diff options
| author | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:04:47 -0700 |
|---|---|---|
| committer | Roger Frank <rfrank@pglaf.org> | 2025-10-14 20:04:47 -0700 |
| commit | 1ea889b8635339ef3fe441a8ce84e483e13c67a0 (patch) | |
| tree | 7bb505897b496df12c3e1b3c86ae308d7ade9041 /35937-h | |
Diffstat (limited to '35937-h')
| -rw-r--r-- | 35937-h/35937-h.htm | 5113 | ||||
| -rw-r--r-- | 35937-h/images/circle.jpg | bin | 0 -> 67579 bytes | |||
| -rw-r--r-- | 35937-h/images/thermo.jpg | bin | 0 -> 120444 bytes | |||
| -rw-r--r-- | 35937-h/images/thermo_tmb.jpg | bin | 0 -> 49837 bytes | |||
| -rw-r--r-- | 35937-h/images/title.jpg | bin | 0 -> 111780 bytes |
5 files changed, 5113 insertions, 0 deletions
diff --git a/35937-h/35937-h.htm b/35937-h/35937-h.htm new file mode 100644 index 0000000..9c7d4c3 --- /dev/null +++ b/35937-h/35937-h.htm @@ -0,0 +1,5113 @@ +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN" + "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd"> + +<html xmlns="http://www.w3.org/1999/xhtml"> + <head> + <meta http-equiv="Content-Type" content="text/html;charset=iso-8859-1" /> + <title> + The Project Gutenberg eBook of Are the Planets Inhabited?, by E. Walter Maunder. + </title> + + <style type="text/css"> + + p {margin-top: .75em; text-align: justify; margin-bottom: .75em;} + + body {margin-left: 12%; margin-right: 12%;} + + .pagenum {position: absolute; left: 92%; font-size: smaller; text-align: right; font-style: normal;} + + h1,h2,h3,h4,h5,h6 {text-align: center; clear: both;} + + hr {width: 33%; margin-top: 2em; margin-bottom: 2em; margin-left: auto; margin-right: auto; clear: both;} + + table {margin-left: auto; margin-right: auto;} + .br {border-right: solid black 1px; padding-left: 0.5em; padding-right: 0.5em;} + .bbr {border-bottom: solid black 1px; border-right: solid black 1px; padding-left: 0.5em; padding-right: 0.5em;} + .btr {border-top: solid black 1px; border-right: solid black 1px; padding-left: 0.5em; padding-right: 0.5em;} + .blrd {border-left: solid black 1px; border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + .btlrd {border-top: solid black 1px; border-left: solid black 1px; border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + .brd {border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + .btrd {border-top: solid black 1px; border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + .bbrd {border-bottom: solid black 1px; border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + .bblrd {border-bottom: solid black 1px; border-left: solid black 1px; border-right: double; padding-left: 0.5em; padding-right: 0.5em;} + + .giant {font-size: 200%} + .huge {font-size: 150%} + .big {font-size: 125%} + + .blockquot {margin-left: 5%; margin-right: 10%;} + .poem {margin-left:15%;} + .index {margin-left: 20%;} + + .right {text-align: right;} + .center {text-align: center;} + + .smcap {font-variant: small-caps;} + + .figcenter {margin: auto; text-align: center;} + + p.dropcap:first-letter{float: left; padding-right: 3px; font-size: 250%; line-height: 83%; width:auto;} + .caps {text-transform:uppercase;} + + a:link {color:#0000ff; text-decoration:none} + a:visited {color:#6633cc; text-decoration:none} + + .spacer {padding-left: 1em; padding-right: 1em;} + + .vertsbox {margin-left: 20%; margin-right: 20%; border: solid 2px; padding-left: 1em; padding-right: 1em;} + + </style> + </head> +<body> + + +<pre> + +Project Gutenberg's Are the Planets Inhabited?, by E. Walter Maunder + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + + +Title: Are the Planets Inhabited? + +Author: E. Walter Maunder + +Release Date: April 23, 2011 [EBook #35937] + +Language: English + +Character set encoding: ISO-8859-1 + +*** START OF THIS PROJECT GUTENBERG EBOOK ARE THE PLANETS INHABITED? *** + + + + +Produced by Jonathan Ingram and the Online Distributed +Proofreading Team at https://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive/American Libraries.) + + + + + + +</pre> + + + + +<p class="center"><span class="huge"><span class="smcap">Harper’s Library</span> <i>of</i> <span class="smcap">Living Thought</span></span></p> +<p> </p> +<div class="figcenter"><img src="images/circle.jpg" alt="" /></div> + +<p> </p><p> </p><p> </p> +<div class="figcenter"><img src="images/title.jpg" alt="" /></div> +<p> </p><p> </p><p> </p> + +<p class="center"><span class="giant">ARE THE PLANETS<br />INHABITED?</span></p> +<p> </p> +<p class="center">BY<br /> +<span class="big">E. WALTER MAUNDER, F.R.A.S.</span><br /> +<small>SUPERINTENDENT OF THE SOLAR DEPARTMENT, ROYAL OBSERVATORY<br />GREENWICH<br /><br /> +AUTHOR OF “ASTRONOMY WITHOUT A TELESCOPE”<br /> +“THE ROYAL OBSERVATORY, GREENWICH, ITS HISTORY AND WORK”<br /> +“THE ASTRONOMY OF THE BIBLE,” “THE HEAVENS AND THEIR STORY”<br />ETC.</small></p> +<p> </p> +<p class="center">HARPER & BROTHERS<br /> +LONDON AND NEW YORK</p> +<p class="center">45 ALBEMARLE STREET, W.<br />1913</p> +<p> </p><p> </p> + +<p class="center"><i>Published March, 1913</i></p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<h2>CONTENTS</h2> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td><small>CHAPTER</small></td><td> </td><td align="right"><small>PAGE</small></td></tr> +<tr><td align="right"><a href="#CHAPTER_I">I.</a></td><td><span class="smcap">The Question Stated</span></td><td align="right"><a href="#Page_1">1</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_II">II.</a></td><td><span class="smcap">The Living Organism</span></td><td align="right"><a href="#Page_6">6</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_III">III.</a></td><td><span class="smcap">The Sun</span></td><td align="right"><a href="#Page_20">20</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_IV">IV.</a></td><td><span class="smcap">The Distribution of the Elements in Space</span></td><td align="right"><a href="#Page_33">33</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_V">V.</a></td><td><span class="smcap">The Moon</span></td><td align="right"><a href="#Page_43">43</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VI">VI.</a></td><td><span class="smcap">The Canals of Mars</span></td><td align="right"><a href="#Page_57">57</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VII">VII.</a></td><td><span class="smcap">The Condition of Mars</span></td><td align="right"><a href="#Page_71">71</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_VIII">VIII.</a></td><td><span class="smcap">The Illusions of Mars</span></td><td align="right"><a href="#Page_96">96</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_IX">IX.</a></td><td><span class="smcap">Venus, Mercury and the Asteroids</span></td><td align="right"><a href="#Page_111">111</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_X">X.</a></td><td><span class="smcap">The Major Planets</span></td><td align="right"><a href="#Page_122">122</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XI">XI.</a></td><td><span class="smcap">When the Major Planets Cool</span></td><td align="right"><a href="#Page_133">133</a></td></tr> +<tr><td align="right"><a href="#CHAPTER_XII">XII.</a></td><td><span class="smcap">The Final Question</span></td><td align="right"><a href="#Page_143">143</a></td></tr> +<tr><td> </td><td><span class="smcap">Index</span></td><td align="right"><a href="#Page_163">163</a></td></tr></table> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_1" id="Page_1">[Pg 1]</a></span></p> +<p class="center"><span class="giant">ARE THE PLANETS INHABITED?</span></p> +<p> </p> +<h2><a name="CHAPTER_I" id="CHAPTER_I"></a>CHAPTER I</h2> +<p class="center"><span class="big">THE QUESTION STATED</span></p> + +<p class="dropcap"><span class="caps">The</span> first thought that men had concerning the heavenly bodies was an +obvious one: they were lights. There was a greater light to rule the day; +a lesser light to rule the night; and there were the stars also.</p> + +<p>In those days there seemed an immense difference between the earth upon +which men stood, and the bright objects that shone down upon it from the +heavens above. The earth seemed to be vast, dark, and motionless; the +celestial lights seemed to be small, and moved, and shone. The earth was +then regarded as the fixed centre of the universe, but the Copernican +theory has since deprived it of this pride of place. Yet from another +point of view the new conception of its position involves a promotion, +since the earth itself is now regarded as a heavenly body of the same +order as some of those which shine down upon us. It is<span class="pagenum"><a name="Page_2" id="Page_2">[Pg 2]</a></span> amongst them, and +it too moves and shines—shines, as some of them do, by reflecting the +light of the sun. Could we transport ourselves to a neighbouring world, +the earth would seem a star, not distinguishable in kind from the rest.</p> + +<p>But as men realized this, they began to ask: “Since this world from a +distant standpoint must appear as a star, would not a star, if we could +get near enough to it, show itself also as a world? This world teems with +life; above all, it is the home of human life. Men and women, gifted with +feeling, intelligence, and character, look upward from its surface and +watch the shining members of the heavenly host. Are none of these the home +of beings gifted with like powers, who watch in their turn the movements +of that shining point which is our world?”</p> + +<p>This is the meaning of the controversy on the Plurality of Worlds which +excited so much interest some sixty years ago, and has been with us more +or less ever since. It is the desire to recognize the presence in the orbs +around us of beings like ourselves, possessed of personality and +intelligence, lodged in an organic body.</p> + +<p>This is what is meant when we speak of a world being “inhabited.” It would +not, for example, at all content us if we could ascertain that Jupiter was +covered by a shoreless ocean, rich in every variety of fish; or that the +hard rocks of the Moon were delicately veiled by lichens. Just as no +richness<span class="pagenum"><a name="Page_3" id="Page_3">[Pg 3]</a></span> of vegetation and no fulness and complexity of animal life would +justify an explorer in describing some land that he had discovered as +being “inhabited” if no men were there, so we cannot rightly speak of any +other world as being “inhabited” if it is not the home of intelligent +life. If the life did not rise above the level of algæ or oysters, the +globe on which they flourish would be uninhabited in our estimation, and +its chief interest would lie in the possibility that in the course of ages +life might change its forms and develop hereafter into manifestations with +which we could claim a nearer kinship.</p> + +<p>On the other hand, of necessity we are precluded from extending our +enquiry to the case of disembodied intelligences, if such be conceived +possible. All created existences must be conditioned, but if we have no +knowledge of what those conditions may be, or means for attaining such +knowledge, we cannot discuss them. Nothing can be affirmed, nothing +denied, concerning the possibility of intelligences existing on the Moon +or even in the Sun if we are unable to ascertain under what limitations +those particular intelligences subsist. Gnomes, sylphs, elves, and +fairies, and all similar conceptions, escape the possibility of discussion +by our ignorance of their properties. As nothing can be asserted of them +they remain beyond investigation, as they are beyond sight and touch.</p> + +<p><span class="pagenum"><a name="Page_4" id="Page_4">[Pg 4]</a></span>The only beings, then, the presence of which would justify us in regarding +another world as “inhabited” are such as would justify us in applying that +term to a part of our own world. They must possess intelligence and +consciousness on the one hand; on the other, they must likewise have +corporeal form. True, the form might be imagined as different from that we +possess; but, as with ourselves, the intelligent spirit must be lodged in +and expressed by a living material body. Our enquiry is thus rendered a +physical one; it is the necessities of the living body that must guide us +in it; a world unsuited for living organisms is not, in the sense of this +enquiry, a “habitable” world.</p> + +<p>The discussion, as it was carried on sixty years ago by Dr. Whewell and +Sir David Brewster, was essentially a metaphysical, almost a theological +one, and it was chiefly considered in its supposed relationship to certain +religious conceptions. It was urged that it was derogatory to the wisdom +and goodness of the Creator to suppose that He would have created so many +great and glorious orbs without having a definite purpose in so doing, and +that the only purpose for which a world could be made was that it might be +inhabited. So, again, when Dr. A. R. Wallace revived the discussion in +1903, he clearly had a theological purpose in his opening paper, though he +was taking the opposite view from that held by Brewster half a century +earlier.</p> + +<p><span class="pagenum"><a name="Page_5" id="Page_5">[Pg 5]</a></span>For myself, if there be any theological significance attaching to the +solving of this problem, I do not know what it is. If we decide that there +are very many inhabited worlds, or that there are few, or that there is +but one—our own—I fail to see how it should modify our religious +beliefs. For example: explorers have made their way across the Antarctic +continent to the South Pole but have found no “inhabitant” there. Has this +fact any theological bearing? or if, on the contrary, a race of men had +been discovered there, what change would it have made in the theological +position of anyone? And if this be so with regard to a new continent on +this earth, why should it be different with regard to the continents of +another planet?</p> + +<p>The problem therefore seems not to be theological or metaphysical, but +purely physical. We have simply to ask with regard to each heavenly body +which we pass in review: “Are its physical conditions, so far as we can +ascertain them, such as would render the maintenance of life possible upon +it?” The question is not at all as to how life is generated on a world, +but as to whether, if once in action on a particular world, its activities +could be carried on.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_6" id="Page_6">[Pg 6]</a></span></p> +<h2><a name="CHAPTER_II" id="CHAPTER_II"></a>CHAPTER II</h2> +<p class="center"><span class="big">THE LIVING ORGANISM</span></p> + +<p class="dropcap"><span class="caps">A world</span> for habitation, then, is a world whereon living organisms can +exist that are comparable in intelligence with men. But “men” presuppose +the existence of living organisms of inferior grades. Therefore a world +for habitation must first of all be one upon which it is possible for +living organisms, as such, to exist.</p> + +<p>It does not concern us in the present connection how life first came into +existence on this planet. It is sufficient that we know from experience +that life does exist here; and in whatsoever way it was first generated +here, in that same way we may consider that it could have been generated +on another planet.</p> + +<p>Nor need any question trouble us as to the precise line of demarkation to +be drawn between inorganic and organic substances, or amongst the latter, +between plants and animals. These are important subjects for discussion, +but they do not affect us here, for we are essentially concerned with the +highest form of organism, the one furthest from these two dividing lines.</p> + +<p><span class="pagenum"><a name="Page_7" id="Page_7">[Pg 7]</a></span>It suffices that living organisms do exist here, and exist under +well-defined conditions. Wanting these conditions, they perish. We can, to +a varying degree, determine the physical conditions prevailing upon the +heavenly bodies, and we can ascertain whether these physical conditions +would be favourable, unfavourable, or fatal to the living organism.</p> + +<p>What is a living organism? A living organism is such that, though it is +continually changing its substance, its identity, as a whole, remains +essentially the same. This definition is incomplete, but it gives us a +first essential approximation, it indicates the continuance of the whole, +with the unceasing change of the details. Were this definition complete, a +river would furnish us with a perfect example of a living organism, +because, while the river remains, the individual drops of water are +continually changing. There is then something more in the living organism +than the continuity of the whole, with the change of the details.</p> + +<p>An analogy, given by Max Verworn, carries us a step further. He likens +life to a flame, and takes a gas flame with its butterfly shape as a +particularly appropriate illustration. Here the shape of the flame remains +constant, even in its details. Immediately above the burner, at the base +of the flame, there is a completely dark space; surrounding this, a bluish +zone that is faintly luminous;<span class="pagenum"><a name="Page_8" id="Page_8">[Pg 8]</a></span> and beyond this again, the broad spread of +the two wings that are brightly luminous. The flame, like the river, +preserves its identity of form, while its constituent details—the gases +that feed it—are in continual change. But there is not only a change of +material in the flame; there is a change of condition. Everywhere the gas +from the burner is entering into energetic combination with the oxygen of +the air, with evolution of light and heat. There is change in the +constituent particles as well as change of the constituent particles; +there is more than the mere flux of material through the form; there is +change of the material, and in the process of that change energy is +developed.</p> + +<p>A steam-engine may afford us a third illustration. Here fresh material is +continually being introduced into the engine there to suffer change. Part +is supplied as fuel to the fire there to maintain the temperature of the +engine; so far the illustration is analogous to that of the gas flame. But +the engine carries us a step further, for part of the material supplied to +it is water, which is converted into steam by the heat of the fire, and +from the expansion of the steam the energy sought from the machine is +derived. Here again we have change in the material with development of +energy; but there is not only work done in the subject, there is work done +by it.</p> + +<p>But the living organism differs from artificial machines in that, of +itself and by itself, it is <span class="pagenum"><a name="Page_9" id="Page_9">[Pg 9]</a></span>continuously drawing into itself non-living +matter, converting it into an integral part of the organism, and so +endowing it with the qualities of life. And from this non-living matter it +derives fresh energy for the carrying on of the life of the organism.</p> + +<p>The engine and the butterfly gas flame do not give us, any more than the +river, a complete picture of the living organism. The form of the river is +imposed upon it from without; the river is defined by its bed, by the +contour of the country through which it flows. The form and size of the +flame are equally defined by exterior conditions; they are imposed upon it +by the shape of the burner and the pressure of the gas passing through it. +The form of the engine is as its designer has made it. But the form of the +living organism is imposed upon it from within; and, as far as we can +tell, is inherent in it. Here is the wonder and mystery of life: the power +of the living organism to assimilate dead matter, to give it life and +bring it into the law and unity of the organism itself. But it cannot do +this indiscriminately; it is not able thus to convert every dead material; +it is restricted, narrowly restricted, in its action. “One of the chief +characteristics of living matter is found in the continuous range of +chemical reactions which take place between living cells and their +inorganic surroundings. Without cease certain substances are taken up and +disappear in the endless round of chemical reactions in the cell. Other +substances<span class="pagenum"><a name="Page_10" id="Page_10">[Pg 10]</a></span> which have been produced by the chemical reactions in living +matter pass out of the cell and reappear in inorganic nature as waste +products of the life process. The whole complex of these chemical +transformations is generally called <i>Metabolism</i>. Inorganic matter +contrasts strikingly with living substance. However long a crystal or a +piece of metal is kept in observation, there is no change of the +substance, and the molecules remain the same and in the same number. For +living matter the continuous change of substances is an indispensable +condition of existence. To stop the supply of food material for a certain +time is sufficient to cause a serious lesion of the life process or even +the death of the cell. But the same happens when we hinder the passing out +of the products of chemical transformation from the cell. On the other +hand, we may keep a crystal of lifeless matter in a glass tube carefully +shut up from all exchange of substance with the external world for as many +years as we like. The existence of this crystal will continue without end +and without change of any of its properties. There is no known living +organism which could remain in a dry resting state for an infinitely long +period of time. The longest lived are perhaps the spores of mosses which +can exist in a dry state more than a hundred years. As a rule the seeds of +higher plants show their vital power already weakened after ten years; +most of them do not germinate if kept<span class="pagenum"><a name="Page_11" id="Page_11">[Pg 11]</a></span> more than twenty to thirty years. +These experiences lead to the opinion that even dry seeds and spores of +lower plants in their period of rest of vegetation continue the processes +of metabolism to a certain degree. This supposition is confirmed by the +fact that a very slight respiration and production of carbonic acid can be +proved when the seeds contain a small percentage of water. It seems as if +life were weakened in these plant organs to a quite imperceptible degree, +but never, not even temporarily, really suspended.</p> + +<p>“Life is, therefore, quite inseparable from chemical reactions, and on the +whole what we call life is nothing else but a complex of innumerable +chemical reactions in the living substance which we call protoplasm.”<small><a name="f1.1" id="f1.1" href="#f1">[1]</a></small></p> + +<p>The essential quality, therefore, of life is continual change, but not +mere change in general. It is that special process of the circulation of +matter which we call metabolism, and this circulation is always connected +with a particular chemical substance—protoplasm.</p> + +<p>In this substance five elements are always present and +predominant—carbon, oxygen, nitrogen, hydrogen, and sulphur. The +compounds which these five elements form with each other are<span class="pagenum"><a name="Page_12" id="Page_12">[Pg 12]</a></span> most complex +and varied, and they also admit to combination—but in smaller +proportions—some of the other elements, of which phosphorus, potassium, +calcium, magnesium, and iron are the most important.</p> + +<p>For protoplasm—using the term in the most general sense—is a chemical +substance, not a mere mixture of a number of chemical elements, nor a mere +mechanical structure. “However differently the various plasma substances +behave in detail, they always exhibit the same general composition as the +other albuminoids out of the five ‘organo-genetic elements’—namely in +point of weight, 51-54% carbon, 21-23% oxygen, 15-17% nitrogen, 6-7% +hydrogen, and 1-2% sulphur.”<small><a name="f2.1" id="f2.1" href="#f2">[2]</a></small></p> + +<p>Haeckel, the writer just quoted, describes the plasm, the universal basis +of all the vital phenomena, in the following terms: “In every case where +we have with great difficulty succeeded in examining the plasm as far as +possible and separating it from the plasma-products, it has the appearance +of a colourless, viscous substance, the chief physical property of which +is its peculiar thickness and consistency. The physicist distinguishes +three conditions of inorganic matter—solid, fluid, and gaseous. Active +living protoplasm cannot be strictly described as either fluid or solid in +the physical sense. It presents an intermediate<span class="pagenum"><a name="Page_13" id="Page_13">[Pg 13]</a></span> stage between the two +which is best described as viscous; it is best compared to a cold jelly, +or solution of glue. Just as we find the latter substance in all stages +between the solid and the fluid, so we find in the case of protoplasm. The +cause of this softness is the quantity of water contained in the living +matter, which generally amounts to a half of its volume and weight. The +water is distributed between the plasma molecules or the ultimate +particles of living matter in much the same way as it is in the crystals +of salts, but with the important difference that it is very variable in +quantity in the plasm. On this depends the capacity for the absorption or +imbibition in the plasm, and the mobility of its molecules, which is very +important for the performance of the vital actions. However, this capacity +of absorption has definite limits in each variety of plasm; living plasm +is not soluble in water, but absolutely resists the penetration of any +water beyond this limit.”<small><a name="f3.1" id="f3.1" href="#f3">[3]</a></small> And Czapek further tells us that “the most +striking feature of cell life is the fact that an enormous number of +chemical reactions take place within the narrowest space. Most plant cells +do not exceed 0·1 to 0·5 millimetres in diameter. Their greatest volume +therefore can only be an eighth of a cubic millimetre. Nevertheless, in +this minute space we notice in every stage of cell life a considerable +number of chemical reactions which<span class="pagenum"><a name="Page_14" id="Page_14">[Pg 14]</a></span> are carried on contemporaneously, +without one disturbing the other in the slightest degree.”<small><a name="f4.1" id="f4.1" href="#f4">[4]</a></small></p> + +<p>It is clear if organic bodies were built up of chemical compounds of small +complexity and great stability that this continuous range of chemical +reactions, this unceasing metabolism, could not take place. It is +therefore a necessary condition for organic substances that they should be +built up of chemical compounds that are most complex and unstable. +“Exactly those substances which are most important for life possess a very +high molecular weight, and consequently very large molecules, in +comparison with inorganic matter. For example: egg-albumin is said to have +the molecular weight of at least 15,000, starch more than 30,000, whilst +the molecular weight of hydrogen is 2, of sulphuric acid and of potassium +nitrate about 100, and the molecular weight of the heaviest metal salts +does not exceed about 300.”<small><a name="f5.1" id="f5.1" href="#f5">[5]</a></small></p> + +<p>To sum up: the living organism, whether it be a simple cell, or the +ordered community of cells making up the perfect plant or animal, is an +entity, a living individual, wherein highly complex and unstable compounds +are unceasingly undergoing chemical reactions, a metabolism essentially +associated with protoplasm. But these complex compounds are, nevertheless, +formed by the combinations of but a few of the elements now known to us.</p> + +<p><span class="pagenum"><a name="Page_15" id="Page_15">[Pg 15]</a></span>Many writers on the subject of the habitability of other worlds, from +contemplating the rich and apparently limitless variety of the forms of +life, and the diversity of the conditions under which they exist, have +been led to assume that the basis of life must itself also in like manner +be infinitely broad and infinitely varied. In this they are mistaken. As +we have seen, the elements entering into the composition of organic bodies +are, in the main, few in number. The temperatures at which they can exist +are likewise strictly limited. But, above all, that circulation of matter +which we call Life—the metabolism of vital processes—requires for its +continuance the presence of one indispensable factor—WATER.</p> + +<p>Protoplasm itself, as Czapek puts it, is practically an <i>albumin sol</i>; +that is to say, it is a chemical substance of which the chief constituents +are albuminous matter and water, and the protoplasm can only take from +without material dissolved in water; it can only eject matter in the same +way. This <i>osmosis</i> is an indispensable condition in the vital process. +And the “streaming” of protoplasm, its continual movement in the cell, can +only be carried on in water.</p> + +<p>WATER is the compound of oxygen and hydrogen in the proportion of two +atoms of hydrogen to one of oxygen. It is familiar to us in three states: +solid, liquid, and gaseous, or ice, water, and steam. But it is only in +the liquid state that water is<span class="pagenum"><a name="Page_16" id="Page_16">[Pg 16]</a></span> available for carrying on the processes of +life. This fact limits the temperatures at which the organic functions can +be carried on, for water under terrestrial conditions is only liquid for a +hundred degrees; it freezes at 0° Centigrade, it boils at 100° Centigrade. +Necessarily, our experiences are mostly confined within this range, and +therefore we are apt unconsciously to assume that this range is all the +range that is possible, whereas it is but a very small fraction of the +range conceivable, and indeed existing, in cosmical space. In its liquid +state water is a general solvent, and yet pure water is neutral in its +qualities, both characteristics being essential to its usefulness as a +vehicle for the protoplasmic actions. Naturally, this function of water as +a solvent can only exist when water is in the liquid state; solid water, +that is ice, neither dissolves nor flows; and water, when heated to +boiling point, passes into vapour, and so leaves the organism +moistureless, and therefore dead. It is possible to grind a living +organism to a pulp so that the structure of the cells is practically +destroyed, and yet for some reactions which are quite peculiar to life +still to show themselves for some appreciable time. But when the cell-pulp +is heated to the temperature of boiling water, these chemical processes +cannot be longer observed. What is left may then be considered as +definitely dead.