and of the meteoric +asteroids, is so rich and complicated in its form, it +remains for us to speak of the ring of zodiacal light. +Those who have lived for many years in the zone of +palms must retain a pleasing impression of the mild +radiance with which the zodiacal light, shooting +pyramidally upward, illumines a part of the uniform +length of tropical nights. I have seen it shine with +an intensity of light equal to the Milky Way in Saggitarius, +and that not only in the rare and dry atmosphere +of the summit of the Andes, at an elevation of +from thirteen to fifteen thousand feet, but even on the +boundless grassy plains of Venezuela, and on the seashore, +beneath the ever-clear sky of Cumana. This +phenomenon was often rendered especially beautiful +by the passage of light, fleecy clouds, which stood out +in picturesque and bold relief from the luminous background.</p> + +<p>“This phenomenon, whose primordial antiquity +can scarcely be doubted, is not the luminous solar atmosphere +itself, which can not be diffused beyond +nine-tenths of the distance of Mercury. With much +probability we may regard the existence of a very +compressed ring of nebulous matter, revolving freely +in space around the sun between the orbits of Venus +and Mars, as the material cause of the zodiacal light. +These nebulous particles may either be self-luminous +or receive their light from the sun.</p> + +<p>“I have occasionally been astonished, in the tropical<span class="pagenum" id="Page_266">[Pg 266]</span> +climates of South America, to observe the variable +intensity of the zodiacal light. As I passed the nights, +during many months, in the open air, on the shores of +rivers and on plains, I enjoyed ample opportunities of +carefully examining this phenomenon. When the +zodiacal light had been most intense, I have observed +that it would be weakened for a few minutes, until it +again suddenly shone forth in full brilliancy. In a +few instances I have thought I could perceive, not +exactly a reddish coloration, nor the lower portion +darkened in an arc-like form, nor even a scintillation, +but a kind of flickering and wavering of the light. +Must we suppose that changes are actually in progress +in the nebulous ring? Or is it not more probable that +processes of condensation may be going on in the uppermost +strata of the air, by means of which the transparency—or, +rather, the reflection of light—may be +modified in some peculiar and unknown manner? An +assumption of the existence of such meteorological +causes on the confines of our atmosphere is strengthened +by the sudden flash and pulsations of light which +have been observed to vibrate for several seconds +through the tail of a comet. During the continuation +of these pulsations it has been noticed that the +comet’s tail was lengthened by several degrees, and +then again contracted.”</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_267">[Pg 267]</span></p> + +<h2 class="nobreak" id="c22">CHAPTER XXII.</h2> +</div> + +<p class="c sp">MANY SUNS.</p> + + +<p><span class="smcap large">Once</span> more we have to wing our flight far, far away +from the busy Solar System where we live; away from +whirling planets, moons, meteorites, all shining with +reflected sunlight; away from the great central sun +himself, our own particular bright star. Once more +we have, in imagination, to cross the vast, black, +empty space—<i>is</i> it black, and <i>is</i> it empty, had we +sight to see things as they are?—separating our sun +from other suns, our star from other stars. For the +sun is a star—only a star. And stars are suns—big, +blazing suns. One is near, and the others are far +away. That is the difference.</p> + +<p>We have no longer to do with bodies merely reflecting +another’s light—always dark on one side and +bright on the other—but with burning bodies, shining +all round by their own light. We have no longer to +picture just one single star with his surrounding +worlds, but we have to fix our thoughts upon the +great universe of stars or suns in countless millions.</p> + +<p>The earth is forgotten, with its small and ephemeral +history. The sun himself, with all his immense +system, has sunk in the infinite night. On the wings +of inter-sidereal comets we have taken our flight towards +the stars, the suns of space. Have we exactly +measured, have we worthily realized the road passed +over by our thoughts? The nearest star to us reigns +at a distance of 275,000 times our distance from the<span class="pagenum" id="Page_268">[Pg 268]</span> +sun; out to that star an immense desert surrounds us, +the most profound, the darkest, and the most silent +of solitudes.</p> + +<p>The solar system seems to us very vast; the abyss +which separates our world from Mars, Jupiter, Saturn, +and Neptune, appears to us immense; relatively to +the fixed stars, however, our whole system represents +but an isolated family immediately surrounding us: +a sphere as vast as the whole solar system would be +reduced to the size of a simple point if it were transported +to the distance of the nearest star. The space +which extends between the solar system and the stars, +and which separates the stars from each other, appears +to be entirely void of visible matter, with the exception +of nebulous fragments, cometary or meteoric, +which circulate here and there in the immense voids. +Nine thousand two hundred and fifty systems like +ours, bounded by Neptune, would be contained in the +space which isolates us from the nearest star!</p> + +<p>It is marvelous that we can perceive the stars at +such a distance. What an admirable transparency +in these immense spaces to permit the light to pass, +without being wasted, to thousands of billions of +miles! Around us, in the thick air which envelops +us, the mountains are already darkened and difficult +to see at seventy miles; the least fog hides from us +objects on the horizon. What must be the tenuity, +the rarefaction, the extreme transparency of the ethereal +medium which fills the celestial spaces!</p> + +<p>The sun is center and ruler and king in his own +system. But as a star, he is only one among many +stars, some greater, some less than himself. From the<span class="pagenum" id="Page_269">[Pg 269]</span> +far siderial heavens he is hardly recognized even as a +star among the constellations, so faint is his light.</p> + +<p>Do the suns which surround us form a system +with that which illuminates us, as the planets form +one round our solar focus, and does our sun revolve +round an attractive center? Does this center, the +point of the revolutions of many suns, itself revolve +round a preponderating center? In a word, is the +visible universe organized in one or several systems? +No Divine revelation comes to instruct men on the +mysteries which interest them most—their personal or +collective destinies. We have now, as ever, but science +and observation to answer us.</p> + +<p>A problem so vast as this is still far from receiving +even an approximate solution. From whatever point +of view we consider it, we find ourselves face to face +with the infinite in space and time. The present aspect +of the universe immediately brings into question +its past and its future state, and then the whole of +united human learning supplies us in this great research +with but a pale light, scarcely illuminating the +first steps of the dark and unknown road on which we +are traveling. However, such a problem is worthy of +engaging our attention, and positive science has already +made sufficient discoveries in the knowledge of +the laws of nature to permit us to attempt to penetrate +these great mysteries. What is it that the general +observation of the heavens—what is it that sidereal +synthesis teaches us on our real situation in +infinitude?</p> + +<div class="figcenter" id="f48"> +<img src="images/fig48.jpg" alt="field"> +<p class="caption">A TELESCOPIC FIELD IN THE MILKY WAY.</p> +</div> + +<p>In the calm and silent hours of beautiful evenings, +what pensive gaze is not lost in the vague windings +<span class="pagenum" id="Page_270">[Pg 270]</span>of the Milky Way, in the soft and celestial gleam of +that cloudy arch, which seems supported on two opposite +points of the horizon, and elevated more or less +in the sky according to the place of the observer and +the hour of the night? While one-half appears above +the horizon, the other sinks below it, and if we removed +the earth, or if it were rendered transparent, +we should see the complete Milky Way, under the +form of a great circle, making the whole circuit of the +sky. The scientific study of this trail of light, and +its comparison with the starry population of the<span class="pagenum" id="Page_271">[Pg 271]</span> +heavens, begins for us the solution of the great +problem.</p> + +<p>Let us point a telescope towards any point of this +stupendous arch. Suddenly hundreds, thousands of +stars show themselves in the telescopic field, like +needle-points on the celestial vault. Let us wait for +some moments, that our eye may become accustomed +to the darkness of the background, and the little +sparks shine out by thousands. Let us leave the instrument +pointed motionless towards the same region, +and there slowly passes before our dazzled vision the +distant army of stars. In a quarter of an hour we +see them appear by thousands and thousands. William +Herschel counted three hundred and thirty-one +thousand in a width of 5° in the constellation Cygnus, +so nebulous to the naked eye. If we could see the +whole of the Milky Way pass before us, we should see +eighteen millions of stars.</p> + +<p>This seed-plot of stars is formed of objects individually +invisible to the naked eye, below the sixth +magnitude; but so crowded that they appear to touch +each other, and form a nebulous gleam which all human +eyes, directed to the sky for thousands of years, +have contemplated and admired. Since it is developed +like a girdle round the whole circuit of the sky, +we ourselves must be in the Milky Way. The first +fact which impresses our mind is, that <i>our sun is a star +of the Milky Way</i>.</p> + +<p>Thought travels fast—faster than a comet, faster +than light. A rushing comet would, it is believed, +take twenty millions of years to cross the chasm between +the nearest known fixed star and us. Light,<span class="pagenum" id="Page_272">[Pg 272]</span> +flashing along at the rate of about one hundred and +eighty-six thousand miles a second, will perform the +same journey in four years and a third. But thought +can overleap the boundary in less than a single +moment.</p> + +<p>Each star that we see in the heavens is to our eyesight +simply one point of light. The brighter stars +are said to be of greater magnitude, and the fainter +stars of lesser magnitude; yet, one and all, they have +no apparent size. The most powerful telescope, though +it can increase their brilliancy, can not add to their +size. A planet, which to the naked eye may look like +a star, will, under a telescope, show a disk, the breadth +of which can be measured or divided; but no star has +any real, visible disk in the most powerful telescope +yet constructed. The reason of this is the enormous +distance of the stars. Far off as many of the planets +lie, yet the farthest of them is as a member of our +household compared with the nearest star.</p> + +<p>I have already tried to make clear the fact of their +vast distance. Light, which comes to us from the +sun in eight minutes and a half, takes over four and a +third years to reach us from Alpha Centauri. From +this four-years-and-a-third length of journey between +Alpha Centauri and earth, the numbers rise rapidly to +twenty years, fifty years, seventy years, even hundreds +of years. The distance of most of the stars is completely +beyond our power to measure. The whole +orbit of our earth, nay, the whole wide orbit of the +far-off Neptune, would dwindle down to one single +point, if seen from the greater number of the stars.</p> + +<p>It used to be believed that, taking the stars generally,<span class="pagenum" id="Page_273">[Pg 273]</span> +there was probably no very marked difference +in their size, their kind, their brightness. Some of +course would be rather larger, and others rather +smaller; still it was supposed that they might be +roughly classed as formed much on the same scale +and the same plan. But doubts are now felt about +this notion. For a very similar idea used to be held +with regard to the Solar System. The wonderful variety +of form and richness in numbers, now known to +abound within its limits, are discoveries of late years. +May not the same variety in kind and size be found +also among the stars? The more we look into the +heavens, the more we find that dull, blank uniformity +is not to be seen there.</p> + +<p>It is the same upon earth. Man builds his little +rows of boxlike houses side by side, each one exactly +like all the rest, or dresses his thousand soldiers in +coats of the same cut and color, or repeats a neat leaf-design +hundreds of times on carpets or wall-papers; +but God never makes two leafs or two blades of grass +alike. Wholesale turning out of things after one pattern +is quite a human idea, not divine.</p> + +<p>We know so much about the stars as that some are +at least considerably larger and some considerably +smaller than others. When one star is seen to shine +brightly, and another beside it shines dimly, we are +apt to think that the brightest must be the nearest. +Yet it is often impossible for us to say how much +of the difference is owing to the greater distance of +one or the other, to the greater size of one or the +other, or to the greater brilliancy of one or the other. +In many instances we do know enough to be quite<span class="pagenum" id="Page_274">[Pg 274]</span> +sure that there is a great difference, not only in the +distance of the stars, but in their size, their kind, their +brightness.</p> + +<p>The stars have been lately classed by one or two +astronomers into four distinct orders or degrees—partly +depending on their color. The first class is +that of the White Suns. These are said to be the +grandest and mightiest of all. The star Sirius belongs +to the order of White Suns. Secondly comes +the class of Golden Suns. To these blazing furnaces +of yellow light, second only to the white-light stars, +belongs our own sun. Thirdly, there are numbers of +stars called Variable Stars, the light of which is constantly +changing, now becoming more, now becoming +less. Fourthly, there is the class of small Red Suns, +about which not much is known.</p> + +<p>These four orders or divisions do not by any means +include all the stars, or even all the single stars. +Roughly speaking, however, the greater number of +single stars, and many also of the double stars, belong +to one or another of the above classes.</p> + +<p>When we talk of the different sizes of the different +stars, it should be plainly understood that we have no +means of directly measuring them. A point of light +showing no disk, no surface, no breadth, can not be +measured, for there is nothing to measure.</p> + +<p>In certain cases we are not entirely without the +power of judging. The distances of a few of the +stars from us have been found out. Knowing how +far off any particular star is, astronomers are able to +calculate exactly how bright our own sun would look +at that same distance. If they find that our sun<span class="pagenum" id="Page_275">[Pg 275]</span> +would shine just as the star in question shines, there +is some reason for supposing that our sun and the +star may be of the same size. If our sun would +shine more brightly than the star shines, there is +some reason for supposing that the star may be +smaller than our sun. If our sun would shine more +dimly than the star shines, there is some reason for +supposing that the star may be larger than our sun.</p> + +<p>Other matters, however, have to be considered. +Suppose we find a star at a certain distance shining +twice as brilliantly as our own sun would shine at +that same distance. Naturally, then, we say, That +star must be much larger than our sun.</p> + +<p>The reasoning may be mistaken. We do not know +the fact. What if, instead of being a much <i>larger</i> +sun, it is only a much <i>brighter</i> sun? This possibly +must be allowed for. It has, indeed, been strongly +doubted by one astronomer, after close study of the +sun, whether any surface of any star <i>could</i> exceed the +surface of our sun in its power of light and heat.</p> + +<p>But Sirius sheds actually forty-eight times as much +light around it as does our sun; we are not exactly +entitled to say that Sirius is forty-eight times as big as +the sun, but we can say that Sirius is forty-eight times as +brilliant or as splendid. In making this calculation +we have taken a lower determination of the brightness +of Sirius relatively to the sun than some other +careful observations would have warranted. It will +thus be seen that if there be any uncertainty in +our result it must only be as to whether Sirius is not +really more than forty-eight times as bright as the +sun.</p> + +<p><span class="pagenum" id="Page_276">[Pg 276]</span></p> + +<p>When we picture to ourselves the star-depths, the +boundless reaches of heavenly space, with these countless +blazing suns scattered broadcast throughout, we +have not to picture an universe in repose. On the +contrary, all is life, stir, energy. Just as in the busy +whirl of our Solar System no such thing as rest is to +be found, so also it seems to be in the wide universe.</p> + +<p>Every star is in motion. “Fixed,” as we call +them, they are not fixed. Invisible as their movements +are to our eyes through immensity of distance, +yet all are moving. Those silent, placid, twinkling +specks of light are, in reality, huge, roaring, seething, +tumultuous furnaces of fire and flame, heat and +radiance.</p> + +<p>Each, too, is hurrying along his appointed pathway +in space. Some move faster, some move more slowly. +One mile per second; ten miles per second; twenty, +thirty, forty, fifty miles per second,—thus varying are +their rates of speed. But whether fast or whether +slowly, still onward and ever onward they press. +Some are rushing towards us, some are rushing away +from us. Some are speeding to the right, some are +speeding to the left.</p> + +<p>The fine star Arcturus, which any one may admire +every evening on the prolongation of the tail of the +Great Bear, is slowly withdrawing from the fixed point +where the celestial charts placed it two thousand years +ago, and is moving towards the southwest. It takes +eight hundred years to describe a space in the sky +equal to the apparent diameter of the moon; nevertheless, +this displacement was sufficiently perceptible +to attract attention more than a century and a half<span class="pagenum" id="Page_277">[Pg 277]</span> +ago, for Halley had noticed it in 1718, as well as those +of Sirius and Aldebaran. However slow it may appear +at the distance we are from Arcturus, this motion +is, at a minimum, 1,637 millions of miles a year. +Sirius takes 1,338 years to pass over the same angular +space in the sky; at the distance of that star this is, +at a minimum, 397 millions of miles per annum. The +study of the proper motions of the stars has made the +greatest progress in the last half-century, and especially +in recent years. All the stars visible to the +naked eye and a large number of telescopic stars +show displacements of this kind.</p> + +<p>Where are they going? Does any single star ever +return to his starting-point—wherever that starting-point +may have been? Do they journey in vast circles +or ellipses, round some far-distant center? What +controls them all? Is it the mighty power of some +such center, or does each star, by his faint and distant +attraction, help to control all his brother-stars, to guide +them on their appointed path, to preserve the delicate +balance of a universe?</p> + +<p>How little we know about the matter! Only so +much we can tell—that the controlling and restraining +hand of God is over the whole. Whether by the +attraction of one great center or by the united influences +of a thousand fainter attractions, he steers each +radiant sun upon its heavenly path, “upholding all +things by the words of his power.” There is no +blundering, no confusion, no entanglement. All is +perfect order, calm arrangement, restrained energy.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_278">[Pg 278]</span></p> + +<h2 class="nobreak" id="c23">CHAPTER XXIII.</h2> +</div> + +<p class="c sp">SOME PARTICULAR SUNS.</p> + + +<p><span class="smcap large">In</span> the constellation of the Swan there is a little, +dim, sixth-magnitude star, scarcely to be seen without +a telescope. This star, 61 Cygni by name, is the first +whose distance from us it was found possible to determine.</p> + +<p>We may think it strange that so faint a star was +even attempted. Would not astronomers have naturally +supposed it to be one of the farther-distant +stars? No, they did not. For though 61 Cygni +showed but a dim light, yet his motion—not the daily +apparent motion, but the real motion as seen from +earth—was found to be so much more rapid than the +motion of most other stars that they rightly guessed +61 Cygni to be a rather near neighbor of ours.</p> + +<p>Do not misunderstand me, when I speak of a “more +rapid motion,” and of “rather near neighborhood.” +The real rate of 61 Cygni’s rush through space is believed +to be about forty miles each second, or one +thousand four hundred and fifty millions of miles +each year. All we can perceive of this quick motion +is that, in the course of three hundred and +fifty years, 61 Cygni travels over a space in the sky +about as long as the breadth of the full moon. Little +enough, yet very far beyond what can be detected in +the greater number of even the brightest stars.</p> + +<p>Then, again, as to the near neighborhood of this<span class="pagenum" id="Page_279">[Pg 279]</span> +star, 61 Cygni is near enough to have his distance +measured, and that is saying a good deal. Alpha +Centauri, the nearest star of which we know in the +southern heavens, is two hundred and seventy-five +thousand times as far distant as the sun. But 61 Cygni, +the nearest star of which we know in the northern +heavens, is nearly twice as far away as Alpha Centauri.</p> + +<div class="figright" id="f49"> +<img src="images/fig49.jpg" alt="cygnus"> +<p class="caption">CYGNUS.</p> +</div> + +<p>We call 61 Cygni a star, for so he appears to common +observers. In reality, instead of being only one +star, the speck of +light which we call +61 Cygni consists +of <i>two stars</i>. The +two are separated +by a gap about half +as wide again as +the wide gap between +the sun and +Neptune. Yet so +great is their distance +from us that to the naked eye the two seem to be +one. These two suns would together make a sun only +about one-third as large as our sun. They differ in +size, the quicker movements of one showing it to be +the smaller; and it is by means of their known distance +from one another, and their known rate of motion, +that their size, or rather their weight, can be +roughly calculated. Of course neither of the two +shows any actual measurable disk. So much and so +little is with tolerable certainty known about this +particular pair of suns.</p> + +<p>Next let us turn to Alpha Centauri—named <i>Alpha</i>,<span class="pagenum" id="Page_280">[Pg 280]</span> +the first letter of the Greek alphabet, because it is +the brightest star in the constellation of the Centaur. +The second brightest star in a constellation is generally +called Beta, the third Gamma, the fourth Delta, +and so on; just as if we were to name them A, B, +C, D, in order of brightness.</p> + +<p>The constellation Centaur lies in the southern +heavens, close to the beautiful constellation called the +Southern Cross, and is invisible in the northern hemisphere. +Of all the stars shining in the heavens +round our earth, two only—Sirius and Canopus—show +greater brilliancy than Alpha Centauri.</p> + +<p>As in the case of 61 Cygni, astronomers were led to +attempt the measurement of Alpha Centauri’s distance, +by noticing how much more distinct were his +movements than the movements of other stars, though +less rapid both to the eye and in reality than those of +61 Cygni. Alpha Centauri’s rate of motion is some +thirteen miles each second.</p> + +<p>And this, so far as we yet know, is our sun’s nearest +neighbor in the heavens outside his own family +circle.</p> + +<p>Strange to say, Alpha Centauri, like 61 Cygni, consists, +not of a single star, but of a pair of stars. It is +a two-sun system—whether or no surrounded by planets +can not be told. We can only reason from what +we see to what we do not see. And as God did not +form our earth “in vain,” and did not form our sun +“in vain,” so we firmly believe that he did not form +“in vain” any one of his myriads of suns scattered +through space. What is, has been, or will be the +particular use of each one, it would be rash to attempt<span class="pagenum" id="Page_281">[Pg 281]</span> +to say. But that many among them have, like +our own sun, systems of worlds revolving round them, +we may safely consider very probable.</p> + +<div class="figcenter" id="f50"> +<img src="images/fig50.jpg" alt="stars"> +<p class="caption">STARS WHOSE DISTANCES ARE BEST KNOWN. (See Table.)</p> +</div> + +<p>The two suns of the Alpha Centauri double-star +are separated by a distance about twenty-two times as +great as the distance of the earth from the sun, yet to +the naked eye they show as a single star. Here again +one is much smaller than the other; and the smaller +revolves round the larger in about eighty-five years.</p> + +<p>It is believed that the two together would form a<span class="pagenum" id="Page_282">[Pg 282]</span> +sun about twice as large and heavy as our sun. This +belief is strengthened by the great brilliancy of Alpha +Centauri. Our own sun, placed at that distance from +us, would shine only one-third as brightly as he does.</p> + + +<p class="c">STARS WHOSE DISTANCES ARE BEST KNOWN.</p> + +<table> + +<tr> + <td class="tdl bl bt br bb"></td> + <td class="tdc bt br bb">NAME OF STAR.</td> + <td class="tdc bt br bb">MAG-<br>NITUDE.</td> + <td class="tdc bt br bb">DISTANCE<br> IN MILES.</td></tr> + +<tr> + <td class="tdr bl br">1</td> + <td class="tdl br">Alpha Centauri,</td> + <td class="tdc br">1.0</td> + <td class="tdl br">25 trillions.</td></tr> + +<tr> + <td class="tdr bl br">2</td> + <td class="tdl br">61 Cygni,</td> + <td class="tdc br">5.1</td> + <td class="tdl br">43     ”</td></tr> + +<tr> + <td class="tdr bl br">3</td> + <td class="tdl br">2,398, Draco,</td> + <td class="tdc br">8.2</td> + <td class="tdl br">55     ”</td></tr> + +<tr> + <td class="tdr bl br">4</td> + <td class="tdl br">Sirius,</td> + <td class="tdc br">1.0</td> + <td class="tdl br">58     ”</td></tr> + +<tr> + <td class="tdr bl br">5</td> + <td class="tdl br">9,352, Lacaille,</td> + <td class="tdc br">7.5</td> + <td class="tdl br">66     ”</td></tr> + +<tr> + <td class="tdr bl br">6</td> + <td class="tdl br">Procyon,</td> + <td class="tdc br">1.3</td> + <td class="tdl br">71     ”</td></tr> + +<tr> + <td class="tdr bl br">7</td> + <td class="tdl br">Lalande, 21,258,</td> + <td class="tdc br">8.5</td> + <td class="tdl br">74     ”</td></tr> + +<tr> + <td class="tdr bl br">8</td> + <td class="tdl br">Œltzen, 11,677,</td> + <td class="tdc br">9.0</td> + <td class="tdl br">74     ”</td></tr> + +<tr> + <td class="tdr bl br">9</td> + <td class="tdl br">Sigma Draconis,</td> + <td class="tdc br">4.7</td> + <td class="tdl br">78     ”</td></tr> + +<tr> + <td class="tdr bl br">10</td> + <td class="tdl br">Aldebaran,</td> + <td class="tdc br">1.5</td> + <td class="tdl br">81     ”</td></tr> + +<tr> + <td class="tdr bl br">11</td> + <td class="tdl br">Epsilon Indi,</td> + <td class="tdc br">5.2</td> + <td class="tdl br">87     ”</td></tr> + +<tr> + <td class="tdr bl br">12</td> + <td class="tdl br">Œltzen, 17,415,</td> + <td class="tdc br">9.0</td> + <td class="tdl br">94     ”</td></tr> + +<tr> + <td class="tdr bl br">13</td> + <td class="tdl br">1,516, Draco,</td> + <td class="tdc br">7.0</td> + <td class="tdl br">101   ”</td></tr> + +<tr> + <td class="tdr bl br">14</td> + <td class="tdl br">Omicron Eridani,</td> + <td class="tdc br">4.4</td> + <td class="tdl br">101   ”</td></tr> + +<tr> + <td class="tdr bl br">15</td> + <td class="tdl br">Altair,</td> + <td class="tdc br">1.6</td> + <td class="tdl br">101   ”</td></tr> + +<tr> + <td class="tdr bl br">16</td> + <td class="tdl br">Bradley, 3,077,</td> + <td class="tdc br">5.5</td> + <td class="tdl br">101   ”</td></tr> + +<tr> + <td class="tdr bl br">17</td> + <td class="tdl br">Eta Cassiopeiæ,</td> + <td class="tdc br">3.6</td> + <td class="tdl br">118   ”</td></tr> + +<tr> + <td class="tdr bl br">18</td> + <td class="tdl br">Vega,</td> + <td class="tdc br">1.0</td> + <td class="tdl br">128   ”</td></tr> + +<tr> + <td class="tdr bl br">19</td> + <td class="tdl br">Capella,</td> + <td class="tdc br">1.2</td> + <td class="tdl br">174   ”</td></tr> + +<tr> + <td class="tdr bl br">20</td> + <td class="tdl br">Arcturus,</td> + <td class="tdc br">1.0</td> + <td class="tdl br">204   ”</td></tr> + +<tr> + <td class="tdr bl br">21</td> + <td class="tdl br">Pole Star,</td> + <td class="tdc br">2.1</td> + <td class="tdl br">215   ”</td></tr> + +<tr> + <td class="tdr bl br">22</td> + <td class="tdl br">Mu Cassiopeiæ,</td> + <td class="tdc br">5.2</td> + <td class="tdl br">320   ”</td></tr> + +<tr> + <td class="tdr bl br bb">  23</td> + <td class="tdl br bb">1,830, Groombridge,</td> + <td class="tdc br bb">6.5 </td> + <td class="tdl br bb">426   ”</td></tr> + + + +</table> + +<p>This table presents the most trustworthy data which +we have yet obtained with reference to stellar distances. +As a great number of attempts have been +made on stars which, by their brightness or by the +magnitude of their proper motion, would appear to be +the nearest to us, we may believe that the star now +considered as the nearest is really so, and that there +is no other less distant. Thus our sun, a star in the +immensity, is isolated in infinitude, and <i>the nearest</i><span class="pagenum" id="Page_283">[Pg 283]</span> +sun reigns at twenty-five trillions of miles from our +terrestrial abode. Notwithstanding its unimaginable +velocity of 186,400 miles a second, light moves, flies, +during four years and one hundred and twenty-eight +days to come from this sun to us. Sound would take +more than three millions of years to cross the same +abyss. At the constant velocity of thirty-seven miles +an hour, <i>an express train starting from the sun Alpha +Centauri would not arrive here till after an uninterrupted +course of nearly seventy-five millions of years</i>.</p> + +<p>Here, then, are the nearest suns to us. These stars, +twenty-three in number, are almost the only ones +which have shown a perceptible parallax; still the result +is very doubtful for the last four, of which the +parallax is less than a tenth of a second. Attempts +have been made to ascertain the parallax of all the +stars of the first magnitude, and the result has been +negative for those which are not entered in this +list. Canopus, Rigel, Betelgeuse, Achernar, Alpha of +the Cross, Antares, Spica, and Fomalhaut, do not show +a perceptible parallax. The fine star Alpha Cygni, +which shines near 61 Cygni, does not present to the +most accurate researches any trace of fluctuation: it is, +then, incomparably more distant than its modest neighbor—at +least five times, and perhaps twenty times, +fifty times, one hundred times beyond that. What must +be the colossal size and amazing light of these suns, +of which the distance is greater than three hundred +to four hundred trillions of miles, and which nevertheless +still shine with so splendid a brightness!</p> + +<p>We did not know the distance of any stars till the +year 1840. This shows how recent this discovery is;<span class="pagenum" id="Page_284">[Pg 284]</span> +indeed, we have hardly now begun to form an approximate +idea of the real distances which separate the +stars from each other. The parallax of 61 Cygni, the +first which was known, was determined by Bessel, +and resulted from observations made at Königsberg +from 1837 to 1840. Since then, the first figure obtained +has been corrected by a series of more recent +observations.