</p> + +<p>Water is, then, indispensable for the living<span class="pagenum"><a name="Page_17" id="Page_17">[Pg 17]</a></span> organism; but there are two +great divisions of such organisms—plants and animals. Animals are +generally, but not universally, free to move, and therefore to travel to +seek their food. But their food is restricted; they cannot directly +convert inorganic matter to their own use; they can only assimilate +organic material. The plant, on the other hand, unlike the animal, can +make use of inorganic material. Plant life, therefore, requires an +abundant supply of water in which the various substances necessary for its +support can be dissolved; it must either be in water, or, if on land, +there must be an active circulation of water both through the atmosphere +and through the soil, so as to bring to it the food that it requires. +Animal life presupposes plant life, for it is always dependent upon it.</p> + +<p>Many writers have assumed that life is very widely distributed in +connection with this planet. The assumption is a mistaken one, as has been +well pointed out by Garrett P. Serviss, a charming writer on astronomical +subjects: “On the Earth we find animated existence confined to the surface +of the crust of the globe, to the lower and denser strata of the +atmosphere, and to the film of water that constitutes the oceans. It does +not exist in the heart of the rocks forming the body of the planet nor in +the void of space surrounding it outside the atmosphere. As the Earth +condensed from the original nebula, and cooled and solidified, a<span class="pagenum"><a name="Page_18" id="Page_18">[Pg 18]</a></span> certain +quantity of matter remained at its surface in the form of free gases and +unstable compounds, and, within the narrow precincts where these things +were, lying like a thin shell between the huge inert globe of permanently +combined elements below, and the equally unchanging realm of the ether +above, life, a phenomenon depending upon ceaseless changes, combinations +and re-combinations of chemical elements in unstable and temporary union, +made its appearance, and there only we find it at the present time.”<small><a name="f6.1" id="f6.1" href="#f6">[6]</a></small></p> + +<p>“The huge inert globe of permanently combined elements below, and the +equally unchanging realm of the ether above,” offer no home for the living +organism; least of all for the highest of such organisms—Man. Both must +be tempered to a condition which will permit and favour continual change, +the metabolism which is the essential feature of life.</p> + +<p>“When the earth had to be prepared for the habitation of man, a veil, as +it were, of intermediate being was spread between him and its darkness, in +which were joined, in a subdued measure, the stability and the +insensibility of the earth, and the passion and perishing of mankind.</p> + +<p>“But the heavens, also, had to be prepared for his habitation. Between +their burning light,—their deep vacuity, and man, as between the earth’s +gloom of iron substance, and man, a veil had to be<span class="pagenum"><a name="Page_19" id="Page_19">[Pg 19]</a></span> spread of intermediate +being;—which should appease the unendurable glory to the level of human +feebleness, and sign the changeless motion of the heavens with the +semblance of human vicissitude. Between the earth and man arose the leaf. +Between the heaven and man came the cloud. His life being partly as the +falling leaf and partly as the flying vapour.”<small><a name="f7.1" id="f7.1" href="#f7">[7]</a></small></p> + +<p>The leaf and the cloud are the signs of a habitable world. The leaf—that +is to say, plant life, vegetation—is necessary because animal life is not +capable of building itself up from inorganic material. This step must have +been previously taken by the plant. The cloud, that is to say +water-vapour, is necessary because the plant in its turn cannot directly +assimilate to itself the nitrogen from the atmosphere. The food for the +plant is brought to it by water, and it assimilates it by the help of +water. It is, therefore, upon the question of the presence of water that +the question of the habitability of a given world chiefly turns. In the +physical sense, man is “born of water,” and any world fitted for his +habitation must “stand out of the water and in the water.”</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_20" id="Page_20">[Pg 20]</a></span></p> +<h2><a name="CHAPTER_III" id="CHAPTER_III"></a>CHAPTER III</h2> +<p class="center"><span class="big">THE SUN</span></p> + +<p class="dropcap"><span class="caps">The</span> Sun is, of all the heavenly bodies, the most impressive, and has +necessarily, at all times, attracted the chief attention of men. There are +only two of the heavenly bodies that appear to be more than points of +light, only two that show a surface to the naked eye, and the Sun, being +so much the brighter of the two, and the obvious source of all our light +and heat, and the fosterer of vegetation, readily takes the premier place +in interest. In the present day we know too much about the Sun for anyone +to suppose that it can be the home of organic life; but it is not many +years since its habitability was seriously suggested even by so high an +authority as Sir William Herschel. He conceived that it was possible that +its stores of light and heat might be confined to a relatively thin shell +in its upper atmosphere, and that below this shell a screen of clouds +might so check radiation downward that it would be possible for an inner +nucleus to exist which should be cool and solid. This fancied inner globe +would then necessarily enjoy perpetual daylight, and a climate which knew +no variation from pole to pole. To its<span class="pagenum"><a name="Page_21" id="Page_21">[Pg 21]</a></span> inhabitants the entire heavens +would be generally luminous, the light not being concentrated into any one +part of the vault; and it was supposed that, ignorant of time, a happy +race might flourish, cultivating the far-spread solar fields, in perpetual +daylight, and in the serenity of a perpetual spring that was distracted by +no storm.</p> + +<p>The picture thus conjured up is a pleasing one, though probably, to the +restless sons of Earth, it would seem to suffer somewhat from monotony. +But we now know that it corresponds in not a single detail to the actual +facts. The study of solar conditions carried on through the last hundred +years has revealed to us, not serenity and peace, but storm, stress, and +commotion on the most gigantic scale. But though we now can dismiss from +our minds the possibility that the Sun can be inhabited, yet it is of such +importance to the maintenance of life on this planet, and by parity of +reasoning to life on any other planet, that a review of its conditions +forms a necessary introduction to our subject. Further, those conditions +themselves will bring out certain principles that are of necessary +application when we come to consider the case of particular planets.</p> + +<p>The distance of the Sun from the Earth is often spoken of as the +“astronomical unit”; it is the fundamental measure of astronomy, and all +our information as to the sizes and distances of the various planets rests +upon it. And, as we shall<span class="pagenum"><a name="Page_22" id="Page_22">[Pg 22]</a></span> shortly see, the particular problem with which +we are engaged—the habitability of worlds—is directly connected with +these two factors: the size of the world in question, and its distance +from the Sun.</p> + +<p>The distance of the Sun has been determined by several different methods +the principles of which do not concern us here, but they agree in giving +the mean distance of the Sun as a little less than 93,000,000 miles; that +is to say, it would require 11,720 worlds as large as our own to be put +side by side in order to bridge the chasm between the two. Or a traveller +going round the Earth at its equator would have to repeat the journey 3730 +times before he had traversed a space equal to the Sun’s distance.</p> + +<p>But knowing the Sun’s distance, we are able to deduce its actual diameter, +its superficial extent, and its volume, for its apparent diameter can +readily be measured. Its actual diameter then comes out as 866,400 miles, +or 109·4 times that of the Earth. Its surface exceeds that of the Earth +11,970 times; its volume, 1,310,000 times.</p> + +<p>But the weight of the Sun is known as well as its size; this follows as a +consequence of gravitation. For the planets move in orbits under the +influence of the Sun’s attraction; the dimensions of their orbits are +known, and the times taken in describing them; the amount of the +attractive force therefore is also known, that is to say, the mass of the +Sun. This is 332,000 times the mass of the<span class="pagenum"><a name="Page_23" id="Page_23">[Pg 23]</a></span> Earth; and as the latter has +been determined as equal to about</p> + +<p class="center">6,000,000,000,000,000,000,000 tons</p> + +<p>that of the Sun would be equal to</p> + +<p class="center">2,000,000,000,000,000,000,000,000,000 tons.</p> + +<p>It will be seen that the proportion of the volume of the Sun to that of +the Earth is greater than the proportion of its mass to the Earth’s +mass—almost exactly four times greater; so that the mean density of the +Sun can be only one-fourth that of the Earth. Yet, if we calculate the +force of gravity at the surfaces of both Sun and Earth, we find that the +Sun has a great preponderance. Its mass is 332,000 times that of the +Earth, but to compare it with the attraction of the Earth’s surface we +must divide by (109·4)<sup>2</sup>, since the distance of the Sun’s centre from its +surface is 109·4 times as great as the corresponding distance in the case +of the Earth, and the force of gravity diminishes as the square of the +increased distance. This gives the force of gravity at the solar surface +as 27·65 times its power at the surface of the Earth, so that a body +weighing one ton here would weigh 27 tons 13 cwt. if it were taken to the +Sun.<small><a name="f8.1" id="f8.1" href="#f8">[8]</a></small></p> + +<p>This relation is one of great importance when we realize that the pressure +of the Earth’s atmosphere<span class="pagenum"><a name="Page_24" id="Page_24">[Pg 24]</a></span> is 14·7 lb. on the square inch at the sea +level; that is to say, if we could take a column of air one square inch in +section, extending from the surface of the Earth upwards to the very limit +of the atmosphere, we should find that it would have this weight. If we +construct a water barometer, the column of water required to balance the +atmosphere must be 34 feet high, while the height of the column of mercury +in a mercurial barometer is 30 inches high, for the weight of 30 cubic +inches of mercury or of 408 cubic inches of water (34 × 12 = 408) is 14·7 +lb.</p> + +<p>If, now, we ascend a mountain, carrying a mercurial barometer with us we +should find that it would fall about one inch for the first 900 feet of +our ascent; that is to say, we should have left one-thirtieth of the +atmosphere below us by ascending 900 feet. As we went up higher we should +find that we should have to climb more than 900 feet further in order that +the barometer might fall another inch; and each successive inch, as we +went upward, would mean a longer climb. At the height of 2760 feet the +barometer would have fallen three inches; we should have passed through +one-tenth of the atmosphere. At the height of 5800 feet, we should have +passed through one-fifth of the atmosphere, the barometer would have +dropped six inches; and so on, until at about three and a third miles +above sea level the barometer would read fifteen inches, showing that we +had passed through<span class="pagenum"><a name="Page_25" id="Page_25">[Pg 25]</a></span> half the atmosphere. Mont Blanc is not quite three +miles high, so that in Europe we cannot climb to the height where half the +atmosphere is left below us, and there is no terrestrial mountain anywhere +which would enable us to double the climb; that is to say, to ascend six +and two-third miles. Could we do so, however, we should find that the +barometer had fallen to seven and a half inches; that the second ascent of +three and a third miles had brought us through half the remaining +atmosphere, so that only one-fourth still remained above us. In the +celebrated balloon ascent made by Mr. Coxwell and Mr. Glaisher on +September 5, 1861, an even greater height was attained, and it was +estimated that the barometer fell at its lowest reading to seven inches, +which would correspond to a height of 39,000 feet.</p> + +<p>But on the Sun, where the force of gravity is 27·65 times as great as at +the surface of the Earth, it would, if all the other conditions were +similar, only be necessary to ascend one furlong, instead of three and a +third miles, in order to reach the level of half the surface pressure, and +an ascent of two furlongs would bring us to the level of quarter pressure, +and so on. If then the solar atmosphere extends inwards, below the +apparent surface, it should approximately double in density with each +furlong of descent. These considerations, if taken alone, would point to a +mean density of the Sun not as we know it to be, less than that of the +Earth,<span class="pagenum"><a name="Page_26" id="Page_26">[Pg 26]</a></span> but immeasurably greater; but the discordance is sufficiently +explained when we come to another class of facts.</p> + +<p>These relate to the temperature of the Sun, and to the enormous amount of +light and heat which it radiates forth continually. This entirely +transcends our power to understand or appreciate. Nevertheless, the +astonishing figures which the best authorities give us may, by their +vastness, convey some rough general impression that may be of service. +Thus Prof. C. A. Young puts the total quantity of sunlight as equivalent +to</p> + +<p class="center">1,575,000,000,000,000,000,000,000,000 standard candles.</p> + +<p>The intensity of sunlight at each point of the Sun’s surface is variously +expressed as</p> + +<p class="blockquot">190,000 times that of a standard candle,<br /> +5300 times that of the metal in a Bessemer converter,<br /> +146 times that of a calcium light,<br /> +or, 3·4 times that of an electric arc.</p> + +<p>The same authority estimates at 30 <i>calories</i> the value of the <i>Solar +Constant</i>; that is to say, the heat which, if our atmosphere were removed, +would be received from the Sun in a minute of time upon a square metre of +the Earth’s surface that had the Sun in its zenith, would be sufficient to +raise the temperature of a kilogram of water 30 degrees Centigrade. This +would involve that the heat radiation from each square metre of the Sun’s +<span class="pagenum"><a name="Page_27" id="Page_27">[Pg 27]</a></span>surface would equal 1,340,000 calories; or sufficient to melt through in +each minute of time a shell of ice surrounding the Sun to the thickness of +58·2 feet. Prof. Abbot’s most recent determination of the solar constant +diminishes these estimates by one third; but he still gives the probable +temperature of the solar surface as not far short of 7000 degrees +Centigrade, or about 12,000 degrees Fahrenheit.</p> + +<p>The Sun, then, presents us with temperatures and pressures which entirely +surpass our experience on the Earth. The temperatures, on the one hand, +are sufficient to convert into a permanent gas every substance with which +we are acquainted; the pressures, on the other hand, apart from the high +temperatures, would probably solidify every element, and the Sun, as a +whole, would present itself to us as a comparatively small solid globe, +with a density like that of platinum. With both factors in operation, we +have the result already given: a huge globe, more than one hundred times +the diameter of the Earth, yet only one-fourth its density, and gaseous +probably throughout the whole of its enormous bulk.</p> + +<p>What effect have these two factors, so stupendous in scale, upon its +visible surface? What is the appearance of the Sun?</p> + +<p>It appears to be a large glowing disc, sensibly circular in outline, with +its edge fairly well-defined both as seen in the telescope and as +registered on<span class="pagenum"><a name="Page_28" id="Page_28">[Pg 28]</a></span> photographs. In the spectroscope, or when in an eclipse of +the Sun the Moon covers the whole disc, a narrow serrated ring is seen +surrounding the rim, like a velvet pile of a bright rose colour. This +crimson rim, the sierra or <i>chromosphere</i> as it is usually called, is +always to be found edging the entire Sun, and therefore must carpet the +surface everywhere. But under ordinary conditions, we do not see the +chromosphere itself, but look down through it on the <i>photosphere</i>, or +general radiating surface. This, to the eye, certainly looks like a +definite shell, but some theorists have been so impressed with the +difficulty of conceiving that a gaseous body like the Sun could, under the +conditions of such stupendous temperatures as there exist, have any +defined limit at all, that they deny that what we see on the Sun is a real +boundary, and argue that it only appears so to us through the effects of +the anomalous refraction or dispersion of light. Such theories introduce +difficulties greater and more numerous than those that they clear away, +and they are not generally accepted by practical observers of the Sun. +They seem incompatible with the apparent structure of the photosphere, +which is everywhere made up of a complicated mottling: minute grains +somewhat resembling those of rice in shape, of intense brightness, and +irregularly scattered. This mottling is sometimes coarsely, sometimes +finely textured; in some regions it is sharp and well defined, in others<span class="pagenum"><a name="Page_29" id="Page_29">[Pg 29]</a></span> +misty or blurred, and in both cases they are often arranged in large +elaborate patterns, the figures of the pattern sometimes extending for a +hundred thousand miles or more in any direction. The rice-like grains or +granules of which these figures are built up, and the darker pores between +them, are, on the other hand, comparatively small, and do not, on the +average, exceed two to four hundred miles in diameter.</p> + +<p>But the Sun shows us other objects of quite a different order in their +dimensions. Here and there the bright granules of the photosphere become +disturbed and torn apart, and broad areas are exposed which are relatively +dark. These are <i>sunspots</i>, and in the early stages of their development +they are usually arranged in groups which tend to be stretched out +parallel to the Sun’s equator. A group of spots in its later stages of +development is more commonly reduced to a single round, well-defined, dark +spot. These groups, when near the edge of the Sun, are usually seen to be +accompanied by very bright markings, arranged in long irregular lines, +like the foam on an incoming tide. These markings are known as the +<i>faculae</i>, from their brightness. In the spectroscope, when the serrated +edges of the chromosphere are under observation, every now and then great +<i>prominences</i>, or tongues and clouds of flame, are seen to rise up from +them, sometimes changing their form and appearance so rapidly that the +motion can almost be followed by<span class="pagenum"><a name="Page_30" id="Page_30">[Pg 30]</a></span> the eye. An interval of fifteen or +twenty minutes has frequently been sufficient to transform, quite beyond +recognition, a mass of flame fifty thousand miles in height. Sometimes a +prominence of these, or even greater, dimensions has formed, developed, +risen to a great distance from the Sun, and completely disappeared within +less than half an hour. The velocity of the gas streams in such eruptions +often exceeds one hundred miles a second; sometimes, though only rarely, +it reaches a speed twice as great.</p> + +<p>Sunspots do not offer us examples of motions of this order of rapidity, +but the areas which they affect are not less astonishing. Many spot groups +have been seen to extend over a length of one hundred thousand, or one +hundred and fifty thousand miles, and to cover a total area of a thousand +million square miles. Indeed, the great group of February, 1905, at its +greatest extent, covered an area four times as great as this. Again, in +the normal course of the development of a spot group, the different +members of the group frequently show a kind of repulsion for each other in +the early stages of the group’s history, and the usual speed with which +they move away from each other is three hundred miles an hour.</p> + +<p>The spots, the faculae, the prominences, are all, in different ways, of +the nature of storms in an atmosphere; that is to say, that, in the great +gaseous bulk of the Sun, certain local differences of constitution,<span class="pagenum"><a name="Page_31" id="Page_31">[Pg 31]</a></span> +temperature, and pressure are marked by these different phenomena. From +this point of view it is most significant that many spots are known to +last for more than a month; some have been known to endure for even half a +year. The nearest analogy which the Earth supplies to these disturbances +may be found in tropical cyclones, but these are relatively of far smaller +area, and only last a few days at the utmost, while a hundred miles an +hour is the greatest velocity they ever exhibit, and this, fortunately, +only under exceptional circumstances. For a wind of such violence mows +down buildings and trees as a scythe the blades of grass; and were +tornadoes moving at a rate of 300 miles an hour as common upon the Earth +as spots are upon the Sun, it would be stripped bare of plants and +animals, as well as of men and of all their works.</p> + +<p>It is not an accident that the Sun, when storm-swept, shows this violence +of commotion, but a necessary consequence of its enormous temperature and +pressures. As we have seen, the force of gravity at its surface is 27·65 +times that at the surface of the Earth, where a body falls 16·1 feet in +the first second of time; on the Sun, therefore, a body would fall 445 +feet in the first second; and the atmospheric motions generally would be +accelerated in the same proportion.</p> + +<p>The high temperatures, the great pressures, the violent commotions which +prevail on the Sun are,<span class="pagenum"><a name="Page_32" id="Page_32">[Pg 32]</a></span> therefore, the direct consequence of its enormous +mass. The Sun is, then, not merely the type and example of the chief +source of light and heat in a given planetary system; it indicates to us +that size and mass are the primary tokens by which we may judge the +temperature of a world, and the activity to be expected in its changes.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_33" id="Page_33">[Pg 33]</a></span></p> +<h2><a name="CHAPTER_IV" id="CHAPTER_IV"></a>CHAPTER IV</h2> +<p class="center"><span class="big">THE DISTRIBUTION OF THE ELEMENTS IN SPACE</span></p> + +<p class="dropcap"><span class="caps">It</span> is now an old story, but still possessing its interest, how Fraunhofer +analysed the light of the Sun by making it pass through a narrow slit and +a prism, and found that the broad rainbow-tinted band of light so obtained +was interrupted by hundreds of narrow dark lines, images in negative of +the slit; and how Kirchhoff succeeded in proving that two of these dark +lines were caused by the white light of the solar photosphere having +suffered absorption at the Sun by passing through a stratum of glowing +sodium vapour. From that time forward it has been known that the Sun is +surrounded by an atmosphere of intensely heated gases, among which figure +many of those elements familiar to us in the solid form on the Earth, such +as iron, cobalt, nickel, copper, manganese, and the like. These metals, +here the very types of solid bodies, are permanent gases on the Sun.</p> + +<p>The Sun, then, is in an essentially gaseous condition, enclosed by the +luminous shell which we term the photosphere. This shell Prof. C. A. Young +and the majority of astronomers regard as<span class="pagenum"><a name="Page_34" id="Page_34">[Pg 34]</a></span> consisting of a relatively thin +layer of glowing clouds, justifying the quaint conceit of R. A. Proctor, +who spoke of the Sun as a “Bubble”; that is, a globe of gas surrounded by +an envelope so thin in comparison as to be a mere film. There has been +much difference of opinion as to the substance forming these clouds, but +the theory is still widely held which was first put forward by Dr. +Johnstone Stoney in 1867, that they are due to the condensation of carbon, +the most refractory of all known elements. Prof. Abbot, however, refuses +to believe in a surface of this nature, holding that the temperature of +the Sun is too high even at the surface to permit any such condensation.</p> + +<p>The application of the spectroscope to astronomy is not confined to the +Sun, but reaches much further. The stars also yield their spectra, and we +are compelled to recognize that they also are suns; intensely heated +globes of glowing gas, rich in the same elements as those familiar to us +on the Earth and known by their spectral lines to be present on the Sun. +The stars, therefore, cannot themselves be inhabited worlds any more than +the Sun, and at a stroke the whole of the celestial luminaries within the +furthest range of our most powerful telescopes are removed from our +present search. Only those members of our solar system that shine by +reflecting the light of the Sun can be cool enough for habitation; the +true stars cannot<span class="pagenum"><a name="Page_35" id="Page_35">[Pg 35]</a></span> be inhabited, for, whatever their quality and order, +they are all suns, and must necessarily be in far too highly heated a +condition to be the abode of life. Many of them may, perhaps, be a source +of light and heat to attendant planets, but there is no single instance in +which such a planet has been directly observed; no dark, non-luminous body +has ever been actually seen in attendance on a star. Many double or +multiple stars are known, but these are all instances in which one +sun-like body is revolving round another of the same order.<small><a name="f9.1" id="f9.1" href="#f9">[9]</a></small> We see no +body shining by reflected light outside the limits of the solar system. +Planets to the various stars may exist in countless numbers, but they are +invisible to us, and we cannot discuss conditions where everything is +unknown. Enquiry in such a case is useless, and speculation vain.</p> + +<p>The stars, as revealed to us by the spectroscope are all of the same order +as the Sun, but they are not all of the same species. Quite a large number +of stars, of which Arcturus is one of the best-known examples, show +spectra that are essentially the same as that of the Sun, but there are +other stars of which the spectra bear little or no semblance to<span class="pagenum"><a name="Page_36" id="Page_36">[Pg 36]</a></span> it. +Nevertheless, it remains true that, on the whole, stellar spectra bear +witness to the presence of just the same elements as we recognize in the +Sun, though not always in the same proportions or in the same +conditions—hydrogen, calcium, sodium, magnesium, iron, titanium, and many +more are recognized in nearly all. It is true that not all the known +terrestrial elements have yet been identified in either Sun or stars; but, +in general, those missing are either “negative” elements like the +halogens, or elements of great atomic weight like mercury and platinum. +That elements of one class should, as a rule, reveal their presence in Sun +and stars wherever these are placed, and, correspondingly, that other +classes should as generally fail to show themselves, indicate that such +absence is more likely to be due to the general structure of the stellar +photospheres and reversing layers than to any irregularity in the +distribution of matter in the universe. It is easy, for example, to +conceive that the heavy metals may lie somewhat deeper down within the Sun +or star than those of low atomic weight. In the case of the Sun, there +seems a clear connection between atomic weight and the distinctness with +which the element is recognized in the spectrum of the photosphere, the +lower atomic weights showing themselves more conspicuously.</p> + +<p>It is clear that not all elements present in a Sun or star show themselves +in its spectrum. Oxygen<span class="pagenum"><a name="Page_37" id="Page_37">[Pg 37]</a></span> is very feebly represented by its elemental +lines, but the flutings of titanium oxide are found in sunspots, and with +great distinctness in a certain type of stars. Nitrogen, too, though not +directly recognized, proves its presence by the lines of cyanogen. The +case of helium is one of particular interest; this element was recognized +by a very bright yellow line in the solar prominences before it was known +to exist on the Earth; indeed, it received the name <i>helium</i> because it +then seemed to be a purely solar constituent. Now it is seen as a strong +absorption line in the spectrum of many stars; but for some reason it is +not in general seen as an absorption line over the Sun’s disc, and if our +Sun were removed to such distance so as to appear to us only as a star, we +should have no evidence that it contained any helium at all. So far, then, +as the evidence of the spectroscope goes, the elements present in the +Earth are present throughout the whole extent of the universe within our +view: the same elements and with the same qualities. For the lines of the +spectrum of an element are the revelation of its innermost molecular +structure, so that we can confidently affirm that hydrogen and oxygen on +Sirius, Arcturus, or the Sun, are essentially the same elements as +hydrogen and oxygen on the Earth. On a planet attached to any of these +stars, the two gases would combine together to form water under just the +same conditions as they do here on the Earth; and at suitable +<span class="pagenum"><a name="Page_38" id="Page_38">[Pg 38]</a></span>temperatures that water would be a neutral liquid, capable of dissolving +just the same chemical substances that it does here. It would freeze as it +does here; it would evaporate as it does here; it would be water as +completely in all its qualities and conditions as earthly water is. And +what applies to one element or compound applies to all. Throughout the +whole extent of space, the same building materials have been employed, and +throughout they retain the same qualities.</p> + +<p>Hydrogen is seen in the spectra of nearly all stars, and also in those of +nebulæ. The elemental lines of oxygen are not indeed seen in stellar +spectra, but that the element is present is shown by the flutings of +titanium oxide which distinguish stars like Antares. Nitrogen and carbon +again are not recognized by their elemental lines, but the lines of +cyanogen are seen in the spectra of comets and of sunspots, and +hydrocarbon flutings in the spectra of comets and red stars; while in a +few of the hottest stars even sulphur has recently been identified.<small><a name="f10.1" id="f10.1" href="#f10">[10]</a></small> +All the five organo-genetic elements are therefore abundantly diffused +through space; the materials for protoplasm, “the albuminous substance +with water,” are at hand everywhere. This being so, it is reasonable to +infer that if organic life exists elsewhere than on this Earth, its +essential feature, there as here, is the <span class="pagenum"><a name="Page_39" id="Page_39">[Pg 39]</a></span>metabolism of nitrogenous carbon +compounds in association with protoplasm.</p> + +<p>But it is objected that “we are not yet able to identify all the lines in +solar or stellar spectra; may not some of these lines be due to elements +of which we know nothing here, and may not such new elements form complex +and unstable compounds with each other, or with some of those familiar to +us, that would take the place of the five organo-generators, and so give +rise to a physical basis of life, different from that we know on this +Earth?”</p> + +<p>But the development of Mendeléeff’s Periodic Law has shown that the +elements are not to be regarded as disconnected entities. The Law as given +in Mendeléeff’s own words, runs: “The properties of the elements as well +as the forms and properties of their compounds are in periodic dependence +on, or (expressing ourselves algebraically) form a periodic function of +the atomic weights of the elements.” In other words, they form a series, +not only as it regards their atomic weights, but also as it regards their +own properties and the forms and properties of their compounds. We are no +longer at liberty, as we might have been many years ago, to call into +fancied existence new elements having no relation in their properties and +compounds to those with which we are acquainted. New elements, no doubt, +will be discovered in the future, as in the past; and indeed we<span class="pagenum"><a name="Page_40" id="Page_40">[Pg 40]</a></span> may be +able to discover them and learn their atomic weights and properties +without ever being able to handle them in a terrestrial laboratory.</p> + +<p>In a series of remarkable papers communicated to the Royal Astronomical +Society during the past year (1911-1912), Dr. J. W. Nicholson has given +the result of his computation of the positions of the spectral lines of +two elements of simple structure, and has found that the resulting lines +correspond, for one dynamical system, to the chief unidentified lines +observed in the spectra of nebulæ, and for the other, to the chief +unidentified lines in the spectrum of the corona. The latter element is +probably associated with the halogens, but of much lower atomic weight +(namely, 1·3), than fluorine; he therefore gives it the name of +<i>Protofluorine</i>. The other element, to which he gives the name <i>Nebulium</i>, +will have an atomic weight of 2·1. Prof. Max Wolf, of Heidelberg, has +recently pointed out<small><a name="f11.1" id="f11.1" href="#f11">[11]</a></small> the evidence of the presence of two other unknown +gases in the Ring nebula in Lyra, and there is no reason to suppose that +the process of discovery has come to an end. But we cannot imagine that we +shall discover any new elements that are more abundant and more +universally diffused than the five which give us protoplasm—“the physical +basis of life.” To take an analogy from the solar system: many hundreds of +planetoids have now been discovered between the orbits of Mars and +Jupiter,<span class="pagenum"><a name="Page_41" id="Page_41">[Pg 41]</a></span> and probably many hundreds more remain to be discovered; but of +one thing we are certain, that none of the planetoids yet to be discovered +will be of the same rank as either of those two guardians, Mars and +Jupiter, who revolve on the confines of the planetoidal zone. Indeed, +Ceres, the planetoid first discovered, has a greater mass than the +aggregate of all discovered since, and probably of all that exist in the +zone.</p> + +<p>Water is essential for life here, but the quality in water which restricts +the range of terrestrial life is that it freezes at 0° Centigrade, and +boils at 100° Centigrade; it is only in the liquid state during the +intermediate range of 100 degrees. In order to extend the range for living +organisms, we should have, therefore, to discover a new vehicle, that, +possessing all the other qualities of water, is not restricted to the +liquid state within the same limits. But we are at once met with the +difficulty that the first essential for the vehicle is that it should be +abundant, and there are no other elements more abundant than hydrogen and +oxygen. This new vehicle must, like water, be both neutral and stable, or +it would itself interfere with the highly unstable compounds that are a +necessity for metabolism. And, if we could find this new vehicle, liquid +at temperatures outside the 0° to 100° Centigrade, have we any reason to +suppose that protoplasm itself would be able to endure these outlying +temperatures? Looking through the<span class="pagenum"><a name="Page_42" id="Page_42">[Pg 42]</a></span> range of substances available, we can +only say that none other presents itself as approaching water in +suitability for its essential office. If we, ourselves, were able to +create a vehicle, could we imagine one more perfectly suited?</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_43" id="Page_43">[Pg 43]</a></span></p> +<h2><a name="CHAPTER_V" id="CHAPTER_V"></a>CHAPTER V</h2> +<p class="center"><span class="big">THE MOON</span></p> + +<p class="dropcap"><span class="caps">The</span> Sun and Moon offer to our sight almost exactly the same apparent +diameters; to the eye, they look the same size. But as we know the Sun to +be 400 times as distant as the Moon, it is necessarily 400 times as large; +its surface must exceed that of the Moon by the square of 400, or 160,000; +its volume by the cube of 400, or 64,000,000. As the Sun is of low mean +density, its mass does not exceed that of the Moon in quite the same high +ratio; but it is equal in mass to</p> + +<p class="center">27,000,000 moons.</p> + +<p>Compared with the Sun, the Moon is therefore an insignificant little +ball—a mere particle; but as a world for habitation it possesses some +advantages over the Sun. The first glance at it in a telescope is +sufficient to assure the observer that he is looking at a solid, +substantial globe. It is not only substantial, it is rugged; its surface +is broken up into mountains, hills, valleys, and plains; the mountains +stand out in sensible relief; it looks like a ball of solid silver boldly +embossed and chased.</p> + +<p>So far all is to the good for the purpose of<span class="pagenum"><a name="Page_44" id="Page_44">[Pg 44]</a></span> habitation. Wherever men +are, they must have a solid platform on which to stand; they must have a +stable terrene whereon their food may grow, and this the Moon could +supply. “The Earth’s gloom of iron substance” is necessary for man here, +and the Moon appears to offer a like stability.</p> + +<p>Another favourable condition is that we know that the Moon receives from +the Sun a sufficient supply of light and heat. Each square yard of its +surface receives, on the average, the same amount of light and heat that +would fall upon a square yard on the Earth that was presented towards the +Sun at the same inclination; and we know from our own experience that this +is sufficient for the maintenance of life.</p> + +<p>And the Moon is near enough for us to subject her to a searching scrutiny. +Every part of the hemisphere turned toward us has been repeatedly +examined, measured, and photographed; to that extent our knowledge of its +topography is more complete than of the world on which we live. There are +no unexplored regions on our side of the Moon. The great photographs taken +in recent years at the observatories of Paris and of the University of +Chicago have shown thousands of “crater-pits,” not more than a mile +across; and narrow lines on the Moon’s surface have been detected with a +breadth less than one-tenth of this. An elevation on the Moon, if it rose +up abruptly from an open plain, would make its<span class="pagenum"><a name="Page_45" id="Page_45">[Pg 45]</a></span> presence apparent by the +shadow which it would cast soon after sunrise or near sunset; in this way +an isolated building, if it were as large as the great pyramid of Ghizeh, +would also show itself, and all our great towns and cities would be +apparent as areas of indistinct mottling, though the details of the cities +would not be made out.</p> + +<p>But if vegetation took the same forms on the Moon as on the Earth, and +passed through the same changes, we should have no difficulty in +perceiving the evidence of its presence. If we were transported to the +Moon and turned our eyes earthward, we should not need the assistance of +any telescope in order to detect terrestrial changes which would be +plainly connected with the seasonal changes of vegetation. The Earth would +present to us a disc four times the apparent diameter of the Moon, and on +that disc Canada would offer as great an area as the whole of the Moon +does to us. We could easily follow with the naked eye the change from the +glittering whiteness of the aspect of Canada when snow-covered in winter, +to the brown, green and gold which would succeed each other during the +brighter months of the year. And this type of change would alternate +between the northern and southern hemispheres, for the winter of Canada is +the summer of the Argentine, and conversely.</p> + +<p>We ought, therefore, to have no difficulty in observing seasonal changes +on the Moon, if such<span class="pagenum"><a name="Page_46" id="Page_46">[Pg 46]</a></span> take place. But nothing of the kind has ever been +remarked; no changes sufficiently pronounced for us to be sure of them are +ever witnessed. Here and there some slight mutations have been suspected, +nearly all accomplishing their cycle in the course of a lunar day; so that +it is difficult to separate them from changes purely apparent, brought +about by the change in the incidence of the illumination.</p> + +<p>The difference in appearance of a given area on the Moon when viewed under +a low Sun and when the Sun is on the meridian is very striking. In the +first case everything is in the boldest relief; the shadows are long and +intensely black; the whole area under examination in the telescope seems +as if it might be handled. Under the high Sun, the contrasts are gone; the +scenery appears flat, many of the large conspicuous markings are only +recognized with difficulty. Thus the terse remark of Mädler, “The full +Moon knows no Maginus,” has become a proverb amongst selenographers; yet +Maginus is a fine walled plain some eighty miles in diameter, and its +rampart attains a height in parts of 14,000 feet. Maginus lies near Tycho, +which has been well named “the lunar metropolis,” for from it radiates the +principal system of bright streaks conspicuous on the full Moon. These +white streaks appear when the shadows have vanished or are growing short; +they are not seen under a low Sun.</p> + +<p><span class="pagenum"><a name="Page_47" id="Page_47">[Pg 47]</a></span>The changes which appear to take place in the lunar formations owing to +the change in their illumination are much more striking and varied than +would be anticipated. But the question arises whether all the changes that +are associated with the progress of the lunar day can be ascribed to this +effect. Thus, Prof. W. H. Pickering writes concerning a well-known pair of +little craters of about nine miles in diameter, “known as Messier and +Messier A, situated side by side not far from the centre of the Mare +Fecunditatis. When the Sun rises first on them, the eastern one, A, is +triangular and larger than Messier, which latter is somewhat pear-shaped. +About three days after sunrise they both suddenly turn white, Messier +rapidly grows in size, soon surpasses A, and also becomes triangular in +shape. Six days after sunrise the craters are again nearly of the same +size, owing to the diminution of Messier. The shape of A has become +irregular, and differs in different lunations. At nine days after sunrise +the craters are exactly alike in size and shape, both now being +elliptical, with their major axes lying in a nearly N. and S. direction. +Just before sunset A is again the larger, being almost twice the size of +Messier.”<small><a name="f12.1" id="f12.1" href="#f12">[12]</a></small></p> + +<p>Some observers explain this cycle of changes as due merely to the peculiar +contour of the two<span class="pagenum"><a name="Page_48" id="Page_48">[Pg 48]</a></span> objects, the change in the lighting during the lunar +day altering their apparent figures. Prof. W. H. Pickering, on the other +hand, while recognizing that some portion of the change of shape is +probably due to the contour of the ground, conceives that, in order to +explain the whole phenomenon, it is necessary to suppose that a white +layer of hoar frost is formed periodically round the two craters. It is +also alleged that whereas Mädler described the two craters as being +exactly alike eighty years ago, Messier A is now distinctly the larger; +but it is very doubtful whether Mädler’s description can be trusted to +this degree of nicety. If it could, this would establish a permanent +change in the actual structure of the lunar surface at this point.</p> + +<p>There are several other cases of the same order of ambiguity. The most +celebrated is Linné, a white spot about six miles in diameter on the Mare +Serentatis. This object appears to change in size during the progress of +the lunar day, and, as with Messier, some selenographers consider that it +has also suffered an actual permanent change in shape within the last +sixty or seventy years. Here again the evidence is not decisive; Neison is +by no means convinced that a change has taken place, yet does not think it +impossible that Linné may once have been a crater with steep walls which +have collapsed into its interior through the force of gravity.</p> + +<p>Another type of suspected change is associated with the neighbourhood of +Aristarchus, the brightest<span class="pagenum"><a name="Page_49" id="Page_49">[Pg 49]</a></span> formation on the Moon, so bright indeed that +Sir William Herschel, observing it when illuminated by earthshine in the +dark portion of the Moon, thought that he was watching a lunar volcano in +eruption. In 1897, on September 21, the late Major Molesworth noticed that +the crater was at that time under the rays of the setting Sun, and filled +with shadow, and the inner terraces, which should have been invisible, +were seen as faint, knotted, glimmering streaks under both the eastern and +western walls, and the central peak was also dimly discernible. He thought +this unusual lighting up of rocks on which the Sun had already set might +be due either to phosphorescence produced by long exposure to the Sun’s +rays, or to inherent heat, or to reflected glare from the western rampart. +Still more important, both Major Molesworth and Mr. Walter Goodacre, each +on more than one occasion, observed what seemed to be a faint bluish mist +on the inner slope of the east wall, soon after sunrise, but this was +visible only for a short time. Other selenographers too, on rare +occasions, have made observations accordant with these, relating to +various regions on the Moon.</p> + +<p>These, and a few other similar instances, are all that selenography has to +offer by way of evidence of actual lunar change. Of seeming change there +is abundance, but beyond that we have only cases for controversy, and one +of the most industrious of the present-day observers of the Moon, M.<span class="pagenum"><a name="Page_50" id="Page_50">[Pg 50]</a></span> +Philip Fauth, declares that “as a student of the Moon for the last twenty +years, and as probably one of the few living investigators who have kept +in practical touch with the results of selenography, he is bound to +express his conviction that no eye has ever seen a physical change in the +plastic features of the Moon’s surface.”<small><a name="f13.1" id="f13.1" href="#f13">[13]</a></small></p> + +<p>In this matter of change, then, the Earth and Moon stand in the greatest +contrast to each other. As we have seen, from the view-point of the Moon, +the appearance of the Earth would change so manifestly with the progress +of the seasons that no one could fail to remark the difference, even +though observing with the naked eye. But from the view-point of the Earth, +the Moon when examined by our most experienced observers, armed with our +most powerful telescopes, offers us only a few doubtful enigmatical +instances of possible change confined to small isolated localities; we see +no evidence that the “gloom of iron substance” below is ever concealed by +a veil of changing vegetation, or that “between the burning light and deep +vacuity” of the heavens above, the veil of the flying vapour has ever been +spread out. We see the Moon so clearly that we are assured it holds no +water to nourish plant life; we see it so clearly because there is no air +to carry the vapour that might dim our view.</p> + +<p>Life is change, and a planet where there is no<span class="pagenum"><a name="Page_51" id="Page_51">[Pg 51]</a></span> change, or where that +change is very small, can be no home for life. The “stability and +insensibility” are indeed required in the platform upon which life is to +appear, but there must be the presence of “the passion and the perishing,” +or life will be unable to find a home.</p> + +<p>We infer the absence of water and air from the Moon not only from the +unchanging character of its features and the distinctness with which we +see them; we are able to make direct observations. Galileo, the first man +to observe the Moon to better advantage than with the naked eye, was not +long before he decided that the Moon contained no water, for though +Milton, in a well-known passage, makes Galileo discover</p> + +<p class="center">“Rivers or mountains on her spotty globe,”</p> + +<p>Galileo himself wrote: “I do not believe that the body of the Moon is +composed of earth and water.” The name of <i>maria</i> was given to the great +grey plains of the Moon by Hevelius, but this was simply for convenience +of nomenclature, not because he actually believed them to be seas. One +observation is, in itself, sufficient to prove that the maria are not +water surfaces. The Moon’s “terminator,” that is to say, the line dividing +the part in sunlight from that in darkness, is clearly irregular when it +passes over the great plains; were they actually sea it would be a bright +line and perfectly smooth. The grey plains are therefore not expanses of +water now, nor were they in time past.<span class="pagenum"><a name="Page_52" id="Page_52">[Pg 52]</a></span> It is obvious that in some remote +antiquity their surface was in a fluid condition, but it was the fluidity +of molten rock. This is seen by the way in which the maria have invaded, +breached, broken down, and submerged many of the circular formations on +their margins. Thus the Mare Humorum has swept away half the wall of the +rings, Hippalus and Doppelmayer, and far out in the open plain of the Mare +Nubium, great circles like Kies, and that immediately north of Flamsteed, +stand up in faint relief as of half-submerged rings. Clearly there was a +period after the age in which the great ring mountains and walled plains +came into existence, when an invasive flood attacked and partially +destroyed a large proportion of them. And the flood itself evidently +became more viscous and less fluid the further it spread from its original +centre of action, for the ridges and crumpling of the surface indicate +that the material found more and more difficulty in its flow.</p> + +<p>We have evidence just as direct that there is no atmosphere. This is very +strikingly shown when the Moon, in its monthly progress among the stars, +passes before one of them and occults it. Such an occultation is +instantaneous, and is particularly impressive when either a disappearance +or a reappearance occurs at the defective limb; that is to say, at the +limb which is not illuminated by the Sun, and is therefore invisible. The +observer may have a bright star in the field of view, showing<span class="pagenum"><a name="Page_53" id="Page_53">[Pg 53]</a></span> steadily in +a cloudless sky; there is not a hint of a weakening in its light; suddenly +it is gone. The first experience of such an observation is most +disconcerting; it is hardly less disconcerting to observe the reappearance +at the dark limb. One moment the field of view of the telescope is empty; +the next, without any sort of dawning, a bright star is shining steadily +in the void, and it almost seems to the observer as if an explosion had +taken place. If the Moon had an atmosphere extending upwards from its +surface in all directions and of any appreciable density, an occultation +would not be so exceedingly abrupt; and, in particular, if the occultation +were watched through a spectroscope, then, at the disappearance, the +spectrum of the star would not vanish as a whole, but the red end would go +first, and the rest of the spectrum would be swept out of sight +successively, from orange to the violet. This does not happen; the whole +spectrum goes out together, and it is clear that no appreciable atmosphere +can exist on the Moon. In actual observation so inappreciable is it that +its density at the Moon’s surface is variously estimated as <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">300</span>th of +that of the Earth by Neison, and as <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">10000</span>th by W. H. Pickering. If the +Moon possessed an atmosphere bearing the same proportion to her total mass +as we find in the case of the Earth, she would have a density of +one-fortieth of our atmosphere at the sea level.</p> + +<p>The Moon is at the same mean distance from the<span class="pagenum"><a name="Page_54" id="Page_54">[Pg 54]</a></span> Sun as the Earth, and +therefore, surface for surface, receives from it on the average the same +amount of light and heat. But it makes a very different use of these +supplies. Bright as the Moon appears when seen at the full on some winter +night, it has really but a very low power of reflection, and is only +bright by contrast with the darkness of the midnight sky. If the full Moon +is seen in broad daylight, it is pale and ghost-like. Sir John Herschel +has put it on record that when in South Africa he often had the +opportunity of comparing the Moon with the face of Table Mountain, the Sun +shining full upon both, and the Moon appeared no brighter than the +weathered rock. The best determinations of the <i>albedo</i> of the Moon, that +is to say, of its reflective power, give it as 0·17, so that only +one-sixth of the incident light is reflected, the other five-sixths being +absorbed. It is difficult to obtain a good determination of the Earth’s +<i>albedo</i>, but the most probable estimate puts it as about 0·50, or three +times as great as that of the Moon. This high reflective power is partly +to be accounted for by the great extent of the terrestrial polar caps, but +chiefly by the clouds and dust layer always present in its atmosphere.</p> + +<p>A larger proportion, therefore, of the solar rays are employed in heating +the soil of the Moon than in heating that of the Earth, and in this +connection the effect of an important difference between the two worlds +must be noted. The Earth rotates on<span class="pagenum"><a name="Page_55" id="Page_55">[Pg 55]</a></span> its axis in 23 hours 56 minutes 4 +seconds, the mean length of its rotation as referred to the Sun being 24 +hours. The rotation of the Moon, on the other hand, takes 27 days 7 hours +43 minutes to accomplish, giving a mean rotation, as referred to the Sun, +of 29 days 12 hours 44 minutes. The lunar surface is therefore exposed +uninterruptedly to the solar scorching for very nearly fifteen of our days +at a time, and it is, in turn, exposed to the intense cold of outer space +for an equal period. As the surface absorbs heat so readily, it must +radiate it as quickly; hence radiation must go on with great rapidity +during the long lunar night. Lord Rosse and Prof. Very have both obtained +measures of the change in the lunar heat radiation during the progress of +a total eclipse of the Moon, with the result that the heat disappeared +almost completely, though not quite at the same time as the light. Prof. +Langley succeeded in obtaining from the Moon, far down in the long wave +lengths of the infra-red, a heat spectrum which was only partly due to +reflection from the Sun; part coming from the lunar soil itself, which, +having absorbed heat from the Sun, radiated it out again almost +immediately. In 1898, Prof. Very, following up Langley’s line of work, +concluded that the temperature of the lunar soil must range through about +350° Centigrade, considerably exceeding 100° at the height of the lunar +day, and falling to about the temperature of liquid air during the<span class="pagenum"><a name="Page_56" id="Page_56">[Pg 56]</a></span> lunar +night. So wide a range of temperature must be fatal to living organisms, +particularly when the range is repeated at short, regular intervals of +time. But this range of temperature comes directly from the length of the +Moon’s rotation period; for the longer the day of the Moon, the higher the +temperature which may be attained in it; the longer the night, the greater +the cold which will in turn be experienced. We learn, therefore, that the +time of rotation of a planet is an important factor in its habitability.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_57" id="Page_57">[Pg 57]</a></span></p> +<h2><a name="CHAPTER_VI" id="CHAPTER_VI"></a>CHAPTER VI</h2> +<p class="center"><span class="big">THE CANALS OF MARS</span></p> + +<p class="dropcap"><span class="caps">Both</span> of the two worlds best placed for our study are thus, for different +reasons, ruled out of court as worlds for habitation. The Sun by its +vastness, its intolerable heat and the violence of its changes, has to be +rejected on the one hand, while the Moon, so small, and therefore so +rigid, unchanging and bare, is rejected on the other.</p> + +<p>Of the other heavenly bodies, the planet Mars is the one that we see to +best advantage. Two other planets, Eros and Venus, at times come nearer to +us, but neither offers us on such occasions equal facilities for their +examination. But of Mars it has been asserted not only that it is +inhabited, but that we know it to be the case, since the evidence of the +handiwork of intelligent beings is manifest to us, even across the +tremendous gulf of forty or more million miles of space.</p> + +<p>A claim so remarkable almost captures the position by its audacity. There +is a natural desire among men to believe the marvellous, and the very<span class="pagenum"><a name="Page_58" id="Page_58">[Pg 58]</a></span> +boldness of the assertion goes no small way to overcome incredulity. And +when we consider how puny are men as we see them on this our planet, how +minute their greatest works, how superhuman any undertaking would be which +could demonstrate our existence to observers on another planet, we must +admit that it is a marvel that there should be any evidence forthcoming +that could bear one way or another on the solution of a problem so +difficult.</p> + +<p>The first fact that we have to remember with regard to the planet Mars is +the smallness of its apparent size. To the eye it is nearly a star—a +point of light without visible surface. It is almost twice the size of the +Moon in actual diameter, but as its mean distance from the Earth is 600 +times that of the Moon, its mean apparent diameter is 300 times smaller. +We cannot, however, watch Mars in all parts of its orbit; it is best +placed for observation, and, therefore, most observed, when in opposition, +and oppositions may be favourable or unfavourable. At the most favourable +opposition, Mars is 140 times as distant as the Moon; at the least +favourable, 260 times; so that on such occasions its apparent size varies +from <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">70</span>th of the +diameter of the Moon to <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">130</span>th. But a telescope with a +magnifying power of 70 could never, under the most perfect conditions, +show Mars, even in the closest opposition, as well as the Moon is seen +with the naked eye, for the<span class="pagenum"><a name="Page_59" id="Page_59">[Pg 59]</a></span> practical magnifying power of a telescope is +never as great as the theoretical. In practice, a child’s spy-glass +magnifying some six diameters will show the full Moon to better advantage +than Mars has ever been seen, even in our most powerful telescopes.</p> + +<p>The small apparent size of the planet explains how it was that Galileo +does not seem to have been able to detect any markings upon it. In 1659, +Huyghens laid the foundation stone of areography by observing some dark +spots, and determining from their apparent movements that the planet had a +rotation on its axis, which it accomplished in about the same time as the +Earth. Small and rough as are the drawings that Huyghens made, the +identification of one or two of his spots is unmistakable. Seven years +later, in 1666, both Cassini and Hooke made a number of sketches, and +those by Hooke have been repeatedly used in modern determinations of the +rotation period of the planet. The next great advance was made by Sir +William Herschel, who, during the oppositions of 1777, 1779, 1781, and +1783, determined the inclination of the axis of Mars to the plane of its +orbit, measured its polar and equatorial diameters, and ascertained the +amount of the polar flattening. He paid also special attention to two +bright white spots upon the planet, and he showed that these formed round +the planet’s poles and increased in size as the winter of<span class="pagenum"><a name="Page_60" id="Page_60">[Pg 60]</a></span> each several +hemisphere drew on and diminished again with the advance of summer, +behaving therefore as do the snow caps of our own polar regions.