</p> + +<p>Such distances are amazing and almost terrifying +to the imagination. The mind is bewildered and almost +overwhelmed when attempting to form a conception +of such portions of immensity, and feels its own +littleness, the limited nature of its powers, and its utter +incapacity for grasping the amplitudes of creation. +But though it were possible for us to wing our flight +to such a distant orb as 61 Cygni, we should still find +ourselves standing only on the verge of the starry firmament +where ten thousands of other orbs a thousand +times more distant would meet our view. We +have reason to believe that a space equal to that +which we are now considering intervenes between +most of the stars which diversify our nocturnal sky. +The stars appear of different magnitudes; but we +have the strongest reason to conclude that in the majority +of instances this is owing, not to the difference +of their real magnitudes, but to the different distances at +which they are placed from our globe.</p> + +<p>If, then, the distance of a star of the first or second +magnitude, or those which are nearest to us, be so immensely +great, what must be the distance of stars of +the sixteenth or twentieth magnitude, which can be +distinguished only by the most powerful telescopes?<span class="pagenum" id="Page_285">[Pg 285]</span> +Some of these must be many millions of times more +distant than the nearest star whose distance now appears +to be determined. And what shall we think of +the distance of those which lie beyond the reach of +any telescope that has yet been constructed, stretching +beyond the utmost limits of mortal vision, within +the unexplored regions of immensity? Here even +the most vigorous imagination drops its wing, and +owns itself utterly unable to penetrate this mysterious +and boundless unknown.</p> + +<p>Turning now from the sun, whose distance was +first measured, and from the nearest star with which +we are acquainted, let us think about the most radiant +star in the heavens—Sirius, “the blazing Dog-star of +the ancients;” named by one astronomer “the king of +suns.”</p> + +<p>First, as to the color of Sirius. He belongs to the +order of “White Suns,” and among all the white suns +known to us, Sirius ranks as chief. There may be +many at greater distances far surpassing him in size, +and weight, and brilliancy; but we can only speak so +far as we know. Strange to say, Sirius was not always +a “white sun;” for ancient writers describe him as +being, in their days, a <i>red</i> star. This change is very +singular, and difficult to understand. But Sirius is +not the only example of the kind. Many alterations +in color have been noticed as taking place, often in a +much shorter space of time. For instance, one star, +which was a white sun in the days of Herschel, is now +a golden sun.</p> + +<p>Secondly, as to the distance of Sirius. Like a few +other stars, Sirius lies not quite so far away as to be<span class="pagenum" id="Page_286">[Pg 286]</span> +beyond reach of measurement. No base-line upon +earth would cause the slightest seeming change of +position in him; but as our earth journeys round the +sun, the line from one side of her orbit to the other is +found wide enough. A base-line of one hundred and +eighty-six millions of miles does cause just a tiny +seeming change.</p> + +<p>It is very little even with Alpha Centauri, and with +Sirius it is much less. The “displacement” of Sirius +is so slight that to measure his distance with exactness +is impossible. Sirius lies more than twice as +far away from earth as Alpha Centauri. To reach +Sirius, the straight line between earth and sun must +be repeated six hundred and twenty-six thousand +times. Light, which reaches us from the sun in eight +minutes and a half, and from Alpha Centauri in four +years and a third, can not reach us from Sirius in +less than nine years.</p> + +<p>Thirdly, as to the size of Sirius. Here, of course, +we are in difficulties. Radiantly as Sirius shines on a +clear night, and dazzling as he looks through a powerful +telescope, he shows no real disk or round surface, +but only appears as one point of brilliant light. Some +believe him to be much the same size as our sun, while +others believe him to be very much larger. But we +have no certain ground to rest upon. The only safe +method of calculating the probable size—or, rather, +weight—of a star is through the discovery of a companion, +and a knowledge of its distance from the chief +star, and its time of revolution round the chief star.</p> + +<p>Fourthly, as to the motions of Sirius—not his +nightly apparent movement, caused by the earth’s<span class="pagenum" id="Page_287">[Pg 287]</span> +turning on her axis, but his real journey through +space. For a long while it was only possible to observe +the movements of a star when the star was traveling +<i>sideways</i> to us across the sky. A star coming +straight towards us, or going straight away from us, +would seem to be at rest. Lately, however, by means +of that remarkable instrument, the spectroscope, it +has been found possible to measure the motions of +stars coming towards or going away from us. This +is possible as yet only in a few scattered cases, but +among those few is the brilliant Sirius.</p> + +<p>The sideways motion of Sirius had been known +before. It now appears that he does not move exactly +sideways to us, but is rushing away in a slanting direction +at the rate of thirty miles each second, or about +one thousand millions of miles a year.</p> + +<p>How many millions upon millions of miles Sirius +must now be farther from us than in the days of the +ancients! Yet he shines still, the most brilliant star +in the sky. So small a matter are all those millions +of miles, compared with the whole of his vast distance +from us, that we do not perceive any lessening +of light.</p> + +<p>It is an interesting fact that while Sirius is moving +away from us, we are also moving away from him. +Our “first station ahead,” in the constellation Hercules, +lies exactly in the opposite direction from Sirius. +But the sun does not move so fast as Sirius. He is +believed to accomplish only about one hundred and +fifty millions of miles each year, drawing all his planets +with him.</p> + +<p>Fifthly, has Sirius a family, or system, like that of<span class="pagenum" id="Page_288">[Pg 288]</span> +our sun? Why not? Common sense and reason alike +answer with a “Probably, yes”—not only about Sirius, +but about other stars also. No doubt the systems—the +number, size, weight, speed, distance, and kind of +planets—differ very greatly. No doubt there are +boundless varieties of beauty and grandeur.</p> + +<p>But that our sun should be the head of so wonderful +and complex a system, that his rays should be the +source of life and heat to so many dependents, and +that all the myriads of suns besides should be mere +solitary lamps shining into empty space, warming, +lighting, controlling <i>nothing</i>, is an idea scarcely to be +looked in the face.</p> + +<p>Of course, there may be other and different uses +for some of these suns, beyond our understanding. +We must not be positive in the matter. It seems, +however, pretty certain that Sirius at least is not a +solitary, unattended sun.</p> + +<p>Astronomers, carefully watching his movements, +were somewhat perplexed. As with Uranus, the attraction +of a heavy body beyond was suspected from +the nature of the planet’s motions, so it happened +again with the far more distant Sirius. Astronomers +could only explain his movements by supposing the +attraction of some large and near satellite. No one +knew anything about such a satellite, but it was felt +that one must exist.</p> + +<p>Nearly twenty years had elapsed after Bessel had +predicted the disturber of Sirius before the telescopic +discovery which confirmed it was made. The circumstances +under which that discovery was made are not, +indeed, so dramatic as those which attended the discovery<span class="pagenum" id="Page_289">[Pg 289]</span> +of Neptune, but yet they have an interest of +their own. In February, 1862, Alvan Clark & Sons, +the celebrated telescope-makers, of Cambridge, Massachusetts, +were completing a superb eighteen-inch object-glass +for the Chicago Observatory. Turning the +instrument on Sirius, for the purpose of trying it, the +practiced eye of Alvan Graham Clark, the son, soon +detected something unusual, and he exclaimed, “Why, +father, the star has a companion!” The father looked, +and there was a faint companion due east from the +bright star, and distant about ten seconds of a degree. +This was exactly the predicted direction of the companion +of Sirius, and yet the observers knew nothing +of the prediction. As the news of this discovery +spread, many great telescopes were pointed on Sirius; +and it was found that when observers knew exactly +where to look for the object, many instruments would +show it. The new companion star to Sirius lay in the +true direction, and it was now watched with the keenest +interest, to see whether it also was moving in the +way it should move,—if it were really the body whose +existence had been foretold. Four years of observation +showed that this was the case, so that hardly any +doubt could remain that the telescopic discovery had +been made of the star which had caused the inequality +in the motion of Sirius.</p> + +<p>It is certainly a very remarkable fact that, out of +the thousands of stars with which the heavens are +adorned, no single star has yet been found which certainly +shows an appreciable disk in the telescope. We +are aware that some skillful observers have thought +that certain small stars do show disks; but we may<span class="pagenum" id="Page_290">[Pg 290]</span> +lay this aside, and appeal only to the ordinary fact +that our best telescopes turned on the brightest stars +show merely glittering points of light, so hopelessly +small as to elude our most delicate micrometers. The +ideal astronomical telescope is, indeed, one which will +show Sirius, or any other bright star, as nearly identical +as possible with Euclid’s definition of a point, +being that which has no parts and no magnitude.</p> + +<p>Lastly, what is Sirius made of? The late discovery +of spectrum analysis, or of the instrument called the +spectroscope, helps us here. A little further explanation +on this subject will be given later. It may be +observed in passing that before the said discovery, +astronomers can scarcely be asserted to have known +with any certainty that stars were suns. They could, +indeed, be sure that at the vast distances of the fixed +stars no bodies, shining by merely reflected light, +could possibly be visible to us. But there knowledge +stopped.</p> + +<p>Now we can say more. Now the spectroscope, by +breaking up and dividing for us the slender ray of +light traveling from each star, has shown to us something +of the nature of the stars. Now we know that +the stars, like our sun, are burning bodies, surrounded +by atmospheres full of burning gas.</p> + +<p>It has even been found out that in Sirius there are +large quantities of sodium and magnesium, besides +other metals, and an abundant supply of hydrogen gas.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_291">[Pg 291]</span></p> + +<h2 class="nobreak" id="c24">CHAPTER XXIV.</h2> +</div> + +<p class="c sp">DIFFERENT KINDS OF SUNS.</p> + + +<p><span class="smcap large">Various</span> in kind, various in size, various in color, +various in position, various in motion, are the myriad +suns scattered through space. So far are they from +being formed on the same plan, turned out on the +same model, that it may with reason be doubted +whether any two stars could be found exactly alike. +Why should we expect to find them so? No two oak-leaves, +no two elm-leaves, precisely alike, are to be +found upon earth.</p> + +<p>So some stars are large, some are small. Some are +rapid in movement, some are slow. Some are yellow, +some white, some red, green, blue, purple, or gray. +Some are single stars; others are arranged in pairs, +trios, quartets, or groups. Some appear only for a +time, and then disappear altogether. Others are +changeful, with a light that regularly waxes and +wanes in brightness.</p> + +<p>We have now to give a little time and thought to +variable stars and temporary stars; afterwards to +double stars and colored stars. There are many stars +which pass through gradual and steady changes—first +brightening, then lessening in light, then brightening +again. One such star is to be seen in the constellation +of the Whale. It is named “Mira,” or “The +Marvelous,” and the time in which its changes take +place extends to eleven months. For about one fortnight<span class="pagenum" id="Page_292">[Pg 292]</span> +it is a star of the second magnitude. Through +three months it grows slowly more and more dim, till +it becomes invisible, not only to the naked eye, but +through ordinary telescopes. About five months it +remains thus. Then again, during three months, it +grows brighter and brighter, till it is once more a +second-magnitude star, and after a fortnight’s pause +begins anew to fade.</p> + +<p>At its maximum, this star is yellow; when it is +faint, it is reddish. Spectrum analysis shows in it a +striped spectrum of the third type, and when its light +diminishes it preserves all the principal bright rays +reduced to very fine threads. The most plausible explanation +of this variability is to suppose that it periodically +emits vapors similar to the eruptions observed +in the solar photosphere. Instead of its +periodicity being like that of the sun—eleven years +and hardly perceptible—this variation of the sun of +the Whale is three hundred and thirty-one days and +very considerable. It is subject to oscillations and irregularities +similar to those which we remark in our +sun. Of all the variable stars, this is the easiest to +observe, and it has been known for nearly three hundred +years.</p> + +<p>The most celebrated of all the variable stars is +that known as Algol, in the constellation of Perseus. +This star is very conveniently placed for observation, +being visible every night in the Northern Hemisphere, +and its wondrous and regular changes can be observed +without any telescopic aid. Every one who desires to +become acquainted with the great truths of astronomy +should be able to recognize this star, and should have<span class="pagenum" id="Page_293">[Pg 293]</span> +also followed it during one of its periods of change. +Algol is usually a star of the second magnitude; but +in a period between two or three days—or, more accurately, +in an interval of two days, twenty hours, +forty-eight minutes, and fifty-five seconds—its brilliancy +goes through a most remarkable cycle of variations. +The series commences with a gradual decline +of the star’s brightness, which, in the course of three +or four hours, falls from the second magnitude down +to the fourth. At this lowest stage of brightness, Algol +remains for about twenty minutes, and then begins +to increase, until in three or four hours it regains the +second magnitude, at which it continues for about two +days, thirteen hours, when the same series commences +anew. It seems that the period required by Algol to +go through its changes is itself subject to a slow, but +certain variation.</p> + +<p>Another variable star, Betelgeuse in Orion, undergoes +its variations in about two hundred days; while +yet another, Delta Cephei, takes only six days. Our +own sun is believed to be in some slight degree a +variable star, passing through his changes in eleven +years. When the sun-spots are most numerous, he +would probably appear, if seen from a great distance, +more dim than when there are few or none of them.</p> + +<p>Sometimes a star is not merely variable. Stars have +appeared for a brief space, and then utterly vanished. +They are then named Temporary Stars. Whether +such a star really does go out of existence, or whether +it merely becomes too dim to be seen; whether the +furnace-fires are extinguished, and the glowing sun +changes into a dark body, or whether it merely turns<span class="pagenum" id="Page_294">[Pg 294]</span> +a dark side towards us for a very long period,—these +are questions we can not answer.</p> + +<p>An extraordinary specimen of a temporary star was +seen in 1572. It was not a comet, for it had no coma +or tail, and it never moved from its place. The brightness +of the star was so great as to surpass Sirius and +Jupiter, and to equal Venus at her greatest brilliancy. +Nay, it must have surpassed even Venus, for it was +plainly visible at midday in a clear sky. Gradually +the light faded and grew more dim, till at length it +entirely disappeared. As it lessened in brilliancy, it +also changed in color, passing from white to yellow, +and from yellow to red. This curiously agrees with +the three tints of the first, second, and fourth orders +of suns, as lately classified.</p> + +<p>This star was observed by Tycho Brahe, who gives +the following curious account:</p> + +<p>“One evening, when I was contemplating, as usual, +the celestial vault, whose aspect was so familiar to me, +I saw, with inexpressible astonishment, near the zenith, +in Cassiopeia, a radiant star of extraordinary magnitude. +Struck with surprise, I could hardly believe my +eyes. To convince myself that it was not an illusion, +and to obtain the testimony of other persons, I called +out the workmen employed in my laboratory, and +asked them, as well as all passers-by, if they could +see, as I did, the star, which had appeared all at once. +I learned later on that in Germany carriers and other +people had anticipated the astronomers in regard to a +great apparition in the sky, which gave occasion to +renew the usual railleries against men of science (as +with comets whose coming had not been predicted).</p> + +<p><span class="pagenum" id="Page_295">[Pg 295]</span></p> + +<p>“The new star was destitute of a tail; no nebulosity +surrounded it; it resembled in every way other stars +of the first magnitude. Its brightness exceeded that +of Sirius, of Lyra, and of Jupiter. It could only be +compared with that of Venus when it is at its nearest +possible to the earth. Persons gifted with good sight +could distinguish this star in daylight, even at noonday, +when the sky was clear. At night, with a cloudy +sky, when other stars were veiled, the new star often +remained visible through tolerably thick clouds. The +distance of this star from the other stars of Cassiopeia, +which I measured the following year with the +greatest care, has convinced me of its complete immobility. +From the month of December, 1572, its +brightness began to diminish; it was then equal to +Jupiter. In January, 1573, it became less brilliant +than Jupiter; in February and March, equal to stars +of the first order; in April and May, of the brightness +of stars of the second order. The passage from the +fifth to the sixth magnitude took place between December, +1573, and February, 1574. The following +month the new star disappeared without leaving a +trace visible to the naked eye, having shone for seventeen +months.”</p> + +<p>These circumstantial details permit us to imagine +the influence which such a phenomenon must have exercised +on the minds of men. Few historical events +have caused so much excitement as this mysterious +envoy of the sky. It first appeared on November 11, +1572. General uneasiness, popular superstition, the +fear of comets, the dread of the end of the world, long +since announced by the astrologers, were an excellent<span class="pagenum" id="Page_296">[Pg 296]</span> +setting for such an apparition. It was soon announced +that the new star was the same which had led the wise +men to Bethlehem, and that its arrival foretold the return +of the Messiah and the last judgment. For the +hundredth time, perhaps, this sort of prognostication +was recognized as absurd. It did not, however, prevent +the astrologers from being believed, twelve years +later, when they announced anew the end of the +world for the year 1588; these predictions exercised +the same influence on the public mind.</p> + +<p>After the star of 1572 the most celebrated is that +which appeared in October, 1604, in Serpentarius, and +which was observed by two illustrious astronomers, +Kepler and Galileo. As happened with the preceding, +its light imperceptibly faded. It remained visible for +fifteen months, and disappeared without leaving any +traces. In 1670 another temporary star, blazing out +in the head of the Fox (Vulpecula), showed the singular +phenomenon of being extinguished and reviving +several times before it completely vanished. We know +of <i>twenty-four</i> stars which, during the last two thousand +years, have presented a sudden increase of light; +have been visible to the naked eye, often brilliant; and +have then again become invisible. The last apparitions +of this kind happened before our eyes in 1866, +1876, 1885, and 1892, and spectrum analysis enabled +us to ascertain, as we have seen, that they were due to +veritable combustion—a fire caused by a tremendous +expansion of incandescent hydrogen, and to phenomena +analogous to those which take place in the solar +photosphere. A rather curious fact about these stars +is, that they do not blaze out indifferently in any point<span class="pagenum" id="Page_297">[Pg 297]</span> +of the sky, but in rather restricted regions, chiefly in +the neighborhood of the Milky Way.</p> + +<p>Many other instances have been known, beside +those referred to, of variable and temporary stars.</p> + +<p>There are two distinct kinds of double-stars. First, +we have those which merely seem to be double, because +one lies almost directly behind the other, though +widely distant from it. +Just as a church-tower, +two miles off, may appear +to stand close side +by side with another +church-tower two and +a half miles off, though +they are in fact separated. +Secondly, we +have the real systems +of two suns belonging +to one another; the +smaller moving round +the larger, or more correctly +both traveling +round one central point called the center of gravity, +the smaller having the quicker rate of motion.</p> + +<div class="figright" id="f51"> +<img src="images/fig51.jpg" alt="lyra"> +<p class="caption">LYRA</p> +</div> + +<p>Alpha Centauri and 61 Cygni have been already described, +as examples of true double-stars. In the +constellation Lyra a marked instance is to be seen. +The brightest star in the Lyre is Vega, and near Vega +shines a tiny star, which to people with particularly +clear sight has sometimes rather a longish look. If +you examine this star through an opera-glass, you find +it to consist of two separate stars. But if you get a<span class="pagenum" id="Page_298">[Pg 298]</span> +more powerful telescope, and look again, you will find +that <i>each star</i> of the couple actually consists of <i>two</i> +stars. The four are not at equal distances. Two points +of light seemingly close together are parted by a wide +gap from two other points equally close together. +These four stars are believed to have a double motion. +Each of the separate pairs revolves by itself, the two +suns traveling round one center; and in addition to +this the two <i>couples</i> of suns probably perform a long +journey round another center common to them all.</p> + +<p>Many thousands of double stars have been discovered; +and a large number of these are now known to +be, not merely two distinct suns lying in the same line +of sight, but two brother-suns, each probably the center +of his own system of planets.</p> + +<p>We have not only to consider the number of suns, +though of simple numbers more yet remains to be said. +Attention must also be given to the varying colors of +different stars; for all suns in the universe are not +made after the model of our sun. All suns are not +yellow.</p> + +<p>So far as single stars are concerned, colors seem +rather limited. White stars, golden or orange stars, +ruby-red stars, placed alone, are often seen; but blue +stars, green stars, gray stars, silver stars, purple stars, +are seldom if ever visible to the naked eye, or known +to exist as single stars.</p> + +<p>Take a powerful telescope and examine star-couples, +and a very different result you will find. +Not white, yellow, and red alone, but blue, purple, +gray, green, fawn, buff, silvery white, and coppery +hues, will delight you in turn. As a rule, when the<span class="pagenum" id="Page_299">[Pg 299]</span> +two stars of a couple are alike in color, they are +either white, or yellow, or red. Also in the case of +double-stars of different colors, the larger of the two +is almost invariably white or some shade of yellow +or red.</p> + +<p>There are, however, exceptions to all such rules. +Blue stars are almost never seen alone, and as one of +a pair the blue star is generally, if not invariably, the +smaller. But instances are known of double-stars, +both of which are blue; and one group in the southern +heavens is entirely made up of a multitude of +bluish suns.</p> + +<p>It is when we come to consider double-stars of two +colors that the most striking effects are found. Now +and then the two suns are nearly the same in size; but +more commonly one is a good deal larger than the other. +This is known by the brighter light of the largest, and +the more rapid movements of the smallest. The lesser +star is often only small by comparison, and may be +in reality a very goodly and brilliant sun.</p> + +<p>Among nearly six hundred “doubles” examined by +one astronomer, there were three hundred and seventy-five +in which the two stars were of one color, +generally white, yellow, orange, or red. The rest were +different in tint, the difference between the two suns +in about one hundred and twenty cases being very +marked.</p> + +<p>For instance, a red “primary,” as the larger star is +called, will be seen with a small green satellite; or a +white primary will have a little brother-sun of purple, +or of dark ruby, or of light red. Sometimes the larger +sun is orange, the companion being purple or dark<span class="pagenum" id="Page_300">[Pg 300]</span> +blue. Again, the chief star will be red with a blue +satellite, or yellow with a green satellite, or orange +with an emerald satellite, or golden with a reddish-green +satellite. We hear of golden and lilac couples, +of cream and violet pairs, of white and green companions. +But, indeed, the variety is almost endless.</p> + +<div class="figcenter" id="f52"> +<img src="images/fig52.jpg" alt="northern"> +<p class="caption">CONSTELLATIONS IN THE NORTHERN HEMISPHERE.</p> +</div> + +<p>There may be worlds circling around these suns—worlds, +perhaps, with living creatures on them. +We know little about how such systems of suns and +worlds may be arranged. Probably each sun would<span class="pagenum" id="Page_301">[Pg 301]</span> +have his own set of planets, and both suns with their +planets would travel round one central point. Perhaps, +where the second sun is much the smallest, it +might occasionally be like a big blazing satellite among +the planets—a kind of burning Jupiter-sun to the chief +sun.</p> + +<p>Among colored stars, single and double, a few may +be mentioned by name as examples. Sirius, as already +observed, is a brilliant white sun; and brilliant +white also are Vega, Altair, Regulus, Spica, and many +others. Capella, Procyon, the Pole-star, and our own sun, +are examples of yellow stars. Aldebaran, Betelgeuse, +and Pollux, are ruby-red. Antares is a red star, with +a greenish “scintillation” or change of hue in its +twinkling. A tiny green sun belonging to this great +and brilliant red sun has been discovered. Some have +called Antares “the Sirius of Red Suns.”</p> + +<p>It is during the fine nights of winter that the constellation +Taurus, or The Bull, with the star Aldebaran +marking its eye, shines in the evening above our +heads. No other season is so magnificently constellated +as the months of winter. While nature deprives +us of certain enjoyments in one way, it offers us in +exchange others no less precious. The marvels of the +heavens present themselves from Taurus and Orion +in the east to Virgo and Boötes on the west. Of eighteen +stars of the first magnitude, which are counted in +the whole extent of the firmament, a dozen are visible +from nine o’clock to midnight, not to mention +some fine stars of the second magnitude, remarkable +nebulæ, and celestial objects well worthy of the attention +of mortals. It is thus that nature establishes an<span class="pagenum" id="Page_302">[Pg 302]</span> +harmonious compensation, and while it darkens our +short and frosty days of winter, it gives us long nights +enriched with the most opulent creations of the sky. +The constellation of Orion is not only the richest in +brilliant stars, but it conceals for the initiated treasures +which no other is known to afford. We might +almost call it the California of the sky.</p> + +<p>To the southeast of Orion, on the line of the +Three Kings, shines the most magnificent of all the +stars, <i>Sirius</i>, or <i>Alpha</i> of the constellation of the Great +Dog. This constellation rises in the evening at the +end of November, passes the meridian at midnight +at the end of January, and sets at the end of March. +It played the greatest part in Egyptian astronomy, for +it regulated the ancient calendar. It was the famous +Dog Star; it predicted the inundation of the Nile, the +summer solstice, great heats and fevers; but the precession +of the equinoxes has in three thousand years +moved back the time of its appearance by a month and +a half; and now this fine star announces nothing, +either to the Egyptians who are dead or to their successors. +But we shall see farther on what it teaches +us of the grandeur of the sidereal universe.</p> + +<p>The <i>Little Dog</i>, or Procyon, is found above the +Great Dog and below the Twins (Castor and Pollux), +to the east of Orion. With the exception of Alpha +Procyon, no brilliant star distinguishes it.</p> + +<p>The two double-stars, 61 Cygni and Alpha Centauri, +are formed each of two orange suns.</p> + +<p>In the Southern Cross there is a wonderful group +of stars, consisting of about one hundred and ten +suns, nearly all invisible to the naked eye. Among the<span class="pagenum" id="Page_303">[Pg 303]</span> +principal stars of this group, which Sir John Herschel +described as being, when viewed through a powerful +telescope, like “a casket of variously-colored precious +stones,” are two red stars, two bright green, three pale +green, and one of a greenish blue.</p> + +<p>The splendor of these natural illuminations can +hardly be conceived by our terrestrial imagination. +The tints which we admire in these stars from here +can give but a distant idea of the real value of their +colors. Already, in passing from our foggy latitudes +to the limpid regions of the tropics, the colors of the +stars are accentuated, and the sky becomes a veritable +casket of brilliant gems. What would it be if we +could transport ourselves beyond the limits of our +atmosphere? Seen from the moon, these colors would +be splendid. Antares, Alpha Herculis, Pollux, Aldebaran, +Betelgeuse, Mars, shine like rubies; the Polar +Star, Capella, Castor, Arcturus, Procyon, are veritable +celestial topazes; while Sirius, Vega, and Altair are +diamonds, eclipsing all by their dazzling whiteness. +How would it be if we could approach the stars so as +to perceive their luminous disks, instead of merely +seeing brilliant points destitute of all diameter?</p> + +<p>Blue days, violet days, dazzling red days, livid green +days! Could the imagination of poets, could the caprice +of painters, picture on the palette of fancy a +world of light more astounding than this? Could the +mad hand of the chimera, throwing on the receptive +canvas the strange lights of its fancy, erect by chance +a more astonishing edifice?</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_304">[Pg 304]</span></p> + +<h2 class="nobreak" id="c25">CHAPTER XXV.</h2> +</div> + +<p class="c sp">GROUPS AND CLUSTERS OF SUNS.</p> + + +<p><span class="smcap large">We</span> have been thinking a good deal about single +stars and double stars, as seen from earth. Now we +have to turn our attention to groups, clusters, <i>masses</i> +of stars, in the far regions of space.</p> + +<p>Have you ever noticed on a winter night, when +the sky was clear and dotted with twinkling stars, a +band of faintly-glimmering light stretching across the +heavens from one horizon to the other? The band is +irregular in shape, sometimes broader, sometimes narrower; +here more bright, there more dim. If you +were in the Southern Hemisphere you would see the +same soft belt of light passing all across the southern +heavens. This band or belt is called the Milky Way.</p> + +<p>But what is the Milky Way? It is made up of +stars. So much we know. As the astronomer turns +his telescope to the zone of faintly-gleaming light, he +finds stars appearing behind stars in countless multitudes; +and the stronger his telescope, the more the +white light changes into distant stars.</p> + +<p>Our sun we believe to be one of the stars of the +Milky Way; merely one star among millions of stars; +merely one golden grain among the millions of sparkling +gold-dust grains scattered lavishly through creation. +Scattered, not recklessly, not by chance, but +placed, arranged, and guided each by its Maker’s upholding +hand.</p> + +<p><span class="pagenum" id="Page_305">[Pg 305]</span></p> + +<p>The Milky Way, or the Galaxy, as it has been +called, has great interest for astronomers. Many have +been the attempts made to discover its actual size, its +real shape, how many stars it contains, how far it extends; +but to all such questions the only safe answers +to be returned are fenced around with “perhaps” and +“may be.” There are many very remarkable clusters of +stars to be seen in the heavens—some few visible as +faint spots of light to the naked eye, though the greater +number are only to be seen through a telescope. +Either with the naked eye, or in telescopes of varying +power, they show first as mere glimmers of light, +which, viewed with a more powerful telescope, separate +into clusters of distant stars.</p> + +<div class="figcenter" id="f53"> +<img src="images/fig53.jpg" alt="cluster"> +<p class="caption">A CLUSTER OF STARS IN CENTAURUS.</p> +</div> + +<p>The most common shape of these clusters is globular—to +the eye appearing simply round. Stars gather<span class="pagenum" id="Page_306">[Pg 306]</span> +densely near the center, and gradually open out to +a thin scattering about the edge. Thousands of suns +are often thus collected into one cluster.</p> + +<p>The clusters are to be seen in all parts of the sky; +but the greater number seem to be gathered into the +space covered by the Milky Way and by the famous +south Magellanic Clouds.</p> + +<p>Some of them are beautifully colored; as, for instance, +a cluster in Toucan, not visible from England, +the center of which is rose-colored, bordered with +white. No doubt it contains a large number of +bright red suns, surrounded by a scattering of white +suns.</p> + +<p>It used to be supposed that many of these clusters +were other vast gatherings or galaxies of stars, like +the Milky Way, lying at enormous distances from us. +This now seems unlikely. The present idea rather is, +that each cluster, in place of being another “Milky +Way” of millions of widely-scattered suns, is one +great <i>star-system</i>, consisting indeed of thousands of +suns, but all moving round one center. Probably +most of these clusters are themselves a part of the +collection of stars to which our sun belongs.</p> + +<p>If this be so, and if worlds are traveling among +the suns—as may well be, since they are doubtless +quite far enough apart for each sun to have his own +little or great system of planets—what sights must be +seen by the inhabitants of such planets!</p> + +<p>We do not indeed know the distance between the +separate suns of a cluster, which may be far greater +than appears to us. But if astronomers calculate +rightly, they are near enough together to shed bright<span class="pagenum" id="Page_307">[Pg 307]</span> +light on all sides of a planet revolving in their midst. +The said planet might perhaps not have within view +a single sun equal in apparent size to our sun as seen +from earth; yet thousands of lesser suns, shining +brightly in the firmament night and day, would cause +a radiance which we never enjoy.</p> + +<p>No, not <i>night</i>. In such a world there could be no +night. Worlds in the midst of a star-cluster must be +regions of perpetual day. No night, no starry heaven, +no sunrise lights or sunset glories, no shadow mingling +with sunshine, but one continual, ceaseless blaze of +brightness. We can hardly picture, even in imagination, +such a condition of things.</p> + +<div class="figcenter" id="f54"> +<img src="images/fig54.jpg" alt="nebula"> +<p class="caption">THE GREAT NEBULA IN ANDROMEDA, COMPARED WITH<br> +SIZE OF THE SOLAR SYSTEM.</p> +</div> + +<p>Besides star-clusters there are also nebulæ. The +word <i>nebula</i> comes from the Latin word for “cloud,” +and the nebulæ are so named from their cloudlike +appearance.</p> + +<p>It is not easy to draw a line of clear division between<span class="pagenum" id="Page_308">[Pg 308]</span> +nebulæ and distant star-clusters; for both have +at first sight the same dim, white, cloudy look. In +past days the star-clusters were included by astronomers +under the general class of nebulæ. And as with +the star-clusters, so with many of the nebulæ, the +more powerful telescopes of modern days have shown +them to be great clusters, or systems, or galaxies of +stars, at vast distances from us.</p> + +<p>It was supposed with the nebulæ, as with some of +the star-clusters, that they were other “Milky Ways” +of countless stars, far beyond the outside boundaries +of our Milky Way. This may still be true of some or +many nebulæ, but certainly not of all.</p> + +<p>For there are different kinds of nebulæ. Some +may, as just said, be vast gatherings of stars lying at +distances beyond calculation, almost beyond imagination. +Others appear rather to be clusters of stars, +like those already described, probably situated in our +own galaxy of stars. There is also a third kind of +nebula. Many nebulæ, once supposed to be clusters +of stars, having been lately examined by means of the +spectroscope, are found to be enormous masses of +glowing gas, and not solid bodies at all.</p> + +<p>The number of nebulæ known amounts to many +thousands. They are commonly divided into classes, +according to their seeming shape. There are nebulæ +of regular form, and nebulæ of irregular form. There +are circular nebulæ, oval nebulæ, annular nebulæ, +conical nebulæ, cometary nebulæ, spiral nebulæ, and +nebulæ of every imaginable description. These +shapes would no doubt entirely change, if we could +see them nearer; and indeed, even in more powerful<span class="pagenum" id="Page_309">[Pg 309]</span> +telescopes, they are often found to look quite different. +While on the subject of clusters and nebulæ, mention +should be made of the famous Magellanic Clouds +in the southern heavens. Sometimes they are called +the Cape Clouds. They differ from other nebulæ in +many points, and more particularly in their apparent +size. The Great Cloud is about two hundred times +the size of the full moon, while the Small Cloud is +about one-quarter as large. In appearance they are +not unlike two patches of the Milky Way, separated +and moved to a distance from the main stream.</p> + +<p>These clouds are surrounded by a very barren portion +of the heavens, containing few stars; but in +themselves they are peculiarly rich. Seen through a +powerful telescope, they are found to abound with +stars. The Greater Cloud alone contains over six +hundred from the seventh to the tenth magnitudes, +countless tiny star-points of lesser magnitudes, star-clusters +of all descriptions, and nearly three hundred +nebulæ,—all crowded into this seemingly limited +space.</p> + +<p>Among many famous nebulæ, the one in Orion and +the one in Andromeda may be particularly mentioned. +The size of the latter, as compared with the size of +our Solar System, is shown in the cut of this nebula. +On the hypothesis of a complete resolvability into stars, +the mind is lost in numbering the myriads of suns, the +agglomerated individual lights of which produce these +nebulous fringes of such different intensities. What +must be the extent of this universe, of which each sun +is no more than a grain of luminous dust!</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_310">[Pg 310]</span></p> + +<h2 class="nobreak" id="c26">CHAPTER XXVI.</h2> +</div> + +<p class="c sp">THE PROBLEM OF SUN AND STAR DISTANCES.</p> + + +<p><span class="smcap large">One</span> question had long occupied the minds of scientific +men without the finding of any satisfactory +answer, and this was the distance of the sun from +our earth.</p> + +<p>At length the sun had fully gained his rightful position +in the minds of men as center and controller of +the Solar System, and earth was fully dethroned from +her old false position. In point of fact, the sun had +gained <i>more</i> than his rightful position; since he was +now looked upon very much as the earth had been +formerly looked upon; since he was regarded practically +as the motionless Universe-Center. The earth +might and did move—people had grown used to that +idea—but the sun, at all events, was fixed. The sun, +beyond turning upon his axis, was motionless.</p> + +<p>Still, as to the true distance of the sun from ourselves, +ignorance reigned. Tycho Brahe had made a great +advance on earlier notions by placing the light-giver +4,000,000 miles away in imagination. Kepler, a +quarter of a century later, increased this to 14,000,000. +Galileo afterwards reverted to the 4,000,000. +All this, however, was sheer guesswork.</p> + +<p>Not till well on in the seventeenth century did Cassini +make a definite attempt at actual measurement of +the sun’s distance, and this attempt gave as a result +some 82,000,000 miles—not far removed from the<span class="pagenum" id="Page_311">[Pg 311]</span> +truth. But at the same period other observers gave +results of 41,000,000 and 136,000,000; so for years +the question still remained swathed in mist. Better +modes and better instruments were required before it +could receive settlement.</p> + +<p>The measurement of the distance of objects a good +way off is by means of their “parallax,” or the apparent +change in their position when viewed from two +different points at some distance from each other. +To this method of calculating distance we have already +referred.</p> + +<p>This kind of measurement of distances is not confined +to our earth’s surface alone. The distances of +bright bodies in the heavens may be calculated after +just the same method, provided only that the heavenly +body is not too far distant to be made to change its +seeming position in the sky.</p> + +<p>Suppose you wished to find out how far off the +moon is. You would have to make your observation +of the moon’s exact position in the sky—of just that +spot precisely where she is to be seen among heavenly +scenery at a particular moment; and you would have +to get somebody else to make a similar observation, at +the same time, from some other part of earth, at a +good distance from your post.</p> + +<p>There are no hills or woods in the sky for the moon +to be seen against; but there are plenty of stars, bright +points of light far beyond the moon. If you look at +her from one place, and your friend looks at her from +another place a good way off, there will be a difference +in your two “views.” You will see her very +close to certain stars; and your friend will see her not<span class="pagenum" id="Page_312">[Pg 312]</span> +quite so close to those stars, but closer to others. This +difference of view would give the moon’s parallax.</p> + +<p>If your observation were very careful, very exact, +and if you had the precise distance between the spot +where you stood, and the spot where your friend stood,—then, +from that base-line, and from the two angles +formed by its junction with the lines from the two +ends of it straight to the moon, you might reckon +how many miles away the moon is. The greater the +distance between the two places of observation, the +better,—as, for instance, at Greenwich and the Cape +of Good Hope.</p> + +<p>Practically, this is not nearly so simple a matter as +it may sound, because our earth is always on the move, +and the moon herself is perpetually journeying onward. +All such motions have to be most scrupulously allowed +for. So the actual measurement of moon-distance requires +a great deal of knowledge and of study. Many +other difficulties and complications besides these enter +into the question, and have to be overcome.</p> + +<p>Now, the sun is very much farther away than the +moon, and the stumbling-blocks in the way of finding +out his distance become proportionately greater +and more numerous. To observe him from two parts +of England, or from two parts of Europe, would give +him no parallax. That is to say, there would be no +change of position on his part apparent to us.</p> + +<p>I do not say that there would be no change at all; +but only that it would be so minute as to be quite unseen +by human eyes, even with the help of most careful +and accurate measurement. A very long base-line +is needed to make the sun distinctly appear to change<span class="pagenum" id="Page_313">[Pg 313]</span> +his position ever so little. Only the very longest +base-line which can be found on earth will do for +this,—nothing less than the earth’s whole diameter +of nearly eight thousand miles. And I think you +will see that the success of the calculation would +then depend, not alone on most careful observation +from two posts at the opposite sides of earth; not +alone on mathematical gifts and powers of close reckoning; +but also, essentially, on a true knowledge of +our earth’s diameter; that is, of <i>the exact length of +the base-line</i> from which the whole calculation would +have to be made, and upon which the answer would +largely depend.</p> + +<p>For a long while the earth’s diameter was not well +known. As time went on, fresh measurements were +again and again made of different portions of earth’s +surface, fresh calculations following therefrom; and +gradually clear conclusions were reached. A very +important matter it was that they should be reached; +for the semi-diameter of our earth has been adopted +as a “standard measure” for the whole universe; and +the slightest error in that standard measure would +affect all after calculations.</p> + +<p>When actual observations of sun-distance came to be +made, innumerable difficulties arose. Foremost stood +the huge amount of that distance. This made precise +observations more difficult; and at the same time +it made every mistake in observation so much the +worse. A little mistake in observing the moon +might mean only a hundred miles or so wrong in the +answer; but a mistake equally small in observing the +sun would lead to an error of many millions of miles.</p> + +<p><span class="pagenum" id="Page_314">[Pg 314]</span></p> + +<p>Again, to observe the sun’s exact position among +the stars, as with the moon, was not possible; because +when the sun is visible, the stars are not visible. +Then, too, the dazzling brightness of the sun balked +the needed exactitude.</p> + +<p>Halley had a brilliant thought before he died. He +could not carry it out himself, but he left it to others +as a legacy; that was, by observing the transit of +Venus from two different points on the earth’s surface. +At his suggestion, on the first opportunity—which +was not till after his death—the above mode +was tried of measuring the sun’s distance.</p> + +<p>A certain observer, stationed on one part of earth, +saw the tiny dark body of Venus take one particular +line across the sun’s bright face. Another observer, +standing on quite another and a far-off part of earth, +saw the little dark body take quite another line across +the sun’s bright face. Not that there were two little +dark bodies, but that the one body was seen by different +men in different places.</p> + +<p>From these separate views of the path of Venus +across the face of the sun, in connection with what +was already known of the earth’s diameter, and therefore +of the length of base-line between the two places, +the distance of the sun was reckoned to be about 95,000,000 +miles.</p> + +<p>Since that date many fresh attempts have been +made, and errors have been set right. Mercury as +well as Venus has been used in this matter, and other +newer modes of measurement have also been successfully +tried. We know now, with tolerable accuracy, +that the sun’s greater distance from earth is between<span class="pagenum" id="Page_315">[Pg 315]</span> +92,000,000 and 93,000,000 miles. A curious illustration +of sun-distance has been offered by one writer. +Sound and light, heat and sensation, all require <i>time</i> +for journeying. When a child puts his finger into a +candle-flame, he immediately shrieks with pain. Yet, +quickly as the cry follows the action, his brain is not +really aware of the burn until a certain interval has +elapsed. True, the interval is extremely minute; still +it is a real interval. News of the burn has to be telegraphed +from the finger, through the nerves of the +arm, up to the brain; and it occupies time in transmission, +though so small a fraction of a second that +we can not be conscious of it.</p> + +<p>Now, try to imagine a child on earth with an arm +long enough to reach the sun. His fingers might be +scorched by the raging fires there, while yet his brain +on earth would remain quite unaware of the fact for +about one hundred and thirty years. All through +those years, sensation would be darting along the +arm exactly as fast as it darts from the finger-tips of +an ordinary child on earth to that child’s brain.</p> + +<p>If the scorching began before he was one year old, +he would have become a very aged man, one hundred +and thirty years old, before he could know in his mind +what was happening in the region of his hand. Moreover, +if, on receiving the intimation, he should decide +to withdraw his hand from that unpleasantly-hot +neighborhood, another hundred and thirty years would +elapse before the fingers could receive and act upon +the message, telegraphed from the brain, through the +nerves of the arm. So much for the distance of the +sun from our earth!</p> + +<p><span class="pagenum" id="Page_316">[Pg 316]</span></p> + +<p>But the stars! How far off are the stars?</p> + +<p>The distance of the moon is a mere nothing. The +distances of the planets have been found out. The +distance of the sun has been measured. But the +stars—those wondrous points of light, twinkling on, +night after night, century after century, unchanged in +position save by the seeming nightly pilgrimage of +them all across the sky in company, caused only by +our earth’s restless, continual whirl,—</p> + +<p>What about the distances of the stars? Can we +measure their distance by means of their parallax? +This mode of measurement was tried successfully on +the moon, on the planets, and on the sun. But when +it was tried upon the stars, from two stations as far +apart as any two stations on earth could be, the attempt +was a failure. Not a ghost of parallax could +be detected with any one star. Not the faintest sign +of displacement was seen in the position of a single +star when most critically and carefully examined.</p> + +<p>Then arose a brilliant thought! What of earth’s +yearly journey round the sun? If a base-line of 8,000 +miles were not enough, compared with the great distance +of the stars, this at least remained. Our earth +at midsummer is somewhere about 185,000,000 miles +away from where she is at midwinter, comparing her +position with that of the sun, and reckoning him to +be at rest.</p> + +<p>In reality, the sun is not at rest, but is in ceaseless +motion, carrying with him, wherever he goes, the +whole Solar System with as much ease as a train +carries its passengers. Those passengers are truly in +motion, yet, with regard merely to the train, they are<span class="pagenum" id="Page_317">[Pg 317]</span> +at rest. So each member of the Solar System—attached +to the sun, not by Ptolemaic bars, but by the +bond of gravity—is borne along by him through +space; yet, with respect to each member of that system, +the central sun is always and absolutely at rest.</p> + +<p>At one time of the year, our earth is on one side of +the sun, over 92,000,000 miles distant. Six months +later, the earth is on the other side of the sun, not +quite 93,000,000 miles away from him in that opposite +direction. Twice 93,000,000 comes to 186,000,000. +This line, therefore—the diameter of the earth’s whole +yearly orbit, may be roughly stated as about 185,000,000 +of miles in length.</p> + +<p>Here surely was a base-line fit to give parallax to +any star—or, rather, to make parallax visible in the +case of any star. For it is, after all, a question, not of +fact, but of visibility; not of whether the thing <i>is</i>, but +of whether we are able to <i>see</i> it.</p> + +<p>As the earth journeys on her annual tour round the +sun, following a slightly elliptic pathway, the diameter +of which is about 185,000,000 miles, each star in the +sky must of necessity undergo a change of position, +however minute, performing a tiny apparent annual +journey in exact correspondence with the earth’s great +annual journey.</p> + +<p>The question is not, Does the star do this? but, +Can we <i>see</i> the star do this? Its apparent change of +position may be so infinitesimal, through enormous +distance, that no telescopes or instruments yet made +by man can possibly show it to us.</p> + +<p>The star-motion of which I am now speaking is +purely a seeming movement, not real. Be very clear<span class="pagenum" id="Page_318">[Pg 318]</span> +on this point in your mind. <i>Real</i> star-movements, +though suspected earlier, were not definitely surmised—one +may even say “discovered”—until the year +1718, by Halley. And though Cassini in 1728 referred +to this discovery of Halley’s, yet very little was +heard about the matter until the days of Herschel. +Only <i>apparent</i> star-motions were generally understood +and accepted.</p> + +<p>The first and simplest of such seeming star-motions +is one which we can all see—the nightly journey of +the whole host of stars, caused by our earth’s whirl +upon her axis.</p> + +<p>The second is also simple, but by no means also +easily seen. Astronomers reasoned out the logical +necessity for such an apparent motion long before it +could be perceived. As far back as the days of Copernicus +it was felt that if the Copernican System +were true, if the earth in very deed traveled round +the sun, then the stars ought to change their positions +in the sky when viewed from different parts of earth’s +annual journey. Observations were taken, divided by +six months of time and by one hundred and eighty-five +millions of miles of space. And the stars +stirred not!</p> + +<p>Stupendous as was this base-line, it proved insufficient. +So much <i>more</i> stupendous was the distance of +the stars that the base-line sank to nothing, and once +again parallax could not be detected. Not that the +seeming change of position in the star did not take +place, but that human eyes were unable to see it, +human instruments were unable to register it.</p> + +<p>There lies the gist of the matter. If the change<span class="pagenum" id="Page_319">[Pg 319]</span> +of position can be observed, well and good! The +length of the base-line being known, the distance of +the star may be mathematically calculated. For the +size of the tiny apparent path, followed in a year by +the star, is and must be exactly proportioned to the +distance of the star from that base-line. If the tiny +oval be so much larger, then the star is known to be +so much nearer. If the tiny oval be so much smaller, +then the star is known to be so much farther away.</p> + +<p>But when not the minutest token could be discovered +of a star’s position in the sky being in the least +degree affected by the earth’s great annual change of +position, astronomers were at a loss. There was absolutely +nothing to calculate from. The star was a +motionless point to earth. The whole yearly orbit of +earth was a motionless point to the star. One slender +beam of light united the two. Reckoners had +nothing to stand upon.</p> + +<p>It is interesting to know that Copernicus had actually, +long before, suggested this as a possible explanation +of the absence of star-parallax. He thought +that astronomers might fail altogether to find it, because +the stars might be “at a practically infinite distance” +from our earth.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_320">[Pg 320]</span></p> + +<h2 class="nobreak" id="c27">CHAPTER XXVII.</h2> +</div> + +<p class="c sp">MEASUREMENT OF STAR DISTANCES.</p> + + +<p><span class="smcap large">Until</span> the days of Sir William Herschel, little attention +was bestowed upon the universe of distant stars. +Before his advent the interest of astronomers had been +mainly centered in the sun and his revolving worlds. +The “fixed stars” were indeed studied, as such, with +a certain amount of care, and numberless efforts were +made to discover their distances from earth; but the +thought of a vast Starry System, in which our little +Solar System should sink to a mere point by comparison +with its immensity, had not yet dawned.</p> + +<p>With larger and yet larger telescopes of his own +making, Herschel studied the whole Solar System, and +especially the nature of sun-spots, the rings of Saturn, +the various motions of attendant moons, together +with countless other details. He enlarged the system +by the discovery of another planet outside Saturn—the +planet Uranus, till then unknown.</p> + +<p>These were only first steps. The work which he +did in respect of the Solar System was as nothing +compared with the work which he did among the +stars. His work in our system was supplementary to +other men’s labors; his work among the stars was the +beginning of a new era. Like many before him, he, +too, sought eagerly to find star-parallax, and he, too, +failed. Not yet had instruments reached a degree of<span class="pagenum" id="Page_321">[Pg 321]</span> +finish which should permit measuring operations of +so delicate a nature.</p> + +<p>Although he might not detect star-parallax, he +sprang a mine upon the older notions of star-fixity. He +shook to its very foundations the sidereal astronomy of +the day,—the theory, long held, of a motionless universe, +motionless stars, and a rotating but otherwise +motionless sun. He did away with the mental picture, +then widely believed in, of vast interminable fixity +and stillness, extending through space, varied only +by a few little wandering worlds. As he swept the +skies, and endeavored to gauge the fathomless depths, +and vainly pursued the search for the parallax of one +star after another, he made a great and unlooked-for +discovery. This was in connection with double-stars.</p> + +<p>Double-stars had long been known, and were generally +recognized. But whether the doubleness were +purely accidental, due merely to the fact of two stars +happening to lie almost in the same line of sight, as +viewed from earth, or whether any real connection +existed between the two, no man living could say. +Indeed, so long as all stars were regarded as utter +fixtures, the question was of no very great interest.</p> + +<p>But light dawned as Herschel watched. He found +the separate stars in a certain pair to be moving. +Each from time to time had slightly, very slightly, +changed its place. Then, at least, if all other stars in +the universe were fixed, those two were not fixed. He +watched on, and gradually he made out that their motions +were steady, were systematic, and were connected +the one with the other. That was one of the first<span class="pagenum" id="Page_322">[Pg 322]</span> +steps towards breaking down the olden notion, so +widely held, of a fixed and unchanging universe.</p> + +<p>Another double-star, and yet another, responded to +Herschel’s intense and careful searching. These other +couples, too, were revolving, not separately, but in +company; journeying together round one center; +bound together apparently by bonds of gravitation, +even as our sun and his planets are bound together.</p> + +<p>Other stars besides binary stars are found to move +with a real and not merely a seeming movement. +Viewed carelessly, the stars do indeed appear to remain +fixed in changeless groups; fixed even through +centuries. But, to exceedingly close watching and +accurate measurement, many among them are distinctly +<i>not</i> fixed; many among them can be actually +seen to move.</p> + +<p>Of course the observed motions are very small and +slow. One may be found to creep over a space as +wide as the whole full moon in the course of three +hundred or four hundred years; and this is rapid traveling +for a star in earth’s sky! Another will perhaps +cross a space one-tenth or one-twentieth or one-fiftieth +of the moon’s width in one hundred years.</p> + +<p>Such motions had never been carefully noted or +examined, until Herschel came to do away with +the old received notions of star-fixity. Happily, +Herschel was no slave to “received ideas.” Like +Galileo in earlier times, he wished to “prove all +things” personally, anxious only to find out what +was the truth. And he found that the stars were <i>not</i> +fixed! He found that numbers of them were moving. +He conjectured that probably all the rest were<span class="pagenum" id="Page_323">[Pg 323]</span> +moving also; that in place of a fixed universe of +changeless stars we have a whirling universe of rushing +suns.</p> + +<p>Herschel could not, of course, watch any one star +for a hundred years, much less for several centuries. +But in a very few years he could, by exceedingly close +measurement, detect sufficient motion to be able to +calculate how long it would take a certain star to creep +across a space as wide as the full moon.</p> + +<p>From step to step he passed on, never weary of his +toil. He sought to gauge the Milky Way, and to form +some notion of its shape. He noted a general drift of +stars to right and to left, which seemed to speak of a +possible journey of our sun through space, with all +the planets of the Solar System. He flung himself +with ardor into the study of star-clusters and of nebulæ. +He saw, with an almost prophetic eye, the +wondrous picture of a developing universe—of nebulæ +growing slowly into suns, and of suns cooling gradually +into worlds—so far as to liken the heavens to a +piece of ground, containing trees and plants in every +separate stage of growth.</p> + +<p>And still the search for star parallax went on, so +long pursued in vain. No longer base-line than that +of the diameter of earth’s yearly orbit lay within man’s +reach. But again and yet again the attempt was +made. Instruments were improved, and measurements +became ever more delicate; and at length some +small success crowned these persistent endeavors. The +tiny sounding-line of earth, lowered so often into the +mysterious depths of space, did at last “touch bottom.”</p> + +<p>Herschel died, full of years and honors, in 1822;<span class="pagenum" id="Page_324">[Pg 324]</span> +and some ten years later three different attempts +proved, all to some extent, and almost at the same +date, successful. Bessel, however, was actually the +first in point of time; and his attempt was upon the +double-star, 61 Cygni; not at all a bright star, but only +just visible to the naked eye.</p> + +<p>There are stars and stars, enough to choose from. +The difficulty always was, which to select as a subject +for trial with any reasonable prospect of a good result. +Some astronomers held that the brightest stars were the +most hopeful, since they were probably the nearest; +and of course the nearer stars would show parallax +more readily, because their parallax would be the +greater. But certain very bright stars indeed are +now known to be far more distant than certain very +dim stars.</p> + +<p>Again, some astronomers thought that such stars +as could be perceived to move most rapidly in the +course of years would be the most hopeful objects to +attack, since the more rapid movement might be supposed +to mean greater nearness, and so greater ease +of measurement. But some stars, seen to move rapidly, +are now known to be more distant than others +which are seen to move more sluggishly. So neither +of these two rules could altogether be depended on; +yet both were, on the whole, the best that could be +followed, either separately or together.</p> + +<p>The star 61 Cygni is not one of the brighter stars, +but it is one of those stars which can be seen to travel +most quickly across the sky in the course of a century. +Therefore it was selected for a trial; and that +trial was the first to meet with success.