</p> + +<p>The next stage in the development of our knowledge of Mars must be +ascribed to the two German astronomers, Beer and Mädler, who made a series +of drawings in the years 1830, 1832 and 1837, by means of a telescope of 4 +inches aperture, from which they were able to construct a chart of the +entire globe. This chart may be considered classic, for the features which +it represents have been observed afresh at each succeeding opposition. +Mars, therefore, possesses a permanent topography, and some of the +markings in question can be identified, not only in the rough sketches +made by Sir William Herschel, but even in those made by Hooke and Cassini +as far back as the year 1666. In the forty years that followed, the planet +was studied by many of the most skilled observers, particularly by Mr. J. +N. Lockyer in 1862, and the Rev. W. R. Dawes in 1864. In 1877, the late +Mr. N. E. Green, drawing-master to Queen Victoria, and a distinguished +painter in water colours, made a series of sketches of the planet from a +station in the island of Madeira 2000 feet above sea-level. When the +opposition was over, Mr. Green collected together a large number of +drawings, and formed a chart of the planet, much richer in detail than any +that had preceded it, and from his skill, experience and<span class="pagenum"><a name="Page_61" id="Page_61">[Pg 61]</a></span> training as an +artist he reproduced the appearance of the planet with a fidelity that had +never been equalled before and has never been surpassed since. At this +time it was generally assumed that Mars was a miniature of our own world. +The brighter districts of its surface were supposed to be continents, the +darker, seas. As Sir William Herschel had already pointed out long before, +the little world evidently had its seasons, its axis being inclined to the +plane of its orbit at much the same angle as is the case with the Earth; +it had its polar caps, presumably of ice and snow; its day was but very +little longer than that of the Earth; and the only important difference +seemed to be that it had a longer year, and was a little further off the +Sun. But the general conclusion was that it was so like the Earth in its +conditions that we had practically found out all that there was to know; +all that seemed to be reserved for future research was that a few minor +details of the surface might be filled in as the power of our telescopes +was increased.</p> + +<p>But fortunately for progress, this sense of satisfaction was to be rudely +disturbed. As Mars, in its progress round the Sun, receded from the Earth, +or rather as the Earth moved away from it, the astronomers who observed so +diligently during the autumn of 1877 turned their attention to other +objects. One of them, however, Schiaparelli, the most distinguished +astronomer on the continent<span class="pagenum"><a name="Page_62" id="Page_62">[Pg 62]</a></span> of Europe, still continued to watch the +planet, and, as the result of his labours, he published some months later +the first of a magnificent series of <i>Memoirs</i>, bringing to light what +appeared to be a new feature. His drawings not only showed the “lands” and +“seas,” that is to say the bright and dark areas, that Green and his +predecessors had drawn, but also a number of fine, narrow, dark lines +crossing the “lands” in every direction. These narrow lines are the +markings which have since been so celebrated as the “canals of Mars,” and +the discussion as to the real nature of these canals has focussed +attention upon Mars in a way that, perhaps, nothing else could have done. +Before 1877 the study of planetary markings was left almost entirely to +the desultory labours of amateurs, skilled though many of them were; since +1877, the most powerful telescopes of the great public observatories of +the world have been turned upon Mars, and the most skilful and experienced +of professional astronomers have not been ashamed to devote their time to +it.</p> + +<p>There is no need to pass in review the whole of the immense mass of +observations that have been accumulated since Schiaparelli brought out the +first of his great Memoirs. That Memoir gave rise to an immediate +controversy, for many astronomers of skill and experience had observed the +planet in 1877 without detecting the network of<span class="pagenum"><a name="Page_63" id="Page_63">[Pg 63]</a></span> lines which Schiaparelli +had revealed, and it was natural that they should feel some reluctance in +accepting results so strange and novel. But little by little this +controversy has passed. We now know that the “canals” vary much in their +visibility, and “curiously enough the canals are most conspicuous, not at +the time the planet is nearest to the Earth and its general features are +in consequence best seen, but as the planet goes away the canals come out. +The fact is that the orbital position and the seasonal epoch conspire to a +masking of the phenomena.” This was the chief reason why Schiaparelli’s +discoveries seemed at first to stand so entirely without corroboration; +the “canals” did not become conspicuous until after most observers had +desisted from following the planet. Another reason was that, in 1877, Mars +was low down in the sky for northern observatories, and good definition is +an essential for their recognition. But the careful examination of +drawings made in earlier oppositions, especially those made by Dawes and +Green, afforded confirmation of not a few of Schiaparelli’s “canals”; even +in 1877 a few of the easiest and most conspicuous had been delineated by +other astronomers before any rumour of Schiaparelli’s work had come +abroad, and as Mars came under observation again and again at successive +oppositions, the number of those who were able to verify Schiaparelli’s +discoveries increased. It has now long been known<span class="pagenum"><a name="Page_64" id="Page_64">[Pg 64]</a></span> that the great Italian +astronomer was not the victim of a mere optical illusion; there were +actual markings on the planet Mars where he had represented them; markings +which, when seen under like conditions and with equal instrumental +equipment, did present the appearance of straight, narrow lines. The +“canals of Mars” are not mere figments of the imagination, but have a real +objective basis.</p> + +<p>As this controversy has passed away, another and a very different one has +arisen out of an unfortunate mistranslation of the term chosen by +Schiaparelli to indicate these linear streaks. In conformity with the type +of nomenclature adopted by previous areographers who had divided Mars into +“seas,” “continents,” “islands,” “isthmuses,” “straits” and the like, +Schiaparelli had called the narrow lines he detected “<i>canali</i>”, that is +to say “channels,” but without intending to convey the idea of artificial +construction. Indeed, he himself was careful to point out that these +designations “were not intended to prejudge the nature of the spot, and +were nothing but an artifice for helping the memory and for shortening +descriptions.” And he added, “We speak in the same way of the lunar seas, +although we well know that there are no true seas on the Moon.” But +“<i>canali</i>” was unhappily rendered in English as “canals,” instead of +“channels.” “Channel” would have left the nature of the marking an open<span class="pagenum"><a name="Page_65" id="Page_65">[Pg 65]</a></span> +question, but, in English, “canal” means an artificial waterway. Here then +the question as to whether or no Mars is inhabited comes definitely before +us. Have we sufficient grounds for believing that the “canals” are +artificial constructions, or may they be merely natural formations?</p> + +<p>In 1894, Mr. Percival Lowell founded at Flagstaff, Arizona, U.S.A., a +well-equipped observatory for the special study of Mars, and he has +continued his scrutiny of the planet from that time to the present with +the most unrelaxing perseverance. The chief results that he has obtained +have been the detection of many new “canals”; the discovery of a number of +dark, round dots, termed by him “oases,” at the junctions of the “canals”; +and the demonstration that the “canals” and certain of the dusky regions +are subject to strictly seasonal change, as really as the polar caps +themselves. In addition, he has formed the conclusion, which he has +supported with much ingenuity and skill, that the regularity of the +“canals” and “oases” quite precludes the possibility of their being +natural formations. Hence there has arisen the second controversy: that on +the nature of the “canals”; for Mr. Lowell considers that their presence +proves the existence of inhabitants on Mars, who, by means of a Titanic +system of irrigation, are fighting a losing battle against the gradual +desiccation of their planet.</p> + +<p><span class="pagenum"><a name="Page_66" id="Page_66">[Pg 66]</a></span>In a paper published in the <i>International Scientific Review</i>, “Scientia,” +in January, 1910, Mr. Lowell gave a summary of his argument.</p> + +<div class="blockquot"><p>“Organic life needs water for its existence. This water we see exists +on Mars, but in very scant amount, so that if life of any sort exists +there, it must be chiefly dependent on the semi-annual unlocking of +the polar snows for its supply, inasmuch as there are no surface +bodies of it over the rest of the planet. Now the last few years, +beginning with Schiaparelli in 1877, and much extended since at +Flagstaff, have shown:</p> + +<p>“The surface of the planet to be very curiously meshed by a fine +network of lines and spots.</p> + +<p>“Now if one considers first the appearance of this network of lines +and spots, and then its regular behaviour, he will note that its +geometrism precludes its causation on such a scale by any natural +process and, on the other hand, that such is precisely the aspect +which an artificial irrigating system, dependent upon the melting of +the polar snows, would assume. Since water is only to be had at the +time it is there unlocked, and since for any organic life it must be +got, it would be by tapping the disintegrated cap, and only so, that +it could be obtained. If Mars be inhabited, therefore, it is precisely +such a curious system we should expect to see, and only by such +explanation does it seem possible to account for the facts.</p> + +<p>“These lines are the so-called canals of Mars. It is not supposed that +what we see is the conduit itself. On the contrary, the behaviour of +these lines indicates that what we are looking at is<span class="pagenum"><a name="Page_67" id="Page_67">[Pg 67]</a></span> vegetation. Now, +vegetation can only be induced by a water-supply. What we see +resembles the yearly inundation of the Nile, of which to a spectator +in space the river itself might be too narrow to be seen, and only the +verdured country on its banks be visible. This is what we suppose to +be the case with Mars. However the water be conducted, whether in +covered conduits, which seems probable, or not, science is not able to +state, but the effects of it are so palpable and so exactly in accord +with what such a system of irrigation would show, that we are +compelled to believe that such is indeed its <i>vera causa</i>.”</p></div> + +<p>Beside the bulky <i>Memoirs</i> in which Prof. Lowell has published the +scientific results obtained at his observatory at Flagstaff, and papers +and articles appearing in various scientific journals, he has brought out +three books of a more popular character: “<i>Mars</i>”; “<i>Mars and its +Canals</i>”; and “<i>Mars as the Abode of Life</i>.” In these he shows that to the +assiduity of the astronomer he adds the missionary’s zeal and eagerness +for converts as he pleads most skilfully for the acceptance of his chosen +doctrine of the presence of men on Mars. In the last of the three books +mentioned, he deals directly with “Proofs of Life on Mars.” The presence +of vegetation may be inferred from seasonal changes of tint, just as an +observer on the Moon might with the naked eye watch effects on the Earth. +But though “vegetable life could thus reveal itself directly, animal life +could not.<span class="pagenum"><a name="Page_68" id="Page_68">[Pg 68]</a></span> Not by its body but by its mind would it be known. Across the +gulf of space it could be recognized only by the imprint it had made on +the face of Mars.”</p> + +<div class="blockquot"><p>“Confronting the observer are lines and spots that but impress him the +more, as his study goes on, with their non-natural look. So uncommonly +regular are they, and on such a scale as to raise suspicions whether +they can be by nature regularly produced” (p. 188).</p> + +<p>“... Unnatural regularity, the observations showed, betrays itself in +everything to do with the lines: in their surprising straightness, +their amazing uniformity throughout, their exceeding tenuity, and +their immense length” (p. 189).</p> + +<p>“As a planet ages, its surface water grows scarce. Its oceans in time +dry up, its rivers cease to flow, its lakes evaporate (p. 203).... +Now, in the struggle for existence, water must be got.... Its +procuring depends on the intelligence of the organisms that stand in +need of it.... As a planet ages, any organisms upon it will share in +its development. They must evolve with it, indeed, or perish. At first +they change only, as environment offers opportunity, in a lowly, +unconscious way. But, as brain develops, they rise superior to such +occasioning.... The last stage in the expression of life upon a +planet’s surface must be that just antecedent to its dying of +thirst.... With an intelligent population this inevitable end would be +long foreseen.... Both polar caps would be pressed into service in +order to utilize the whole available supply and also to accommodate +most easily the inhabitants of each hemisphere” (pp. 204-11).</p> + +<p><span class="pagenum"><a name="Page_69" id="Page_69">[Pg 69]</a></span>“That intelligence should thus mutely communicate its existence to us +across the far reaches of space, itself remaining hid, appeals to all +that is highest and most far-reaching in man himself. More +satisfactory than strange this; for in no other way could the +habitation of the planet have been revealed. It simply shows again the +supremacy of mind.... Thus, not only do the observations we have +scanned lead us to the conclusion that Mars at this moment is +inhabited, but they land us at the further one that these denizens are +of an order whose acquaintance was worth the making” (p. 215).</p></div> + +<p>For the moment, let us leave Prof. Lowell’s argument as he puts it. +Whether we accept it or not, it remains that it is a marvellous +achievement of the optician’s skill and the observer’s devotion that from +a planet so small and so distant as Mars any evidence should be +forthcoming at all that could bear upon the question of the existence of +intelligent organisms upon its surface. But it is of the utmost +significance to note that the whole question turns upon the presence of +water—of water in the liquid state, of water in a sufficient quantity; +and the final decision, for Mr. Lowell’s contention, or against it, must +turn on that one point. The search for Life on Mars is essentially a +search for Water; a search for water, not only in the present state of +Mars, but in its past as well. For, without water in sufficient quantities +in the past, life on Mars could not have passed through<span class="pagenum"><a name="Page_70" id="Page_70">[Pg 70]</a></span> the evolutionary +development necessary to its attaining its highest expression,—that where +the material living organism has become the tabernacle and instrument of +the conscious intelligent spirit.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_71" id="Page_71">[Pg 71]</a></span></p> +<h2><a name="CHAPTER_VII" id="CHAPTER_VII"></a>CHAPTER VII</h2> +<p class="center"><span class="big">THE CONDITION OF MARS</span></p> + +<p class="dropcap"><span class="caps">The</span> planet Mars is the debatable ground between two opinions. Here, the +two opposing views join issue; the controversy comes to a focus. The point +in debate is whether certain markings—some linear, some circular—are +natural or artificial. If, it is argued, some are truly like a line, +without curve or break, as if drawn with pen, ink, and ruler; or others, +so truly circular, without deviation or break, as if drawn with pen, ink, +and compass; if, moreover, when we obtain more powerful telescopes, +erected in better climates for observing, these markings become more truly +lines and circles the better we see them; then they are <i>artificial</i>, not +natural structures.</p> + +<p>But artificial structures imply artificers. And if the structures are so +designed as to meet the needs of a living organism, it implies that the +living organism that designed them must have a reasonable mind lodged in a +natural body. If, then, the “lines” and “circles” that Prof. Lowell and +his disciples assert to be artificial canals and oases are really such, +they premise the order of being that we call Man. But these canals and +oases also premise the liquid that we call Water—water that flows and +water utilized in cultivation. In this chapter we will leave out of count +the first premiss—Man—and only deal with what concerns the second +premiss—Water; with water that flows and is utilized in vegetation.</p> + +<p><span class="pagenum"><a name="Page_72" id="Page_72">[Pg 72 & 73]</a></span></p> +<p class="center">PLANETARY STATISTICS</p> + +<table border="0" cellpadding="0" cellspacing="0" summary="table"> +<tr><td class="btlrd"> </td> + <td class="btrd" align="center">Minor<br />Planets.</td> + <td class="btrd" colspan="4" align="center">Inner Planets.</td> + <td class="btrd"> </td> + <td class="btr" colspan="4" align="center">Outer Planets.</td></tr> +<tr><td class="blrd"> </td> + <td class="btrd" align="center">Ceres</td> + <td class="btr" align="center">Moon</td> + <td class="btr" align="center">Mercury</td> + <td class="btr" align="center">Mars</td> + <td class="btrd" align="center">Venus</td> + <td class="btrd" align="center">Earth</td> + <td class="btr" align="center">Uranus</td> + <td class="btr" align="center">Neptune</td> + <td class="btr" align="center">Saturn</td> + <td class="btr" align="center">Jupiter</td></tr> +<tr><td class="btlrd"><span class="smcap">Proportions of the Planets</span>:—</td> + <td class="btrd" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btrd" align="center"> </td> + <td class="btrd" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btr" align="center"> </td> + <td class="btr" align="center"> </td></tr> +<tr><td class="blrd">Diameter in miles</td> + <td class="brd" align="center">477</td> + <td class="br" align="center">2163</td> + <td class="br" align="center">3030</td> + <td class="br" align="center">4230</td> + <td class="brd" align="center">7700</td> + <td class="brd" align="center">7918</td> + <td class="br" align="center">31900</td> + <td class="br" align="center">34800</td> + <td class="br" align="center">73000</td> + <td class="br" align="center">86500</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>⊕ = 1</td> + <td class="brd" align="center">0·06</td> + <td class="br" align="center">0·273</td> + <td class="br" align="center">0·383</td> + <td class="br" align="center">0·534</td> + <td class="brd" align="center">0·972</td> + <td class="brd" align="center">1·000</td> + <td class="br" align="center">4·029</td> + <td class="br" align="center">4·395</td> + <td class="br" align="center">9·219</td> + <td class="br" align="center">10·924</td></tr> +<tr><td class="blrd">Surface,<span class="spacer"> </span>⊕ = 1</td> + <td class="brd" align="center">0·004</td> + <td class="br" align="center">0·075</td> + <td class="br" align="center">0·147</td> + <td class="br" align="center">0·285</td> + <td class="brd" align="center">0·945</td> + <td class="brd" align="center">1·000</td> + <td class="br" align="center">16·2</td> + <td class="br" align="center">19·3</td> + <td class="br" align="center">85·0</td> + <td class="br" align="center">119·3</td></tr> +<tr><td class="blrd">Volume,<span class="spacer"> </span>⊕ = 1</td> + <td class="brd" align="center">0·0002</td> + <td class="br" align="center">0·02</td> + <td class="br" align="center">0·06</td> + <td class="br" align="center">0·15</td> + <td class="brd" align="center">0·92</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">65·</td> + <td class="br" align="center">85·</td> + <td class="br" align="center">760·</td> + <td class="br" align="center">1304·</td></tr> +<tr><td class="blrd">Density, Water = 1</td> + <td class="brd" align="center">2·8 ?</td> + <td class="br" align="center">3·39</td> + <td class="br" align="center">4·72</td> + <td class="br" align="center">3·92</td> + <td class="brd" align="center">4·94</td> + <td class="brd" align="center">5·55</td> + <td class="br" align="center">1·22</td> + <td class="br" align="center">1·11</td> + <td class="br" align="center">0·72</td> + <td class="br" align="center">1·32</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>⊕ = 1</td> + <td class="brd" align="center">0·5 ?</td> + <td class="br" align="center">0·61</td> + <td class="br" align="center">0·85</td> + <td class="br" align="center">0·71</td> + <td class="brd" align="center">0·89</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">0·22</td> + <td class="br" align="center">0·20</td> + <td class="br" align="center">0·13</td> + <td class="br" align="center">0·24</td></tr> +<tr><td class="blrd">Mass,<span class="spacer"> </span>⊕= 1</td> + <td class="brd" align="center">0·0001</td> + <td class="br" align="center">0·012</td> + <td class="br" align="center">0·048</td> + <td class="br" align="center">0·107</td> + <td class="brd" align="center">0·820</td> + <td class="brd" align="center">1·000</td> + <td class="br" align="center">14·6</td> + <td class="br" align="center">17·0</td> + <td class="br" align="center">94·8</td> + <td class="br" align="center">317·7</td></tr> +<tr><td class="blrd">Gravity at surface, ⊕ = 1</td> + <td class="brd" align="center">0·028</td> + <td class="br" align="center">0·17</td> + <td class="br" align="center">0·33</td> + <td class="br" align="center">0·38</td> + <td class="brd" align="center">0·87</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">0·90</td> + <td class="br" align="center">0·89</td> + <td class="br" align="center">1·18</td> + <td class="br" align="center">2·65</td></tr> +<tr><td class="blrd">Rate of Fall, Feet in the First Second</td> + <td class="brd" align="center">0·45</td> + <td class="br" align="center">2·73</td> + <td class="br" align="center">5·30</td> + <td class="br" align="center">6·11</td> + <td class="brd" align="center">13·99</td> + <td class="brd" align="center">16·08</td> + <td class="br" align="center">14·47</td> + <td class="br" align="center">14·31</td> + <td class="br" align="center">18·97</td> + <td class="br" align="center">42·61</td></tr> +<tr><td class="blrd">Albedo</td> + <td class="brd" align="center">0·14</td> + <td class="br" align="center">0·17</td> + <td class="br" align="center">0·14</td> + <td class="br" align="center">0·22</td> + <td class="brd" align="center">0·76</td> + <td class="brd" align="center">0·50 ?</td> + <td class="br" align="center">0·60</td> + <td class="br" align="center">0·52</td> + <td class="br" align="center">0·72</td> + <td class="br" align="center">0·62</td></tr> +<tr><td class="blrd"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd"><span class="smcap">Details of Orbit</span>:—</td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd">Mean Distance from Sun in millions of miles</td> + <td class="brd" align="center">257·1</td> + <td class="br" align="center">92·9</td> + <td class="br" align="center">36·0</td> + <td class="br" align="center">141·5</td> + <td class="brd" align="center">67·2</td> + <td class="brd" align="center">92·9</td> + <td class="br" align="center">1781·9</td> + <td class="br" align="center">2791·6</td> + <td class="br" align="center">886·0</td> + <td class="br" align="center">483·3</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>Earth’s distance = 1</td> + <td class="brd" align="center">2·767</td> + <td class="br" align="center">1·000</td> + <td class="br" align="center">0·387</td> + <td class="br" align="center">1·524</td> + <td class="brd" align="center">0·723</td> + <td class="brd" align="center">1·000</td> + <td class="br" align="center">19·183</td> + <td class="br" align="center">30·055</td> + <td class="br" align="center">9·539</td> + <td class="br" align="center">5·203</td></tr> +<tr><td class="blrd">Period of Revolution, in years</td> + <td class="brd" align="center">4·60</td> + <td class="br" align="center">1·00</td> + <td class="br" align="center">0·24</td> + <td class="br" align="center">1·88</td> + <td class="brd" align="center">0·62</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">84·02</td> + <td class="br" align="center">164·78</td> + <td class="br" align="center">29·46</td> + <td class="br" align="center">11·86</td></tr> +<tr><td class="blrd">Velocity, in miles per second</td> + <td class="brd" align="center">11·1</td> + <td class="br" align="center">18·5</td> + <td class="br" align="center">9·7</td> + <td class="br" align="center">15·0</td> + <td class="brd" align="center">21·9</td> + <td class="brd" align="center">18·5</td> + <td class="br" align="center">4·2</td> + <td class="br" align="center">3·4</td> + <td class="br" align="center">6·0</td> + <td class="br" align="center">8·1</td></tr> +<tr><td class="blrd">Eccentricity</td> + <td class="brd" align="center">0·0763</td> + <td class="br" align="center">0·0168</td> + <td class="br" align="center">0·2056</td> + <td class="br" align="center">0·0933</td> + <td class="brd" align="center">0·0068</td> + <td class="brd" align="center">0·0168</td> + <td class="br" align="center">0·0463</td> + <td class="br" align="center">0·0090</td> + <td class="br" align="center">0·0561</td> + <td class="br" align="center">0·0483</td></tr> +<tr><td class="blrd">Aphelion Distance, Perihelion = 1</td> + <td class="brd" align="center">1·157</td> + <td class="br" align="center">1·034</td> + <td class="br" align="center">1·517</td> + <td class="br" align="center">1·207</td> + <td class="brd" align="center">1·013</td> + <td class="brd" align="center">1·034</td> + <td class="br" align="center">1·097</td> + <td class="br" align="center">1·018</td> + <td class="br" align="center">1·107</td> + <td class="br" align="center">1·101</td></tr> +<tr><td class="blrd">Inclination of Equator to Orbit</td> + <td class="brd" align="center">(?)</td> + <td class="br" align="center">1°·32´</td> + <td class="br" align="center">(?)</td> + <td class="br" align="center">24°·0´</td> + <td class="brd" align="center">(?)</td> + <td class="brd" align="center">23°·27´</td> + <td class="br" align="center">(?)</td> + <td class="br" align="center">(?)</td> + <td class="br" align="center">26°·49´</td> + <td class="br" align="center">3°·5´</td></tr> +<tr><td class="blrd"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center">d h m</td> + <td class="br" align="center">d</td> + <td class="br" align="center">h m s</td> + <td class="brd" align="center"> </td> + <td class="brd" align="center">h m s</td> + <td class="br" align="center">h m</td> + <td class="br" align="center"> </td> + <td class="br" align="center">h m</td> + <td class="br" align="center">h m</td></tr> +<tr><td class="blrd"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd">Rotation period</td> + <td class="brd" align="center">(?)</td> + <td class="br" align="center">27·7·43</td> + <td class="br" align="center">88(?)</td> + <td class="br" align="center">24·37·23</td> + <td class="brd" align="center">(?)</td> + <td class="brd" align="center">23·56·4</td> + <td class="br" align="center">9·30(?)</td> + <td class="br" align="center">(?)</td> + <td class="br" align="center">10·14±</td> + <td class="br" align="center">9·55±</td></tr> +<tr><td class="blrd"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd"><span class="smcap">Atmosphere</span>, assuming the total mass of the atmosphere<br /> +<span style="margin-left: 1em;">to be proportional to the mass of the planet:—</span></td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd">Pressure at the surface in lb. per sq. inch.