</p> + +<p><span class="pagenum" id="Page_325">[Pg 325]</span></p> + +<p>For 61 Cygni was found to have an apparent parallax; +in other words, its tiny seeming journey through +the year, caused by our earth’s great journey round +the sun, could be detected. Small as the star-motion +was, it might, through careful measurement, be perceived. +And, in consequence, the distance of the star +from earth could be measured. Not measured with +anything like such exactitude as the measurements of +sun-distance, but with enough to give a fair general +notion of star-distance.</p> + +<p>One success was speedily followed by others. By +a few others,—not by many. Among the thousands of +stars which can be seen by the naked eye, one here and +one there responded faintly to the efforts made. One +here and one there was found to stir slightly in the +sky, when viewed from earth’s summer and winter +positions, or from her spring and autumn positions, in +her yearly pathway round the sun.</p> + +<p>It was a very, very delicate stir on the part of the +star. Somewhat like the difference in position which +you might see in a penny a few miles off, if you looked +at it first out of one window and then out of another +window in the same house. You may picture the +penny as radiantly bright, shining through pitch darkness; +and you may picture yourself as looking at it +through a telescope. But even so, the apparent change +of position in the penny, viewed thus, would be exceedingly +minute, and exceedingly difficult to see.</p> + +<p>There are two ways of noting this little seeming +movement on the part of a star in the sky.</p> + +<p>Either its precise place in the sky may be observed—its +exact position, as in a map of the heavens—or<span class="pagenum" id="Page_326">[Pg 326]</span> +else its place may be noted as compared with another +more distant star, near to it in the sky, though +really far beyond. Parallax, if visible, would make it +alter its precise place in the sky. Parallax, if visible, +would bring it nearer to or farther from any other +star more distant than itself from earth. The more +distant star would have a much smaller parallax—probably +so small as to be invisible to us—and so it +would do nicely for a “comparison star.”</p> + +<p>The first of these methods was the first tried; and +the second was the first successful.</p> + +<p>To find star-distance through star-parallax sounds +quite simple, when one thinks of the general principle +of it. Just merely the question of a base-line, accurately +measured; and of two angles, accurately observed; +and of another angle, a good way off, accurately calculated,—all +resting on the slight seeming change of +position in a certain distant object, watched from two +different positions, about 185,000,000 miles apart.</p> + +<p>Quite simple, is it not? Only, when one comes to +realize that the “change of position” is about equal +to the change of position in a penny piece, miles away, +looked at from two windows in one house,—then the +difficulty grows.</p> + +<p>Besides this, one has to remember all the “corrections” +necessary, before any true result can be +reached.</p> + +<p>A penny piece, miles away, seen from two windows, +would be difficult enough as a subject for measurement. +But, at least, the penny would be at rest; and +you yourself would be at rest; and light would pass +instantaneously from it to you; and there would be no<span class="pagenum" id="Page_327">[Pg 327]</span> +wobbling and nodding motions of everything around +to add to your perplexities.</p> + +<p>In the measurement of star-parallax, all these +things have to be considered and allowed for; all have +to be put out of the question, as it were, before any +correct answer is obtained.</p> + +<p>The refraction of light must be considered; because +that displaces the star, and makes it seem to us to be +where it is not. And the aberration of light must be +considered; because, in a different way, that does the +same thing, making the star seem to take a little journey +in the course of the year. And the precession, or +forward motion, of the equinoxes, and nutation, or +vibratory motion, have both to be separately considered; +because they, too, affect the apparent position +of every star in the sky.</p> + +<p>To watch the star in comparison with another star +is easier than merely to note its exact position in the +sky; for the other star—the “companion-star”—is +equally with itself affected by refraction of light and +by aberration of light. But, then, another question +comes in seriously: whether or no the companion-star +shows any parallax also; since, if it does, that parallax +must be carefully calculated and allowed for.</p> + +<p>So the measurement of star-distance, even when +parallax can be detected, is by no means a light or +easy matter. On the contrary, it bristles with difficulties. +It is a most complicated operation, needing +profound knowledge, accurate observation, trained +powers of reasoning and calculation.</p> + +<p>Nothing short of what has been termed “the terrific +accuracy” of the present day could grapple with<span class="pagenum" id="Page_328">[Pg 328]</span> +the truly tremendous difficulties of this problem of star-distance. +It has, however, been grappled with, and +grappled with successfully. We now know, not indeed +with anything like exactitude, yet with reasonable +certainty, the distances of a good many stars, as +expressed roughly in round number of “about” so +many trillions of miles.<a id="FNanchor_3" href="#Footnote_3" class="fnanchor">[3]</a> We have at least learned +enough to gain some notion of the immeasurable distances +of countless other stars, lying far beyond reach +of earth’s longest measuring-line.</p> + +<div class="footnote"> + +<p><a id="Footnote_3" href="#FNanchor_3" class="label">[3]</a> The diameter of the moon as seen from the earth is equal to one thousand +eight hundred and sixty eight seconds of space. When the parallax of a star +is ascertained, it is a simple matter to calculate the distance of the star by the +use of the following table. If the star shows a displacement of one second in +space, or one eighteen-hundred-and-sixty-eighth part of the width of the moon, +that star is distant two hundred and six thousand two hundred and sixty-five +times the distance of the earth from the sun.</p> + +<table> + +<tr> + <td class="tdl">An angle of</td> + <td class="tdl">1″</td> + <td class="tdl">is equivalent to</td> + <td class="tdl">206,265 times</td> + <td class="tdl">93,000,000 of miles.</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.9</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">229,183     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.8</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">257,830     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.7</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">294,664     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.6</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">343,750     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.5</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">412,530     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.4</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">515,660     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.3</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">687,500     “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.2</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">1,031,320  “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.1</td> + <td class="tdl"> “         “         “</td> + <td class="tdl">2,062,650  “</td> + <td class="tdl">           “         “     “</td> +</tr> + +<tr> + <td class="tdl">  “       “     “ </td> + <td class="tdl">0″.0</td> + <td class="tdl"> “         “         “</td> + <td class="tdl"><span class="less">Immeasurable.</span>  </td> + <td class="tdl">                       </td> +</tr> + +</table> + + +<p>The nearest star, Alpha Centauri, shows a parallax of less than one second +(0″.75). The farthest star, the distance of which has been ascertained, is 1830 +Groombridge, which shows a parallax of only 0″.045, and is distant 4,583,000 +times earth’s distance from the sun, or 426 trillions of miles.</p> + +</div> + +<p>The very thought of such unimaginable depths of +space, of suns beyond suns “in endless range,” toned +down by simple distance to mere quivering specks of +light, is well-nigh overwhelming.</p> + +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_329">[Pg 329]</span></p> +<h2 class="nobreak" id="c28">CHAPTER XXVIII.</h2> +</div> + +<p class="c sp">THE MILKY WAY.</p> + + +<p><span class="smcap large">The Milky Way</span> forms a soft band of light round +the whole heavens. In the Southern Hemisphere, as +in the Northern Hemisphere, it is to be seen. In some +parts the band narrows; in some parts it widens. Here +it divides into two branches; there we find dark spaces +in its midst. One such space in the south is so black +and almost starless as to have been named the Coal-sack. +All along, over the background of soft, dim +light, lies a scattering of brighter stars shining on its +surface. Much interest and curiosity have long been felt +about this mysterious Milky Way. That it consists +of innumerable suns, and that our sun is one among +them, has been believed for a considerable time. But +other questions arise. How many stars does the +Milky Way contain? What is its shape? How far +does it reach?</p> + +<p>No harm in asking the questions, only we have to +be satisfied in astronomy to ask many questions which +can not yet receive answers. No harm for man to +learn that the utmost reach of his intellect must fall +short in any attempt to sound the depths of God’s +universe, even as the arm of a child would fall short +in seeking to sound the depths of the ocean over the +side of a little boat. For the attempt has been made +to sound the depths of our star-galaxy out of this little +earth-boat.</p> + +<p><span class="pagenum" id="Page_330">[Pg 330]</span></p> + +<p>The idea first occurred to the great Herschel, as +we have already mentioned, and a grand idea it was—only +a hopeless one. He turned his powerful telescope +north, south, east, west. He counted the stars +visible at one time in this, in that, in the other directions. +He found a marked difference in the numbers. +The portion of sky seen through his telescope was +about one quarter the size of that covered by the +moon. Sometimes he could merely perceive two or +three bright points on a black background. At other +times the field of his telescope was crowded. In the +fuller portions of the Milky Way, he had four or five +hundred stars under view at once. In one place he +saw about one hundred and sixteen thousand stars +pass before him in a single quarter of an hour.</p> + +<p>Herschel took it for granted that the stars of the +Milky Way, uncountable in numbers, are, as a rule, +much the same in size—so that brightest stars would, +as a rule, be nearest, and dimmest stars would, as a +rule, be farthest off. Where he found stars clustering +thickly, beyond his power to penetrate, he believed +that the Milky Way reached very far in that direction. +Where he found black space, unlighted by stars +or lighted by few stars, he decided that he had found +the borders of our galaxy in that direction.</p> + +<p>Following these rules which he had laid down, he +made a sort of rough sketch of what he supposed +might be the shape of the Milky Way. He thought +it was somewhat flat, extending to a good distance +breadthways and a much greater distance lengthways, +and he placed our sun not far from the middle. This +imagined shape of the Milky Way is called “The<span class="pagenum" id="Page_331">[Pg 331]</span> +Cloven-disk Theory.” To explain the appearance of +the Milky Way in the sky, Herschel supposed it to be +cloven or split through half of its length, with a black +space between the two split parts.</p> + +<p>It seems that Herschel did not hold strongly to +this idea in later years, and doubts are now felt +whether the rules on which he formed it have sufficient +foundation.</p> + +<p>For how do we know that the stars of the Milky +Way are, as a rule, much the same in size? Certainly +the planets of the Solar System are very far from being +uniform, and the few stars whose weight can with +any certainty be measured, seem to vary considerably. +There is a great difference also between the large and +small suns in many of the double-stars!</p> + +<p>Again, how do we know that the bright stars are, +as a rule, the nearest, and the dim stars the farthest +off? Here, also, late discoveries make us doubtful. +Look at Sirius and 61 Cygni—Sirius the most radiant +star in the heavens, and 61 Cygni almost invisible to +the naked eye. According to this rule, 61 Cygni +ought to lie at an enormous distance beyond Sirius. +Yet in actual fact, Sirius is the farthest away of +the two.</p> + +<p>The illustrious Herschel believed that he had penetrated, +on one occasion, into the star-cluster on the +sword-hand in the constellation of Perseus until he +found himself among sidereal depths, from which the +light could not have reached him in less than four +thousand years.</p> + +<p>The distance of those stars had not, and has not, +been mathematically measured. Herschel judged of<span class="pagenum" id="Page_332">[Pg 332]</span> +it by their dimness, by the strong power needed to +make them visible, and by the rules which he had +adopted as most likely true.</p> + +<p>Again, when Herschel found black spaces in the +heavens almost void of stars, and believed that he +had reached the outside borders of the Milky Way, +he may have been in the right, or he may have been +mistaken. The limit might lie there, or thousands +more of small stars might extend in that very direction, +too far off for their little glimmer to be seen +through the most powerful telescope.</p> + +<div class="figcenter" id="f55"> +<img src="images/fig55.jpg" alt="cluster"> +<p class="caption">A CLUSTER OF STARS IN PERSEUS.</p> +</div> + +<p>If this latter idea about the Milky Way being +formed of a great many brilliant suns, and of vast +numbers of lesser suns also, be true, astronomers<span class="pagenum" id="Page_333">[Pg 333]</span> +will, in time, be able to prove its truth. For in that +case, many faint telescopic stars being much nearer +to us than bright stars of the greater magnitudes, it +will be found possible to measure their distance. +The journey of our earth round the sun must cause +a seeming change in their position between summer +and winter.</p> + +<p>The theory also that some of the nebulæ are other +outlying Milky Ways, or galaxies of stars, separated +by tremendous distances from our own, is interesting, +and was long held as almost certain, yet we have no +distinct proof either one way or the other. Many of +the nebulæ may be such gatherings of countless stars +outside our own, or every nebula visible may be actually +part and parcel of our galaxy.</p> + +<p>Much attention has of late been paid to the arrangement +of stars in the sky. The more the matter +is looked into, the more plainly it is seen that stars +are neither regular in size nor regular in distribution. +They are not merely scattered carelessly, as it were, +here, there, and anywhere, but certain laws and plans +of arrangement seem to have been followed which +astronomers are only now beginning dimly to perceive.</p> + +<p>Stars are not flung broadcast through the heavens, +each one alone and independent of the rest. They +are placed often, as we have already seen, in pairs, in +triplets, in quartets, in clusters. Also, the great masses +of them in the heavens seem to be more or less arranged +in streams, and sprays, and spirals. So remarkable +are the numbers and forms of many of these +streams that the idea has been suggested, with regard +to the Milky Way, whether it also may not be a vast<span class="pagenum" id="Page_334">[Pg 334]</span> +stream of stars, like a mighty river, collecting into itself +hundreds of lesser streams.</p> + +<p>The contemplation of the heavens affords no spectacle +so grand and so eloquent as that of a cluster of +stars. Most of them lie at such a distance that the +most powerful telescopes still show them to us like +star-dust. “Their distance from us is such that they +are beyond, not only all our means of measurement,” +says Newcomb, “but beyond all our powers of estimation. +Minute as they appear, there is nothing that we +know of to prevent our supposing each of them to be +the center of a group of planets as extensive as our +own, and each planet to be as full of inhabitants as +this one. We may thus think of them as little colonies +on the outskirts of creation itself, and as we see +all the suns which give them light condensed into one +little speck, we might be led to think of the inhabitants +of the various systems as holding intercourse with +each other. Yet, were we transported to one of these +distant clusters, and stationed on a planet circling one +of the suns which compose it, instead of finding the +neighboring suns in close proximity, we should see a +firmament of stars around us, such as we see from the +earth. Probably it would be a brighter firmament, in +which so many stars would glow, with more than the +splendor of Sirius, as to make the night far brighter +than ours; but the inhabitants of the neighboring +worlds would as completely elude telescopic vision as +the inhabitants of Mars do here. Consequently, to +the inhabitants of every planet in the cluster, the question +of the plurality of worlds might be as insolvable +as it is to us.”</p> + +<p><span class="pagenum" id="Page_335">[Pg 335]</span></p> + +<p>These are clusters of stars of regular form in which +attraction appears to mark its secular stamp. Our +mind, accustomed to order in the cosmos, anxious for +harmony in the organization of things, is satisfied with +these agglomerations of suns, with these distant universes, +which realize in their entirety an aspect approaching +the spherical form. More extraordinary, +more marvelous still, are the clusters of stars which +appear organized in spirals.</p> + +<p>In considering stars of the first six magnitudes +only—stars visible to the naked eye—a somewhat +larger number is found in the Southern Hemisphere +than in the Northern Hemisphere. In both hemispheres +there are regions densely crowded with stars, +and regions by comparison almost empty.</p> + +<p>It has been long questioned whether the number +of bright stars is or is not greater in the Milky Way +than in other parts of the sky. Careful calculations +have at length been made. It appears that the whole +of the Milky Way—that zone of soft light passing +round the earth—covers, if we leave out the Coal-sack +and other such gaps, between one-tenth and one-eleventh +of the whole heavens.</p> + +<p>The entire number of naked-eye stars, or stars of +the first six magnitudes, does not exceed six thousand; +and of these, eleven hundred and fifteen lie scattered +along the bed of the Milky Way stream. If the +brighter stars were scattered over all the sky as thickly +as throughout the Milky Way, their number would +amount to twelve thousand instead of only six thousand. +This shows us that the higher-magnitude stars +really are collected along the Milky Way in greater<span class="pagenum" id="Page_336">[Pg 336]</span> +numbers than elsewhere, and is an argument used by +those who believe the Milky Way to be a mighty +stream of streams of stars.</p> + +<p>In the dark spaces of the Milky Way, on the contrary, +bright stars are so few that if they were scattered +in the same manner over all the sky, their present +number of six thousand would come down to +twelve hundred and forty. This would be a serious +loss.</p> + +<p>We know in the sky 1,034 clusters of stars and +more than 11,000 nebulæ. The former are composed +of associated stars; the latter may be divided into two +classes: First, nebulæ which the ever-increasing progress +of optics will one day resolve into stars, or which +in any case are composed of stars, although their distances +may be too great to enable us to prove it; +second, nebulæ properly so called, of which spectrum +analysis demonstrates their gaseous constitution. +Here is an instructive fact. The clusters of stars +present the same general distribution as the telescopic +stars—they are more numerous in the plane of the +Milky Way, while it is the contrary which is presented +by the nebulæ properly so called; they are rare, thinly +spread in the Milky Way, and thickly scattered to the +north as well as to the south of this zone up to its +poles. The constitution of the Milky Way—not nebulous, +but stellar—is a very significant fact. The +nebulæ properly so called are distributed, in a sense, +contrary to the stars, being more numerous towards +the poles of the Milky Way and in regions poor in +stars, as if they had absorbed the matter of which the +stars are formed.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_337">[Pg 337]</span></p> + +<h2 class="nobreak" id="c29">CHAPTER XXIX.</h2> +</div> + +<p class="c sp">A WHIRLING UNIVERSE.</p> + + +<p><span class="smcap large">No rest,</span>, no quiet, no repose, in that great universe, +which to our dim eyesight looks so fixed and +still, but one perpetual rush of moving suns and +worlds. For every star has its own particular motion, +every sun is pressing forward in its own appointed +path. And among the myriads of stars—bright, +blazing furnaces of white or golden, red, blue, +or green flame—sweeping with steady rush through +space, our sun also hastens onwards.</p> + +<p>The rate of his speed is not very certain, but it is +generally believed to be about one hundred and fifty +million miles each year. Possibly he moves in reality +much faster.</p> + +<p>When I speak of the sun’s movement, it must of +course be understood that the earth and planets all +travel with him, much as a great steamer on the sea +might drag in his wake a number of little boats. +From one of the little boats you could judge of the +steamer’s motion quite as well as if you were on the +steamer itself. Astronomers can only judge of the +sun’s motion by watching the seeming backward drift +of stars to the right and left of him; and the watching +can be as well accomplished from earth as from +the sun himself.</p> + +<p>After all, this mode of judging is, and must be, +very uncertain. Among the millions of stars visible,<span class="pagenum" id="Page_338">[Pg 338]</span> +we only know the real distances of about twenty-five; +and every star has its own real motion, which has to +be separated from the apparent change of position +caused by the sun’s advance.</p> + +<p>It seems now pretty clear that the sun’s course is +directed towards a certain point in the constellation +Hercules. If the sun’s path were straight, he might be +expected by and by, after long ages, to enter that constellation. +But if orbits of suns, like orbits of planets, +are ellipses, he will curve away sideways long before +he reaches Hercules.</p> + +<div class="figcenter" id="f56"> +<img src="images/fig56.jpg" alt="hercules"> +<p class="caption">HERCULES</p> +</div> + +<p>One German astronomer thought he had found the +center of the sun’s orbit. He believed the sun and +the stars of the Milky Way to be traveling round the +chief star in the Pleiades, Alcyone. This is not impossible; +but it is now felt that much stronger proof +will be required before the idea can be accepted.</p> + +<p>In the last chapter mention was made of star-streams +as a late discovery. Though a discovery still +in its infancy, it is one of no small importance. Briefly<span class="pagenum" id="Page_339">[Pg 339]</span> +stated, the old theory as to the plan of the Milky Way +was as follows: Our sun was a single star among millions +of stars forming the galaxy, some comparatively +near, some lying at distances past human powers of +calculation, and all formed upon much the same model +as to size and brightness. Where the band of milky +light showed, stars were believed to extend in countless +thousands to measureless distances. Where dark +spaces showed, it was believed that we looked beyond +the limits of our universe into black space. Stars scattered +in other parts of the sky were supposed generally +to be outlying members of the same great Milky Way. +Many of the nebulæ and star-clusters were believed to +be vast and distant gatherings of stars, like the Milky +Way itself, but separated by unutterably wide reaches +of space. Some of these views may yet be found to +contain truth, though at the present moment a different +theory is afloat.</p> + +<p>It is still thought probable that our sun is one among +many millions of suns, forming a vast system or collection +of stars, called by some a universe. It is also +thought possible that other such mighty collections of +stars may exist outside and separate from our own at +immense distances. It is thought not impossible or +improbable that some among the nebulæ may be such +far-off galaxies of stars; though, on the other hand, it +is felt that every star-cluster and nebula within reach +of man’s sight may form a part of our own “universe.”</p> + +<p>According to this view of the question, the Milky +Way, instead of being an enormous universe of countless +suns reaching to incalculable distances, may<span class="pagenum" id="Page_340">[Pg 340]</span> +rather be a vast and mighty star-stream, consisting of +hundreds of brilliant leading suns, intermixed with +thousands or even millions of lesser shining orbs. If +this be the true view, the lesser suns would often be +nearer than the greater suns, although more dim; +and the Milky Way would not be itself a universe, +though a very wonderful and beautiful portion of our +universe.</p> + +<p>Which of these two different theories or opinions +contains the most truth remains to be found out. But +respecting the arrangement of stars into streams, interesting +facts have lately been discovered. We certainly +see in the Solar System a tendency of heavenly +bodies to travel in the same lines and in companies. +Not to speak of Jupiter and his moons, or Saturn and +his moons, we see it more remarkably in the hundreds +of asteroids pursuing one path, the millions of meteorites +whirling in herds. Would there be anything +startling in the same tendency appearing on a mightier +scale? Should we be greatly astonished to find +streams of stars, as well as streams of planets?</p> + +<p>For such, indeed, appears to be the case. Separated +by abysses of space, brother suns are plainly to +be seen journeying side by side through the heavens, +towards the same goal.</p> + +<p>The question of star-drift is too complex and difficult +to be gone into closely in a book of this kind. +One example, however, may be given. Almost everybody +knows by sight the constellation of the Great +Bear—the seven principal stars of which are called also +Charles’s Wain, a corruption of the old Gothic <i>Karl +Wagen</i>, the churl’s or peasant’s wagon. It is also<span class="pagenum" id="Page_341">[Pg 341]</span> +called the Great Dipper. Four bright stars form a +rough sort of oblong, and from one of the corners +three more bright stars stretch away in a curve, representing +the Bear’s tail. Many smaller stars are intermixed.</p> + +<div class="figcenter" id="f57"> +<img src="images/fig57.jpg" alt="bear"> +<p class="caption">THE GREAT BEAR.</p> +</div> + +<p>These seven bright stars have always been bound +together in men’s minds, as if they belonged to one +another. But who, through the centuries past, since +aught was known of the real distances of the stars +from ourselves and from one another, ever supposed +that any among the seven were <i>really</i> connected together?</p> + +<p>One of these seven stars, the middle one in the +tail, has a tiny companion-star, close to it, visible to<span class="pagenum" id="Page_342">[Pg 342]</span> +the naked eye. For a good while it was uncertain +whether the two were a “real double,” or only a seeming +double. In time it became clear that the two did +actually belong to one another.</p> + +<p>Mizar is the name of the chief star, and Alcor of +the companion. Alcor is believed to be about three +thousand times as far away from Mizar, as our earth +from the sun. Now, if this be the width of space between +those two bright points, lying seemingly so close +together as almost to look to the naked eye like one, +what must be the distance between the seven leading +stars of the Great Bear, separated by broad sky-spaces? +Who could imagine that one of these suns had aught +to do with the rest?</p> + +<p>Yet among other amazing discoveries of late years +it has been found by means of the new instrument, +the spectroscope, that <i>five</i> out of these seven suns are +traveling the same journey, with the same speed. Two +of the seven appear to be moving in another direction, +but three of the body-stars and two of the tail-stars +are hastening in the direction away from us, all in the +same line of march, all rushing through space at the +rate of twenty miles each second. Some smaller stars +close to them are also moving in the same path. Is +not this wonderful? We see here a vast system of +suns, all moving towards one goal, and each probably +bearing with him his own family of worlds.</p> + +<p>Many such streams have been noticed, and many +more will doubtless be found. For aught we know, +our own sun may be one among such a company of +brother-suns, traveling in company.</p> + +<p>It is difficult to give any clear idea of the immensity<span class="pagenum" id="Page_343">[Pg 343]</span> +of the universe—even of that portion of the universe +which lies within reach of our most powerful +telescopes. How far beyond such limits it may reach, +we lose ourselves in imagining.</p> + +<p>Earlier in the book we have supposed possible models +of the Solar System, bringing down the sun and +worlds to a small size, yet keeping due proportions. +What if we were to attempt to make a reduced model +of the universe; that is of just so much of it as +comes within our ken?</p> + +<p>Suppose a man were to set himself to form such a +model, including every star which has ever been seen. +Let him have one tiny ball for the sun, and another +tiny ball for Alpha Centauri; and let him, as a beginning, +set the two <i>one yard apart</i>. That single yard +represents ninety-three millions of miles, two hundred +and seventy-five thousand times repeated. Then let +him arrange countless multitudes of other tiny balls, +at due distances—some five times, ten times, twenty +times, fifty times, as far away from the sun as Alpha +Centauri.</p> + +<p>It is said that the known universe, made upon a +model of these proportions, would be many miles in +length and breadth. But the model would appear +fixed as marble. The sizes and distances of the stars +being so enormously reduced, their rates of motion +would be lessened in proportion. Long intervals of +time would need to pass before the faintest motion in +one of the millions of tiny balls could become visible +to a human eye.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_344">[Pg 344]</span></p> + +<h2 class="nobreak" id="c30">CHAPTER XXX.</h2> +</div> + +<p class="c sp">READING THE LIGHT.</p> + +<div class="figcenter" id="f58"> +<img src="images/fig58.jpg" alt="prism"> +<p class="caption">THE PRISM AND SPECTRUM.</p> +</div> + +<p><span class="smcap large">Several</span> times, in the course of this book, mention +has been made of a wonderful new instrument called +the spectroscope. We now proceed to give a brief +account of the origin and achievements of this newest +of scientific appliances. The first step towards its +formation was made by Sir Isaac Newton, when he +discovered the power of the prism to decompose light. +This consists in the fact that a ray of light, after passing +through a transparent prism, becomes expanded +into an elongated spectrum, no longer white, but presenting +an invariable succession of colors from red to +violet. These are called the seven primary colors; +namely, red, orange, yellow, green, blue, indigo, and +violet. The rainbow is a familiar illustration of this<span class="pagenum" id="Page_345">[Pg 345]</span> +spectrum with its various colors; and the raindrops +are the prisms which reflect and decompose the light.</p> + +<div class="figcenter" id="f59"> +<img src="images/fig59.jpg" alt="spectroscope"> +<p class="caption">THE SPECTROSCOPE.</p> +</div> + +<p>Optical science was long satisfied with this glance +into the interior constitution of light, occupying itself +with the phenomena of the prismatic colors, and theorizing +on the nature of white light. In 1802, Dr. +W. H. Wollaston, in closely examining a spectrum, +found it to be crossed by at least four fine dark lines. +It is only when an extremely narrow slit is employed +in admitting the sunlight that they become visible. +Dr. Wollaston, supposing them to be merely “natural +boundaries” of the different color-bands, inquired no +further; and there for a while the matter rested. Not +many years later, in 1815, the matter was taken up by +a German optician and scientist of Munich, Joseph +von Fraunhofer. Applying more delicate means of +observation, he was surprised to find very numerous +dark lines crossing the spectrum.</p> + +<p>With patience he went into the question, using the<span class="pagenum" id="Page_346">[Pg 346]</span> +telescope as well as a very narrow slit, and soon he +discovered that the dark lines were to be numbered, +not by units or by tens, but by hundreds—or, as we +now know, by thousands. Some were in the red, some +were in the violet, some were in the intermediate +bands; but each one had, and has, its own invariable +position on the solar spectrum. For, be it understood, +these dark lines are constant, not variable. Where a +line is seen, there it remains. Whenever a ray of sunlight +is properly examined, with slit and with prism, +that line will be found always occupying precisely the +same spot in the spectrum.</p> + +<p>Some of the chief and more distinct lines were +named by Fraunhofer after certain letters of the alphabet, +and by those letter-names they are still known. +He began with A in the red and went on to H in the +violet. Fraunhofer made a great many experiments +connected with these mysterious lines, anxious to discover, +if possible, their meaning. For although he +now saw the lines, which had scarcely so much as +been seen before, he could not understand them—he +could not read what they said. They spoke to him, +indeed, about the sun; but they spoke in a foreign +language, the key to which he did not possess. He +tried making use of prisms of different materials, +thinking that perhaps the lines might be due to something +in the nature of the prism employed. But let +the prism be what it might, he found the lines still +there. Then he examined the light which shines from +bright clouds, instead of capturing a ray direct from +the sun. And he found the lines still there. For +cloudlight is merely reflected sunlight.</p> + +<p><span class="pagenum" id="Page_347">[Pg 347]</span></p> + +<p>Then he examined the light of the moon, to see if +perchance the spectrum might be clear of breaks. +And he found the lines still there. For moonlight is +only reflected sunlight. Next he set himself to examine +the light which travels to us +from some of the planets, imagining +that a different result might follow. +And he found the lines still there. +For planet-light again is no more than +reflected sunlight.</p> + +<div class="figright" id="f60"> +<img src="images/fig60.jpg" alt="spectra"> +<p class="caption">SPECTRA, SHOWING<br> +THE DARK LINES.</p> +</div> + +<p>Lastly, he turned his attention to +some of the brighter stars, examining, +one by one, the ray which came from +each. And, behold! he found the lines +<i>not</i> there. For starlight is not reflected +sunlight. That is to say, the +identical lines which distinguish sunlight +were not there. Each star had +a spectrum as the sun has a spectrum, +and each star-spectrum was crossed by +faint dark lines, more or less in number. +But the spectra of the stars differed +from the spectrum of the sun. +Each particular star had its own particular +spectrum of light, different +from that of the sun, and different +from that of every other star. For now, +Fraunhofer was examining, not sunlight, +but starlight; not the light of our sun, either +direct from himself or reflected from some other +body, such as planet or moon or cloud, but the light +of other suns very far distant, each one varying<span class="pagenum" id="Page_348">[Pg 348]</span> +to some extent from the rest in its make. The +fact of the stars showing numerous sets of black +lines, all unlike those of our sun, showed conclusively +that those lines could not possibly be due to +anything in our earthly atmosphere. Sunlight and +starlight travel equally through the air, and are equally +affected by it. If our atmosphere were the cause of +the black lines in sunlight, it would cause the <i>same</i> +lines in starlight. But the sun and each individual +star has its own individual lines, quite irrespective of +changeful states of the air.</p> + +<p>So, also, the light from any metal sufficiently heated +will give a spectrum, just as sunlight gives a spectrum, +under the needful conditions. That is to say, there +must be slit and prism, or slit and diffraction-grating, +for the light to pass through. But the kind of spectrum +is by no means always the same.</p> + +<p>Putting aside for a few minutes the thought of +sunlight and starlight, let us look at the kind of rays +or beams which are given forth by heated earthly +substances. Any very much heated substance sends +forth its light in rays or beams, and any such rays or +beams may be passed through a prism, and broken +up or “analyzed,” just as easily as sunlight may be +“analyzed.”</p> + +<p>Suppose that we have a solid substance first—a +piece of iron or of steel wire. If it is heated so far as +to give out, not only heat, but also light, and if that +light is made to travel through the slit and prism of a +spectroscope, the ray will then be broken up into its +sub-rays. They, like the sub-rays of a sunbeam, will +form a continuous row of soft color-bands, one melting<span class="pagenum" id="Page_349">[Pg 349]</span> +into another. This is the characteristic spectrum +of the light which is given forth by a burning or glowing +<i>solid</i>.</p> + +<p>Next, suppose we take a liquid—some molten iron +or some molten glass, for instance. If you have ever +been to a great plate-glass manufactory, like that at +St. Helens, not far from Manchester, you will have +seen streams of liquid glass pouring about, carried to +and fro in huge caldrons, bright with a living light of +fire from its intensity of heat. If a ray of <i>that</i> light +had been passed through slit and prism, what do you +think would have been the result? A continuous +spectrum once more, the same as with the glowing +iron or steel. The light-ray from a heated and radiant +<i>liquid</i>, when broken up by a prism, lies in soft bands +of color, side by side.</p> + +<p>Both of them a good deal like the solar spectrum, +you will say. Only here are no mysterious dark lines +crossing the bright bands of color. But how about +gases? Suppose we have a substance in the state of +gas or vapor, as almost every known substance might +be under the requisite conditions, and suppose that +substance to be heated to a glowing brilliance. Then +let its light be passed through the slit and prism of a +spectroscope. What result shall we find this time? +Entirely different from anything seen before. Instead +of soft, continuous bands of color, there are <i>bright +lines</i>, well separated and sharply defined.</p> + +<p>How many bright lines? Ah, that depends upon +which particular gas is having its ray analyzed. Try +sodium first—one of the commonest of earthly substances. +Enormous quantities of it are distributed<span class="pagenum" id="Page_350">[Pg 350]</span> +broadcast in earth and air and water. More than +two-thirds of the surface of our globe lies under an +enfolding vesture of water saturated with salt, which +is a compound of sodium. That is to say, sodium +enters largely into the make of salt. Every breeze +which sweeps over the ocean carries salt inland, to +float through the atmosphere. Sir H. E. Roscoe +writes: “There is not a speck of dust, or a mote seen +dancing in the sunbeam, which does not contain chloride +of sodium”—otherwise salt. The very air which +surrounds us is full of compounds of sodium, and we +can not breathe without taking some of it into our bodies. +Sodium is an “elementary substance.” By which +I mean that it is one of a number of substances called +by us “simple,” because chemists have never yet +succeeded in breaking up those substances, by any +means at their command, into other and different +materials.</p> + +<p>Iron is, so far as we know, a simple substance. It +is found as iron in the earth. No chemist has ever +been able to make iron by combining other materials +together. No chemist has ever managed to separate +iron into other materials unlike itself. Iron it is, and +iron it remains, whether as a solid, as a liquid, or as a +gas. Gold is another simple substance, and so is silver. +Sodium is another. All these we know best in the +solid form. Mercury, another simple substance, we +know best as a liquid.</p> + +<p>Water is not a simple substance; for it can be separated +into two different gases. Glass is not a simple +substance; for it is manufactured out of other substances +combined together.</p> + +<p><span class="pagenum" id="Page_351">[Pg 351]</span></p> + +<p>We can speak quite positively as to such substances +as are not simple; but with regard to so-called “elements,” +we may only venture to assert that, thus far, +nobody has succeeded in breaking them up. Therefore, +at least for the present, they are to us “elementary.”</p> + +<p>All the simple substances, and very many of the +combinations of them, though often known to us only +in the solid form, may, under particular conditions, be +rendered liquid, and even gaseous. Every metal may +be either in the solid form, or the liquid form, or the +vapor form. Iron, as we commonly see it, is solid—in +other words, it is frozen, like ice. Just as increase +of warmth will turn ice into water, so a certain amount +of heat will make solid iron become liquid iron. And +just as yet greater warmth will turn water into steam, +so a very much increased amount of heat will turn +liquid iron into vapor of iron. A little heat will do +for ice what very great heat will do for iron.</p> + +<p>Whether iron and other metals exist in the sun, as +on earth, in a hard and solid form, it is impossible to +say. It is only in the form of gas that man can become +aware of their presence at that distance. The +intense, glowing, furnace-heat of the sun causes many +metals to be present in large quantities in the sun’s +atmosphere in the form of vapor.</p> + +<p>Not only have we learned about some of the metals +in the sun, but this strange spectrum analysis has +taught us about some of the metals and gases in the +stars as well. It is found that in Sirius, sodium and +magnesium, iron and hydrogen, exist. In Vega and +Pollux there are sodium, magnesium, and iron. In<span class="pagenum" id="Page_352">[Pg 352]</span> +Aldebaran, these substances and many others, including +mercury, seem to abound. These are merely a few +examples among many stars, each being in some degree +different from the rest.</p> + +<p>But how can we know all this? How could the +wildest guessing reveal to us the fact of iron in the +sun, not to speak of the stars? We know it by means +of the spectrum analysis—or, as we may say, by means +of the spectroscope. This instrument may be looked +upon as the twin-sister to the telescope. The telescope +gathers together the scattered rays of light into +a small spot or focus. The spectroscope tears up these +rays of light into ribbons, sorts them, sifts them, and +enables us to read in them hidden meanings.</p> + +<p>When a ray of light reaches us from the sun, that +ray is <i>white</i>; but in the white ray there are bright +colors concealed. Newton was the first to discover +that a ray of white light is really a bundle of colored +rays, so mixed up together as to appear white. If a +ray of sunlight is allowed to pass through a small +round hole in a wall, it will fall upon the opposite +wall in a small round patch of white light. But if a +<i>prism</i>—a piece of glass cut in a particular shape—is +put in the path of the ray, it has power to do two +curious things. First, it bends the ray out of a +straight course, causing the light to fall upon a different +part of the wall. Secondly, it breaks up or +divides the ray of white light into the several rays +of colored light of which the white ray is really +composed. This breaking up, or dividing, is called +“analyzing.”</p> + +<p>If in place of a round hole the ray of light is made<span class="pagenum" id="Page_353">[Pg 353]</span> +to pass through a very narrow slit, it is proved that +the bright bands of color do not overlap. Instead of +this, dark lines, or gaps, show here and there. Now, +these lines or gaps are always to be seen in the spectrum +or image of bright colors formed by a broken-up +ray of <i>sunlight</i>. There is always a certain number of +dark lines in each colored band—some near together, +some far apart; here one or two, there a great many. +Where a simple ray of sunlight is concerned, the exact +arrangement of the lines never changes.</p> + +<p>When the stars were examined—when the rays of +light coming from various stars were split up and +analyzed—it was found that they too, like the sun, +gave a spectrum of bright colors with dark lines. +But the lines were different in number and different +in arrangement from the sun’s lines. Each star has +his own particular number and his own particular arrangement, +and that arrangement and number do not +change.</p> + +<p>If a white-hot metal is burnt, and the light of it as +it burns is allowed to pass through a prism, a row of +bright colors appears as in the sun’s spectrum, only +there are no dark lines. If a gas is burnt, and the +light is allowed to pass through a prism, no bright +color-bands appear, and no dark lines either; but instead +of this, there are <i>bright lines</i>. Each gas or +vapor has its own number of lines and its own arrangement. +Sodium shows two bright lines, side by +side. Iron shows sixty bright lines, arranged in a +particular way.</p> + +<p>Now you see how a row of bright colors without +bands of color may appear. But what about color-bands<span class="pagenum" id="Page_354">[Pg 354]</span> +and dark lines together? That discovery came +latest. It was found that if a white-hot metal were +burned, and if its light were allowed before touching +the prism to shine through the flame of a burning gas, +<i>then</i> there were dark lines showing in the colored +bands. These dark lines changed in position and +number and arrangement with each different kind +of gas, just as the bright lines changed if the gases +were burned alone. If the light of the burning +metal passed through a flame colored with gas of +sodium, two dark lines showed on one part of the +spectrum; but if it passed through a flame colored +with vapor of iron, sixty dark lines showed on another +part of the spectrum.</p> + +<p>So now, by means of this spectrum analysis, we +know with all but certainty that the sun and stars +are solid, burning bodies, sending their light through +burning, gas-laden atmospheres. By examining the +little black lines which appear in the spectrum of one +or another, it is possible to say the names of many +metals existing as gas in those far-off heavenly +bodies. Is not this a wonderful way of reading light?</p> + +<p>The split-up rays tell us much more than the kinds +of metals in different stars. When a nebula is examined, +and is found to give no spectrum of bright bands +and dark lines, but only a certain number of bright +lines, we know it to be formed of gas, unlike stars +and other nebulæ. Also, it is by means of the spectroscope +that so much has lately been discovered about +the motions and speed of the stars coming towards or +going from us.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_355">[Pg 355]</span></p> + +<h2 class="nobreak" id="c31">CHAPTER XXXI.</h2> +</div> + +<p class="c sp">STELLAR PHOTOGRAPHY.</p> + + +<p><span class="smcap large">Photography</span> is not only a useful handmaid to +astronomy as a whole, but also it is so, peculiarly, to +that division of astronomy with which we are now +chiefly concerned—to spectroscopy. A few pages may +therefore with advantage be given to the subject of +celestial photography.</p> + +<p>Photography is, indeed, the greatest possible help +to the astronomer. It pictures for him those stars +which his eyes can see but dimly, or even can not see +at all; it paints for him those light-rays of which he +would obtain but a passing glance, and which he +could not accurately remember in all their details; it +maps out for him the wide heavens, which he, unaided, +could never do with anything like equal completeness +by eye and hand alone.</p> + +<p>Only recently a vast photographic map of the +whole sky was undertaken. About eighteen different +observatories, in divers parts of the world, divided the +task among them, stars down to the sixteenth magnitude +being most carefully registered in a complete +series of something like fifteen hundred separate photographs. +The whole result, when finally completed, +will be a grand achievement of the present century. +Each individual star, in the entire heavens all around +our earth, from the first to the sixteenth magnitudes, +will have its exact position in the sky accurately<span class="pagenum" id="Page_356">[Pg 356]</span> +known, and the smallest change in the position of anyone +of those stars may then be detected.</p> + +<p>Even in the delicate and abstruse operation earlier +described, the measurement of star-distances through +annual parallax, photography again steps in. Dr. +Pritchard, Savilian professor of Astronomy at Oxford, +pressed photography into the service of this task also. +Measurements for parallax were made under his direction +upon photographic plates—a work of no small +interest. Here, as elsewhere, peculiar advantages belong +to the photographic method when it can be followed. +Its records are lasting, the limited number of +hours which are fully suitable for direct astronomical +work may be employed in obtaining those records, +and in broad daylight the examination of them can be +carried on.</p> + +<p>One very curious use is made of star-photographs, +more especially of the photographs of unseen stars—that +is, of stars too distant or too dim to be detected +by the eye. These photographs, when taken, may +be afterwards looked into further with a microscope. +So, first, the far-off, invisible suns of the universe are +photographed on a prepared plate, with the help of a +powerful telescope, this being needful to secure sufficient +starlight; and then the tiny picture of those +suns is examined more closely with the help of a +powerful microscope.</p> + +<p>Spectroscopy has much to say to us. It tells us +about the positions of the different stars. It tells us +about the structure of the stars. It tells us about the +various classes to which the various stars belong. And +also it tells us about the motions of the stars—not<span class="pagenum" id="Page_357">[Pg 357]</span> +mere apparent motions, caused by movements of our +own earth, but true onward journeyings of the stars +themselves through the depths of space.</p> + +<p>For by means of photography we do not obtain +simple pictures of the stars themselves <i>only</i>, but pictures +also of the <i>spectra</i> of the stars. An instrument +is made uniting the spectroscope with the photographic +apparatus, and this is called a spectrograph. By its +means the disintegrated or broken-up star-ray is photographed +in its broken-up condition, so that an exact +picture is obtained of the bands and lines characteristic +of any particular star.</p> + +<p>No easy matter, as may be imagined, are these +spectroscopic observations and these spectroscopic +photographings of the stars. To bring the image of +a star exactly opposite a slender opening or slit, perhaps +only about the <i>three-hundredth part of an inch +in width</i>, and to keep it there, is a task which might +well be looked upon as practically impossible.</p> + +<p>No sooner is a star found in the field of a telescope +than it vanishes again. As the astronomer gazes, the +ground beneath him is ever whirling onward, leaving +the star behind; and although clockwork apparatus +in all observatories of any importance is made to +counteract this motion of the earth, and to keep the +heavenly object, whether star or moon, or comet, +within view by following its apparent motion, yet, as +can easily be imagined, to follow thus the seeming +motion of a dim star through an opening so minute, +demands exceeding care and delicacy of adjustment.</p> + +<p>It is not indeed, for purposes of analysis, <i>always</i> +needful to pass the light of a star through a narrow<span class="pagenum" id="Page_358">[Pg 358]</span> +slit. In the case of a nearer body, such as the sun or +moon or one of the planets, light flows from all parts +of the body, one ray crossing another; and for the +examination of such light, a slit is imperatively +needed, all side-rays having to be cut off. But the +whole of the brightest star in the sky is only one +point of light to us, and a slitless telescope may be +used with no confused results. Where, however, direct +comparison is required, the star-lines being made +to appear, side by side or above and below, with the +solar spectrum, or with the lines of earthly metals, +then the slit becomes unavoidable.</p> + +<p>By such comparison of the two, side by side—the +light from an intensely-heated earthly substance and +the light from a star, the rays of both being broken up +in the spectroscope—the oneness or difference of lines +in the rays can be easily made out.</p> + +<p>One main difficulty in such observations arises from +the diminution of starlight, caused by its passage +through a prism. If a rope of a dozen strands is untwisted, +each of those strands is far weaker than the +whole rope was; and each strand of color in the +twisted rope of light is of necessity much more feeble, +seen by itself, than the whole white ray seen in one. +Another difficulty in our country generally is the climate, +which gives so few days or hours in the year for +effective work. Yet the full amount accomplished by +seizing upon every possible opportunity is, in the aggregate, +astonishing. A third and very pressing difficulty +attendant upon examination of star-spectra is +caused by the incessant motion of our air, through +which, as through a veil, all observations have to be<span class="pagenum" id="Page_359">[Pg 359]</span> +made. The astronomer can never get away from the +atmosphere; and unless the air be very still—that is +to say, as still as it ever can remain—the spectrum-lines +are so uncertainly seen as to make satisfactory +results impossible. Dr. Huggins has sometimes +passed hours in the examination of a single line, +unable to determine whether or no it precisely coincided +with the comparison-line of some earthly substance. +In <i>this</i> matter, no leaping at conclusions is +admissible.</p> + +<p>The photography of stars would be easy enough +if one could just expose a plate to the shining of the +star, and there leave it to be impressed—there leave +the star-ray to sketch slowly its own image. But +this is hardly possible. The unceasing motion of the +earth, causing the star perpetually to pass away from +the telescopic field, and the exceeding narrowness of +the slit opposite to which the star has to be kept in a +stationary position, make the most accurate adjustment +needful.</p> + +<p>Clockwork alone can not be trusted. If it could, +the star and the photographic apparatus might be +comfortably “fixed,” and left to do their own work. +Instead of which, while a photograph is proceeding, +it is desirable that an observer should sit gazing patiently +at the telescope-tube, where the image of the +star is seen, ready at any moment to correct by a +touch the slightest irregularity in the clockwork motion +of the telescope, and so to prevent a blurred +and spoilt reproduction of the star, or of its spectrum.</p> + +<p>One hour, two hours, three hours, at a stretch, this +unceasing watchfulness may have to be kept up, and<span class="pagenum" id="Page_360">[Pg 360]</span> +no small amount of enthusiasm in the cause of +science is requisite for so monotonous and wearying +a vigil.</p> + +<p>As noted earlier, it has been found possible, if the +photograph of a star or nebula is not completed in +one night, to renew the work and carry it on the +next night, or even for many nights in succession. +This is especially practicable in spectroscopic photography.</p> + +<p>From four to five hours, sometimes from eight to +ten hours, may be needful before the clear image of +the star or of its spectrum appears—a dim little star +probably to us, yet perhaps in reality a splendid sun, +shedding warmth and light and life upon any number +of such worlds as ours.</p> + +<p>Eight or ten hours of photography at one stretch +with a star are impossible; for the stars, ever seemingly +on the move, do not remain long enough in a +good position. For three to six hours, a telescope +may be made, by means of its clockwork machinery, +to keep a star steadily in sight, and all that while +the photograph is progressing. If further exposure +is needed, the process has to be resumed the next +night.</p> + +<p>The more one considers the matter, the more +plainly one perceives how enormously our powers of +sky-observation are increased by photography. It is +not only that one photographer, with his apparatus, +may accomplish in a single night the work of many +astronomers who have to depend upon the power of +the eye alone. It is not only that, with the help of +photography, as much can now be done in a lifetime<span class="pagenum" id="Page_361">[Pg 361]</span> +as formerly must have occupied many generations. It +is not only that the photograph, once taken, remains a +permanent possession, instead of a record, more or less +imperfect, in which otherwise the astronomer would +have to trust.</p> + +<p>It is not even only that in the photograph details +come out which could not be detected by the eye, and +that stars are actually brought to our knowledge which +no man has ever seen, which perhaps no man ever will +see from this earth with the assistance of the most +powerful telescope. For the weak shining, which can +by no possibility make itself felt by the retina of a +man’s eye, <i>can</i> slowly impress its picture on the photographic +plate. Hundreds of stars, thousands of +stars, utterly invisible to man, have had their photographs +taken as truly as you have had your photograph +taken, and by the same process, only it has +been a longer business.</p> + +<p>But in addition to all this, we see reproduced upon +the plate those ultra-violet and infra-red portions of +the spectrum of light which but for the handmaid, +photography, would still be to us as things which +have no existence. And by means of photography +we can observe and study in those same unseen portions +of the spectra, when looking into a ray from sun +or star, the innumerable dark lines, every one of which +has its own tale to tell. To these tales we must have +remained blind and deaf, but for photographic aid to +our limited powers.</p> + +<p>Look at some dim star in the sky, and try how long +you can gaze without blinking. You will very soon +find that you have done your best, and that to gaze<span class="pagenum" id="Page_362">[Pg 362]</span> +longer only means a sense of fatigue in your eyes, a +growing dimness in the star. How different with the +photographic plate! There, no exertion is wasted, no +weariness is felt. Faint though the light may be, +which travels earthward and falls upon the plate, it is +all collected, all used.</p> + +<p>It is easy to photograph the sun, and this has been +done. When we come to the moon the operation is +more difficult on account of the feeble intensity of its +light, and the difference of tint of the various parts +of its surface. Skill and perseverance have, however, +surmounted the greatest difficulties, and now we have +photographs of the moon enlarged to more than a +yard in diameter, which show the smallest details +with a truly admirable clearness.</p> + +<p>In the first second of time, your eye receives as +much light from the star as does the photographic +plate in the same time. But during the course of +one hour, the plate receives and stores up about thirty-six +hundred times as much light as it or you received +in the first instant. There is the secret of the matter. +The photographic plate does not only receive, it can +also keep and treasure up the light, and that our eyes +are not able to do.</p> + +<p>If you magnify the amount received in one hour +by five or ten, and remember that it is all retained, +then you will begin to understand how feeble stars, +unseen by man, should become known to us through +photography.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_363">[Pg 363]</span></p> + +<h2 class="nobreak" id="c32">CHAPTER XXXII.</h2> +</div> + +<p class="c sp">THE DAWN OF ASTRONOMY.</p> + + +<p><span class="smcap large">The</span> beginnings of astronomy lie in the distance of +earliest historical ages. It is no easy matter to say +when first, in all probability, this science grew into +existence. Astronomy was alive before the British +nation was heard of; before Saxons or Franks had +sprung into being; before the Roman Empire extended +its iron rule; before the Grecian Empire began to +flourish; before the Persian Empire gained power; before +the yet earlier Assyrian Empire held sway.</p> + +<p>Among the ancient Chaldeans were devoted star-gazers—much +more devoted than the ordinary run of +educated Anglo-Saxons in this present century. They +earnestly sought, in the dim light of those ages, to +decipher the meaning of heaven’s countless lamps. +We have better instruments, and more practiced modes +of reasoning; also, we have the collected piles of knowledge +built up by our forefathers through tens of centuries. +Yet our search is in essence the same as was +theirs, to know the truth about the stars: not merely +to start some attractive theory, and then to prove that +our theory must be right, because we have been so +clever as to start it; but to discover that which is in +those regions of space. No lower aim than this is +worthy to be called scientific.</p> + +<p>Mistakes, of course, are made; how should it be +otherwise? A man finding his way at night, for the<span class="pagenum" id="Page_364">[Pg 364]</span> +first time, through a wild and unknown country, will +almost certainly take some wrong turns before he discovers +the right road. In astronomy, as in all other +natural sciences, blunders are a necessity if advance is +to be made. We have to grope our way to knowledge +through observation and conjecture; in simpler +terms, through gazing and guessing. Observation of +facts leads to conjecture as to the possible causes for +those facts; and each conjecture is proved by later observation +to be either right or wrong. If proved to be +right, it takes its place among accepted truths; if proved +to be wrong, it is flung aside. Some pet delusions +die hard, because of people’s love for them.</p> + +<p>Astronomy, as an infant science, mixed up with astrology, +existed in the days when the Pyramids were +juvenile, and when the Assyrian sculptures were modern. +How much farther back who shall say? By +astrology, those who studied the heavens endeavored +to determine the fate of men and of nations, to predict +events, and to interpret results. They paid particular +attention to the aspect of the planets, and the +general appearance of the firmament.</p> + +<p>These observations were at first simple remarks +made by the shepherds of the Himalayas after sunset +and before sunrise: The phases of the moon, and diurnal +retrograde motion of that body with reference to +the sun and stars; the apparent motion of the starry +sky accomplished silently above our heads; the movements +of the beautiful planets through the constellations; +the shooting star, which seems to fall from the +heavens; eclipses of the sun and moon, mysterious +subjects of terror; curious comets, which appear with<span class="pagenum" id="Page_365">[Pg 365]</span> +disheveled hair in the heights of heaven,—such were +the first subjects of these old observations made during +thousands of years.</p> + +<p>The ancient Chaldean star-gazers had rivals among +the early Egyptians; and the Chinese profess to have +kept actual record of eclipses during between three +and four thousand years. The earlier records are not +trustworthy; but of thirty-six eclipses reckoned by +the Chinese sage, Confucius, no less than thirty-one +have been proved true by modern astronomers.