</td> + <td class="brd" align="center">0·014</td> + <td class="br" align="center">0·40</td> + <td class="br" align="center">1·6</td> + <td class="br" align="center">2·1</td> + <td class="brd" align="center">11·1</td> + <td class="brd" align="center">14·7</td> + <td class="br" align="center">11·9</td> + <td class="br" align="center">11·5</td> + <td class="br" align="center">19·4</td> + <td class="br" align="center">103·8</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>" in “atmospheres”</td> + <td class="brd" align="center">0·0009</td> + <td class="br" align="center">0·027</td> + <td class="br" align="center">0·108</td> + <td class="br" align="center">0·143</td> + <td class="brd" align="center">0·754</td> + <td class="brd" align="center">1·000</td> + <td class="br" align="center">0·81</td> + <td class="br" align="center">0·78</td> + <td class="br" align="center">1·32</td> + <td class="br" align="center">7·06</td></tr> +<tr><td class="blrd">Level of half surface pressure in miles</td> + <td class="brd" align="center">119·0</td> + <td class="br" align="center">19·6</td> + <td class="br" align="center">10·1</td> + <td class="br" align="center">8·8</td> + <td class="brd" align="center">3·8</td> + <td class="brd" align="center">3·3</td> + <td class="br" align="center">3·7</td> + <td class="br" align="center">3·8</td> + <td class="br" align="center">2·8</td> + <td class="br" align="center">1·3</td></tr> +<tr><td class="blrd">Boiling point of water at the surface</td> + <td class="brd" align="center"> </td> + <td class="br" align="center">22°C</td> + <td class="br" align="center">53°C</td> + <td class="br" align="center">53°C</td> + <td class="brd" align="center">92°C</td> + <td class="brd" align="center">100°C</td> + <td class="br" align="center">94°C</td> + <td class="br" align="center">93°C</td> + <td class="br" align="center">108°C</td> + <td class="br" align="center">166°C</td></tr> +<tr><td class="blrd"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd"><span class="smcap">Temperature</span>:—</td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="brd" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td> + <td class="br" align="center"> </td></tr> +<tr><td class="blrd">Light and heat received from Sun, ⊕ = 1</td> + <td class="brd" align="center">0·13</td> + <td class="br" align="center">1·00</td> + <td class="br" align="center">6·67</td> + <td class="br" align="center">0·43</td> + <td class="brd" align="center">1·91</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">0·003</td> + <td class="br" align="center">0·001</td> + <td class="br" align="center">0·011</td> + <td class="br" align="center">0·037</td></tr> +<tr><td class="blrd">Reciprocal of square-root of distance, ⊕ = 1</td> + <td class="brd" align="center">0·60</td> + <td class="br" align="center">1·00</td> + <td class="br" align="center">1·61</td> + <td class="br" align="center">0·81</td> + <td class="brd" align="center">1·18</td> + <td class="brd" align="center">1·00</td> + <td class="br" align="center">0·23</td> + <td class="br" align="center">0·18</td> + <td class="br" align="center">0·32</td> + <td class="br" align="center">0·44</td></tr> +<tr><td class="blrd">Equatorial temp. of ideal planet, Absolute</td> + <td class="brd" align="center">188</td> + <td class="br" align="center">312°</td> + <td class="br" align="center">502°</td> + <td class="br" align="center">253°</td> + <td class="brd" align="center">368°</td> + <td class="brd" align="center">312°</td> + <td class="br" align="center">71°</td> + <td class="br" align="center">56°</td> + <td class="br" align="center">101°</td> + <td class="br" align="center">137°</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>Centigrade</td> + <td class="brd" align="center">-65</td> + <td class="br" align="center">+39</td> + <td class="br" align="center">+229</td> + <td class="br" align="center">-20</td> + <td class="brd" align="center">+95</td> + <td class="brd" align="center">+39</td> + <td class="br" align="center">-202</td> + <td class="br" align="center">-217</td> + <td class="br" align="center">-172</td> + <td class="br" align="center">-136</td></tr> +<tr><td class="blrd">Average temp. of ideal planet, Absolute</td> + <td class="brd" align="center">174</td> + <td class="br" align="center">290</td> + <td class="br" align="center">467</td> + <td class="br" align="center">235</td> + <td class="brd" align="center">342</td> + <td class="brd" align="center">290</td> + <td class="br" align="center">66</td> + <td class="br" align="center">52</td> + <td class="br" align="center">94</td> + <td class="br" align="center">127</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>Centigrade</td> + <td class="brd" align="center">-99</td> + <td class="br" align="center">+17</td> + <td class="br" align="center">+194</td> + <td class="br" align="center">-38</td> + <td class="brd" align="center">+69</td> + <td class="brd" align="center">+17</td> + <td class="br" align="center">-207</td> + <td class="br" align="center">-221</td> + <td class="br" align="center">-179</td> + <td class="br" align="center">-146</td></tr> +<tr><td class="blrd">Upper limit under zenith sun, Absolute</td> + <td class="brd" align="center">248</td> + <td class="br" align="center">412</td> + <td class="br" align="center">664</td> + <td class="br" align="center">337</td> + <td class="brd" align="center">486</td> + <td class="brd" align="center">412</td> + <td class="br" align="center">94</td> + <td class="br" align="center">74</td> + <td class="br" align="center">133</td> + <td class="br" align="center">180</td></tr> +<tr><td class="blrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>Centigrade</td> + <td class="brd" align="center">-25</td> + <td class="br" align="center">+139</td> + <td class="br" align="center">+391</td> + <td class="br" align="center">+64</td> + <td class="brd" align="center">+213</td> + <td class="brd" align="center">+139</td> + <td class="br" align="center">-179</td> + <td class="br" align="center">-199</td> + <td class="br" align="center">-140</td> + <td class="br" align="center">-93</td></tr> +<tr><td class="blrd">Average temp. of equivalent disc, Absolute</td> + <td class="brd" align="center">223</td> + <td class="br" align="center">371</td> + <td class="br" align="center">598</td> + <td class="br" align="center">300</td> + <td class="brd" align="center">438</td> + <td class="brd" align="center">371</td> + <td class="br" align="center">84</td> + <td class="br" align="center">67</td> + <td class="br" align="center">120</td> + <td class="br" align="center">162</td></tr> +<tr><td class="bblrd"><span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>"<span class="spacer"> </span>Centigrade</td> + <td class="bbrd" align="center">-50</td> + <td class="bbr" align="center">+98</td> + <td class="bbr" align="center">+325</td> + <td class="bbr" align="center">+27</td> + <td class="bbrd" align="center">+165</td> + <td class="bbrd" align="center">+98</td> + <td class="bbr" align="center">-189</td> + <td class="bbr" align="center">-206</td> + <td class="bbr" align="center">-153</td> + <td class="bbr" align="center">-111</td></tr></table> + +<p><span class="pagenum"><a name="Page_74" id="Page_74">[Pg 74]</a></span>For in regard to this particular premiss we can do away with hypothesis, +and deal only with certain physical facts that are not controversial and +are not in dispute.</p> + +<p>The first of this series of facts concerning Mars about which there can be +no controversy or dispute relates to its size and mass. As the foregoing +Table shows, it comes between the Moon and the Earth in these respects.</p> + +<p>The figures show at a glance that Mars ranks in its dimensions between the +Moon and the Earth, and that, on the whole, it is more like to the Moon +than it is to the Earth.</p> + +<p>But in what way would this affect Mars as a suitable home for life? In +many ways; and amongst these the distribution of its atmosphere and the +sluggishness of its atmospheric circulation are not the least important.</p> + +<p>It was mentioned in Chapter III that at a height of about three and a +third miles the barometer will stand at 15 inches, or half its mean height +at sea level, showing that one half the atmosphere has been passed +through. Mont Blanc, the highest mountain in Europe, is<span class="pagenum"><a name="Page_75" id="Page_75">[Pg 75]</a></span> under 3 miles in +height, so that it is not possible, in Europe, to climb to the level of +half-pressure; Mt. Everest, the highest mountain in the world, is not +quite six miles high, so that no part of the solid substance of our planet +reaches up to the level of the quarter pressure. On a very few occasions +daring aeronauts have soared into the empyrean higher than the summits of +even our loftiest mountains, but the excursion has been a dangerous one, +and they have with difficulty brought their life back from so rare and +cold, so inhospitable a region. When Gay-Lussac, in 1804, attained a +height of 23,000 feet above sea level, the thermometer, which on the +ground read 31° C., sank to 9° below zero, and the rare atmosphere was so +dry that paper crumpled up as if it had been placed near the fire, and his +pulse rose to 120 pulsations a minute instead of his normal 66. When Mr. +Glaisher and Mr. Coxwell made their celebrated ascent between 1 and 2 +o’clock on the afternoon of September 5, 1861, they found that at a height +of 21,000 feet the temperature sank to -10·4°; at 26,000 feet to -15·2°; +and at 39,000 feet the temperature was down to -16·0° C. At this height +the rarefaction of the air was so great and the cold so intense that Mr. +Glaisher fainted, and Mr. Coxwell’s hands being rendered numb and useless +by the cold, he was only able to bring about their descent in time by +pulling the string of the safety valve with his teeth. Yet when they +<span class="pagenum"><a name="Page_76" id="Page_76">[Pg 76]</a></span>attained this height they were far above all cloud or mist, and the Sun’s +rays fell full upon them. The Sun’s rays had all the force that they had +at the surface of the Earth, but in the rare atmosphere of seven miles +above the Earth, the radiation from every particle not in direct sunlight +was so great that while the right hand, exposed to the Sun, might burn, +the left hand, protected from his direct rays, might freeze.</p> + +<p>But gravity at the surface of Mars is much feebler than at the surface of +the Earth, and in order to reach the level of half-pressure a Martian +mountaineer would have to climb, not three and a third miles, but eight +and three-quarter miles; that is to say, the distance to be ascended is in +the inverse proportion of the force of gravity at the surface of the +planet. The atmosphere of Mars, therefore, is much deeper than that of the +Earth, and one great cause of precipitation here is much weakened there. A +current of air heavily laden with moisture, if it encounters a range of +mountains, is forced upwards, and consequently expands, owing to the +diminished pressure. The expansion brings about a cooling, and from both +causes the atmosphere is unable to retain as much water-vapour as it +carried before. On Mars, the same relative expansion and cooling would +only follow if the ascent were nearly three times as great, and the feeble +force of gravity has its effect in another way; for just as a weight on +Mars will only fall<span class="pagenum"><a name="Page_77" id="Page_77">[Pg 77]</a></span> six feet in the first second as against sixteen on +the Earth, so a dense and heavy column of air will fall with proportionate +slowness and a light column ascend in the same languid manner. An +ascending current on Mars would therefore take <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">0·38</span> × +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">0·38</span> = +<span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">0·145</span>, +or seven times as long to attain the same relative expansion as on the Earth.</p> + +<p>The winds of Mars are therefore sluggish, and precipitation is slight. So +far at least it resembles</p> + +<p class="poem">“The island valley of Avilion;<br /> +Where falls not hail, or rain, or any snow,<br /> +Nor ever wind blows loudly;”</p> + +<p>and R. A. Proctor, acute and accurate writer on planetary physics as he +was, fell into a mistake when he referred to Mars as being +“hurricane-swept.” There are no hurricanes on Mars; its fiercest winds can +never exceed in violence what a sailor would call a “capful.”</p> + +<p>This holds good for Mars, but it also holds good for every planet where +the force of gravity at the surface is relatively feeble. The greater the +force of gravity the more active the atmospheric circulation, and more +violent its disturbances; the feebler the action of gravity the more +languid the circulation, and the slighter the disturbances.</p> + +<p>The atmosphere of Mars is relatively deeper than that of the Earth, so +that we, in observing the details of its surface, are looking down through +an<span class="pagenum"><a name="Page_78" id="Page_78">[Pg 78]</a></span> immense thickness of an obscuring medium. And yet the details of the +surface are seen with remarkable distinctness; not as clearly indeed as we +can see those of the Moon, but nearly so. For instance, the “canals” +appear to have a breadth of from 15 to 20 miles, corresponding to <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">16</span>th, +and <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">12</span>th, of a second of arc, at an average opposition. The oases, as a +rule, are about 120 miles in diameter, that is to say about half a second +of arc. These are extraordinarily fine details to be perceived and held, +even if Mars had no atmosphere at all; it would certainly be impossible to +detect them unless the atmosphere were exceedingly thin and transparent. +For we must remember that, though our own atmosphere is a hindrance to our +observing, yet the atmosphere of the planet into which we are looking is a +greater hindrance still. Like the lace curtains of the window of a house, +it is a much greater obstacle to looking inward than to looking outward, +and as the perfect distinctness with which we see the Moon is a proof that +it is practically without an atmosphere, so the great detail visible on +Mars bears unmistakable testimony to the slightness of the atmospheric +veil around that planet.</p> + +<p>And when we turn again to the statistics of Mars, we see that this must +inevitably be the case. Of two planets, one heavier than the other, it is +not possible to suppose that the lighter should secure the greater +proportional amount of <span class="pagenum"><a name="Page_79" id="Page_79">[Pg 79]</a></span>atmosphere. With planets, as with persons, it is +the most powerful that gets the lion’s share: “to him that hath it is +given, and from him that hath not is taken away even that which he seemeth +to have.” But if we assume that Mars has acquired an atmosphere +proportional to its mass, then we see from the Table that this must be a +little less than <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">9</span>th of that of the Earth; exactly 0·107. It is +distributed over a smaller surface, 0·285. Consequently the amount of air +above each square inch of Martian surface is 0·107 ÷ 0·285 = 0·38. But +since the force of gravity at the surface of Mars is less than on the +Earth, this column of air will only weigh 0·38 × 0·38 = 0·145; or +one-seventh of the column of air resting on a square inch of the Earth’s +surface. The pressure at the surface of Mars will therefore be 2·1 lb.; +and the aneroid barometer would read 4·3 inches. (In order to express the +diminished pressure of the Martian atmosphere, it is necessary to refer it +to the aneroid barometer. The mercury in a mercurial barometer, or the +water in a water barometer would lose in weight in consequence of the +diminished force of gravity in the same proportion as the air would, and +the mercurial barometer would read 11·4 inches.)</p> + +<p>But a pressure of 2·1 lb. on the square inch is far less than that +experienced by Coxwell and Glaisher in their great ascent; it is about +one-half the pressure that is experienced on the top of the very highest +terrestrial mountains. But the habitable<span class="pagenum"><a name="Page_80" id="Page_80">[Pg 80]</a></span> regions of the Earth do not +extend even so far upward as to the level of a pressure of 7·3 lb. on the +square inch; that is, of half the terrestrial surface pressure. Plant life +dies out before we reach that point, and though birds or men may +occasionally attain greater heights, they cannot domicile there, and are, +indeed, only able thus to ascend in virtue of nourishment which they have +procured in more favoured regions. If we could suppose the conditions of +the whole Earth changed to correspond with those prevailing at the summit +of Mt. Everest, or even at the summit of Mont Blanc, it is clear that the +life now present on this planet would be extinguished, and that speedily. +Much more would this be the case if the atmosphere were diminished to one +half the pressure on the summit of the highest earthly mountain.</p> + +<p>The tenuity of the atmosphere on Mars has another consequence. Here water +freezes at 0° C. and boils at 100° C.; so that for one hundred degrees it +remains in a liquid condition. On Mars, under the assumed conditions, +water would boil at 53° C., and the range of temperature within which it +would be liquid would be much curtailed. But it is only water in the +liquid state that is useful for sustaining life.</p> + +<p>The above estimate of the density of the atmosphere of Mars is an outside +limit, for it assumes that Mars has retained an atmosphere to the full +proportion of its mass. But as the molecules of a<span class="pagenum"><a name="Page_81" id="Page_81">[Pg 81]</a></span> gas are in continual +motion, and in every direction, the lighter, most swiftly moving molecules +must occasionally be moving directly outwards from the planet at the top +of their speed, and in this case, if the speed of recession should exceed +that which the gravity of the planet can control, the particle is lost to +the planet for ever. A small planet therefore is subject to a continual +drain upon its atmosphere, a drain of the lightest constituents. Hence it +is, no doubt, that free hydrogen is not a constituent of the atmosphere of +the Earth.</p> + +<p>To what extent, then, has the atmosphere of Mars fallen below its full +proportion? Mr. Lowell has adopted an ingenious method of obtaining some +light on this question, by comparing the relative albedoes of the Earth +and Mars; that is to say the relative power of reflection possessed by the +two planets. Of course the method is rough; we have first of all no +satisfactory means of determining the albedo of the Earth itself, and Mr. +Lowell puts it higher than most astronomers would do; then there is the +difficulty of determining what portion of the total albedo is to be +referred to the atmosphere and what to the actual soil or surface of the +planet. But, on the whole, Mr. Lowell concludes that the amount of +atmosphere above the unit of surface of Mars is 0·222 of that above the +unit of surface of the Earth. This would bring down the pressure on each +square inch of Mars to 1·2 lb., and the aneroid barometer would<span class="pagenum"><a name="Page_82" id="Page_82">[Pg 82]</a></span> read 2·5 +inches; and water would boil at 44° C. The range of temperature from day +to night, from summer to winter, at any place on the planet would be +increased, while the range within which water could retain its liquid form +would be diminished.</p> + +<p>These statistics may seem rather dull and tiresome, but if we are to deal +with the problem before us at all, it is important to understand that one +factor in the condition of a planet cannot be altered and all the other +factors retained unchanged. It will be seen that in computing the density +of the atmosphere of Mars, we had to take into consideration not only the +diameter of the planet, but the surface, which varies as the square of the +diameter; the volume, which varies as the cube; the mass, which varies in +a higher power still; and various combinations of these numbers. Novelists +who write tales of journeys to other worlds or of the inhabitants of other +worlds visiting this one, usually assume that the atmosphere is of the +same density on all planets, and the action of gravity unchanged. In their +view it is only that men would have a little less ground to walk upon on +Mars, and a good deal more on Jupiter. Dean Swift, in <i>Gulliver’s +Travels</i>, made the Lilliputians take a truer view of the effect of the +alteration of one dimension, for, finding that Gulliver was twelve times +as tall as the average Lilliputian, they did not appoint him the rations +of twelve<span class="pagenum"><a name="Page_83" id="Page_83">[Pg 83]</a></span> Lilliputians, which would have been rather poor feeding for +that veracious mariner, but allotted him the cube of twelve, viz. +seventeen hundred and twenty-eight rations. Mr. J. Holt Schooling, in one +of his ingenious and interesting statistical papers, tried to bring home +the vast extent of the British Empire by supposing that it seceded, and +taking the portion of Earth that has fallen to it, set up a world of its +own—the planet “Victoria.” He allots to the British Empire 21 per cent of +the land surface of the world. If the Earth were divided so as to form two +globes with surfaces in proportion of 21 to 79, the smaller globe, which +would correspond to Mr. Schooling’s new planet “Victoria,” would be less +than half the present Earth in diameter; it would be considerably smaller +than Mars. But “the rest of the world” would be 0·96 of the present Earth +in diameter, or very nearly the size of Venus, and it would contain just +eight-ninths of the substance of the Earth, leaving only one-ninth for +“Victoria.” The statistics given above will suggest to the reader that, +could such a secession be carried out, the inhabitants of the British +Empire would not be happier for the change during the very short continued +existence that remained to them. The “rest of the world” could spare our +fraction of the planet much better than we could spare theirs.</p> + +<p>This is a principle which applies to worlds <span class="pagenum"><a name="Page_84" id="Page_84">[Pg 84]</a></span>anywhere; not merely within +the limits of the solar system but wherever they exist. Everywhere the +surface must vary with the square of the diameter; the volume with the +cube; everywhere the smaller planet must have the rarer atmosphere, and +with a rare atmosphere the extreme range of temperature must be great, +while the range of temperature within which water will flow will be +restricted. Our Earth stands as the model of a world of the right size for +the maintenance of life; much smaller than our Earth would be too small; +much larger, as we shall see later, would be too large.</p> + +<p>So far we have dealt with Mars as if it received the same amount of light +and heat from the Sun that the Earth does. But, as the Table shows, from +its greater distance from the Sun, Mars receives per unit of surface only +about three-sevenths of the light and heat of that received by the Earth.</p> + +<p>The inclination of the axis of Mars is almost the same as that of the +Earth, so that the general character of the seasons is not very different +on the two planets, and the torrid, temperate, and frigid zones have +almost the same proportions. The length of the day is also nearly the same +for both, the Martian day being slightly longer; but the most serious +factor is the greater distance of Mars, and the consequent diminution in +the light and heat received from the Sun. The light and heat received by +the Earth are not so excessive that<span class="pagenum"><a name="Page_85" id="Page_85">[Pg 85]</a></span> we could be content to see them +diminished, even by 5 per cent, but for Mars they are diminished by 57 per +cent. How can we judge the effect of so important a difference?</p> + +<p>The mean temperature of our Earth is supposed to be about 60°F., or 16°C. +Three-sevenths of this would give us 7°C. as the mean temperature of Mars, +which would signify a planet not impossible for life. But the zero of the +Centigrade scale is not the absolute zero; it only marks the +freezing-point of water. The absolute zero is computed to be -273° on the +Centigrade scale; the temperature of the Earth on the absolute scale +therefore should be taken as 289°, and three-sevenths of this would give +124° of absolute temperature. But this is 149° below freezing-point, and +no life could exist on a planet under such conditions.</p> + +<p>But the mean temperature of Mars cannot be computed quite so easily. The +hotter a body is the more rapidly it radiates heat; the cooler it is the +slower its radiation. According to Stefan’s Law, the radiation varies for +a perfect radiator with the 4th power of the absolute temperature; so that +if Mars were at 124° abs., while the Earth were at 289° abs., the Earth +would be radiating its heat nearly 30 times faster than Mars. The heat +income of Mars would therefore be in a much higher proportion than its +expenditure; and necessarily its heat capital would increase until income +and expenditure<span class="pagenum"><a name="Page_86" id="Page_86">[Pg 86]</a></span> balanced. Prof. Poynting has made the temperature of the +planets under the 4th power law of radiation the subject of an interesting +enquiry, and the figures which he has obtained for Mars and other planets +are included in the Table.</p> + +<p>The equatorial and average temperatures are given under the assumption +that Mars possesses an atmosphere as efficient as our own in equalizing +the temperature of the whole planet. If, on the other hand, its atmosphere +has no such regulating power, then under the zenith Sun the upper limit of +the temperature of a portion of its surface reflecting one-eighth would +be, as shown in the Table, 64°C. This would imply that the temperature on +the dark side of the planet was very nearly at the absolute zero. “If we +regard Mars as resembling our Moon, and take the Moon’s effective average +temperature as 297° abs., the corresponding temperature for Mars is 240° +abs., and the highest temperature is four-fifths of 337° = 270° abs. But +the surface of Mars has probably a higher coefficient of absorption than +the surface of the Moon—it certainly has for light—so that we may put +his effective average temperature, on this supposition, some few degrees +above 240° abs., and his equatorial temperature some degrees higher still. +It appears as exceedingly probable, then, that whether we regard Mars as +like the Earth or, going to the other extreme, as like the Moon, the<span class="pagenum"><a name="Page_87" id="Page_87">[Pg 87]</a></span> +temperature of his surface is everywhere below the freezing-point of +water.”<small><a name="f14.1" id="f14.1" href="#f14">[14]</a></small> As the atmospheric circulation on Mars must be languid, and +the atmosphere itself is very rare, the general condition of the planet +will approximate rather to the lunar type than to the terrestrial, and the +extremes, both of heat and cold, will approach those which would prevail +on a planet without a regulating atmosphere.</p> + +<p>There is another way of considering the effect on the climate of Mars and +its great distance from the Sun, which, though only rough and crude, may +be helpful to some readers. If we take the Earth at noonday at the time of +the equinox, then a square yard at the equator has the Sun in its zenith, +and is fully presented to its light and heat. But, as we move away from +the equator, we find that each higher latitude is less fully presented to +the Sun, until, when we reach latitude 64½°—in other words just +outside the Arctic Circle—7 square yards are presented to the Sun so as +to receive only as much of the solar radiation as 3 square yards receive +at the equator. We may take, then, latitude 64½° as representing Mars, +while the equator represents the Earth. Or, we may take it that we should +compare the climate of Archangel with the climate of Singapore.</p> + +<p><span class="pagenum"><a name="Page_88" id="Page_88">[Pg 88]</a></span>Now the mean temperature of latitude 64½°, say the latitude of +Archangel, is just about freezing-point (0°C.), while that of the equator +is about 28°C. We should therefore expect from this a difference between +the mean temperatures of the Earth and Mars of 28°; that is to say, as the +Earth stands at 16°C, Mars would be at -12°C. But, on the Earth, the +evaporation and precipitation is great, and the atmospheric circulation +vigorous. Evaporation is always going on in equatorial regions, and the +moisture-laden winds are continually moving polewards, carrying with them +vast stores of heat to be liberated as the rain falls. The oceanic +currents have the same effect, and how great the modification which they +introduce may be seen by comparing the climates of Labrador and Scotland. +There appear to be no great oceans on Mars. The difference of 28° which we +find on the Earth between the equator and the edge of the Arctic Circle is +a difference which remains after the convection currents of air and sea +have done much to reduce the temperature of the equator and to raise that +of high latitudes. If we suppose that their effect has been to reduce this +difference to one half of what it would have been were each latitude +isolated from the rest, we shall not be far wrong, and we should get a +range of 56° as the true equivalent difference between the mean +temperatures of Singapore and Archangel; i.e. of the Earth and Mars; and +Mars would stand at -40°C. The<span class="pagenum"><a name="Page_89" id="Page_89">[Pg 89]</a></span> closeness with which this figure agrees +with that reached by Prof. Poynting suggests that it is a fair +approximation to the correct figure.</p> + +<p>The size of Mars taught us that we have in it a planet with an atmosphere +of but one half the density of that prevailing on the top of our highest +mountain; the distance of Mars from the Sun showed us that it must have a +mean temperature close to that of freezing mercury. What chance would +there be for life on a world the average condition of which would +correspond to that of a terrestrial mountain top, ten miles high and in +the heart of the polar regions? But Mars in the telescope does not look +like a cold planet. As we look at it, and note its bright colour, the +small extent of the white caps presumed to be snow, and the high latitudes +in which the dark markings—presumed to be water or vegetation—are seen, +it seems difficult to suppose that the mean temperature of the planet is +lower than that of the Earth. Thus on the wonderful photographs taken by +Prof. Barnard in 1909, the Nilosyrtis with the Protonilus is seen as a +dark canal. Now the Protonilus is in North Lat. 42°, and on the date of +observation—September 28, 1909—the winter solstice of the northern +hemisphere of Mars was just past. There would be nothing unusual for the +ground to be covered with snow and the water to be frozen in a +corresponding latitude if in a continental situation on the Earth. Then, +again, in the summer, the<span class="pagenum"><a name="Page_90" id="Page_90">[Pg 90]</a></span> white polar caps of Mars diminish to a far +greater extent than the snow and ice caps of the Earth; indeed, one of the +Martian caps has been known to disappear completely.</p> + +<p>Yet, as the accompanying diagram will show, something of this kind is +precisely what we ought to expect to see. The diagram has been constructed +in the following manner: A curve of mean temperatures has been laid down +for every 10° of latitude on the Earth, derived as far as possible from +accepted isothermals in continental countries in the northern hemisphere. +From this curve ordinates have been drawn at each 10°, upward to show +average deviation from the mean temperature for the hottest part of the +day in summer, downward for the deviation for the coldest part of the +night in winter. Obviously, on the average, the range from maximum to +minimum will increase from the equator to the poles. The mean temperature +of the Earth has been taken as 16°C, and as representing that prevailing +in about 42° lat. The diagram shows that the maximum temperature of no +place upon the Earth’s surface approaches the boiling-point of water, and +that it is only within the polar circle that the mean temperature is below +freezing-point. Water, therefore, on the Earth must be normally in the +liquid state.</p> + +<p> <span class="pagenum"><a name="Page_91" id="Page_91">[Pg 91]</a></span></p> +<div class="figcenter"><img src="images/thermo_tmb.jpg" alt="" /><br /> +<a href="images/thermo.jpg"><small>Larger Image</small></a></div> +<p class="center"><span class="smcap">Thermographs of the Earth and Mars</span></p> +<p> </p> + +<p><span class="pagenum"><a name="Page_92" id="Page_92">[Pg 92]</a></span>In constructing a similar diagram for Mars, three modifications have to be +made. First of all, the mean temperature of the planet must be +considerably lower than that of the Earth. Next, since the atmospheric +circulation is languid and there are no great oceans, the temperatures of +different latitudes cannot be equalized to the same extent as on the +Earth. It follows, therefore, that the range in mean temperature from +equator to pole must be considerably greater on Mars than on the Earth. +Thirdly, the range in temperature in any latitude, from the hottest part +of the day in summer to the coldest part of the night in winter, must be +much greater than with us; partly on account of the very slight density of +the atmosphere, and partly on account of the length of the Martian year.</p> + +<p>We cannot know the exact figures to adopt, but the general type of the +thermograph for Mars as compared with that of the Earth will remain. The +mean temperature of Mars will be lower, the range of temperature from +equator to pole will be greater, and the extremes of temperature in any +given latitude more pronounced than upon the Earth. And the general lesson +of the diagram may be summed up in a sentence. The maximum temperature on +the planet is well above freezing-point, and the part of the planet at +maximum temperature is precisely the part that we see the best. But while +this is so, it is clear that water on Mars must normally be in the state +of ice; Mars is essentially a frozen planet; and the extremes of cold +experienced there, not only every year but<span class="pagenum"><a name="Page_93" id="Page_93">[Pg 93]</a></span> every night, far transcend the +bitterest extremes of our own polar regions.</p> + +<p>The above considerations do not appear to render it likely that there is +any vegetation on Mars. A planet ice-bound every night and with its mean +temperature considerably below freezing-point does not seem promising for +vegetation. If vegetation exists, it must be of a kind that can pass +through all the stages of its life-history during the few bright hours of +the Martian day. Every night will be for it a winter, a winter of +undescribable frost, which it could only endure in the form of spores. So +if there be vegetation it must be confined to some hardy forms of a low +type. At a distance of forty millions of miles it is not easy to +discriminate between the darkness of sheets of water and the darkness of +stretches of vegetation. Some of the so-called “seas” may possibly be +really of the latter class, but that there must be expanses of water on +the planet is clear, for if there were no water surfaces there would be no +evaporation; and if there were no evaporation from whence could come the +supply of moisture that builds up the winter pole cap?</p> + +<p>The great American astronomer, Prof. Newcomb, gave in <i>Harper’s Weekly</i> +for July 25, 1908, an admirable summary of the verdict of science as to +the character of the meteorology of Mars. “The most careful calculation +shows that if there are any considerable bodies of water on our +neighbouring<span class="pagenum"><a name="Page_94" id="Page_94">[Pg 94]</a></span> planet they exist in the form of ice, and can never be +liquid to a depth of more than one or two inches, and that only within the +torrid zone and during a few hours each day.... There is no evidence that +snow like ours ever forms around the poles of Mars. It does not seem +possible that any considerable fall of such snow could ever take place, +nor is there any necessity of supposing actual snow or ice to account for +the white caps. At a temperature vastly below any ever felt in Siberia, +the smallest particles of moisture will be condensed into what we call +hoar frost, and will glisten with as much whiteness as actual snow.... +Thus we have a kind of Martian meteorological changes, very slight indeed +and seemingly very different from those of our earth, but yet following +similar lines on their small scale. For snowfall substitute frostfall; +instead of feet or inches say fractions of a millimetre, and instead of +storms or wind substitute little motions of an air thinner than that on +the top of the Himalayas, and we shall have a general description of +Martian meteorology.”</p> + +<p>What we know of Mars, then, shows us a planet, icebound every night, but +with a day temperature somewhat above freezing-point. As we see it, we +look upon its warmest regions, and the rapidity with which it is cleared +of ice, snow, and cloud shows the atmosphere to be rare and the moisture +little in amount and readily evaporated. The seas are probably shallow +depressions, filled with<span class="pagenum"><a name="Page_95" id="Page_95">[Pg 95]</a></span> ice to the bottom, but melted as to their +surfaces by day. From the variety of tints noted in the seas, and the +recurrent changes in their outlines, they are composed of congeries of +shallow pools, fed by small sluggish streams; great ocean basins into +which great rivers discharge themselves are quite unknown.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_96" id="Page_96">[Pg 96]</a></span></p> +<h2><a name="CHAPTER_VIII" id="CHAPTER_VIII"></a>CHAPTER VIII</h2> +<p class="center"><span class="big">THE ILLUSIONS OF MARS</span></p> + +<p class="dropcap"><span class="caps">The</span> two preceding chapters have led to two opposing, two incompatible +conclusions. In Chapter VI, a summary was given of Prof. Lowell’s claim to +have had ocular demonstration of the handiwork of intelligent organisms on +Mars. In Chapter VII, it was shown that the indispensable condition for +living organisms, water in the liquid state, is only occasionally present +there, the general temperature being much below freezing-point, so that +living organisms of high development and more than ephemeral existence are +impossible.</p> + +<p>Prof. Lowell argues that the appearance of the network of lines and spots +formed by the canals and oases, and its regular behaviour, “preclude its +causation on such a scale by any natural process,” his assumption being +that he has obtained finality in his seeing of the planet, and that no +improvement in telescopes, no increase in experience, no better eyesight +will ever break up the perfect regularity of form and position, which he +gives to the canals, into finer and more complex detail.</p> + +<p>But the history of our knowledge of the planet’s surface teaches us a +different lesson. Two small<span class="pagenum"><a name="Page_97" id="Page_97">[Pg 97]</a></span> objects appear repeatedly on the drawings +made by Beer and Mädler in 1830; these are two similar dark spots, the one +isolated, the other at the end of a gently curved line. Both spots +resemble in form and character the oases of Prof. Lowell, and the curved +line, at the termination of which one of the spots appears, represents +closely the appearance presented by several of the canals. In the year +1830 no better drawings of Mars had appeared; and in representing these +two spots as truly circular and the curved line as narrow, sharp, and +uniform, Beer and Mädler undoubtedly portrayed the planet as actually they +saw it. The one marking was named by Schiaparelli the Lacus Solis, the +other, the Sinus Sabæus, and they are two of the best known and most +easily recognized of the planet’s features; so that it is easy to trace +the growth of our knowledge of both of them from 1830 up to the present +time. They were drawn by Dawes in 1864, by Schiaparelli in 1877 and the +succeeding years, by Lowell in 1894 and since, and by Antoniadi in 1909 +and 1911. But whereas the drawings of Beer and Mädler, made by the aid of +a telescope of 4 inches aperture, show the two spots as exactly alike, in +those of Dawes, made with a telescope of 8 inches, the resemblance between +the two has entirely vanished, and neither is shown as a plain circular +dot. Since then, observers of greater experience and equipped with more +powerful instruments have directed their<span class="pagenum"><a name="Page_98" id="Page_98">[Pg 98]</a></span> attention to these two objects, +and a mass of complicated structure has been brought out in the regions +which were so simple in the sight of Beer and Mädler, so that not a trace +of resemblance remains between the two objects that to them appeared +indistinguishable.</p> + +<p>Now the gradation in size, from the Lacus Solis down to the smallest oasis +of Lowell, is a complete one. If a future development in the power of +telescopes should equal the advance made from the 4-inch of Beer and +Mädler, to the 33-inch which Antoniadi used in 1909, is it reasonable to +suppose that Prof. Lowell’s oases will refuse to yield to such +improvement, and will all still show themselves as uniform spots, +precisely circular in outline? It is clear that Beer and Mädler would have +been mistaken if they had argued that the apparently perfect circularity +of the two oases which they observed proved them to be artificial, because +the increase in telescopic power has since shown us that neither is +circular. The obvious reason why they appeared so round to Beer and Mädler +was that they were too small to be defined in their instruments; their +minor irregularities were therefore invisible, and their apparent +circularity covered detail of an altogether different form.</p> + +<p>Beer and Mädler only drew two such spots; Lowell shows about two hundred. +Beer and Mädler’s two spots seemed to them exactly alike; these two spots +as we see them to-day have no <span class="pagenum"><a name="Page_99" id="Page_99">[Pg 99]</a></span>resemblance to each other. Prof. Lowell’s +two hundred oases, with few exceptions, seem all of the same character; is +it possible to suppose, if telescopes develop in the future as they have +done in the past, that the two hundred oases will preserve their +uniformity of appearance any more than the Lacus Solis and the head of the +Sinus Sabæus? If a novice begins to work upon Mars with a small telescope, +he will draw the Lacus Solis and the Sinus Sabæus as two round, uniform +spots, and as he gains experience, and his instrumental power is +increased, he will begin to detect detail in them, and draw them as Dawes +and Schiaparelli and others have shown them later. It is no question of +planetary change; it is a question of experience and of “seeing.”</p> + +<p>There is a much simpler explanation of the regularity of the canals and +oases than to suppose that an industrious population of geometers have dug +them out or planted them; it is connected with the nature of vision.</p> + +<p>A telegraph wire seen against a background of a bright cloud can be +discerned at an amazing distance—in fact, at 200,000 times the breadth of +the wire; a distance at which the wire subtends a breadth of a second of +arc. For average normal sight the perception of the wire will be quite +unmistakable, but at the same time it would be quite untrue to say that +the perception of the wire was of the nature of defined vision, as would +be<span class="pagenum"><a name="Page_100" id="Page_100">[Pg 100]</a></span> seen at once if small objects of irregular shape were threaded on the +wire; these would have to be many times the breadth of the wire in order +to be detected. Again, if instead of a wire of very great length extending +right across the field of view of both eyes, a short, black line be drawn +on a white ground, it will be found that as the length of the line is +diminished below a certain point so its breadth must be increased. If the +observer is distant from the line 6000 times its length, then the breadth +must be increased to be equal to the length, and the object, whatever its +actual shape, can be just recognized as a small circular spot, which will +subtend about 34 seconds of arc.</p> + +<p>But though a black spot, 34 seconds in diameter, can be perceived on a +white ground, we have not yet attained to defined vision. For if we place +two black spots each 34 seconds of arc in diameter, near each other, they +will not be seen as separate spots unless there is a clear space between +them of six times that amount. Nearer than that they will give the +impression that they form one circular spot, or an oval one, or even a +uniform straight line, according to the amount of separation. If two equal +round spots be placed so that the distance between their centres is equal +to two diameters, then the diameter of each spot must be, at least, 70 +seconds of arc for them to be distinctly defined; that is to say for the +spots to be seen as two separate objects.</p> + +<p><span class="pagenum"><a name="Page_101" id="Page_101">[Pg 101]</a></span>It will be seen that there is a wide range between objects that are large +enough to be quite unmistakably perceived, and objects which are large +enough to have their true outline really defined. It is a question of +seconds of arc in the one case and of minutes of arc in the other. Within +this range, between the limit at which objects can be just perceived and +that where they can be just defined, objects must all appear as of one of +two forms—the straight line and the circular dot.</p> + +<p>This depends upon the structure of the eye and of the retina; the eye +being essentially a lens with its defining power necessarily limited by +its aperture, and the retina a sensitive screen built up of an immense +number of separate elements each of which can only transmit a single +sensation. Different eyes will have different limits, both for the +smallest objects which can be discerned and for the smallest objects that +can be defined, but for any sight the range between the two will be of the +order just indicated.</p> + +<p>Prof. Lowell has drawn attention to the “strangely economic character of +both the canals and oases in the matter of form.” It is true that straight +lines and circles are economic forms, but they are economic not only in +the construction of irrigation works but also in vision. “The circle is +the figure which encloses the maximum area for the minimum average +distance from its centre to any point situated within it;”<span class="pagenum"><a name="Page_102" id="Page_102">[Pg 102]</a></span> therefore, if +a small spot be perceived by the sight but be too small to have its actual +outline defined, it will be recognized by the eye as being truly circular, +on the principle of economy of effort. So, again, a straight line is the +shortest that can be drawn between two points; and a straight line can be +perceived as such when of an angular breadth quite 40 times less than that +of the smallest spot. A straight line is that which gives the least total +excitement in order to produce an appreciable impression, and therefore +the smallest appreciable impression produces the effect of a straight +line.</p> + +<p>It is sufficient, then, for us to suppose that the surface of Mars is +dotted over with minute irregular markings, with a tendency to aggregate +in certain directions, such as would naturally arise in the process of the +cooling of a planet when the outer crust was contracting above an +unyielding nucleus. If these markings are fairly near each other it is not +necessary, in order to produce the effect of “canals,” that they should be +individually large enough to be seen. They may be of any conceivable +shape, provided that they are separately below the limit of defined +vision, and are sufficiently sparsely scattered. In this case the eye +inevitably sums up the details (which it recognizes but cannot resolve) +into lines essentially “canal-like” in character. Wherever there is a +small aggregation of these minute markings, an impression will be<span class="pagenum"><a name="Page_103" id="Page_103">[Pg 103]</a></span> given +of a circular spot, or, to use Prof. Lowell’s nomenclature, an “oasis.” If +the aggregation be greater still and more extended, we shall have a shaded +area—a “sea.”</p> + +<p>The above remarks apply to observation with the unaided eye, but the same +principle applies yet more strongly to telescopic vision. No star is near +enough or sufficiently large to give the least impression of a true disc; +its diameter is indistinguishable; it is for us a mathematical point, +“without parts or magnitude.” But the image of a star formed by a +telescope is not a point but a minute disc, surrounded by a series of +diffraction rings. This disc is “spurious,” for the greater the aperture +of the telescope the smaller the apparent disc.</p> + +<p>That which holds good for a bright point like a star holds good for every +individual point of a planetary surface when viewed through the telescope; +that is to say, each point is represented by a minute disc; all lines and +outlines therefore are slightly blurred, so that minute irregularities are +inevitably smoothed out.</p> + +<p>When we come to photographs, the process is carried to a third stage. The +image is formed by the telescope, subject to all the limitations of +telescopic images, and is received on a plate essentially granular in +structure, and is finally examined by the eye. The granular structure of +the plate acts as the third factor in concealing<span class="pagenum"><a name="Page_104" id="Page_104">[Pg 104]</a></span> irregularities and +simplifying details; a third factor in producing the two simplest types of +form—the straight line and the circular dot.</p> + +<p>Prof. Lowell describes the canals as like lines drawn with pen, ink and +ruler, but not a few of our best observers have advanced much beyond this +stage. Even as far back as 1884, some of the canals were losing their +strict rectilinear appearance to Schiaparelli, and the observers of the +planet who have been best favoured by the power of the telescope at their +disposal, by the atmospheric conditions under which they worked, and by +their own skill and experience—such as Antoniadi, Barnard, Cerulli, +Denning, Millochau, Molesworth, Phillips, Stanley Williams and +others—have found them to show evident signs of resolution. Thus, in +1909, Antoniadi found that of 50 canals, 14 were resolved into +disconnected knots of diffused shadings, 4 were seen as irregular lines, +10 as more or less dark bands; and he found that, in good seeing, there +was no trace whatever of the geometrical network.</p> + +<p>The progress of observation, therefore, has left Prof. Lowell behind, and +has dispelled the fable which he has defended with so much ingenuity. But, +indeed, there never was any more reason for taking seriously his theory as +to the presence of artificial waterways on Mars than for believing in the +actual existence of the weird creatures described by H. G. Wells in the +<i>War of the Worlds</i>.</p> + +<p><span class="pagenum"><a name="Page_105" id="Page_105">[Pg 105]</a></span>There are too many oversights in the canal theory.</p> + +<p>Thus no source is indicated for the moisture supposed to be locked up in +the winter pole cap. Prof. Lowell holds that there are no large bodies of +water on the planet; that the so-called seas are really cultivated land. +In this case there could be little or no evaporation, and so no means by +which the polar deposits could be recruited.</p> + +<p>Yet it is certain that the supply of the winter pole cap must come from +the evaporation of water in some region or other. And here is another +oversight of the artificial canal theory. The canals are supposed to be +necessary for the conveyance of water from the pole towards the equator; +although, as this was “uphill,” vast pumping stations at short intervals +had to be predicated. But it is not supposed that the water needed to +travel by way of the canals to the poles. If, however, the moisture is +conveyed as vapour through the atmosphere to the pole as winter +approaches, it cannot be impossible that it should be conveyed in the same +manner from the pole as summer draws on, and in that case the artificial +canals would not be needed. If the canals are necessary for conveying the +water in one direction, they would be necessary for the opposite +direction. But there would be something too farcical in the idea of the +careful Martians dispatching their<span class="pagenum"><a name="Page_106" id="Page_106">[Pg 106]</a></span> water first to the pole to be frozen +there, and then, after it had been duly frozen and melted again, fetching +it back along thousands of miles and through numerous pumping stations for +use in irrigating their fields.</p> + +<p>Of all the many hundreds of canals only a few actually touch the polar +caps. But on the theory that the entire canal system is fed by the polar +cap in summer, the carrying capacity of the polar canals should be equal +to, if not greater than, that of the entire system outside the polar +circle. A glance at the charts of the planet shows that the polar canals +could not supply a twentieth part of the water needed for those in the +equatorial regions. Another oversight is that of the significance of the +alleged uniformity and breadth of the canals. Prof. Lowell repeatedly +insists that the canals are of even breadth from end to end, and spring +into existence at once throughout their whole length. This statement is in +itself a proof that the canals cannot be what he supposes them to be. An +irrigation system could not have these characteristics; the region +fertilized would take time to develop; we should see the canal extending +itself gradually across the continent, and its breadth would not be +uniform from end to end, but the region fertilized would grow narrower +with increase of distance from the fountain head of the canal.</p> + +<p>Under what conditions can we see straight lines,<span class="pagenum"><a name="Page_107" id="Page_107">[Pg 107]</a></span> perfectly uniform from +end to end, spring into existence, in their entirety, without going +through any stages of growth? When the lines are not actual images, but +are suggested by markings perceived, but not perfectly defined. In 1902 +and 1903, in conjunction with Mr. Evans, the headmaster of Greenwich +Hospital School, I tried a number of experiments on this point, with the +aid of about two hundred of the boys of the school. They had several +qualifications in respect of these experiments; they were keen-sighted, +well drilled; accustomed to do what they were told without asking +questions; and they knew nothing whatsoever of astronomy, certainly +nothing about Mars.</p> + +<p>A diagram was hung up, based upon some drawing or other of the planet made +by Schiaparelli, Lowell or other Martian observer, but the canals were not +inserted; only a few dots or irregular markings were put in here and +there. And the boys were arranged at different distances from the diagram +and told to draw exactly what they saw. Those nearest the diagram were +able to detect the little irregular markings and represented them under +their true forms. Those at the back of the room could not see anything of +them, and only represented the broadest features of the diagram, the +continents and seas. Those in the middle of the room were too far off to +define the minute markings, but were near enough for those<span class="pagenum"><a name="Page_108" id="Page_108">[Pg 108]</a></span> markings to +produce some impression upon them; and that impression always was of a +network of straight lines, sometimes with dots at the points of meeting. +Advancing from a distance toward the diagram the process of development +became quite clear. At the back of the room no straight lines were seen; +as the observer came slowly forward, first one straight line would appear +completely, then another, and so on, until all the chief canals drawn by +Schiaparelli and Lowell in the region represented had come into evidence +in their proper places. Advancing still further, the canals disappeared, +and the little irregular markings which had given rise to them were +perceived in their true forms.</p> + +<p>These experiments at the Greenwich Hospital School were merely the +repetition of similar ones that I had myself made privately twelve years +earlier, leading me to the conclusion, published in 1894, that the canals +of Mars were simply the summation of a complexity of detail too minute to +be separately discerned.</p> + +<p>A little later, in his work “<i>Marte nel 1896-7</i>,” Dr. Cerulli +independently arrived at the same conclusion, and wrote: “These lines are +formed by the eye ... which utilizes ... the dark elements which it finds +along certain directions”; and “a large number of these elements forms a +broad band”; and “a smaller number of them gives rise to a narrow line.” +Also, “the <span class="pagenum"><a name="Page_109" id="Page_109">[Pg 109]</a></span>marvellous appearance of the lines in question has its origin, +not in the reality of the thing, but in the inability of the present +telescope to show faithfully such a reality.” In 1907, Prof. Newcomb made +some experiments in the same direction and reached the same general +conclusion. More recently still, Prof. W. H. Pickering has worked on the +same lines and with the same result. The venerable George Pollock, +formerly the Senior Master of the Supreme Court and King’s Remembrancer, +sent to me, in his 91st year, the following note as affording an apt +illustration of the true nature of the canaliform markings on Mars:</p> + +<p>“On Saturday last, journeying in a motor-car, I came into a broad road +bounded by a dark wood. Looking up I was amazed to see distinct, +well-defined, vertical, parallel white lines, the wood forming the dark +background. On getting nearer, these lines resolved themselves into spots, +and they proved to be the white insulators supporting the telegraph +wires.”</p> + +<p>Prof. Lowell has objected that all experiments and illustrations of this +kind are irrelevant; only observations upon the planet itself ought to be +taken into account.</p> + +<p>But such observations have been made upon the planet itself with just the +same result. Observers have seen streaks upon Mars—knotted, broken, +irregular, full of detail—and when the planet has receded to a greater +distance, the very same<span class="pagenum"><a name="Page_110" id="Page_110">[Pg 110]</a></span> marking has shown itself as a narrow straight +line, uniform from end to end, as if drawn with pen, ink and ruler. The +greater distance has caused the irregularities, seen when nearer at hand, +to disappear. In this, and not in any gigantic engineering works, is the +explanation of the artificiality of the markings on Mars as Prof. Lowell +sees them. That artificiality has already disappeared under better seeing +with more powerful telescopes.</p> + +<p>This chapter is entitled “The Illusions of Mars.” Yet the illusions of +Mars are not the straight lines and round dots of the canal system, but +the forced and curious interpretation which has been put upon them. If the +planet be within a certain range of distance and under examination with a +certain telescopic power, the straight lines and round dots are +inevitable. Their artificiality is not a function of the actual Martian +details themselves, but of the mode in which, under given conditions, we +are obliged to see them.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_111" id="Page_111">[Pg 111]</a></span></p> +<h2><a name="CHAPTER_IX" id="CHAPTER_IX"></a>CHAPTER IX</h2> +<p class="center"><span class="big">VENUS, MERCURY AND THE ASTEROIDS</span></p> + +<p class="dropcap"><span class="caps">Of</span> all the planets, Venus appears, to the unassisted eye, by far the +loveliest. When seen in the early morning before sunrise—its “western +elongation”—or after sundown in the evening—its “eastern +elongation”—and still more as it attains its greatest brilliancy, it has +attracted attention everywhere and in all ages. It then shines with +brilliance ten times as great as Jupiter in opposition, and the brightest +members of the heavenly host look pale and dim beside it. It is +emphatically the morning or the evening star, Lucifer, or Vesper, herald +or follower of the Sun; it can even assert itself in the presence of the +Lord of Day, for it has often been seen at noonday by watchers who knew +where to look; sometimes by the general crowd.</p> + +<p>But in the telescope Venus appears less satisfying. It is a pretty +spectacle indeed to watch the phases of the gleaming little globe of +silver, for, like the Moon under varying illumination from the Sun, it +undergoes change of apparent shape. But the surface of the planet yields +little detail, and that little is illusive and ill-defined. The<span class="pagenum"><a name="Page_112" id="Page_112">[Pg 112]</a></span> clear-cut +outlines and black shadows of the Moon have no place here, nor do the +ruddy plains and blue-grey “seas” of Mars find any analogues. All that can +be observed beyond the changes of phase are a few faint, ill-defined +patches, where the molten silver of the general surface is slightly dimmed +and tarnished, and perhaps one or two spots, not less evasive and +difficult to fix, that exceed the rest of the surface in brightness.</p> + +<p>This very difficulty in making out the markings on Venus is hopeful for +our search; it points to a veiling over the planet, a veiling by an +atmosphere. And the statistics of the Table show that Venus closely +resembles our Earth in size and mass, and therefore probably in +atmospheric equipment. If we assume that the atmosphere of any planet is +in direct proportion to its mass—and as Venus is so nearly the twin of +the Earth there is no reason to expect any great difference between the +two in this respect—the atmosphere of Venus would have a pressure of +about 11·2 lb. on the square inch, and the level of half pressure would be +nearly four miles above the surface. In other words the atmosphere would +be both thinner and deeper than that of the Earth, but the difference +would not be important in amount.