</p> + +<p>We can not name with certainty those people whose +shepherds first gazed with intelligent eyes upon the +midnight sky, and noted the steady sweep of stars +across the firmament—intelligent eyes, that is to say, +so far as man then knew how to use his eyes intelligently; +so far as man had begun to note anything in +nature, to watch, to compare, and to conjecture causes.</p> + +<p>In those times, and indeed for long afterwards, men +thought much more about the “influences” of stars +upon their own lives, and about supposed prophecies +of the future to be read in the sky, than about the +actual physical condition of the stars themselves, or +the causes and meanings of the various phenomena +observed in the heavens.</p> + +<p>The desire to know, for the pure delight of knowing, +had perhaps hardly begun to dawn upon the mind +of man. What people did want to know was what +might be going to happen to themselves; whether <i>they</i> +would be happy or unhappy; and the stars were chiefly +of interest as appearing to tell beforehand of troubles +or joys to come.</p> + +<p>The wisest of men in those times knew less of the<span class="pagenum" id="Page_366">[Pg 366]</span> +outspread heavens than many a child now knows in +our public schools. Earth and sky were one vast bewildering +puzzle. They had to discover everything +for themselves—how the sun rose each morning and +set each evening; how the seasons changed in steady +sequence through the year; how the moon and stars +journeyed in the night; how the ocean-tides went and +came; how numberless every-day phenomena took +place.</p> + +<p>In olden days the daily rising and setting of the +sun was a mystery, accounted for by divers theories, +none of which were right; and the march of stars +across the midnight sky was a complete puzzle; and +an eclipse of sun or moon was a fearful perplexity; +and the tides of ocean were a great bewilderment. +These things are mysteries still to barbarous nations; +but they perplex us no longer, because we have found +out the mode in which such movements, or appearances +of movement, are brought about through the action +of quite natural causes.</p> + +<p>As a first step, in earliest times, the journey of the +sun by day, the journeys of moon and stars by night, +across the sky, could hardly fail to arrest attention. +Very early, too, the stars were grouped into constellations, +definite figures and names being attached to +each. Many of the constellations are now known to +us by names which belong to the earliest historic ages.</p> + +<p>The stars were known as “fixed,” because they +continued unchangeably in their relative positions—that +is, in the position held by each star with respect +to its neighbor stars—although the whole array of +them moved nightly in company; constellations rising<span class="pagenum" id="Page_367">[Pg 367]</span> +and setting at night, as the sun rose and set in the +day.</p> + +<p>Ages may well have passed before the planets were +recognized as distinct from the fixed stars; ages more +before any definite plan was noted in their wanderings. +In the course of time men’s attention was directed +to these matters; and one fact after another, of +daily or monthly or yearly occurrence, was observed, +and commented upon, and became familiar to the +minds of people. Very slowly the first beginnings of +systematized knowledge took shape and grew, one +discovery being made after another, one explanation +being offered after another, one theory being started +after another.</p> + +<p>But an essential difference existed between the infantine +science of those primitive days and the matured +astronomy of these later days. The whole ancient +science was built upon a huge mistake. Men held, as +a fact of absolutely unquestionable certainty, that this +earth of ours—this small whirling globe, less than eight +thousand miles in diameter—was the center, around +which sun, moon, and stars all revolved.</p> + +<p>The Greek philosopher Thales, who lived about six +hundred years before Christ, is said to have laid the +foundations of the Grecian astronomy; and Pythagoras +is stated to have been one of his disciples. +Though, in many respects, Thales wandered wide of +the truth, he yet taught many correct ideas; as, for instance, +that the stars were made of fire; that the moon +had all her light from the sun; that the earth was a +sphere in shape, besides other facts respecting the +earth’s zones and the sun’s apparent path in the sky.<span class="pagenum" id="Page_368">[Pg 368]</span> +He was also one of the three ancient astronomers who +were able to calculate and foretell eclipses.</p> + +<p>After him came numerous astronomers, of greater +or less merit, in the Grecian and in other schools. +They watched carefully; they discovered many things +of interest; they held divers theories. But one truth +never took firm root among them, although several of +them dimly apprehended it; and this was the very +foundation-truth, for lack of which they were all going +hopelessly astray—the simple truth that our earth +is <i>not</i> the center of the universe, and that our earth +<i>does</i> move. Yet it is not surprising. No wonder they +were slow to grasp such a possibility.</p> + +<p>Anything more bewildering to the mind of ancient +man than the thought of a solid, substantial world +floating in empty space, supported upon nothing, upheld +by nothing, can hardly be imagined. As yet +little was known of the controlling laws or forces of +nature, and that little was with reference only to our +earth. The very suspicion of gravitation as a universal +law lay in the far-distant future, waiting for the +intellect of a Newton to call it out of apparent chaos; +and the delicate balance of forces, by means of which +the Solar System may almost be said to exist, could +not be so much as guessed at.</p> + +<p>So men still clung to the thought of earth as the +center of all things, and still believed in a little sun, +busily circling round her once in every twenty-four +hours.</p> + +<p>Perhaps the greatest of all ancient astronomers was +Hipparchus, about 150 B. C., who did more than any +other in those early times to gather together the scattered<span class="pagenum" id="Page_369">[Pg 369]</span> +facts of astronomy, and to arrange them into +one united and orderly whole. He it was who discovered +the precession of the equinoxes. He studied +eclipses and the motions of the various planets. He +made elaborate and valuable astronomical tables and +star-catalogues; but he, like others, failed to discover +the gigantic error which lay at the root of the whole +ancient science.</p> + +<p>Despite this great mistake, still persistently believed +in, and despite the crude notions of early astronomers +on many points, it is marvelous how much +they did manage to observe and to learn for themselves,—as +to the sun and his apparent path, as to +the moon and her path, as to the five then known +planets and their paths, as to eclipses and other phenomena.</p> + +<p>By all such careful watching, although they to some +extent missed their aim and fell into mistakes, yet they +paved a way to later discoveries and to fuller knowledge. +Their work was not thrown away, their trouble +was not lost; for out of their very errors grew the fair +form of truth.</p> + +<p>Nearly three hundred years after the time of Hipparchus +came the famous Ptolemy—famous, not, like +certain other astronomers, for stupendous genius, or +for the brilliancy and accuracy of his observations, +but rather noted for the ingenuity of his explanations, +and for the adroit manner in which he systematized +such knowledge, on the subject of the heavenly bodies, +as was then in the possession of mankind.</p> + +<p>Ptolemy’s name is best known in connection with +what is commonly called “The Ptolemaic System of<span class="pagenum" id="Page_370">[Pg 370]</span> +the Universe,” and his greatest astronomical work is +best known as the <i>Almagest</i>.</p> + +<p>A great many of Ptolemy’s leading notions, as well +as the principal mass of facts upon which he worked, +were doubtless borrowed from Hipparchus. The latter +is said to have explained the movements of the sun +and of the moon by means of small epicycles, traveling +round the earth on circular orbits; and even Hipparchus +did not originate this fundamental idea of the +so-called “Ptolemaic System,” which had indeed been +held by the ancients in much earlier days. Hipparchus +worked it out to some extent, and Ptolemy carried +on the process much farther, giving forth the +system to the world in such wise that ever since it has +gone by his name.</p> + +<p>The theory of cycles and epicycles lasted long—lasted +from the time of Ptolemy in the second century +to the time of Copernicus in the sixteenth century, of +whom we have already spoken.</p> + +<p>[For about two thousand years, astronomers observed +attentively the apparent revolutions of the +heavenly bodies, and this attentive study gradually +showed them a large number of irregularities and inexplicable +complications, until at last they recognized +that they were deceived as to the earth’s position, in +the same way that they had been deceived as to its stability. +The immortal Copernicus, in particular, discussed +with perseverance the earth’s motion, already +previously suspected for two thousand years, but always +rejected by man’s self-love; and when this learned +Polish canon bid adieu to our world in the year 1543, +he bequeathed to science his great work, which demonstrated<span class="pagenum" id="Page_371">[Pg 371]</span> +clearly the long-standing error of mankind.—<i>F.</i>]</p> + +<p>The new theory of Copernicus had to make its +way slowly against the dead weight of unreasoning +public opinion, and against wrongly-reasoning hierarchical +opposition. In time, gradually, despite all +resistance, the truth made its way, and was generally +received, though not till Galileo had been forced by +ecclesiastical authority to recant his opinions. All +the same, Copernicus, Kepler, Galileo, were right; +public sentiment and the Church were wrong,—the +earth did move, and was not the fixed universe center, +and, by and by, those who lived on earth had to +acknowledge the same.</p> + +<p>The succession of these great men is interesting to +note. Between the two shining lights, Hipparchus +and Ptolemy, nearly three hundred years intervened. +But as the history of the world advances, we find +brilliant scientific minds appearing more quickly, one +following close upon another, instead of their being +divided by long intervals of blankness.</p> + +<p>Within thirty years from the death of Copernicus, +were born two mighty men of Science: Kepler, who +lived till 1630; and Galileo, who lived till 1642, when +England was plunged in civil strife.</p> + +<p>Between Copernicus and Kepler came Tycho Brahe. +Copernicus was a Roman ecclesiastic, born in Poland. +Tycho Brahe was a wealthy Danish nobleman, an ardent +lover of astronomy, and a most patient and accurate +observer. But Tycho held fast by the old +astronomy. He was not convinced by the arguments +of Copernicus. To him, earth was still the motionless<span class="pagenum" id="Page_372">[Pg 372]</span> +center of all things. He was willing to allow +that the rest of the planets circled round the sun, as +an explanation of things which he could not help seeing; +but the sun itself had still, in Tycho’s imagination, +to revolve daily, with planets and stars and the +whole sky, round our earth.</p> + +<p>As an explainer of causes, therefore, Tycho rose to +no lofty heights. The real good which he did was in +watching and noting actual phenomena, not in trying +to explain how those phenomena were brought about. +This was left for one of his young pupils, a sickly German +lad, named John Kepler.</p> + +<p>In later years, Kepler made a grand use of his +master’s mass of careful and thoroughly dependable +observations. These had really been gathered together +by Tycho, with a view of disproving the +Copernican theory, and of establishing the main features +of the olden astronomy, with certain improvements. +But Kepler used the accumulated information +to disprove the old astronomy, and to establish +the truth of the new Copernican system which Tycho +had rejected. He found a vast advantage, ready to +his hand, in the collection of careful observations systematically +worked out by Tycho in his observatory +during many a long year. And Kepler did not fail to +use his advantage.</p> + +<p>The planets still refused, as they always had refused, +to keep to the paths marked out for them by +astronomers. Kepler grappled with the difficulty. +He particularly turned his attention to Mars, that +near neighbor of ours, in which we are all now so +much interested. A long series of close observations<span class="pagenum" id="Page_373">[Pg 373]</span> +of Mars’s movements, made by Tycho in the course +of many years, lay before him; and he knew that he +could depend upon the absolute honesty and accuracy +of Tycho’s work.</p> + +<p>With immense labor and immense patience, he +went into the matter, still clinging to the old idea of +a circular pathway round the sun. He tried things +this way and that way. He placed his orbit in imagination +after one mode and another mode; he conjectured +various arrangements; he tested and proved +them in turn, comparing each plan with observations +made,—and still Mars defied all his efforts; still the +little world went persistently wrong, traveling contrary +to every theory.</p> + +<p>Thus far, nobody had ever thought of an orbit of +any other shape than a circle. When a straightforward +journey round a circle was found impossible, +then epicycles were introduced to explain the planet’s +perplexing motions. No one had dreamt of an elliptic +pathway. But suddenly a gleam of daylight came +upon this groping in the dark. What if Mars traveled +round the sun—<i>not</i> in a circle, but in an oval?</p> + +<p>Kepler tried this oval and that oval, comparing observations +past—testing, examining, proving or disproving, +with unwearied patience. And at length he +found, beyond dispute, that Mars actually did travel +round the sun in a yearly pathway, which was shaped, +not as a circle, but as the kind of oval known as an +<i>ellipse</i>; and, further, that the sun was not in the exact +center of this ellipse, but to one side of the center, in +one of the foci. Kepler’s success in detecting the true +shape of a planetary orbit is doubtless owing to the fact<span class="pagenum" id="Page_374">[Pg 374]</span> +that the orbit of Mars makes a wider departure from the +circular form than any of the other important planets.</p> + +<p>One step further would have led Kepler to the +knowledge that comets also travel in elliptic orbits—only +in very long and narrow ones generally. But he +had quite made up his mind that all comets merely +paid our sun one visit, and never by any chance returned; +so he did not trouble himself to enter into +calculations with respect to them. This taking for +granted of ideas long held was a very common practice +in those days.</p> + +<p>The above wonderful discovery of elliptic orbits, in +place of circular orbits, was only one among many +made by the illustrious Kepler—discoveries not carelessly +hit upon, as one might pick up in the street a +valuable stone which somebody had dropped, but earnestly +sought for, and found with toil and diligence, +as gems are first found in foreign lands, after much +seeking and long patience. Casual discoveries in +science are rare. Attainment is far more usually +made through intense study, through hard work, +through profound thought, through a gradual groping +upward out of darkness to the point where daylight +breaks forth.</p> + +<p>The three well-known “Laws of Kepler” still lie +at the very foundation of the modern system of astronomy. +They are: First, every planet moves in an +elliptical orbit, in one focus of which the sun is situated; +second, the line drawn from the sun to a +planet moves over equal areas in equal times; and, +third, the square of the periodic times of the planets +varies inversely as the cubes of their distances.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_375">[Pg 375]</span></p> + +<h2 class="nobreak" id="c33">CHAPTER XXXIII.</h2> +</div> + +<p class="c sp">MODERN ASTRONOMY.</p> + + +<p><span class="smcap large">Still</span>, however, the world was not convinced of +the truth of the Copernican system. One man here +or there saw and acknowledged its reality. The mass +of mankind continued firmly to believe that they +dwelt at the universe center, and utterly to scout the +idea of a moving earth. Indeed, it may be very much +doubted whether, not merely the mass of mankind, +but even the most civilized and cultivated portion of +that mass, had as yet, to any wide extent, heard a +whisper of the new theories. Knowledge, in those +days, traveled from place to place with exceeding deliberation.</p> + +<p>Another great man arose, contemporary with Kepler—a +man whose story seizes more strongly upon our +imagination than that of the severe and successful +studies of Kepler. From an ordinary worldly point of +view, Kepler would hardly be looked upon as altogether +a successful man. He was poor, and in sickly health. +His chief book was promptly prohibited by Rome—then +a power in the whole reading world of Europe to +an extent which can hardly be realized in these days +of freedom. Kepler’s book was placed in the forbidden +category, side by side with the dying publication +of Copernicus. This checked all hope of literary +gains, and life with Kepler was one long struggle. +But if he could have looked ahead two or three hundred<span class="pagenum" id="Page_376">[Pg 376]</span> +years; if he could have foreseen the time when +not a few wise men of science alone, but all the civilized +world, including the very Church which condemned +him, should meekly have accepted and indorsed his +discoveries,—then he would have been able to gauge +the measure of his own real success.</p> + +<p>Moreover, with all his troubles, Kepler was so +happy as to escape absolute persecution. He lived in +a country which knew something of liberty as an ideal; +he was left to write and work freely; and, at least, no +public recantation of what he held to be truth was +forced from him.</p> + +<p>Galileo’s was a sadder tale. A Florentine of noble +birth, he turned his attention early to science as the +needle turns to the north, and before the age of twenty-seven +he already occupied a foremost position as mathematical +lecturer at Pisa. There it was that he direfully +offended the philosophers of the day by proving +Aristotle to be in the wrong. For Aristotle was the +great master of the schoolmen. His philosophy and +theories were accepted as final, and whatsoever could +not be proved in accordance with them was regarded +as untrue. Aristotle had declared that if two weights—the +one being ten times as heavy as the other—were +dropped together from a height, the heavier weight +would reach the ground ten times as quickly as the +lighter.</p> + +<p>Everybody believed this, and nobody had ever +thought of putting it to the test of actual trial. Aristotle +had said so, and Aristotle was indorsed as a whole +by all the schools of Europe; and what more could +possibly be wanted by any reasonable human being? +<span class="pagenum" id="Page_378">[Pg 378]</span>But Galileo was not so easily satisfied. He looked +into the matter independently, bent upon finding out, +not what Aristotle had thought or what the Church +might support, but simply what actually <i>was</i>.</p> + +<div class="figcenter" id="f61"> +<img src="images/fig61.jpg" alt="astronomers"> +<p class="caption"><span class="smcap">Prominent Astronomers of the Nineteenth Century.</span></p> +</div> + +<p>Then, in view of many observers, called together +for the occasion, he dropped, at the same instant, from +the top of the leaning tower of Pisa, a shot weighing +one pound and another shot weighing a hundred +pounds. And, behold! both reached the ground simultaneously. +There was not a fraction of difference +between the two. To prove Aristotle wrong was to +prove everybody wrong, the authorities of the Church +included. Men calmly declined to believe their own +eyes, and Galileo was in very evil odor.</p> + +<p>From falling bodies he went on to subjects of yet +wider interest to people in general. He read about +and eagerly embraced the Copernican system. Not +only did he accept it himself, but he vigorously set to +work to teach and convince others also. This, as +might only be expected, aroused vehement opposition. +But Galileo was still in the heyday of his powers, and +he was not to be easily silenced. In those days he +could afford to press onward in the teeth of resistance, +and to laugh at men who would not listen.</p> + +<p>When at Venice, a report reached him of a certain +optician in Holland who had happened to hit upon a +curious “combination of lenses,” through which objects +afar off could be actually seen as if they were +near. Galileo promptly seized upon the notion, and +within twenty-four hours he had rigged up a small, +rough telescope out of an old organ-pipe and two +spectacle-glasses.</p> + +<p><span class="pagenum" id="Page_379">[Pg 379]</span></p> + +<p>Thus the first telescope was made—a very elementary +affair, formed of two lenses, convex and concave, +and capable of magnifying some three times—a +mere child’s toy compared with telescopes of the +present day, but of exceeding value and interest, because +it was the very first; because in all the history +of the world no telescope had ever been manufactured +before.</p> + +<p>This earliest effort was speedily improved upon. +The next trial produced a tube which could magnify +seven or eight times; and in a little while, Galileo +had a telescope magnifying as much as thirty-two +times. Even thirty-two times does not sound very +startling to us; but in those days the revelations of +such an instrument came upon men like a thunderclap.</p> + +<p>Through it could be seen clearly the broken nature +of the moon’s surface—the craters, the shadows, the +mountains. Through it could be seen the phases of +Venus, which no man had ever yet detected, but +which Copernicus had declared must certainly exist, +if indeed his system were a reality. Through it could +be seen four of the moons of Jupiter, and their ceaseless +journeyings. Through it could be seen spots upon +the face of the sun, the movements of which showed +the rotation of the sun upon his axis. Through it +could be seen the very curious shape of Saturn, +caused by his rings, though a much stronger power +was needed to separate the rings from the body of the +planet.</p> + +<p>Of all these discoveries, and many others also made +by Galileo, none seemed worse to the bigoted schoolmen<span class="pagenum" id="Page_380">[Pg 380]</span> +of his day than the preposterous notion of black +spots upon the sun’s face.</p> + +<p>Rather curiously, no human being seems ever before +then to have noticed such spots, though often they +are quite large enough to be detected by the naked +eye. A general belief had been held that the sun was +and must be perfect—an absolutely spotless and unblemished +being, the purest symbol of celestial incorruptibility—and +the said discovery went right +in the teeth of deductions drawn from, and lessons +founded upon, this belief. Therefore the schoolmen +held out and determinedly resisted, and would have +nought to do with Galileo or his telescopes, shutting +their eyes to marvels newly revealed.</p> + +<p>But Kepler was a true scientist, a man who earnestly +pursued truth, and sought to discover it at any hazard. +He and Galileo were contemporaries, and they held +communication on these subjects. Some of Galileo’s +discoveries went quite as much in the teeth of some +of Kepler’s most dearly-loved theories as they did in +the teeth of the schoolmen’s most dearly-loved doctrines. +Yet, none the less, Kepler welcomed them +with great delight and eagerness, showing thereby his +true greatness of character.</p> + +<p>Till after the age of fifty, Galileo was allowed to go +on undisturbed, or at least not materially disturbed, +by opposition in his career of success—observing, +learning, theorizing, calculating, explaining, teaching—a +prominent figure indeed. Not only did he take a +large share in establishing firmly the Copernican system +of astronomy, but some of the principal laws of +motion were discovered by him. He first found the<span class="pagenum" id="Page_381">[Pg 381]</span> +uses of a pendulum, and there is strong reason for believing +that the first microscope, as well as the first +telescope, was from his hands.</p> + +<p>But after the age of fifty, reverses came, and one +blow succeeded another. Rome had been gradually +waking up to the true sense of all that was implied +by his discoveries and his teaching, and at length she +let loose her thunders—impotent thunders enough, so +far as regarded any permanent checking of the progress +of truth, but by no means impotent to crush one +defenseless victim, the champion of scientific truth in +that country and age.</p> + +<p>Years of greater or less opposition, amounting often +to persecution, were followed by an imperious order +commanding him to Rome. There he was examined +and severely “questioned,” and recantation was forced +from him, worth as much as such forced recantations +commonly are worth.</p> + +<p>Even then he did not cease from the work that he +loved; even in prison he carried it on; even when he +might not write, nothing could stop him from thinking. +But his health was broken; his liberty was taken +away; illness followed illness; his favorite daughter +died; his eyesight gradually failed; the last book that +he wrote might not for a long while be printed; and +at last he passed away, mercifully set free from those +who, in an essentially bigoted and intolerant age, were +incapable of appreciating his greatness.</p> + +<p>They would fain <i>then</i> have denied him even a respectable +grave. Now, all the civilized world unites +to honor the name of Galileo.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_382">[Pg 382]</span></p> + +<h2 class="nobreak" id="c34">CHAPTER XXXIII.</h2> +</div> + +<p class="c sp">ISAAC NEWTON.</p> + + +<p><span class="smcap large">Even</span> the great fame of Galileo must be relegated +to a second place in comparison with that of the philosopher +who first saw the light in a Lincolnshire +farmhouse on the 25th of December, 1642, the very +same year of Galileo’s death. His father, Isaac Newton, +had died before his birth. The little Isaac was +at first so frail and weakly that his life was despaired +of. The watchful mother, however, tended her delicate +child with such success that he ultimately acquired +a frame strong enough to outlast the ordinary +span of human life.</p> + +<p>In due time the boy was sent to the public school +at Grantham. That he might be near his work, he +was boarded at the house of Mr. Clark, an apothecary. +He had at first a very low place in the class. His first +incentive to diligent study seems to have been derived +from the circumstance that he was severely kicked by +one of the boys above him in the class. This indignity +had the effect of stimulating young Newton’s activity +to such an extent that he not only attained the +desired object of passing over the head of the boy +who had maltreated him, but continued to rise until +he became the head of the school.</p> + +<p>The play-hours of the great philosopher were devoted +to pursuits very different from those of most +schoolboys. His chief amusement was found in making<span class="pagenum" id="Page_383">[Pg 383]</span> +mechanical toys, and various ingenious contrivances. +He watched, day by day, with great interest, +the workmen engaged in constructing a windmill in +the neighborhood of the school, the result, of which +was that the boy made a working model of the windmill +and of its machinery, which seems to have been +much admired as indicating his aptitude for mechanics. +We are told that he also indulged in somewhat +higher flights of mechanical enterprise. The first +philosophical instrument he made was a clock, which +was actuated by water. He also devoted much attention +to the construction of paper kites, and his skill in +this respect was highly appreciated by his schoolfellows. +Like a true philosopher, even at this stage, +he experimented on the best methods of attaching the +string, and on the proportions which the tail ought +to have.</p> + +<p>When the schoolboy at Grantham was fourteen +years of age, it was thought necessary to recall him +from the school. His recently-born industry had been +such that he had already made good progress in his +studies, and his mother hoped that he would now lay +aside his books, and those silent meditations to which, +even at this early age, he had become addicted. It +was hoped that instead of such pursuits, which were +deemed quite useless, the boy would enter busily into +the duties of the farm and the details of a country +life. But before long it became manifest that the +study of nature and the pursuit of knowledge had +such a fascination for the youth that he could give +little attention to aught else. It was plain that he +would make but an indifferent farmer. He greatly<span class="pagenum" id="Page_384">[Pg 384]</span> +preferred experimenting on water-wheels, and working +at mathematics in the shadow of a hedge.</p> + +<p>Fortunately for humanity, his mother, like a wise +woman, determined to let her boy’s genius have the +scope which it required. He was accordingly sent +back to Grantham school, with the object of being +trained in the knowledge which would fit him for entering +the University of Cambridge.</p> + +<p>It was the 5th of June, 1660, when Isaac Newton, +a youth of eighteen, was enrolled as an undergraduate +of Trinity College, Cambridge. Little did those who +sent him there dream that this boy was destined to be +the most illustrious student who ever entered the portals +of that great seat of learning. Little could the +youth himself have foreseen that the rooms near the +gateway which he occupied would acquire a celebrity +from the fact that he dwelt in them, or that the antechapel +of his college was in good time to be adorned +by that noble statue of himself which is regarded as +the chief art treasure of Cambridge University, both +on account of its intrinsic beauty and the fact that it +commemorates the fame of her most distinguished +alumnus, Isaac Newton, the immortal astronomer. His +advent at the university seemed to have been by no +means auspicious or brilliant. His birth was, as we have +seen, comparatively obscure, and though he had already +given indication of his capacity for reflecting on philosophical +matters, yet he seems to have been but ill-equipped +with the routine knowledge which youths are +generally expected to take with them to the universities.</p> + +<p>From the outset of his college career, Newton’s attention +seems to have been mainly directed to mathematics.<span class="pagenum" id="Page_385">[Pg 385]</span> +Here he began to give evidence of that marvelous +insight into the deep secrets of nature which, +more than a century later, led so dispassionate a judge +as Laplace to pronounce Newton’s immortal work as +pre-eminent above all the productions of the human +intellect. But though Newton was one of the very +greatest mathematicians that ever lived, he was never +a mathematician for the mere sake of mathematics. +He employed his mathematics as an instrument for +discovering the laws of nature.</p> + +<p>His industry and genius soon brought him under +the notice of the university authorities. It is stated +in the university records that he obtained a scholarship +in 1664. Two years later we find that Newton, +as well as many residents in the university, had to +leave Cambridge temporarily on account of the breaking +out of the plague. The philosopher retired for a +season to his old home at Woolsthorpe, and there he +remained until he was appointed a Fellow of Trinity +College, Cambridge, in 1667. From this time onwards, +Newton’s reputation as a mathematician and +as a natural philosopher steadily advanced, so that in +1669, while still but twenty-seven years of age, he +was appointed to the distinguished position of professor +of Mathematics at Cambridge. Here he found +the opportunity to continue and develop that marvelous +career of discovery which formed his life’s work.