</p> + +<p>But Venus is nearer to the Sun than the Earth, and receives nearly double +the light and heat. Its theoretical equatorial temperature is 368°abs., or +95°C, and its corresponding mean temperature<span class="pagenum"><a name="Page_113" id="Page_113">[Pg 113]</a></span> is 69° C. But water under a +pressure of 11·2 lb. will boil at 93° C, so that at the equator of Venus +the upper limit for water as a liquid is just passed, but, for the planet +in general, a fairly safe margin is maintained. Here then is sufficient +explanation why the topography of Venus is concealed. The atmosphere will +always be abundantly charged with water-vapour, and an almost unbroken +screen of clouds be spread throughout its upper regions. Such a screen +will greatly protect the planet from the full scorching of the Sun, and +tend to equalize the temperature of day and night, of summer and winter, +of equator and poles. The temperature range will be slight, and there will +be no wide expanses of polar ice. Water that flows will be abundant +everywhere.</p> + +<p>So far all the facts connected with Venus are favourable for life, even +though the picture called up to the mind may not seem inviting to us. For +views of the heavens must be rare; the Sun must seldom pierce through the +cloud veil; there is no moon and the stars must be almost always hidden. +The Earth with its Moon might form a beautiful ornament at times in the +midnight sky if the cloud-shell should occasionally open, but on the +whole, the planet is shut up to itself in a perpetual vapour-bath, and its +condition will approach that of some of the most humid countries in the +terrestrial tropics during the height of their rainy seasons.</p> + +<p><span class="pagenum"><a name="Page_114" id="Page_114">[Pg 114]</a></span>But it would seem that life both of plants and animals, under such +conditions, might flourish and be abundant. The mean temperature would +not, in general, be high enough to drive off the water as steam, nor low +enough to congeal it into ice; it would remain water—water that flows.</p> + +<p>But there is still a possible hindrance to life on Venus, a hindrance that +actually exists in the case of Mercury.</p> + +<p>Mercury, the “Twinkler,” is not an easy object in our Northern latitudes, +but, in countries near the tropics, is often quite conspicuous, a little +scintillating gem of light in the bright sky, before sunrise or after +sunset. In the telescope it is not so attractive as Venus, partly because +it is smaller, partly because, though it receives more than three times as +much light from the Sun, it is duller in hue. Yet it is not quite so +secretive as its neighbour, and a certain number of markings have been +detected upon its disc, markings which, like those of the Moon, appear to +be permanent.</p> + +<p>A glance at the Table will show that this was to be expected. In size, +Mercury comes between the Moon and Mars, and the atmospheric veil ought +therefore to be, as it evidently is, very slight and transparent; offering +little or no hindrance to an observer scanning it from another world. The +other necessary consequences of small size and mass will follow; the +feeble force of gravitation, the languid atmospheric circulation, the +extreme<span class="pagenum"><a name="Page_115" id="Page_115">[Pg 115]</a></span> range of temperatures, the low temperature at which water will +boil.</p> + +<p>But the heat to which Mercury is exposed far transcends our terrestrial +experience. In the mean it receives nearly seven times as much heat from +the Sun as the Earth does, but this supply is not maintained uniformly, +for Mercury moves round the Sun in a very eccentric orbit, so that when in +aphelion it receives, surface for surface, only about four times as much +heat as the Earth, but some six weeks later when in perihelion it receives +more than eleven times. The great range of temperature due to the thinness +of the atmosphere must therefore be further increased by the varying +distance of the planet from the Sun.</p> + +<p>A reference to Prof. Poynting’s figures shows that the mean temperature of +Mercury must approximate to 194° C., while water will boil at 40° C. or +even lower. Here, then, is a condition the exact reverse of Mars. Water as +a liquid will be rare on Mercury, not because it is congealed, but because +it is evaporated; on the dark side of the planet it may, indeed, pass into +ice, but on the side exposed to the Sun it must exist normally as a +constituent of the atmosphere. Water in a liquid state, water that flows, +must be almost unknown.</p> + +<p>But we have good reason to believe that that which is the dark side of +Mercury at one time is always dark; that which is exposed to the Sun is +always exposed to it.</p> + +<p><span class="pagenum"><a name="Page_116" id="Page_116">[Pg 116]</a></span>Since Mercury wears no concealing veil of atmosphere, and displays +markings that can be identified and followed, a surprising circumstance +has come to light. In 1889, Schiaparelli discovered that Mercury, instead +of rotating on its axis in about 24 hours like the Earth and Mars, rotates +in 88 days; that is to say, it always turns the same face towards the Sun, +just as the Moon turns the same face towards the Earth. This fact, +confirmed theoretically by Prof. G. H. Darwin in his development of the +theory of tidal friction, puts the condition of Mercury in quite a new +light. No alternation of day or night refreshes and restores the little +world; one hemisphere is for ever exposed to the blasting heat of the Sun, +seven times hotter for it than for the Earth; the other hemisphere is for +ever exposed to the darkness and cold of outer space, a range from +something like 390° C. above freezing-point, to 270° C. below. It is true +that between the two hemispheres there is a “debatable land,” for, owing +to the ellipticity of the orbit, the face turned to the Sun is not exactly +the same at all times, and a region about 47° in width on each side of the +planet, that is to say, rather more than a quarter of its entire surface, +has one day and one night in each period of 88 days, but these more +favoured sections can scarcely be considered more habitable than the rest.</p> + +<p>The conditions of Mercury are so unfavourable for life that, even if this +remarkable relation of<span class="pagenum"><a name="Page_117" id="Page_117">[Pg 117]</a></span> rotation period to revolution did not hold good, +it would still be impossible to regard it as a world for habitation. But +its case shows that a further condition of habitability has to be +satisfied by a planet. Size and distance from the Sun afford the first two +conditions; a suitable rotation period is now seen to be a third.</p> + +<p>And it is possible that in this very particular Venus fails to qualify. +Schiaparelli, the first observer of his time, assisted by the clear +Italian sky, believed that he had demonstrated that Venus, like Mercury, +rotates once in her year; her day being thus equal in length to 225 of +ours, and the face that she turns to the Sun being always the same.</p> + +<p>And in her case this statement requires practically no qualification, for, +her orbit being nearly circular, there is hardly any libration; a place +that has the Sun in its zenith has it so for ever; one on the night side +of Venus can never have a sunrise, or gladden in the daylight. The side +exposed to the Sun will wither in a temperature of about 227° C., in which +all moisture will be evaporated; the side remote from it will be bound in +eternal ice. In neither hemisphere will water exist in the liquid state; +in neither hemisphere will life be possible.</p> + +<p>But as yet the evidence is not conclusive that Venus has this long +rotation period. Several observers of high rank believe that our neighbour +rotates in nearly the same time as the Earth, but<span class="pagenum"><a name="Page_118" id="Page_118">[Pg 118]</a></span> its markings are so +faint and elusive that the problem is a difficult one. The spectroscopic +method of determining the speed of rotation has been equally indecisive. +Until, therefore, the rotation period has been decided, the habitability +of Venus must remain in question. If it always turns the same face to the +Sun, there can be no more life upon it than upon Mercury; if on the +contrary it rotates in much the same time as the Earth, then, so far as we +know, it may well be a habitable world. Whether it is actually inhabited +is a matter at present entirely beyond our knowledge.</p> + +<p>A page or two back we touched lightly on the eccentricity of the orbit of +Mercury—lightly, because it was not the chief factor in disabling the +planet for habitation. But the condition introduced by this eccentricity +is one which of itself would be sufficient to put it out of court. In the +six weeks in which Mercury moves from aphelion to perihelion, it +approaches the Sun by fourteen millions of miles, and the heat received by +it is increased 2½ times. Then, in the next six weeks, it recedes as +far, and there is a like diminution. In other words, six weeks makes a +greater proportional change in this one planet’s condition than we should +experience if our Earth were transported from its own orbit to that of +Mars.</p> + +<p>But there are other members of the solar system whose orbits are so +elongated that that of Mercury<span class="pagenum"><a name="Page_119" id="Page_119">[Pg 119]</a></span> seems in comparison almost circular. These +are the comets, some of which all but graze the surface of the Sun at +perihelion, and then recede from him for periods that it takes even +thousands of years to complete. But without dwelling on such extreme +cases, two of the best known of the periodic comets may be taken as +examples of the rest. Encke’s is the comet of shortest period, returning +in about 3·3 years. At perihelion it is 31 millions of miles from the Sun; +one-third the distance of the Earth. It receives, therefore, at this part +of its orbit, 9 times as much light and heat as the Earth. But at aphelion +it retreats deep into the region of the asteroids, and is much more than +four times the mean distance of the Earth. At this part of its orbit it +receives but <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">17</span>th as much heat as the Earth. By far the most famous of +all the comets is that known by the name of Halley, and its mean period is +76 years. At perihelion it comes within the orbit of Venus; indeed, nearly +halfway between that and the orbit of Mercury. At aphelion it recedes to +thirty-five times the distance of the Earth, far beyond the orbit of +Neptune. The range in its light and heat from the Sun is from 3 times that +of the Earth to less than <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">1200</span>th; or, in other words, the supply of heat +at one time is nearly 4000 times that at another, and of the 76 years of +its period, only 80 days are spent within the orbit of the Earth.</p> + +<p>Comets cannot be homes of life; they are not<span class="pagenum"><a name="Page_120" id="Page_120">[Pg 120]</a></span> sufficiently condensed; +indeed, they are probably but loose congeries of small stones. But even if +comets were of planetary size it is clear that life could not be supported +on them; water could not remain in the liquid state on a world that rushed +from one such extreme of temperature to another.</p> + +<p>Between the orbits of Mars and Jupiter there are scattered an untold +number of little planets commonly known as asteroids or minor planets. +Minor planets indeed they are, for the one first +discovered—Ceres—probably outweighs all the rest, known and unknown, put +together, though something like 700 have already been detected, and the +list grows at the rate of about one a week.</p> + +<p>As the Table shows, Ceres is so small that the Earth exceeds it in volume +5000 times; even the Moon is 90 times as large. The mass of Ceres is not +known; being so small, its density is probably less than that of the Moon, +so that the Earth may easily outweigh it 10,000 times. The unfavourable +conditions resulting from smallness of size that the Moon presents are +therefore exaggerated exceedingly in the case of Ceres; its atmosphere +must approach in tenuity what we should regard as a vacuum in a +terrestrial laboratory, and water as a liquid be entirely unknown. Its +distance from the Sun is another hostile factor; for in consequence it +receives per unit of surface only 13 per cent of the light and heat that +falls on the Earth; its maximum temperature under a zenith Sun will<span class="pagenum"><a name="Page_121" id="Page_121">[Pg 121]</a></span> fall +far below freezing-point, the minimum on the dark side will approach the +absolute zero.</p> + +<p>With Ceres the whole of the asteroidal family can be dismissed as possible +abodes of life. No astronomer can regard them as such. Yet they have their +lesson to teach. Life can exist on the Earth only on the upper face of its +crust, and in a very thin film of air and water; but the enormous solid +bulk within, inert though it be, that supports the stage on which the +great drama of life is played, is as really essential as air and water +themselves. If that bulk were much smaller and less massive life could +find no place upon its surface.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_122" id="Page_122">[Pg 122]</a></span></p> +<h2><a name="CHAPTER_X" id="CHAPTER_X"></a>CHAPTER X</h2> +<p class="center"><span class="big">THE MAJOR PLANETS</span></p> + +<p class="dropcap"><span class="caps">It</span> is a striking change to pass from Ceres, the giant of the minor +planets, to Jupiter, the giant of the major planets. Instead of a world +that the Earth exceeds in volume 5000 times, we are confronted by one that +exceeds the Earth 1400 times. Ceres, when viewed through a large +telescope, is just able to present a perceptible disc; Jupiter offers the +largest shown by any heavenly body after the Sun and Moon.</p> + +<p>And that disc is one that never fails to charm the attentive student, for +it abounds in colour, movement and change. The late Prof. James Keeler, an +observer of the first rank, having the advantage of observing the planet +from the summit of Mt. Hamilton and with the great 36-inch telescope of +the Lick Observatory, thus describes the aspect of the planet in 1889.</p> + +<p class="blockquot">“Seen with this instrument on a fine night, the disc of Jupiter was a +most beautiful object, covered with a wealth of detail which could not +possibly be accurately represented in a drawing.... Scarcely any +portion of Jupiter, except the Red Spot and the extreme polar regions, +was of a <span class="pagenum"><a name="Page_123" id="Page_123">[Pg 123]</a></span>uniform tint, the surface being mottled with flocculent and +more or less irregular cloud masses.... The equatorial zone, occupying +the space between the red belts, was marked in the centre by a +salmon-coloured stripe, which was occasionally interrupted by an +extension of the white clouds on the sides of the zone. The edges were +brilliant white, and were formed of rounded cloud-like masses, which +at certain places extended into the red belts as long streamers.... +Near their junction with the equatorial zone, the streamers were white +and definite in outline, but they became redder in tint toward their +outer extremities, and more diffuse, until they were lost in the +general red colour of the background. When the seeing was good they +were seen to be formed of irregular rounded or feathery clouds, fading +toward the outer ends, until the structure could no longer be +distinguished.... The portions of the equatorial zone surrounding the +roots of well-marked streamers were somewhat brighter than at other +places, and it is a curious circumstance that they were almost +invariably suffused with a pale olive-green colour, which seemed to be +associated with great disturbance, and which was rarely seen +elsewhere.... The red belts presented on all occasions the appearance +of a passive medium, in which the phenomena of the streamers and other +forms ... were manifested. The phenomena would be exactly reproduced +by streamers of cloudy white matter floating in a semi-transparent +reddish fluid, sometimes submerged and sometimes rising to the +surface.... The dark spots frequently seen on the red belts usually +occupied spaces left by sharp turns in the streamers, and they were of +the same<span class="pagenum"><a name="Page_124" id="Page_124">[Pg 124]</a></span> colour as the belts, but deeper in tint, as if the fluid +medium could be seen to a greater depth.”<small><a name="f15.1" id="f15.1" href="#f15">[15]</a></small></p> + +<p>In other words, Jupiter is a striped or banded planet, the bands lying +along the direction of turning. These bands are coloured in varying tints, +and the planet rotates very rapidly, for the details in the bands pass +quickly from one limb to the other. And not only is the speed of rotation +of the whole very rapid—Jupiter turns about its axis in a little less +than ten hours, so that a particle at its equator moves through 466 miles +in each minute—but the various items that form the bands rotate in +different times. They may also alter their form and their colour. Jupiter +seems, then, to be a planet with a great and rapidly changing atmosphere +that extends above a shoreless sea formed of some liquified substance or +substances—the whole in a state of flux.</p> + +<p>But if we turn back to the Table, we see that Jupiter at its mean distance +from the Sun is 5·2 times that of the Earth; that is to say, it receives +only <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">27</span>th of the light and heat that we receive. But in Chapter VIII, we +learnt from Mars that as this receives only <span style="font-size: 0.8em;"><sup>3</sup></span>⁄<span style="font-size: 0.6em;">7</span>ths of the Earth’s light +and heat, its mean temperature would sink to -30°C.; the Earth’s being +16°C. Mars is therefore almost always a frozen planet; frozen except on +its mere surface when this is exposed to the full rays of the Sun. No sea +there would ever be<span class="pagenum"><a name="Page_125" id="Page_125">[Pg 125]</a></span> melted to a depth of more than a few inches, even at +noonday in midsummer. And yet Mars has at least ten times the advantages +of Jupiter. Jupiter, then, must be a frozen planet through and through; no +liquid of any sort can exist on its surface; no vapour of any substance +can exist in its atmosphere. It must be icebound even at its summer +noonday.</p> + +<p>Yet, from the description given by Prof. Keeler, it is manifestly not so; +and another item in the Table emphasizes that it cannot be so. The density +of the Sun is 1·4 that of water, Jupiter’s is 1·33, showing that but a +very small proportion (if any) of its bulk can be solid; the rest must be +vaporous, or at least fluid. How then can we reconcile these +inconsistencies?</p> + +<p>It is in the dimensions of Jupiter that we find the answer. The mass of +the planet is 317 times that of the Earth; it is indeed nearly three times +as great as that of all the other planets put together. But the +aggregation of so vast an amount of material is of itself a source of +heat; the chief source at the present time of the enormous output of heat +from the Sun is ascribed to its gradual contraction; the slow falling of +its substance, if we may so express it, a little nearer to its centre. The +great mass of Jupiter points to its inherent store of heat being much +greater than that of any other planet. And of two bodies equally hot, the +larger must cool more slowly than the smaller. If, therefore, all the +members of the solar system had at<span class="pagenum"><a name="Page_126" id="Page_126">[Pg 126]</a></span> one and the same moment possessed the +same surface temperature, that equality would have ceased directly they +began to radiate their heat into space; the temperature of the smaller +bodies falling more rapidly than those of the larger. This is another +example of the principle that has already been noted, that the properties +of a small world are not those of a large world divided by a constant +factor. It is not possible to conceive a model of the solar system in +which all the significant factors should be true to the same scale. If the +diameters and distances were all made on a one-tenth scale, the surfaces +would be one-hundredth of reality, the volumes one-thousandth.</p> + +<p>But a radiating body radiates from its surface, while the store of heat +from which that radiation is kept up is supplied by its volume. It +follows, therefore, that a large and heavy world must differ from a small +light world, not merely in scale, but also in kind.</p> + +<p>The surface of a world is all that we see of it; it is, therefore, very +commonly all that we consider. But unseen, and hence often unconsidered, +beneath the surface lies its substance or mass, and it is this that +determines the state and condition of the surface; it is the underlying +power. Two men may be contending in a financial struggle; to the eye they +may look alike, equally prosperous; both may have the same amount of money +actually in their pockets; but the one has nothing else,<span class="pagenum"><a name="Page_127" id="Page_127">[Pg 127]</a></span> the other has a +great banking account and vast investments, and is, in fact, a +millionaire; and it is his unseen power and resources that will make +themselves felt.</p> + +<p>Jupiter therefore introduces us to a new factor in world-condition; not +all its heat is derived from the Sun; much is inherent to it. And though +it is not possible at present to say that the mass of Jupiter being so +much its inherent heat must be this or that quantity as a function of that +mass, yet in general, and neglecting other considerations, we can say that +of two worlds the one with the greater mass will be that with the higher +inherent temperature. This factor of inherent temperature was one that did +not require to be noticed in dealing with the Moon, or Venus, or Mars, for +these and all the planets yet noticed are less in size, surface, volume, +and mass than the Earth, and hence possess less inherent heat. It is only +now that the greater planets are being considered that the question of a +source of heat, other than the Sun, can arise.</p> + +<p>But the evidence of such heat on Jupiter is not to be disputed. The albedo +or reflective index of Jupiter has been put by the late Prof. G. Bond, of +Harvard College Observatory, as higher than unity; in other words, that it +emits more light than it receives. This is now generally regarded as an +excessive estimate, but the albedo of the disc as a whole cannot be put +lower than 0·72, or about that of white paper. But many of the “belts” or<span class="pagenum"><a name="Page_128" id="Page_128">[Pg 128]</a></span> +dark regions are of a dull copper tint, and the polar caps are dusky, so +that Bond’s estimate must be realized for the most brilliant “zones,” as +the brighter regions are called; certainly for the whitest of the white +spots.</p> + +<p>No direct evidence of inherent luminosity has been obtained, for the +satellites disappear entirely in eclipse. But though their shadows in +transit appear very dark, it is clear that they are not absolutely black, +since sometimes such a shadow is not distinguishable in darkness from the +satellite that casts it; a delicate proof that the background on which it +falls has some intrinsic luminosity.</p> + +<p>Unless there is the counteracting effect of a high temperature, the +atmosphere of Jupiter would have a pressure at the surface of 104 lb. to +the square inch, and the level of half pressure be attained at a mile and +a quarter; the reverse condition to that on Mars would obtain, and the +atmosphere of Jupiter would be much denser and much shallower than that of +the Earth. Denser it probably is; shallower it cannot be, for the great +white spots, each often five or six thousand miles in diameter, that range +themselves at times along the equatorial regions till they look like the +portholes of a ship, evidently rise from depths great even as compared +with their size. But it is only by intense heat that the effect of the +great mass of Jupiter in constricting its atmosphere within shallow depths +can be overcome.</p> + +<p><span class="pagenum"><a name="Page_129" id="Page_129">[Pg 129]</a></span>Again, the extraordinary lightness of the planet, so little above the +density of water, points in the same direction. So, not less unmistakably, +do the magnitude and rapidity of the atmospheric movements. The clouds and +storms of our own atmosphere are worked by solar heat; solar heat it is +that draws up the vapours and provides the chief part of the energy +manifested in the speed and strength of the air-current. But solar heat +can only give <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">27</span>th the amount of that energy at the distance of Jupiter, +so that, if they were entirely dependent on solar radiation, the winds of +Jupiter should be very feeble.</p> + +<p>Further, the difference of presentment due to the difference of latitude +is a fruitful cause of inequalities of temperature and pressure in the +terrestrial atmosphere. But as a degree of latitude on Jupiter is eleven +times as wide as on the Earth, such inequalities connected with a given +difference in latitude are spread over eleven times the distance that they +would be on the Earth, and are, therefore, so much the less pronounced. +Yet, across a gulf of 400 millions of miles we can clearly discern the +bright zones of Jupiter now narrowing down and constricting the red belts, +now thrust apart by them, and can detect changes taking place in an hour +of time over areas equal to that of a terrestrial hemisphere.</p> + +<p>A notable peculiarity of Jupiter is found in the proper motions of its +spots. Many of the white<span class="pagenum"><a name="Page_130" id="Page_130">[Pg 130]</a></span> spots are exceedingly swift, giving a rotation +period of 9h. 50m. while the equatorial belt in general gives a period 5m. +longer; so that in 119 rotations (nearly 49 days) a white spot will have +passed entirely round the belt, gaining upon it at a rate of nearly 240 +miles an hour.</p> + +<p>The most famous of all the markings in Jupiter is the Great Red Spot, +which became conspicuous in 1878, since when the spot itself, or at least +the nest in which it lay, has always been visible. It has been identified +with a great red spot observed by Hooke and Cassini in 1664-6, that +appeared and vanished again eight times between 1665 and 1708. It +therefore has had a history practically as long as our telescopic +knowledge of the planet, and may be looked upon as in some sort a +permanent feature. Yet that it is not in the nature of a portion of a +solid crust is clear. It occupies on Jupiter much the position and +relative area of Australia on the Earth, but whereas Australia of +necessity rotates in one piece with all the other continents, the Great +Red Spot has a rotation period which is neither that of the equatorial +belt, nor of the quickly moving white spots, and is not itself stable. An +“Australia on the loose” is impossible, even unthinkable here, but the +Great Red Spot, for all its long duration, is mobile and inconstant, and +is therefore no portion of a solid permanent crust.</p> + +<p>The giant planet Jupiter, therefore, offers us an<span class="pagenum"><a name="Page_131" id="Page_131">[Pg 131]</a></span> example of what we may +call a “semi-sun”; a world still bubbling with tremendous energies of its +own, still pulsing with its own inherent heat, still without a solid +crust; probably without a solid nucleus, liquid or vaporous throughout. +Whatever the future may hold for such an orb, it is clearly no world for +habitation at present. Full of colour, and movement, and change as it is, +it lacks the Earth’s “gloom of iron substance,” which is necessary, no +less than its veiling by the plant, as a stage for “the passion and +perishing of mankind.”</p> + +<p>But if Jupiter be a semi-Sun, still a source of heat, perhaps even of +light, can it yield the means of life to its satellites? For Jupiter is +sun-like, not merely in its own condition, but also in that it is the +centre and ruler of a system of its own. We know already of eight +satellites revolving round it.</p> + +<p>Of these eight, only four—the four discovered by Galileo, in the first +days of his possession of a telescope—need be considered; the other four +are of the same order of size as the asteroids, and are indeed much +smaller than Ceres.</p> + +<p>But the Galilean satellites are of a higher rank. Europa, the smallest, is +in size a twin to the Moon; Callisto, the outermost, is almost exactly the +size of Mercury; Io, the innermost, is midway between the two in its +dimensions. But Ganymede, the largest, is almost comparable with Mars, its +diameter being 0·45 that of the Earth instead of the 0·53 of Mars.</p> + +<p><span class="pagenum"><a name="Page_132" id="Page_132">[Pg 132]</a></span>But the Moon, Mercury, and Mars have all been shown, on the ground of +their small size, to be worlds unfit for habitation; the satellites of +Jupiter are, therefore, all rejected on the same score. Nor can the +greater nearness of their immediate primary compensate for their +remoteness from the Sun. It is true that Jupiter presents to Ganymede a +disc with more than 200 times the apparent area that the Sun presents to +the Earth, but to make up for the falling-off of the solar radiation, each +unit of this area should radiate about <span style="font-size: 0.8em;"><sup>1</sup></span>⁄<span style="font-size: 0.6em;">250</span>th as much heat as each unit +of the Sun’s surface. In other words, the absolute surface temperature of +Jupiter should be ¼th that of the Sun, or about 1550° C., and this is +higher than can be admitted. The Sun and Jupiter together cannot put +Ganymede in as favourable a position as Mars, much less as favourable as +the Earth.</p> + +<p>The case of Jupiter carries with it those of Saturn, Uranus, and Neptune. +All three, from their high albedoes and low densities, are still in a +vaporous condition; still in some sort, semi-Suns; sources of a certain +amount of heat, and not recipients merely. The days are yet far distant +when a solid crust can form on any one of them, and the water condense +from the steamy atmosphere to form oceans, seas, and rivers. Not till +then, if at all, when water as a liquid, water that flows, is present, can +life begin to appear and enter on its long course of change.