</p> + +<p>The earliest of Newton’s great achievements in +natural philosophy was his detection of the composite +character of light. That a beam of ordinary sunlight +is, in fact, a mixture of a very great number of +different colored lights, is a doctrine now familiar to<span class="pagenum" id="Page_386">[Pg 386]</span> +every one who has the slightest education in physical +science. We must, however, remember that this discovery +was really a tremendous advance in knowledge +at the time when Newton announced it.</p> + +<div class="figcenter" id="f62"> +<img src="images/fig62.jpg" alt="newton"> +<p class="caption">SIR ISAAC NEWTON.</p> +</div> + +<p>A certain story is often told about Newton. It is +said that as he sat in a garden an apple fell from a +tree, and that its fall set him thinking, and that, in +consequence of this train of thought, he found out all +about the law of attraction or gravitation.</p> + +<p>But the fall of an apple could not possibly have set +Newton thinking, because he had already been thinking<span class="pagenum" id="Page_387">[Pg 387]</span> +long and hard upon these difficult questions. Indeed, +it was <i>because</i> he had been so thinking, <i>because</i> +his mind was in a watchful and receptive condition, +that so slight a matter as a falling apple should, perhaps, +have suggested to him a useful train of ideas.</p> + +<p>Newton was a man who really did think, and who +really did think intensely. He was not, like the ordinary +run of people, one who merely had a good +many notions walking loosely through his brain. He +would bend his mind to a subject and be absolutely +absorbed in it; later in life so absorbed that he would +forget to finish his dressing, and would be unable to +say whether or no he had dined. This sort of forgetfulness +does sometimes spring from vacancy of mind; +but with Newton it arose from fullness of thought.</p> + +<p>An apple falls, of course, as a stone or any other +body falls, because the earth attracts it. Otherwise, +it might as easily rise and float away into the sky. +But this was known perfectly well long before Newton’s +days. It was clearly understood that the earth +had a curious power of drawing all things towards +herself. People could not explain why or how it was +so; neither can we explain now; but they were fully +aware of the fact.</p> + +<p>So men knew something of the force called gravity; +but they knew it mainly, almost exclusively, as +having to do with our earth, and with the things upon +our earth. They had not begun definitely to think of +gravity as having to do with bodies in the heavens; +as being a chief controlling force in the whole Solar +System; much less as reigning throughout the vast +universe of stars. It had not come into their minds<span class="pagenum" id="Page_388">[Pg 388]</span> +with any distinctness that, just as the earth pulls towards +her own center a mountain, a horse, a man, so +the sun pulls toward his center the earth, the moon, +and all the planets.</p> + +<p>Certain glimmerings of the notion had, indeed, +begun to dawn on the horizon of learning. Horrocks, +Borelli, Robert Hook, Wren, Halley, and others had +<i>glimpses</i> of universal gravitation; but only glimpses. +A gifted English philosopher, late in the sixteenth century, +Gilbert by name, went so far as to speak of earth +and moon acting one upon the other “like two magnets.” +He also saw the effect of the moon’s attraction +in bringing about ocean tides, though he oddly explained +that the said attraction was not so much exerted +upon ocean waters as upon “subterranean spirits +and humors”—whatever he may have meant by such +an expression.</p> + +<p>Kepler, not long after Gilbert, made further advance. +He gained some definite notions as to the nature +of gravity; and he saw distinctly that the moon’s +attraction was the main cause of the tides. The following +remarkable statement is found in his writings: +“If the earth ceased to attract its waters, the whole +sea would mount up and unite itself with the moon. +The sphere of the attracting force of the moon extends +even to the earth, and draws the waters towards +the torrid zone, so that they rise to the point which +has the moon in the zenith.” Here is a distinct enough +grasp of the fact that gravity can and does act through +distance, between worlds separated by thousands of +miles.</p> + +<p>Yet, though both Gilbert and Kepler saw so much,<span class="pagenum" id="Page_389">[Pg 389]</span> +they failed to go farther. Neither of the two had any +clear knowledge of the modes in which gravitation +acts, or of the laws which govern its working. Gilbert +and Kepler alike, while dimly recognizing, not +only the moon’s attraction for earth’s oceans, but the +mutual attraction of earth and moon each for the other, +were utterly perplexed as to what force could possibly +hold the two bodies asunder. Gilbert could seriously +talk of “subterranean spirits and humors.” +Kepler could soberly write of an “animal force” or +some tantamount power in the moon, which prevented +her nearer approach to earth.</p> + +<p>Galileo was equally vague on the subject. With all +his brilliant gifts, and while acknowledging the earth’s +attractive power over the moon, he would not even +admit the existence of <i>mutual</i> attraction, and talked +of the moon as being compelled to “follow the earth.” +Unquestionably there are times when the moon does +follow the earth, and that is when the earth happens +to go before. But quite as often it happens that the +moon goes before, and the earth follows after.</p> + +<p>All these great men were groping near the truth, +yet none managed to find the clue that was wanted. +They left the unfinished process of thought to be carried +on by the master-mind of Newton. And Newton +set himself to think the question out. He used Kepler’s +observations. He sought to penetrate the secrets +of a Solar System in mysterious and inviolable order. +Some reason or cause for that order he knew must exist—if +only it might be grasped! He pondered deeply; +lost in profound cogitation, through stormy days of +civil strife, of plague and loss and suffering. The<span class="pagenum" id="Page_390">[Pg 390]</span> +object of his life was to discover, if so he might, what +power or what forces retained the different worlds in +their respective pathways; in short, what manner of +celestial guidance was vouchsafed to the planets.</p> + +<p>For although men had now learned the shape of the +planet-orbits, and even knew certain laws which helped +to govern the planet-motions, they had not discovered +one supreme controlling law. They did not dream of +gravity in the heavens as a prevailing force. There +was absolutely no reason, with which men were acquainted, +why each planet should preserve its own +particular distance from the sun; why Mars should not +wander as far away as Jupiter; why Mercury should +not flee to the position of Saturn; why our own +earth should be always about as near as she always +is.</p> + +<p>The resources of Newton’s genius seemed equal to +almost any demand that could be made upon it. He +saw that each planet must disturb the other, and in +that way he was able to render a satisfactory account +of certain phenomena which had perplexed all preceding +investigators. That mysterious movement by +which the pole of the earth sways about among the +stars, had been long an unsolved enigma; but Newton +showed that the moon grasped with its attraction +the protuberant mass at the equatorial regions of the +earth, and thus tilted the earth’s axis in a way that +accounted for the phenomenon which had been known, +but had never been explained, for two thousand years. +All these discoveries were brought together in that +immortal work, Newton’s “Principia,” the greatest +work on science that the world had yet seen.</p> + +<p><span class="pagenum" id="Page_391">[Pg 391]</span></p> + +<p>It may well be that, as Newton pondered this perplexing +question while seated in the garden, an apple +dropping to the ground might have sufficed to turn his +wide-awake and ready mind in the direction of that +familiar force, gravity, which draws all loose bodies towards +earth’s surface. The apple fell because of gravity. +Quite naturally the question might have arisen +in Newton’s mind—“Why not this same gravity in the +heavens also? If the earth draws an apple towards +herself, why should not the earth draw the moon? +Why should not the sun draw the earth? Nay, more, +why should not the sun draw all the planets?” Newton +set himself to work out this problem, allowing for the +distance of the moon from earth, and for the bulk and +weight of both earth and moon.</p> + +<p>And because the answer was <i>not</i> precisely what he +had looked for, he put the calculation aside, and +waited for years. It seems that he mentioned his conjecture +to no living person. After many years he took +it up again, and worked it out afresh. By this time +new measurements of earth’s surface, and new calculations +of earth’s size had been made, and Newton had +fresh figures to go upon. This time the answer came +just as he had originally hoped, and the truth of his +surmise was thus proved.</p> + +<p>Gravity held the moon near the earth, preventing +her from wandering off into unknown distances. Gravity +held earth and moon, Mars, Venus, Jupiter, each +planet, in its own pathway, within a certain distance +of the sun. Gravity held many of the comets as permanent +members of the Solar System. So strong, +indeed, was the drawing of gravity found to be, that<span class="pagenum" id="Page_392">[Pg 392]</span> +only the resisting force of each bright world’s rapid +rush round the sun could keep the sun and his planets +apart.</p> + +<p>Newton had discovered the long-sought secret. He +had found that “every particle of matter in the universe +attracts every other particle?” He had found +also the main laws which govern the working of that +attraction—that it depends, first, upon the mass or +amount of “matter” in each body; that it depends, +secondly, upon the distance of one body from another. +He found, too, how far attraction increases with greater +nearness, and decreases with greater distance. All +these and countless other questions he worked out in +the course of years. But first he had grasped the +great leading principle, after which men had until then +groped in vain, that by the force of gravity the sun +and his worlds and their moons are all bound together +into one large united family or system.</p> + +<p>Though Newton lived long enough to receive the +honor that his astonishing discoveries so justly merited, +and though for many years of his life his renown +was much greater than that of any of his contemporaries, +yet it is not too much to say that, in the years +which have since elapsed, Newton’s fame has been +ever steadily advancing.</p> + +<p>We hardly know whether to admire more the sublime +discoveries at which he arrived, or the extraordinary +character of the intellectual processes by which +those discoveries were reached. He died on Monday, +March 20, 1727, in the eighty-fifth year of his age.</p> +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p><span class="pagenum" id="Page_393">[Pg 393]</span></p> + +<h2 class="nobreak" id="c35">CHAPTER XXXV.</h2> +</div> + +<p class="c sp">LATER ASTRONOMY.</p> + + +<p><span class="smcap large">Sir William Herschel</span> was born in the city of +Hanover, November 15, 1738. He was the second +son of Isaac Herschel, a musician, who brought him +up, with his four other sons, to his own profession.</p> + +<p>A faithful chronicler has given us an interesting account +of the way in which Isaac Herschel educated +his boys; the narrative is taken from the recollections +of one who, at the time, was a little girl of five or six +years old. She writes:</p> + +<p>“My brothers were often introduced as solo performers +and assistants in the orchestra at the court, +and I remember that I was frequently prevented from +going to sleep by the lively criticisms on music on +coming from a concert. Often I would keep myself +awake that I might listen to their animated remarks, +for it made me happy to see them so happy. But +generally their conversation would branch out on +philosophical subjects, when my brother William and +my father often argued with such warmth that my +mother’s interference became necessary when the +names Euler, Leibnitz, and Newton sounded rather +too loud for the repose of her little ones, who had to +be at school by seven in the morning.”</p> + +<p>The child, whose reminiscences are here given, became +afterwards the famous Caroline Herschel. The +narrative of her life is a most interesting book, not<span class="pagenum" id="Page_394">[Pg 394]</span> +only for the account it contains of the remarkable +woman herself, but also because it presents the best +picture we have of the great astronomer, to whom +Caroline devoted her life.</p> + +<p>This modest family circle was, in a measure, dispersed +at the outbreak of the Seven Years’ War in +1756. The French proceeded to invade Hanover, +which, it will be remembered, belonged at this time +to the British dominions. Young William Herschel +had already obtained the position of a regular performer +in the regimental band of the Hanoverian +Guards, and it was his fortune to obtain some experience +of actual warfare in the disastrous battle of +Hastenbeck. He was not wounded, but he had to +spend the night after the battle in a ditch, and his +meditations on the occasion convinced him that soldiering +was not the profession exactly suited to his +tastes. He left his regiment by the very simple, but +somewhat risky, process of desertion. He had, it +would seem, to adopt disguises in order to effect his +escape. By some means he succeeded in eluding detection, +and reached England in safety.</p> + +<p>The young musician must have had some difficulty +in providing for his maintenance during the first few +years of his abode in England.</p> + +<p>It was not until he had reached the age of twenty-two +that he succeeded in obtaining any regular appointment. +He was then made instructor of music to the +Durham Militia. Shortly afterwards, his talents being +more widely recognized, he was appointed as organist +of the parish Church at Halifax.</p> + +<p>In 1766 we find that Herschel had received the<span class="pagenum" id="Page_395">[Pg 395]</span> +further promotion of organist in the Octagon Chapel, +at Bath. Bath was then, as now, a highly fashionable +resort, and many notable personages patronized the +rising musician. Herschel had other points in his +favor besides his professional skill; his appearance was +striking, his address superb, and his conversation animated, +interesting, and instructive; and even his nationality +was a distinct advantage, inasmuch as he +was a Hanoverian in the reign of King George the +Third. From his earliest youth, Herschel had been endowed +with that invaluable characteristic, an intense +desire for knowledge. He naturally wished to perfect +himself in the theory of music, and thus he was +led to study mathematics. When he had once tasted +the charms of mathematics, he saw vast regions of +knowledge unfolded before him, and in this way he +was induced to direct his attention to astronomy. +More and more this pursuit engrossed his attention +until, at last, it had become an absorbing passion.</p> + +<p>It was with quite a small telescope, which had been +lent him by a friend, that Herschel commenced his +career as an observer. However, he speedily discovered +that to see all he wanted to see, a telescope of +far greater power would be necessary.</p> + +<p>He commissioned a friend to procure for him in +London a telescope with high magnifying power. +Fortunately for science the price was so great that it +precluded the purchase, and he set himself at work to +construct one. After many trials he succeeded in making +a reflecting instrument of five feet focal length, +with which he was able to observe the rings of Saturn +and the satellites of Jupiter.</p> + +<p><span class="pagenum" id="Page_396">[Pg 396]</span></p> + +<p>It was in 1774, when the astronomer was thirty-six +years old, that he obtained his first glimpse of the +stars with an instrument of his own construction. +Night after night, as soon as his musical labors were +ended, his telescopes were brought out.</p> + +<p>His sister Caroline, who occupies such a distinct +place in scientific history, the same little girl to whom +we have already referred, was his able assistant, +and when mathematical work had to be done, she +was ready for it. She had taught herself sufficiently +to enable her to perform the kind of calculations—not, +perhaps, very difficult ones—that Herschel’s work required; +indeed, it is not much to say that the mighty +life-work which this man was enabled to perform +could never have been accomplished had it not been for +the self-sacrifice of this ever-loving and faithful sister.</p> + +<p>It was not until 1782 that the great achievement +took place by which Herschel at once sprang into +fame. He appears to have formed a project for making +a close examination of all the stars above a certain +magnitude for the purpose of discovering, if possible, +a parallax among them. Star after star was brought +to the center of the field of view of his telescope, and +after being carefully examined, was then displaced, +while another star was brought forward to be submitted +to the same process.</p> + +<p>In the great review which Herschel undertook, he +doubtless examined hundreds, or perhaps thousands of +stars, allowing them to pass away without note or comment. +But on an ever-memorable night in March, 1782, +it happened that he was pursuing his task among the +stars in the constellation of Gemini. One star was<span class="pagenum" id="Page_397">[Pg 397]</span> +noticed which, to Herschel’s acute vision, seemed different +from the stars which in so many thousands are +strewn over the sky. There was something in the +starlike object that immediately arrested his attention, +and made him apply to it a higher magnifying power. +This at once disclosed the fact that the object possessed +a disk—that is, a definite, measurable size—and +that it was thus totally different from any of the hundreds +and thousands of stars which exist elsewhere in +space. The organist at the Octagon Chapel at Bath +had discovered a new planet with his home-made +telescope. Great was the astonishment of the scientific +world when the Bath organist announced that the +five planets, which had been known from all antiquity, +must now admit the company of a sixth.</p> + +<p>The now great astronomer was invited to Windsor, +and to bring his famous telescope in order to exhibit +the planet to George III, and to tell his majesty all +about it. The king took so great a fancy to Herschel +that he proposed to confer on him the title of “his +majesty’s own astronomer,” to assign him a residence +near Windsor, to provide him with a salary, and to +furnish such funds as might be required for the erection +of great telescopes, and for the conduct of that +mighty scheme of celestial observation on which Herschel +was so eager to enter.</p> + +<p>No single discovery of Herschel’s later years was, +however, of the same momentous description as that +which first brought him to fame. There is no separate +collection of his writings, and very scanty accounts +of his life have been published; but he who has +written his name among the stars needs no other<span class="pagenum" id="Page_398">[Pg 398]</span> +testimonial to his fame. Prior to his time the number +of bodies known as belonging to the Solar System +was eighteen, including secondary planets and +Halley’s comet. To these he added nine; namely, +Uranus and six satellites, and two satellites of Saturn.</p> + +<p>Though no additional honors could add to his fame, +Dr. Herschel, in 1816, received the decoration of the +Guelphic Order of Knighthood. In 1820 he was elected +president of the Astronomical Society, and among their +Transactions, the next year, he published an interesting +memoir on the places of one hundred and forty-five +double-stars. This paper was the last which he +lived to publish. His health had begun to decline, +and on the 24th of August, 1822, he sank under the +infirmities of age, having completed his eighty-fourth +year. He was survived by his widow, Lady Herschel, +an only son, Sir John F. W. Herschel, and his sister +Caroline, who died in 1847, in her ninety-eighth year.</p> + + +<p class="c large"><span class="smcap">Laplace.</span></p> + +<p>The author of “Celestial Mechanics” was born at +Beaumont-en-Auge in 1749, just thirteen years later +than his renowned friend Lagrange. His father was +a farmer, but appears to have been in a position to +provide a good education for a son who seemed promising. +The subject which first claimed his attention +was theology. He was, however, soon introduced to +the study of mathematics, in which he presently became +so proficient that, while he was still no more +than eighteen years old, he obtained employment as a +mathematical teacher in his native town.</p> + +<p>Desiring wider opportunities for study, young Laplace<span class="pagenum" id="Page_399">[Pg 399]</span> +started for Paris, being provided with letters of +introduction to D’Alembert, who then occupied the +most prominent positions as a mathematician in +France, if not in Europe. On presenting these letters, +he seems to have had no reply; whereupon, Laplace +wrote to D’Alembert, submitting a discussion of +some point in dynamics.</p> + +<p>This letter instantly produced the desired effect. +D’Alembert thought that such mathematical talent as +the young man displayed was in itself the best of introductions +to his favor. It could not be overlooked, +and accordingly he invited Laplace to come and see +him. Laplace, of course, presented himself, and erelong +D’Alembert obtained for the rising philosopher +a professorship of Mathematics in the military school +in Paris. This gave the brilliant young mathematician +the opening for which he sought, and he quickly +availed himself of it.</p> + +<p>Laplace’s most famous work is “Celestial Mechanics,” +in which he essayed a comprehensive attempt to +carry out, in much greater detail, the principles which +Newton had laid down. The fact was that Newton +had not only to construct the theory of gravitation, +but he had to invent the mathematical processes by +which his theory could be applied to the explanation +of the movements of the heavenly bodies. In the +course of the century which had elapsed between the +time of Newton and the time of Laplace, mathematics +had been extensively developed. The disturbances +which one planet exercises upon the rest can only be +fully ascertained by the aid of long calculations, and +for these calculations analytical methods are required.</p> + +<p><span class="pagenum" id="Page_400">[Pg 400]</span></p> + +<p>With an armament of mathematical methods +which had been perfected since the days of Newton +by the labors of two or three generations of mathematical +inventors, Laplace essayed in his “Celestial +Mechanics” to unravel the mysteries of the heavens. +It will hardly be disputed that the book which he has +produced is one of the most difficult books to understand +that has ever been written. The investigations +of Laplace are, generally speaking, of too technical a +character to make it possible to set forth any account +of them in such a work as the present. He did, however, +publish one treatise, called the “System of the +Universe,” in which, without introducing mathematical +symbols, he was able to give a general account of the +theories of the celestial movements, and of the discoveries +to which he and others had been led. In this +work Laplace laid down the principles of the nebular +theory, which, in modern days, has been generally +accepted.</p> + +<p>The nebular theory gives a physical account of the +origin of the Solar System, and has already been explained +in this volume. Bach advance in science +seems to make it more certain that this hypothesis +substantially represents the way in which our Solar +System has grown to its present form.</p> + +<p>Not satisfied with a career which was merely scientific, +Laplace sought to connect himself with public +affairs. Napoleon appreciated his genius, and desired +to enlist him in the service of the state. Laplace was +appointed to the office of minister of the interior. The +experiment was not successful, for he was not by nature +a statesman. In despair of Laplace’s capacity as<span class="pagenum" id="Page_401">[Pg 401]</span> +an administrator, Napoleon declared that he carried +the spirit of his infinitesimal calculus into the management +of business. Indeed, Laplace’s political conduct +hardly admits of much defense. While he accepted +the honors which Napoleon showered on him +in the time of his prosperity, he seems to have forgotten +all this when Napoleon could no longer render him +service. Laplace was made a marquis by Louis XVIII. +During the latter part of his life the philosopher lived +in a retired country-place at Arcueile. Here he pursued +his studies, and, by strict abstemiousness, preserved +himself from many of the infirmities of old age.</p> + +<p>He was endowed with remarkable scientific sagacity; +but above all his powers his wonderful memory +shone pre-eminent. His “Celestial Mechanics” is, +next to Newton’s “Principia,” the greatest of astronomical +works.</p> + +<p>He died on March 5, 1827, in his seventy-eighth +year, his last words being, “What we know is but little, +what we do not know is immense.”</p> + + +<p class="c large"><span class="smcap">Leverrier.</span></p> + +<p>We are apt to identify the idea of an astronomer +with that of a man who looks through a telescope at +the stars; but the word astronomer has really a much +wider significance. No man who ever lived has been +more entitled to be designated an astronomer than +Urbain Jean Joseph Leverrier, and yet it is certain +that he never made a telescopic discovery of any kind. +In mathematics, however, he excelled, and he simply +used the observations of others as the basis of his calculations.</p> + +<p><span class="pagenum" id="Page_402">[Pg 402]</span></p> + +<p>These observations form, as it were, the raw material +on which the mathematician exercises his skill. +It is for him to elicit from the observed places the +true laws which govern the movements of the heavenly +bodies. Here is indeed a task in which the +highest powers of the human intellect may be worthily +employed. To Leverrier it has been given to provide +a superb illustration of the success with which +the mind of man can penetrate the deep things of +nature.</p> + +<p>The illustrious Frenchman was born on the 11th of +March, 1811, at Saint-Lô, in the department of Manche. +In the famous polytechnic school for education in the +higher branches of science he acquired considerable +fame as a mathematician. His labors at school had +revealed to Leverrier that he was endowed with the +powers requisite for dealing with the subtlest instruments +of mathematical analysis. When he was +twenty-eight years old his first great astronomical investigation +was brought forth. This was the profound +calculation of the disturbances of the planet +Uranus and the causes of them.</p> + +<p>The talent which his researches displayed brought +Leverrier into notice. At that time the Paris Observatory +was presided over by Arago, a savant who +occupies a distinguished position in French scientific +annals. Arago at once perceived that Leverrier possessed +the qualifications suitable for undertaking a +problem of great importance and difficulty that had +begun to force itself on the attention of astronomers. +What this great problem was, and how astonishing was +the solution it received, must now be considered.</p> + +<p><span class="pagenum" id="Page_403">[Pg 403]</span></p> + +<p>Ever since Herschel brought himself into fame by +the discovery of Uranus, the movements of this new +addition to the Solar System had been scrutinized +with care and attention. The position of Uranus was +thus accurately determined from time to time. When +due allowance was made for whatever influence the +attraction of Jupiter and Saturn and all the other planets +could possibly produce, the movements of Uranus +were still inexplicable. It was perfectly obvious that +there must be some other influence at work besides +that which could be attributed to the planets already +known.</p> + +<p>Astronomers could only recognize one solution of +such a difficulty. It was impossible to doubt that +there must be some other planet in addition to the +bodies at that time known, and that the perturbations +of Uranus, hitherto unaccounted for, were due to the +disturbances caused by the action of this unknown +planet. Arago urged Leverrier to undertake the great +problem of searching for this body. But the conditions +of the search were such that it must be conducted +on principles wholly different from any search +which had ever before been undertaken for a celestial +object. For this was not a case in which mere survey +with a telescope might be expected to lead to the discovery.</p> + +<p>There are in the heavens many millions of stars, +and the problem of identifying the planet, if indeed it +should lie among these stars, seemed a very complex +matter. Of course, it is the abundant presence of the +stars which causes the difficulty.</p> + +<p>The materials available to the mathematician for<span class="pagenum" id="Page_404">[Pg 404]</span> +the solution of this problem were to be derived solely +from the discrepancies between the calculated places +in which Uranus should be found, taking into account +the known causes of disturbances, and the actual +places in which observation had shown the planet to +exist. Here was, indeed, an unprecedented problem, +and one of extraordinary difficulty. Leverrier, however, +faced it, and, to the astonishment of the world, +succeeded in carrying it through to a brilliant solution.</p> + +<p>After many trials, Leverrier ascertained that, by +assuming a certain size, shape, and position for the +unknown planet’s orbit, and a certain value for the +mass of the hypothetical body, it would be possible to +account for the observed disturbances of Uranus. +Gradually it became clear to his perception, not only +that the difficulties in the movements of Uranus +could be thus explained, but that no other explanation +need be sought for. And now for an episode in +this history which will be celebrated so long as science +shall endure. It is nothing less than the telescopic +confirmation of the existence of this new planet, +which had previously been indicated only by mathematical +calculation.</p> + +<p>Great indeed was the admiration of the scientific +world at this superb triumph. Here was a mighty +planet, whose very existence was revealed by the indications +afforded by refined mathematical calculation. +At once the name of Leverrier, already known to +those conversant with the more profound branches of +astronomy, became everywhere celebrated.</p> + +<p>When, in 1854, Arago’s place had to be filled at<span class="pagenum" id="Page_405">[Pg 405]</span> +the head of the great Paris Observatory, it was universally +felt that the discoverer of Neptune was the +suitable man to assume the office. Leverrier died on +Sunday, September 23, 1877, in his sixty-seventh year.</p> + +<p class="gtb">******</p> + +<p><span class="smcap large">Frederick William Bessel</span> was born at Minden +in 1784, and early turned his attention to mathematical +subjects. He devoted himself with ardor to astronomy, +and in 1804 he undertook the reduction of the +observations made on the comet of 1607. His results +were communicated to Olbers, who warmly praised +the young astronomer, and in 1806 recommended him +to Schroeter as an assistant in the observatory of Lilienthal. +In 1810 he was appointed director of the +new observatory then being founded by the king at +Königsberg. He was admirably fitted for this post, +and is distinguished mainly for his discovery of the +parallax of the star 61 Cygni, which he accomplished +by methods of extreme ingenuity and delicacy.</p> + +<p>Two kinds of telescopes are commonly used, the +refractor and the reflector. The first telescopes made +were all refractors, and the very first of them was +made, as you know, by Galileo. The first reflector +was made in later days by Sir Isaac Newton.</p> + +<p>In a refractor the rays of light, from a star or any +other bright body, reach first a large object-glass, +through which they pass, and by which, as they pass, +they are caused to converge, narrowing to a focus or +point. From this point they widen slightly on their +way to the eye-piece. After passing through the eye-piece, +by which they are once more straightened into +parallel rays, they arrive at the eye.</p> + +<p><span class="pagenum" id="Page_406">[Pg 406]</span></p> + +<p>Speaking broadly, the eye receives—actually sees—nearly +as much of the starlight as if its pupil were +the full size of the object-glass of that telescope, and +the power of such an instrument depends upon the +size of the object-glass. A refractor has been made +with an object-glass forty inches across, and this, for +the observer, means looking at a star with an eye pupil +more than three feet in diameter. This refractor +is now in the Yerkes Observatory at Williams Bay, +Lake Geneva, Wisconsin.</p> + +<p>There are several forms of reflectors. With one +form, when it is pointed at a star, the rays of starlight +fall direct through the telescope-tube upon a highly-polished +mirror, so shaped that rays of light reflected +thence are caused to fall converging upon a small +plane-mirror in the center of the tube, from which +they are thrown, parallel to the side of the tube, to the +eye-piece, which converges them to the eye.</p> + +<p>The mirror of a reflector can be made very much +larger than the object-glass of a refractor. The famous +Lord Rosse telescope, which has a tube sixty +feet long, contains a mirror no less than six feet in +diameter. This, to an observer, is tantamount to +looking at the stars with an eye so huge that its pupil +alone would be nearly equal in size to the six-foot +wheel of a steam-engine. It will readily be perceived +how much more starlight can be grasped by such a +fishing-net than by the tiny pupil of your eye or +mine.</p> + +<p>A main difference between the two kinds of telescope +thus resides in the fact that the star-rays—or +any other kind of light-rays—when first captured,<span class="pagenum" id="Page_407">[Pg 407]</span> +pass, in one case, <i>through</i> the glass on which they +fall, and, in the other case, are thrown off <i>from</i> the +mirror. In both cases, the whole amount of light so +captured is gathered into a small compass, so as to be +available for human sight.</p> + +<div class="figcenter" id="f63"> +<img src="images/fig63.jpg" alt="lick"> +<p class="caption">EYE-PIECE OF THE LICK TELESCOPE.</p> +</div> + +<p>Once more, let me remind you, it should be always +kept clearly in mind that every object that is seen by<span class="pagenum" id="Page_408">[Pg 408]</span> +us—from a mote of dust to a sun, from a coal-scuttle +to a star—is perceived purely and solely by the light +which it gives out, either intrinsic or reflected light. +Countless myriads of rays pass from the surface of the +thing seen to our eyes, picturing there, on the sensitive +retina, a fleeting vision of its form.</p> + +<p>All the leading Governments in Europe have observatories +for the study of the heavens, which are +furnished with the best instruments of modern construction. +The principal observatories are those at +Paris, Berlin, Vienna, Nice; Dorpat, the seat of a celebrated +university founded by Gustavus Adolphus, of +Sweden, in 1630; Pulkowa, near St. Petersburg; Lisbon, +and at Greenwich in England. In America, +though only in recent years has astronomy been cultivated +with ardor, there are observatories of more or +less importance,—the National Observatory at Washington, +D. C.; the Cincinnati Observatory, projected +by the late General O. M. Mitchel; the Dudley Observatory, +founded by Mrs. Blandina Dudley in honor +of her husband, at Albany, N. Y.; the Lick Observatory, +founded by James Lick, on Mount Hamilton, Cal.; +and the Yerkes Observatory, connected with the Chicago +University, founded by Charles T. Yerkes. Besides +these, there are observatories connected with some +of our other leading universities and colleges, as those +of Harvard, at Cambridge, Mass.; Yale University; +Williams College; West Point Military Academy; Amherst +College; Princeton; Dartmouth; Michigan University; +Hamilton College, N. Y., and several others.</p> + +<div class="figcenter" id="f64"> +<img src="images/fig64.jpg" alt="lick"> +<p class="caption">LICK OBSERVATORY IN WINTER, FROM THE EAST.</p> +</div> + +<p>The largest and best refracting telescopes in the +world are those at Lick Observatory and at Yerkes +<span class="pagenum" id="Page_410">[Pg 410]</span>Observatory, now in charge of Professor E. E. Barnard, +who, while at the head of the Lick Observatory, discovered +the fifth satellite of Jupiter, and determined +the character of the inner ring of Saturn. The best +reflecting telescope is that of Lord Rosse, at Birr Castle, +in Kings County, Ireland.</p> + +<div class="figcenter" id="f65"> +<img src="images/fig65.jpg" alt="barnard"> +<p class="caption">E. E. BARNARD.</p> +</div> + +<p>In reviewing the path which we have traversed in +this volume, though we have penetrated the sidereal +depths and wandered at will through space, we feel<span class="pagenum" id="Page_411">[Pg 411]</span> +that we have not yet reached the outskirts of creation. +We have never left the center. Beyond us still lies +the circumference. We see opened before us the infinite, +of which the study is not yet begun! We have +seen nothing; we recoil in terror; we fall back astounded. +Indeed, we might fall into the yawning +abyss—fall forever, during a whole eternity; never, +never should we reach the bottom, any more than we +have attained the summit. There is no east nor west, +neither right nor left. There is no up nor down; +there is neither a zenith nor a nadir. In whatever +way we look, it is infinite in all directions.</p> + +<p>In this infinitude of space, the associations of suns +and of worlds which constitute our visible universe form +but an island, a vast archipelago; and in the eternity +of duration, the life of our proud humanity, with all +its concerns, its aspirations, and its achievements, the +whole life of our entire planet, is but the shadow of a +dream! Well might the Hebrew poet, as he looked +forth upon nature, exclaim in his amazement: “When +I consider thy heavens, the work of thy fingers, the +moon and the stars which thou hast ordained, what is +man that thou art mindful of him, and the son of man +that thou visitest him?”</p> + +<p>The constellations, the charts of the sky; the catalogues +of curious stars—variable, double or multiple, +and colored; the description of instruments accessible +to the observer of the heavens, and useful tables to +consult, are only touched upon in this volume. The +reader whose scientific desires are satisfied by the elements +of astronomy, may stop here. Few have time +to pursue the subject further; but it is sweet to live<span class="pagenum" id="Page_412">[Pg 412]</span> +in the sphere of the mind; it is sweet to contemn the +rough noises of a vulgar world; it is sweet to soar in +the ethereal heights, and to devote the best moments +of our life to the study of the true, the infinite, and +the eternal!</p> + + +<div class="figcenter"> +<img src="images/fig3.jpg" alt="decoration"> +</div> + + +<p class="c sp xlarge">PUBLISHERS’ NOTE.</p> + + + +<p>We have now reached the conclusion of “The +Story of the Sun, Moon, and Stars.” Miss Giberne’s +work has been supplemented with a large amount of +matter from other sources. The value of the book +has thus been increased without diminishing its popular +character. In most admirable form it tells the +story of the heavenly world, which is the work of +God’s hands, the moon and the stars which he has +made. The reverent reader, to whom the Word of +God is “sweeter than honey and the honey-comb,” +may here find that “the heavens declare the glory of +God, and the firmament showeth his handiwork.” +We confidently present it to the reader as the best +and completest work in print on the great subject of +which it treats.</p> + + +<hr class="full x-ebookmaker-drop"> + +<div class="chapter"> +<p class="ph2">INDEX</p> +</div> + +<div class="figcenter"> +<img src="images/fig3.jpg" alt="decoration"> +</div> + +<ul class="index"> +<li class="ifrst">Adams, John Couch, <a href="#Page_231">231</a>, <a href="#Page_236">236</a></li> + +<li class="indx">Aërolites, <a href="#Page_84">84</a></li> +<li class="isub1">Size of, <a href="#Page_86">86</a></li> + +<li class="indx">Aldebaran, Movement of, <a href="#Page_277">277</a></li> + +<li class="indx">Alexander at Arbela, <a href="#Page_146">146</a></li> + +<li class="indx">Alpha Centauri, Distance of, <a href="#Page_99">99</a></li> +<li class="isub1">Duration of light journey, <a href="#Page_102">102</a></li> +<li class="isub1">Position, <a href="#Page_279">279</a></li> + +<li class="indx">Alps, Lunar Mountains, <a href="#Page_179">179</a></li> + +<li class="indx">Altai, Lunar Mountains, <a href="#Page_179">179</a></li> + +<li class="indx">Andromeda, Constellation of, <a href="#Page_112">112</a></li> + +<li class="indx">Apennines, Lunar Mountains, <a href="#Page_179">179</a></li> + +<li class="indx">Arago, <a href="#Page_235">235</a>, <a href="#Page_402">402</a></li> + +<li class="indx">Arcturus, Motion of, <a href="#Page_114">114</a></li> +<li class="isub1">Position, <a href="#Page_276">276</a></li> + +<li class="indx">Aristotle, <a href="#Page_376">376</a></li> + +<li class="indx">Asteroids, <a href="#Page_53">53</a></li> + +<li class="indx">Astronomy, The dawn of, <a href="#Page_363">363</a></li> + +<li class="indx">Attraction, <a href="#Page_34">34</a></li> + +<li class="indx">Aurora Borealis, where seen, <a href="#Page_141">141</a></li> + +<li class="indx">Axis of earth slanting, <a href="#Page_44">44</a></li> + + +<li class="ifrst">Barnard, E. E., <a href="#Page_53">53</a>, <a href="#Page_410">410</a></li> + +<li class="indx">Bessel, F. W., <a href="#Page_284">284</a></li> +<li class="isub1">Discovery of star parallax, <a href="#Page_324">324</a></li> +<li class="isub1">Discovers star parallax, <a href="#Page_405">405</a></li> + +<li class="indx">Bolides, <a href="#Page_87">87</a>, <a href="#Page_257">257</a></li> + +<li class="indx">Borelli, <a href="#Page_388">388</a></li> + + +<li class="ifrst">Capella, Duration of light journey, <a href="#Page_103">103</a></li> +<li class="isub1">Velocity of motion, <a href="#Page_114">114</a></li> + +<li class="indx">Caucasian Range, Lunar Mountains, <a href="#Page_179">179</a></li> + +<li class="indx">Carpathian, Lunar Mountains, <a href="#Page_179">179</a></li> + +<li class="indx">Carrington, <a href="#Page_141">141</a></li> + +<li class="indx">Cassini, Measurement of sun’s distance, <a href="#Page_310">310</a></li> + +<li class="indx">Cassiopeia, Constellation of, <a href="#Page_112">112</a></li> + +<li class="indx">Ceres, size of, <a href="#Page_53">53</a></li> + +<li class="indx">Chaldean star-gazers, <a href="#Page_365">365</a></li> + +<li class="indx">Chinese records of eclipses, <a href="#Page_365">365</a></li> + +<li class="indx">Cicero, <a href="#Page_177">177</a></li> + +<li class="indx">Clark, Alvan Graham, <a href="#Page_289">289</a></li> + +<li class="indx">Cloven-disk theory, <a href="#Page_331">331</a></li> + +<li class="indx">Coal sack, <a href="#Page_329">329</a></li> + +<li class="indx">Columbus in Jamaica, <a href="#Page_146">146</a></li> + +<li class="indx">Comet, Biela’s, <a href="#Page_90">90</a>, <a href="#Page_93">93</a></li> +<li class="isub1">Halley’s, <a href="#Page_78">78</a>, <a href="#Page_248">248</a></li> +<li class="isub1">Of 1843, <a href="#Page_80">80</a></li> +<li class="isub1">Newton’s, <a href="#Page_78">78</a></li> +<li class="isub1">With two tails, <a href="#Page_77">77</a></li> +<li class="isub1">Encke’s, <a href="#Page_78">78</a></li> +<li class="isub1">Heat endured by, <a href="#Page_81">81</a></li> +<li class="isub1">Length of tail, <a href="#Page_81">81</a></li> +<li class="isub1">Collision with, <a href="#Page_82">82</a></li> +<li class="isub1">Split in two, <a href="#Page_91">91</a></li> + +<li class="indx">Comets, <a href="#Page_73">73</a>, <a href="#Page_240">240</a>, <a href="#Page_246">246</a></li> +<li class="isub1">Number of, <a href="#Page_75">75</a></li> +<li class="isub1">Nature of, <a href="#Page_74">74</a></li> +<li class="isub1">Captured by Jupiter, <a href="#Page_213">213</a></li> +<li class="isub1">Composition of, <a href="#Page_256">256</a></li> +<li class="isub1">Composition of tails, <a href="#Page_253">253</a></li> +<li class="isub1">Orbits of, <a href="#Page_129">129</a></li> +<li class="isub1">With closed orbits, <a href="#Page_76">76</a></li> + +<li class="indx">Confucius as an astronomer, <a href="#Page_365">365</a></li> + +<li class="indx">Constellations, Grouping, <a href="#Page_366">366</a></li> +<li class="isub1">When named, <a href="#Page_366">366</a></li> + +<li class="indx">Copernicus, Author of “Celestial Spheres,” <a href="#Page_177">177</a>, <a href="#Page_183">183</a>, <a href="#Page_370">370</a>, <a href="#Page_371">371</a>, + <a href="#Page_375">375</a></li> +<li class="isub1">Star parallax, <a href="#Page_319">319</a></li> + +<li class="indx">Copernican system of the universe, <a href="#Page_175">175</a></li> + +<li class="indx">Corona, Description of, <a href="#Page_153">153</a></li> + + +<li class="ifrst">D’Alembert, <a href="#Page_399">399</a></li> + +<li class="indx">Dante, <a href="#Page_121">121</a></li> + +<li class="indx">Demos, Satellite of Mars, <a href="#Page_191">191</a></li> + +<li class="indx">Donati’s Comet, <a href="#Page_248">248</a>, <a href="#Page_250">250</a></li> + +<li class="indx">Draco, Constellation of, <a href="#Page_112">112</a></li> + + +<li class="ifrst">Earth, Globular, <a href="#Page_17">17</a></li> +<li class="isub1">How formed, <a href="#Page_21">21</a></li> +<li class="isub1">Member of the Solar System, <a href="#Page_14">14</a></li> +<li class="isub1">In motion, <a href="#Page_16">16</a></li> +<li class="isub1">Motions, <a href="#Page_18">18</a>, <a href="#Page_41">41</a>, <a href="#Page_126">126</a></li> +<li class="isub1">One of a family, <a href="#Page_14">14</a></li> +<li class="isub1">Size of, <a href="#Page_26">26</a></li> +<li class="isub1">What is it? <a href="#Page_13">13</a></li> + +<li class="indx">Ecliptic, <a href="#Page_43">43</a></li> + +<li class="indx">Eclipses omens of evil, <a href="#Page_145">145</a></li> + +<li class="indx">Egyptian astronomers, <a href="#Page_365">365</a></li> + +<li class="indx">Encke, <a href="#Page_238">238</a></li> + +<li class="indx">Epicycles, <a href="#Page_373">373</a></li> + +<li class="indx">Equinox, <a href="#Page_44">44</a></li> + + +<li class="ifrst">Fire-balls, Speed of, <a href="#Page_88">88</a></li> + +<li class="indx">Fabricius discovers sun-spots, <a href="#Page_27">27</a></li> + +<li class="indx">Fraunhofer, Joseph von, <a href="#Page_345">345</a></li> + + +<li class="ifrst">Galle, <a href="#Page_232">232</a>, <a href="#Page_238">238</a></li> + +<li class="indx">Galileo, <a href="#Page_28">28</a>, <a href="#Page_276">276</a>, <a href="#Page_371">371</a>, <a href="#Page_376">376</a>, <a href="#Page_378">378</a>, + <a href="#Page_380">380</a></li> + +<li class="indx">Gassendi, <a href="#Page_184">184</a></li> + +<li class="indx">George III, <a href="#Page_226">226</a></li> + +<li class="indx">Gilbert, <a href="#Page_388">388</a></li> + +<li class="indx">Great Bear, Constellation of, <a href="#Page_108">108</a>, <a href="#Page_340">340</a></li> + + +<li class="ifrst">Halley, <a href="#Page_388">388</a></li> +<li class="isub1">Transit of Venus, <a href="#Page_314">314</a></li> +<li class="isub1">Star motions, <a href="#Page_318">318</a></li> + +<li class="indx">Hercules, Constellation of, <a href="#Page_112">112</a></li> + +<li class="indx">Herschel, Caroline, <a href="#Page_226">226</a>, <a href="#Page_393">393</a></li> + +<li class="indx">Herschel, Sir John, <a href="#Page_81">81</a>, <a href="#Page_233">233</a>, <a href="#Page_303">303</a>, <a href="#Page_398">398</a></li> + +<li class="indx">Herschel, William, <a href="#Page_96">96</a>, <a href="#Page_119">119</a>, <a href="#Page_225">225</a>, <a href="#Page_271">271</a>, <a href="#Page_393">393</a></li> + +<li class="indx">Hipparchus, <a href="#Page_368">368</a>, <a href="#Page_371">371</a></li> + +<li class="indx">Hodgson, <a href="#Page_141">141</a></li> + +<li class="indx">Holland, Sir Henry, <a href="#Page_237">237</a></li> + +<li class="indx">Hook, Robert, <a href="#Page_388">388</a></li> + +<li class="indx">Horrocks, <a href="#Page_388">388</a></li> + +<li class="indx">Huggins, Dr., <a href="#Page_359">359</a></li> + +<li class="indx">Humboldt, Alexander von, <a href="#Page_265">265</a></li> + + +<li class="ifrst">Jupiter, <a href="#Page_55">55</a></li> +<li class="isub1">Comparative size, <a href="#Page_56">56</a></li> +<li class="isub1">Distance of, <a href="#Page_122">122</a></li> +<li class="isub1">His satellites, <a href="#Page_56">56</a>, <a href="#Page_206">206</a>, <a href="#Page_210">210</a></li> +<li class="isub1">Velocity, <a href="#Page_199">199</a></li> +<li class="isub1">Wind storms, <a href="#Page_204">204</a></li> + + +<li class="ifrst">Kepler, <a href="#Page_75">75</a>, <a href="#Page_296">296</a></li> +<li class="isub1">Laws of, <a href="#Page_371">371</a>, <a href="#Page_374">374</a>, <a href="#Page_380">380</a>, <a href="#Page_388">388</a></li> + +<li class="indx">Kew Observatory, <a href="#Page_141">141</a></li> + + +<li class="ifrst">Lacaille, Catalogue of, <a href="#Page_105">105</a></li> + +<li class="indx">Lalande, Catalogue of, <a href="#Page_105">105</a></li> + +<li class="indx">Laplace, <a href="#Page_385">385</a>, <a href="#Page_398">398</a></li> + +<li class="indx">Later astronomy, <a href="#Page_393">393</a></li> + +<li class="indx">Leverrier, Urbain J. J., <a href="#Page_231">231</a>, <a href="#Page_401">401</a></li> +<li class="isub1">Discovers Neptune, <a href="#Page_321">321</a></li> + +<li class="indx">Light, Rapidity of, <a href="#Page_101">101</a></li> +<li class="isub1">Time, Duration of, <a href="#Page_331">331</a></li> + +<li class="indx">Lowe at Santander, <a href="#Page_147">147</a></li> + +<li class="indx">Lunar craters, Antiquity of, <a href="#Page_172">172</a></li> +<li class="isub1">How formed, <a href="#Page_173">173</a></li> +<li class="isub1">Plato and Copernicus, <a href="#Page_173">173</a></li> +<li class="isub1">Ptolemy, <a href="#Page_174">174</a></li> +<li class="isub1">Schickard, <a href="#Page_174">174</a></li> +<li class="isub1">Tycho, <a href="#Page_174">174</a></li> + +<li class="indx">Lunar Mountains, How formed, <a href="#Page_174">174</a></li> + +<li class="indx">Lyra, Constellation, <a href="#Page_297">297</a></li> + + +<li class="ifrst">Magellanic clouds, <a href="#Page_309">309</a></li> + +<li class="indx">Magnetism, <a href="#Page_140">140</a>, <a href="#Page_141">141</a></li> + +<li class="indx">Mars, <a href="#Page_52">52</a>, <a href="#Page_373">373</a>, <a href="#Page_374">374</a></li> +<li class="isub1">Moons of, <a href="#Page_191">191</a></li> +<li class="isub1">Continents of, <a href="#Page_197">197</a></li> +<li class="isub1">Distance from earth, <a href="#Page_197">197</a></li> + +<li class="indx">Maury, Lieutenant, <a href="#Page_80">80</a></li> + +<li class="indx">Mercury, Atmosphere, <a href="#Page_181">181</a></li> +<li class="isub1">Distance from sun, <a href="#Page_49">49</a></li> +<li class="isub1">Length of year, <a href="#Page_180">180</a></li> +<li class="isub1">Is it inhabited? <a href="#Page_181">181</a></li> +<li class="isub1">Orbit of, <a href="#Page_180">180</a></li> +<li class="isub1">Phases, <a href="#Page_50">50</a></li> +<li class="isub1">Size of, <a href="#Page_49">49</a></li> +<li class="isub1">Transit of, <a href="#Page_184">184</a></li> + +<li class="indx">Meteor, <a href="#Page_84">84</a>, <a href="#Page_257">257</a></li> + +<li class="indx">Meteorites, <a href="#Page_240">240</a>, <a href="#Page_257">257</a></li> +<li class="isub1">Around the sun, <a href="#Page_94">94</a></li> +<li class="isub1">August system, <a href="#Page_90">90</a>, <a href="#Page_242">242</a></li> +<li class="isub1">In Saturn’s rings, <a href="#Page_94">94</a></li> +<li class="isub1">November system, <a href="#Page_90">90</a>, <a href="#Page_94">94</a>, <a href="#Page_241">241</a></li> +<li class="isub1">Number of, <a href="#Page_86">86</a></li> +<li class="isub1">Protection from, <a href="#Page_86">86</a></li> +<li class="isub1">Shower of 1872, <a href="#Page_92">92</a></li> +<li class="isub1">Shower of 1885, <a href="#Page_93">93</a></li> + +<li class="indx">Milky Way, <a href="#Page_270">270</a>, <a href="#Page_329">329</a></li> + +<li class="indx">Mizar, <a href="#Page_342">342</a></li> + +<li class="indx">Modern Astronomy, <a href="#Page_375">375</a></li> + +<li class="indx">Moon, <a href="#Page_62">62</a></li> +<li class="isub1">Appearance at its full, <a href="#Page_63">63</a></li> +<li class="isub1">Atmosphere, <a href="#Page_157">157</a>, <a href="#Page_169">169</a></li> +<li class="isub1">Phases of, <a href="#Page_160">160</a></li> +<li class="isub1">Condition of, <a href="#Page_65">65</a></li> +<li class="isub1">Craters, <a href="#Page_68">68</a>, <a href="#Page_170">170</a></li> +<li class="isub1">Earth’s satellite, <a href="#Page_164">164</a></li> +<li class="isub1">Earth-shine, <a href="#Page_160">160</a></li> +<li class="isub1">Eclipse, <a href="#Page_163">163</a></li> +<li class="isub1">Influence on tides, <a href="#Page_167">167</a></li> +<li class="isub1">Landscape of, <a href="#Page_68">68</a></li> +<li class="isub1">Mountains, <a href="#Page_67">67</a></li> +<li class="isub1">Orbit of, <a href="#Page_166">166</a></li> +<li class="isub1">Temperature on, <a href="#Page_72">72</a></li> +<li class="isub1">Revolution, <a href="#Page_64">64</a></li> +<li class="isub1">Size of, <a href="#Page_64">64</a></li> +<li class="isub1">Surface, <a href="#Page_67">67</a></li> + + +<li class="ifrst">Nasmyth, <a href="#Page_173">173</a></li> + +<li class="indx">Nebulæ, Number of, <a href="#Page_336">336</a></li> + +<li class="indx">Neptune, <a href="#Page_59">59</a></li> +<li class="isub1">Discovery of, <a href="#Page_232">232</a>, <a href="#Page_234">234</a></li> +<li class="isub1">Distance of, <a href="#Page_123">123</a></li> +<li class="isub1">Length of year, <a href="#Page_59">59</a></li> + +<li class="indx">Newton analyzes light, <a href="#Page_385">385</a></li> +<li class="isub1">Birth and childhood, <a href="#Page_382">382</a></li> + +<li class="indx">Nicetos of Syracuse, <a href="#Page_177">177</a></li> + +<li class="indx">Nicias, Athenian General, <a href="#Page_146">146</a></li> + +<li class="indx">Nicolas, Cardinal, <a href="#Page_177">177</a></li> + + +<li class="ifrst">Observatories, <a href="#Page_408">408</a></li> + +<li class="indx">Orbits, Planetary, <a href="#Page_47">47</a></li> + +<li class="indx">Orion, Constellation of, <a href="#Page_112">112</a></li> + + +<li class="ifrst">Parallax, <a href="#Page_311">311</a></li> + +<li class="indx">Phobos, Satellite of Mars, <a href="#Page_191">191</a></li> + +<li class="indx">Photography, Stellar, <a href="#Page_355">355</a></li> + +<li class="indx">Pius IX, <a href="#Page_93">93</a></li> + +<li class="indx">Pisa, Leaning Tower of, <a href="#Page_378">378</a></li> + +<li class="indx">Plane of the Ecliptic, <a href="#Page_201">201</a></li> + +<li class="indx">Planets, Distance from the sun, <a href="#Page_123">123</a></li> +<li class="isub1">First group, <a href="#Page_48">48</a></li> +<li class="isub1">How formed, <a href="#Page_22">22</a></li> +<li class="isub1">Length of years, <a href="#Page_49">49</a></li> +<li class="isub1">Orbits, <a href="#Page_47">47</a></li> +<li class="isub1">Order of formation, <a href="#Page_23">23</a></li> +<li class="isub1">Second group, <a href="#Page_48">48</a>, <a href="#Page_55">55</a></li> + +<li class="indx">Plutarch, <a href="#Page_177">177</a></li> + +<li class="indx">Pole star, Duration of light journey, <a href="#Page_103">103</a></li> +<li class="isub1">Position, <a href="#Page_108">108</a></li> +<li class="isub1">Rate of motion, <a href="#Page_115">115</a></li> + +<li class="indx">Prism, <a href="#Page_344">344</a></li> + +<li class="indx">Pritchard, C., <a href="#Page_356">356</a></li> + +<li class="indx">Ptolemaic system of the universe, <a href="#Page_175">175</a>, <a href="#Page_369">369</a></li> + +<li class="indx">Ptolemy, <a href="#Page_371">371</a>, <a href="#Page_369">369</a></li> + +<li class="indx">Pythagoras, Grecian astronomer, <a href="#Page_367">367</a></li> + + +<li class="ifrst">Rosse, Lord, Telescope, <a href="#Page_406">406</a></li> + +<li class="indx">Rowton siderite, <a href="#Page_258">258</a></li> + + +<li class="ifrst">Saturn, <a href="#Page_57">57</a></li> +<li class="isub1">Composition of rings, <a href="#Page_221">221</a></li> +<li class="isub1">Distance of, <a href="#Page_122">122</a></li> +<li class="isub1">Distance from sun, <a href="#Page_214">214</a></li> +<li class="isub1">Length of year, <a href="#Page_57">57</a></li> +<li class="isub1">Moons, <a href="#Page_217">217</a></li> +<li class="isub1">Rings, <a href="#Page_219">219</a></li> +<li class="isub1">Satellites, <a href="#Page_58">58</a></li> +<li class="isub1">Size, <a href="#Page_214">214</a></li> +<li class="isub1">Weight, <a href="#Page_214">214</a></li> + +<li class="indx">Shickard, Crater on the moon, <a href="#Page_174">174</a></li> + +<li class="indx">Scheiner, <a href="#Page_28">28</a></li> + +<li class="indx">Secchi, <a href="#Page_92">92</a></li> + +<li class="indx">Shooting stars, <a href="#Page_84">84</a></li> + +<li class="indx">Sirius, Brightness of, <a href="#Page_275">275</a>, <a href="#Page_285">285</a></li> +<li class="isub1">Changing color, <a href="#Page_285">285</a></li> +<li class="isub1">Distance of, <a href="#Page_100">100</a></li> +<li class="isub1">Duration of light journey, <a href="#Page_103">103</a></li> +<li class="isub1">Movement of, <a href="#Page_277">277</a></li> + +<li class="indx">Solar cloud, <a href="#Page_148">148</a></li> + +<li class="indx">Solar System, <a href="#Page_60">60</a>, <a href="#Page_122">122</a></li> +<li class="isub1">Model of, <a href="#Page_60">60</a></li> + +<li class="indx">Spectroscope, <a href="#Page_143">143</a>, <a href="#Page_345">345</a></li> + +<li class="indx">Spectroscopic photography, <a href="#Page_360">360</a></li> + +<li class="indx">Spectrum analysis, <a href="#Page_346">346</a>, <a href="#Page_354">354</a></li> + +<li class="indx">Star clusters, <a href="#Page_304">304</a>, <a href="#Page_336">336</a></li> +<li class="isub1">Parallax, <a href="#Page_284">284</a>, <a href="#Page_316">316</a></li> +<li class="isub1">Spectroscopy, <a href="#Page_356">356</a></li> + +<li class="indx">Stars, Apparent motion, <a href="#Page_107">107</a></li> +<li class="isub1">Attraction, <a href="#Page_21">21</a></li> +<li class="isub1">Distance of, <a href="#Page_99">99</a>, <a href="#Page_310">310</a>, <a href="#Page_320">320</a></li> +<li class="isub1">Distance, <a href="#Page_281">281</a>, <a href="#Page_282">282</a></li> +<li class="isub1">Fixed, Why so called, <a href="#Page_20">20</a></li> +<li class="isub1">Fixed, Why, <a href="#Page_366">366</a></li> +<li class="isub1">Golden, <a href="#Page_274">274</a></li> +<li class="isub1">Magnitude of, <a href="#Page_97">97</a></li> +<li class="isub1">How many visible, <a href="#Page_95">95</a></li> +<li class="isub1">Measurement, <a href="#Page_278">278</a></li> +<li class="isub1">Red, <a href="#Page_274">274</a></li> +<li class="isub1">Variable, <a href="#Page_274">274</a>, <a href="#Page_291">291</a></li> +<li class="isub1">White, <a href="#Page_274">274</a></li> + +<li class="indx">Sun, <a href="#Page_24">24</a></li> +<li class="isub1">Attraction of, <a href="#Page_156">156</a></li> +<li class="isub1">Attraction of gravitation, <a href="#Page_34">34</a></li> +<li class="isub1">Chromatosphere, <a href="#Page_32">32</a></li> +<li class="isub1">Cyclones of <a href="#Page_30">30</a>, <a href="#Page_136">136</a></li> +<li class="isub1">Density, <a href="#Page_26">26</a></li> +<li class="isub1">Destination, <a href="#Page_119">119</a></li> +<li class="isub1">Distance of, <a href="#Page_25">25</a></li> +<li class="isub1">Eclipse of, <a href="#Page_143">143</a></li> +<li class="isub1">Flames, Their height, <a href="#Page_31">31</a>, <a href="#Page_151">151</a></li> +<li class="isub1">Flames, Their velocity, <a href="#Page_138">138</a></li> +<li class="isub1">Forces and influences, <a href="#Page_39">39</a></li> +<li class="isub1">Head of our family, <a href="#Page_24">24</a></li> +<li class="isub1">Magnetic power of, <a href="#Page_139">139</a></li> +<li class="isub1">Its mottled appearance, <a href="#Page_142">142</a></li> +<li class="isub1">Rate of motion, <a href="#Page_119">119</a></li> +<li class="isub1">Penumbra, <a href="#Page_133">133</a></li> +<li class="isub1">Photosphere, <a href="#Page_31">31</a>, <a href="#Page_134">134</a></li> +<li class="isub1">Power of, <a href="#Page_39">39</a>, <a href="#Page_137">137</a></li> +<li class="isub1">Rapidity of motion, <a href="#Page_26">26</a></li> +<li class="isub1">Revolution on axis, <a href="#Page_28">28</a></li> +<li class="isub1">Size, <a href="#Page_26">26</a>, <a href="#Page_154">154</a></li> +<li class="isub1">Solar prominence, <a href="#Page_32">32</a></li> +<li class="isub1">Spots, <a href="#Page_27">27</a>, <a href="#Page_30">30</a>, <a href="#Page_133">133</a></li> +<li class="isub1">Symbol of purity, <a href="#Page_380">380</a></li> +<li class="isub1">Umbra, <a href="#Page_133">133</a></li> +<li class="isub1">Weight, <a href="#Page_27">27</a>, <a href="#Page_154">154</a></li> + +<li class="indx">Swift, Voyage to Laputa, <a href="#Page_194">194</a></li> + + +<li class="ifrst">Telescopes, <a href="#Page_378">378</a>, <a href="#Page_379">379</a>, <a href="#Page_405">405</a></li> +<li class="isub1">Refractors and reflectors, <a href="#Page_405">405</a>, <a href="#Page_408">408</a>, <a href="#Page_410">410</a></li> + +<li class="indx">Tides, <a href="#Page_168">168</a></li> + +<li class="indx">Thales, founder of Grecian Astronomy, <a href="#Page_367">367</a></li> + +<li class="indx">Toucan, <a href="#Page_306">306</a></li> + +<li class="indx">Tycho Brahe, <a href="#Page_175">175</a>, <a href="#Page_371">371</a>, <a href="#Page_372">372</a>, <a href="#Page_373">373</a></li> + + +<li class="ifrst">Universe, Definition of, <a href="#Page_19">19</a></li> + +<li class="indx">Uranus, <a href="#Page_58">58</a></li> +<li class="isub1">Discovery of, <a href="#Page_225">225</a></li> +<li class="isub1">Distance of, <a href="#Page_123">123</a></li> + + +<li class="ifrst">Venus, Orbit of <a href="#Page_51">51</a></li> +<li class="isub1">Is it inhabited? <a href="#Page_189">189</a></li> +<li class="isub1">Distance from earth, <a href="#Page_186">186</a></li> +<li class="isub1">Phases of, <a href="#Page_51">51</a>, <a href="#Page_379">379</a></li> +<li class="isub1">Transits of, <a href="#Page_185">185</a></li> + +<li class="indx">Vesta, Size of, <a href="#Page_53">53</a></li> + +<li class="indx">Voltaire, Prophecy of, <a href="#Page_193">193</a></li> + + +<li class="ifrst">Wilson, <a href="#Page_30">30</a></li> + +<li class="indx">Wollaston, Dr. W. H., <a href="#Page_345">345</a></li> + +<li class="indx">Wren, <a href="#Page_388">388</a></li> + + +<li class="ifrst">Yerkes Observatory, <a href="#Page_406">406</a></li> + +<li class="indx">Young, Chas. A., <a href="#Page_142">142</a>, <a href="#Page_148">148</a></li> + + +<li class="ifrst">Zodiacal Light, <a href="#Page_94">94</a>, <a href="#Page_224">224</a>, <a href="#Page_265">265</a></li> +</ul> + +<hr class="full"> + +<div class="transnote"> + +<p class="c">Transcriber’s Notes:</p> + +<p>In the original a link to Sir Isaac Newton was omitted from the List of Illustrations. The transcriber has inserted one.</p> + +<p>Variations in spelling and hyphenation are retained.</p> + +<p>Perceived typographical errors have been changed.</p> + +</div> + +<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 77004 ***</div> +</body> +</html> + diff --git a/77004-h/images/cover.jpg b/77004-h/images/cover.jpg Binary files differnew file mode 100644 index 0000000..c9c2323 --- /dev/null +++ b/77004-h/images/cover.jpg diff --git a/77004-h/images/fig1.jpg b/77004-h/images/fig1.jpg Binary files differnew file mode 100644 index 0000000..f08ea1f --- /dev/null +++ b/77004-h/images/fig1.jpg diff --git a/77004-h/images/fig10.jpg b/77004-h/images/fig10.jpg Binary files differnew file mode 100644 index 0000000..9da0bc6 --- /dev/null +++ b/77004-h/images/fig10.jpg diff --git a/77004-h/images/fig11.jpg b/77004-h/images/fig11.jpg Binary files differnew file mode 100644 index 0000000..1968a40 --- /dev/null +++ b/77004-h/images/fig11.jpg diff --git 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