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_133" id="Page_133">[Pg 133]</a></span></p> +<h2><a name="CHAPTER_XI" id="CHAPTER_XI"></a>CHAPTER XI</h2> +<p class="center"><span class="big">WHEN THE MAJOR PLANETS COOL</span></p> + +<p class="dropcap"><span class="caps">The</span> question has been asked: “It is evident that life cannot exist at the +present time on the outer planets, since they are in a highly heated and +quasi-solar condition; but when they cool down, as cool they must, and a +solid crust is formed, may not a time come when they will be habitable? It +seems impossible to think that worlds so beautiful to our eyes and so vast +in scale are destined never to be peopled by intelligent beings.”</p> + +<p>It is clearly difficult to answer satisfactorily a question that requires +so deep a plunge into the recesses of the unknown future; yet, so far as +our knowledge goes, there is no reason to think that Jupiter will be more +habitable then than it is now. The difficulty of the small supply of light +and heat received from the Sun would apparently still remain, if indeed, +the cooling of the Sun itself would not increase it. We do not know of any +means by which our Sun could so increase its radiation as to supply to +Jupiter from 25 to 30 times as much heat as it now receives, and this +would be necessary to place it in the same favoured condition as the +Earth. If so great a change were<span class="pagenum"><a name="Page_134" id="Page_134">[Pg 134]</a></span> to take place in the Sun, life would be +scorched out of existence on all planets nearer than Jupiter, and, +similarly, if the solar emission were increased to meet the necessities of +Uranus or Neptune, even Jupiter would fall a victim.</p> + +<p>But we may consider it as a conceivable case that a planet of the exact +dimensions of Jupiter may be revolving in an annual period of the same +length as his, round some star that is capable of affording it adequate +nourishment; and so with the three other giant planets. The actual Jupiter +and Saturn of the solar system have, so far as we can tell, neither +present nor future as habitable worlds, but we can consider what would be +the case of imaginary bodies of similar dimensions in systems where the +supply of heat would be sufficient. Or we can neglect the question of +temperature altogether, as we did at first in the case of Mars.</p> + +<p>All the four planets must shrink much in volume before their +solidification will take place. Their average density at present but +little exceeds that of water; indeed, Saturn is not so dense as water; yet +we must suppose that the same elements are in general common to the Earth +and to them all. If we assume, then, that the four planets all cool to the +point of solidification, their densities must be much increased, and their +volumes correspondingly diminished. Since all four greatly exceed the +Earth in mass, it is but natural to expect that, when they<span class="pagenum"><a name="Page_135" id="Page_135">[Pg 135]</a></span> have assumed +the terrestrial condition, they will be more closely compacted than the +Earth, and their densities in consequence will be greater. It will, +however, be simpler if we assume exactly the same density for them as for +the Earth. Jupiter will then have shrunk to about one-fourth of its +present volume, and the statistics for the four planets will run as in the +following Table:</p> + +<p class="center"><span class="smcap">Statistics of the Four Outer Planets if with the Same Density as the Earth</span></p> + +<table border="0" cellpadding="0" cellspacing="5" summary="table"> +<tr><td colspan="3"><span class="smcap">Proportions of the Planets</span>:—</td></tr> +<tr><td> </td> + <td> </td><td><span class="spacer"> </span></td> + <td align="center">Uranus</td><td><span class="spacer"> </span></td> + <td align="center">Neptune</td><td><span class="spacer"> </span></td> + <td align="center">Saturn</td><td><span class="spacer"> </span></td> + <td align="center">Jupiter</td></tr> +<tr><td><span style="margin-left: 1em;">Diameter in miles</span></td> + <td> </td><td> </td> + <td align="center">19300</td><td> </td> + <td align="center">20400</td><td> </td> + <td align="center">36000</td><td> </td> + <td align="center">54000</td></tr> +<tr><td align="center">do</td> + <td align="center">⊕ = 1</td><td> </td> + <td align="center"><span style="margin-left: 1em;">2·44</span></td><td> </td> + <td align="center"><span style="margin-left: 1em;">2·57</span></td><td> </td> + <td align="center"><span style="margin-left: 1em;">4·56</span></td><td> </td> + <td align="center"><span style="margin-left: 1.5em;">6·82</span></td></tr> +<tr><td><span style="margin-left: 1em;">Surface,</span></td> + <td align="center">⊕ = 1</td><td> </td> + <td align="center"><span style="margin-left: .5em;">6·0</span></td><td> </td> + <td align="center"><span style="margin-left: .5em;">6·6</span></td><td> </td> + <td align="center">20·8</td><td> </td> + <td align="center"><span style="margin-left: 1em;">46·6</span></td></tr> +<tr><td><span style="margin-left: 1em;">Mass and Volume,</span></td> + <td align="center">⊕ = 1</td><td> </td> + <td align="center">14·6</td><td> </td> + <td align="center">17·0</td><td> </td> + <td align="center">94·8</td><td> </td> + <td align="center">317·7</td></tr> +<tr><td><span style="margin-left: 1em;">Gravity at surface,</span></td> + <td align="center">⊕ = 1</td><td> </td> + <td align="center"><span style="margin-left: 1em;">2·44</span></td><td> </td> + <td align="center"><span style="margin-left: 1em;">2·57</span></td><td> </td> + <td align="center"><span style="margin-left: 1em;">4·56</span></td><td> </td> + <td align="center"><span style="margin-left: 1.5em;">6·82</span></td></tr> +<tr><td colspan="2">Rate of Fall, Feet in the First Second</td><td> </td> + <td align="center">39·2</td><td> </td> + <td align="center">41·3</td><td> </td> + <td align="center">73·3</td><td> </td> + <td align="center">109·7</td></tr> +<tr><td> </td></tr> +<tr><td colspan="2"><span class="smcap">Atmosphere</span>, assuming the total mass of<br /><span style="margin-left: 1em;">the atmosphere to be proportional to</span><br /> +<span style="margin-left: 1em;">the mass of the planet:—</span></td></tr> +<tr><td colspan="2">Pressure at the surface in lb. per square inch</td><td> </td> + <td align="center">88·2</td><td> </td> + <td align="center">97·0</td><td> </td> + <td align="center">305·8</td><td> </td> + <td align="center">685·0</td></tr> +<tr><td colspan="2">Pressure at the surface in “atmospheres”</td><td> </td> + <td align="center"><span style="margin-left: .5em;">6·0</span></td><td> </td> + <td align="center"><span style="margin-left: .5em;">6·6</span></td><td> </td> + <td align="center"><span style="margin-left: .5em;">20·8</span></td><td> </td> + <td align="center"><span style="margin-left: .5em;">46·6</span></td></tr> +<tr><td colspan="2">Level of half-pressure in miles</td><td> </td> + <td align="center"><span style="margin-left: 1em;">1·37</span></td><td> </td> + <td align="center"><span style="margin-left: 1em;">1·30</span></td><td> </td> + <td align="center"><span style="margin-left: 1.5em;">0·73</span></td><td> </td> + <td align="center"><span style="margin-left: 1.5em;">0·49</span></td></tr> +<tr><td colspan="2">Boiling point of water at surface</td><td> </td> + <td align="center">127°C</td><td> </td> + <td align="center">129°C</td><td> </td> + <td align="center">148°C</td><td> </td> + <td align="center">164°C</td></tr></table> + +<p><span class="pagenum"><a name="Page_136" id="Page_136">[Pg 136]</a></span>Jupiter offers two peculiarities. In its shrunken condition, its diameter, +instead of being eleven times that of the Earth, will be not quite seven, +and the force of gravity at the surface will be greater than that of the +Earth in the same proportion. A man who here weighs 150 lb. will there +weigh over 1000 lb.; and the muscular effort of movement will be increased +in the same ratio. The athlete who here can clear a height 5 ft. 8 in. +will there, with like pains, surmount 10 inches; and other efforts will be +in the same proportion. The atmosphere, supposing it to be in proportion +to the mass of Jupiter, will exercise a pressure of 46½ “atmospheres,” +or more than 680 lb., to the square inch. Following on this enormous +pressure at the surface would be the rapidity with which the atmosphere +would thin out in the upward direction. The level of half-pressure would +be attained by ascending less than half a mile in height; that is to say, +there would be a difference of pressure of 340 lb. on the square inch from +that experienced at the sea-level. We know from the fact that fishes live +at enormous depths in the ocean, that living organisms can be constructed +to endure great pressures, but they are not constructed to endure great +alterations of pressure. The deep-sea fishes are as instantly killed by +being brought up to the surface, as the surface fishes or the land animals +would be if they were plunged into the depths. And it is clear that on +Jupiter a<span class="pagenum"><a name="Page_137" id="Page_137">[Pg 137]</a></span> low range of hills that on the Earth would be considered only +an easy climb, would be an impassable barrier, not only from the immense +exertion of mounting it, but chiefly from the unendurable change of +pressure which the ascent would involve.</p> + +<p>The sevenfold gravity of Jupiter, taken in connection with this enormous +atmospheric pressure, would tend to make the meteorological disturbances +of the planet violent far beyond anything of which the Earth can furnish +an example. The atmosphere would possess a high viscosity, and differences +in condition, pressure and saturation would tend to accumulate, until at +length the balance would be restored with explosive suddenness and force. +Here our most violent tornadoes may reach a speed of 100 miles an hour; on +Jupiter, gales of five or six times that velocity would be common. We +cannot conceive that living organisms would be able to grow, flourish and +multiply where the conditions were so cataclysmic.</p> + +<p>This difficulty must always exist where the planet is great in mass, and +the force of gravity high at the surface. The case of Saturn is not so +extreme as that of Jupiter, though it is probably sufficiently severe to +exclude it from the ranks of worlds that could ever be dwelt in. The +atmospheric pressure would be about 21 “atmospheres,” or more than 300 lb. +on the square inch. The<span class="pagenum"><a name="Page_138" id="Page_138">[Pg 138]</a></span> level of half-pressure would be reached at about +three-quarters of a mile, and the force of gravity be nearly 4½ times +that of the Earth.</p> + +<p>But the serious condition for Saturn would come from that feature which +renders it by far the most attractive of all the planets seen in the +telescope, the presence of the wonderful Ring system.</p> + +<p>To us, viewing Saturn from afar, and from practically the same direction +as the Sun, the Rings are seen lit up; but to a dweller on Saturn, the +Rings during the day are between his world and the Sun, and hence turn +their dark side toward him. More than that, the telescope shows us that +the Rings cast a shadow on the planet; in other words, they eclipse part +of it; and this shadow changes its position with the progress of the +Saturnian year. Proctor computed that if the Rings were a hundred miles in +thickness, the equator would suffer, in consequence, total eclipse for +nearly ten days at each equinox, and partial eclipse for about forty days +more. Moving away from the equator, each higher latitude would have a +longer and longer period of eclipse in the winter half of its year; the +higher the latitude, the later after the autumnal equinox the eclipse +would begin, and the longer it would last, until about latitude 40° was +reached. Here the eclipses would begin nearly three terrestrial years +after the time of the autumnal equinox. At first the Sun would be eclipsed +only in the morning and evening of each day, but the length of<span class="pagenum"><a name="Page_139" id="Page_139">[Pg 139]</a></span> the daily +eclipse would increase, until the Sun was hidden the whole day long. This +period of total eclipse would last for about 6 years 8 months, terrestrial +reckoning, or with the periods of partial eclipse, 8 years and nearly 10 +months. Whatever the efficiency of the Sun that afforded light and heat to +such a planet, it is clear that such eclipses must be fatal to life in two +ways: light and heat would be cut off from wide regions of the planet for +long periods of time, and terrible meteorological convulsions must follow +in the train. Here on the Earth, though a total eclipse generally lasts +only two or three minutes, the atmospheric disturbance is perceptible, and +the fall of temperature very marked, and it does not require much +reflection to see that the analogous disturbance in an atmosphere twenty +times as dense must be terrific indeed during an eclipse that lasts not a +few minutes only, but for more than six of our years.</p> + +<p>The case of Uranus introduces us to another class of conditions fatal to +habitability. The equator of Jupiter is inclined only 3° to the plane of +its orbit; the difference in its seasons is, therefore, almost +imperceptible; there is hardly any alteration in the incidence of the +solar rays; it is, as if on the Earth, the height of the Sun at noon in +mid-winter were what it actually is on the 14th of March, and its height +at midsummer the same as we observe on March 28. The inclination of the +equator of Saturn is considerably greater than<span class="pagenum"><a name="Page_140" id="Page_140">[Pg 140]</a></span> that of Mars or the Earth, +so that its seasons are more pronounced, but not to an extent that would +introduce any radical difference. But for Uranus, the inclination of the +equator to the plane of the orbit is 82°. If this were the case for the +Earth, the noonday sun for London would be, at the spring equinox, 38½° +high as at present, but its altitude day by day would increase with great +rapidity, and before the end of April, the Sun at noon would be right in +the zenith, and 13° above the horizon at midnight. At midsummer, indeed, +it would be only 59° high at noonday, but it would be north of the zenith +instead of south, and at technical midnight, it would still be 44° in +altitude, thus moving round in a very small circle, only 15° in diameter. +From about April 18 to August 25—that is to say, for 129 days—the Sun +would never set, and unlike the summer day of our own polar regions now, +wherein the Sun, though always present, is always low down in the sky, for +much of that period it would pass the meridian quite close to the zenith.</p> + +<p>As the year of Uranus is 84 times the length of our year, the London of +Uranus would have to endure not far short of 30 years continuous +scorching.</p> + +<p>And the winter would be as long; the perpetual day of summer would be +replaced by a night as enduring. More than 29 years of unbroken darkness, +of unmitigated cold, cannot possibly ever<span class="pagenum"><a name="Page_141" id="Page_141">[Pg 141]</a></span> consist with the conditions +necessary for life upon a planet. Whatever the brightness of the imagined +sun of Uranus, if for 29 years at a time that sun were below the horizon, +the water on the planet must be congealed, and during the 29 years of +unbroken day all the water would be as certainly evaporated.</p> + +<p>Thus, though Uranus is not burdened by the enormous mass of Jupiter, nor +overshadowed, like Saturn, by a system of rings, the extraordinary +inclination of its axis introduces a condition which is as fatal to it, as +a world to dwell in, as any of the disabilities of the other planets.</p> + +<p>It is curious that these four outer planets, that resemble each other so +strikingly in many of their conditions—in their vast size, high albedo, +low density, and vaporous envelopes, that show, in their spectra, not +merely the lines of reflected sunlight, but also special lines due to +their own atmospheres (the chief of these being common to all the four +planets)—should yet, in the inclination of their axes to the plane of +their orbits, display every possible variety. The axis of Jupiter is +almost normal to its orbit, that of Uranus lies almost in the plane of its +orbit. The axes of Saturn and Neptune have a mean inclination, but it +would appear that the rotation of Neptune is in the reverse direction to +that of planets in general, so that the true inclination is usually taken +as being the complement of the observed angle, as<span class="pagenum"><a name="Page_142" id="Page_142">[Pg 142]</a></span> if the axis were turned +right over. It is uncertain whether this would have any important effect +upon the habitability of the planet, but it supplies the fourth possible +case for the position of the axis.</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_143" id="Page_143">[Pg 143]</a></span></p> +<h2><a name="CHAPTER_XII" id="CHAPTER_XII"></a>CHAPTER XII</h2> +<p class="center"><span class="big">THE FINAL QUESTION</span></p> + +<p class="dropcap"><span class="caps">In</span> passing in review the various members of the solar system, it has been +seen that there are many conditions that have to be fulfilled before a +planet can be regarded as the possible abode of life, because there are +many conditions necessary in order that water may exist on its surface in +the liquid state. The size and mass of the planet are restricted within +quite narrow limits; and a world much larger or much smaller than our own +is necessarily excluded. The supply of light and heat received from the +Sun must not fall much below that received by the Earth, nor greatly +exceed it; in other words, the distance of the planet from its Sun is +somewhat precisely fixed, since the light and heat vary inversely not as +the distance, but as its square. Of course, in different systems, with +suns of different power, the most favourable distance will not be the same +in each; but in any system there will be one most advantageous distance, +and no great departure from it will be possible. This condition further +implies that the planetary orbits must be nearly circular; pronounced +eccentricity, such as the<span class="pagenum"><a name="Page_144" id="Page_144">[Pg 144]</a></span> orbits of even our short-period comets display, +would be fatal to the persistence of water in the liquid state, and hence +to the continuance of life. A wide discordance between the planes of the +planet’s equator and of its orbit, by rendering the seasons extravagantly +diverse, would act as prejudicially as an eccentric orbit, and a rotation +period equal to that of revolution would mean that one hemisphere was +eternally frozen while the other was exposed to perpetual heat.</p> + +<p>It follows that in any given system there can be at most only one or two +planets upon which life can find a home, and this only where the right +conditions of size and mass, of rotation period, inclination of axis, and +shape of orbit, all co-exist in a globe at the proper distance. But the +type of system offered by our Sun and his planets is not the only one that +exists. A very large proportion of stars are binaries—two suns revolve +round their common centre of gravity. In many cases the two suns are +separable in the telescope, and their relative movements can be measured; +in other cases, termed “spectroscopic binaries,” we only learn that a star +which appears absolutely single has two components from the evidence of +its spectrum; the spectroscope revealing two sets of lines that vibrate to +and fro with respect to each other. Yet, again, a third class of double +stars has made itself known in the “Algol variables.” The optical double +stars are cases where the two <span class="pagenum"><a name="Page_145" id="Page_145">[Pg 145]</a></span>components are far distant from each other, +and hence can be distinguished in our telescopes as separate points of +light. The “spectroscopic binaries” are cases where the two components are +too close to be separately perceived, but where the two are not greatly +unequal in brightness, so that the spectrum of the one does not overpower +that of the other. The “Algol variables” are cases where the two +components are of very unequal brightness, and, being very close to each +other, are so placed with respect to the Earth that the fainter partly +eclipses the brighter in its revolution round it, and so causes a +temporary diminution in its light at regular intervals. All these three +classes of binary systems are now known to be very numerous. Prof. +Campbell estimates that fully one star in six is a spectroscopic binary. +But there must be many binary systems that do not reveal +themselves—double stars where the companion is too faint or too close to +be detected, Algol systems where the companion does not pass before its +primary—and it seems almost certain that simple systems, like that of +which our Sun is the unchallenged autocrat, must be comparatively rare.</p> + +<p>But the problem of the movements of a planet attendant upon two or more +suns is one of amazing complexity, and our greatest mathematicians have as +yet only been able to deal with the approximate solution of a few very +special cases. These are,<span class="pagenum"><a name="Page_146" id="Page_146">[Pg 146]</a></span> however, sufficient to show that the orbit of a +planet so placed would be most irregular; the variations in the supplies +of light and heat received would be as great as even comets experience +within the solar system, and, what would be more disastrous still, these +variations would not be periodic but irregular. One year would be unlike +that which preceded it, and would be followed by changed conditions in the +next. Plants and animals would never have the chance of acclimatizing +themselves to these ever-changing vicissitudes. The stability of condition +essential for the maintenance of water in a liquid state would be wanting; +and, in consequence, Life could neither come into existence, nor persist +if it once appeared.</p> + +<p>So far, therefore, our line of thought has led us to recognize that Life +can exist in comparatively few of the innumerable stellar systems strewn +through infinite space, and in any given system it can at best find only +one or two homes. The conditions for a Life-bearing planet are thus both +numerous and stringent—there is no elasticity about them. It is not +sufficient that a planet might fulfil many or even most of these +conditions; failure in one is failure altogether; “one black ball +excludes;” the candidate who fails in a single subject is “ploughed” +without mercy. And in most cases the failure is final; no opportunity is +given to the candidate to “sit” again.</p> + +<p>But Space is not the only horizon along which<span class="pagenum"><a name="Page_147" id="Page_147">[Pg 147]</a></span> our thought must be +directed; there is also the horizon of Time. Every world must have its +Past and its Future, as well as its Present. For some worlds the +conditions are so fixed that, like Jupiter and Saturn, they are not now +worlds that can be dwelt in, they never were in that condition, and they +never can be; their enormous mass forbids it. Mercury and the Moon at the +other end of the planetary scale are also permanently disabled; their +insignificant size excludes them. There was also a time when the Earth was +not a world of habitation; it was “without form and void”; hot and +vaporous, even as the four outer planets are now. Now it is inhabited, but +there may come a time when this phase of its history has run its course, +and either from a falling off in the tribute of light and heat rendered to +it by the Sun, or from the gradual desiccation of the surface, or, +perchance, from the slow loss of its atmosphere, it may approach the +condition of Mars, and in its turn be no longer an abode of life. Many +planets are essentially debarred from ever entering on the vital stage; +but of those to which such a stage is possible, it can only form an +incident in the entire duration of the orb. And if our Earth is any type +or example of the vital stage in general, vast aeons must run their course +from the first appearance of the humblest germs of life up to the bringing +forth of Life in conscious Intelligence. One hundred million years are +freely spoken of in this connection<span class="pagenum"><a name="Page_148" id="Page_148">[Pg 148]</a></span> by those who study the crust of the +Earth and those who are occupied with the relations of the varied forms of +life. Man is the latest arrival on this planet, and however far back we +try to push the time of his earliest appearance, it is beyond question +that that time, relatively to the entire duration of the Earth since a +solid crust began to form, is but as yesterday. If, from some other globe +in the depths of space, this world of ours could have been watched during +the long aeons that elapsed from its first separation from the solar +nebula down to the time when it first possessed a surface of land and +water, and from that time, again, throughout the hypothetical one hundred +million years that preceded the advent of man, then, during all those +aeons, those imagined observers would have had under their scrutiny a +world as yet without inhabitant. The Earth now is in the inhabited +condition, but science gives us no clue as to how long that condition will +endure; rather such hints as are afforded us would seem to point to its +lasting but for a brief season as compared with the indefinite duration +which preceded it, and the indefinite duration which shall follow.</p> + +<p>If this thought be sound, it places before us an entirely new and most +serious consideration. The world predestined for habitation must not only +have its size within certain narrow limits, its distance from its central +sun in a certain narrow zone, its rotation period, the inclination of its +axis,<span class="pagenum"><a name="Page_149" id="Page_149">[Pg 149]</a></span> the eccentricity of its orbit, all suitable alike, but even if in +these and in all other necessaries it is perfectly adapted for habitation, +yet it will be only during a relatively small fraction of its entire +duration that Intelligent Life, clothed in material form, will find a +place upon it.</p> + +<p>Let us sum shortly what we know and what we conclude. We know that this, +our Earth, is a habitable globe, for we ourselves are living upon it. We +know what constitutes the physical basis of our life, and under what +conditions on this Earth it flourishes, and under what conditions it is +destroyed. If we turn our eyes from this, our Earth, and look out upon the +starry skies, we see the other planets of our system, and the suns which +are the centres of other systems. From the consideration of the planets in +our own system, we have seen how stringent and how many are the conditions +imposed for Life to be possible. Round our Sun there is but a narrow zone +in which a habitable world may circle; in this zone there is room for but +few worlds, and we actually know of three alone, the Earth, the Moon, and +Venus. We know that the Earth can be and is inhabited; that the Moon is +not and cannot be inhabited; and that Venus, though of habitable size, may +yet be subject to the fatal disqualification of always turning the same +face to the Sun. Of other planetary systems than our own, we actually know +of none, but we assume that there are such,<span class="pagenum"><a name="Page_150" id="Page_150">[Pg 150]</a></span> and as numerous as there are +suns in the starry depths. But of these planetary systems we can rule out, +as containing no habitable member, all such as circle round double or +multiple suns or, indeed, round any single star that, from whatever cause, +is largely variable and, therefore, much less stable than our own. Mira +Ceti, which in 5 months increases its brightness 1000 times, may stand as +an example. Probably these disqualifications rule out of court the great +proportion of the stellar systems. Of the few, comparatively speaking, +single and stable suns that remain in the heavenly abyss, we must +conclude, from what we know of our solar system, that they, too, have but +a narrow zone, outside of which no world would be fit to dwell in; whilst +in the zone the few worlds which might exist must violate no one of many +strict conditions. If we assume that there are a hundred million stars +within the ken of our telescopes, we may well believe that not more than +one in a hundred of these would fulfil the condition of being a single and +stable sun, such as ours. Of the planets revolving round these million +suns—stable and efficient suns—can we expect that in more cases than one +in a hundred there will be a planet in the habitable zone fulfilling all +the other conditions of habitability, of size, mass, inclination of axis, +circular orbit, and rotation? Of these ten thousand earths which may be +made fit for the habitation of Man, can we assume that<span class="pagenum"><a name="Page_151" id="Page_151">[Pg 151]</a></span> even one in a +hundred is now at that epoch in its history when it is no longer “without +form and void,” when a division has been made between the waters under the +firmament and those that are above the firmament; when the waters under +the heaven have been gathered into one place, and the dry land has +appeared, and when the earth and the waters have brought forth life +abundantly? Out of a hundred million of planetary systems throughout the +depths of space, can we suppose that there are even one hundred worlds +that are actually inhabited at the present moment? These numbers and +proportions certainly are not, and cannot be, based on knowledge; they are +given as illustrations only; but, vague as they are, they suggest that our +Earth may be neither one of many inhabited earths, nor yet unique, but one +of a few—indeed of a very few.</p> + +<p>And then the objection is raised: “If our own Earth is but one of, +perhaps, two inhabited worlds in the solar system; and of perhaps one or +two hundred inhabited worlds throughout the furthest space that we can +scan; why is all this waste?” Of all the countless millions of stellar +systems without living organisms as inhabitants, we cannot tell the +purpose for the simple reason that we do not know it; but of “waste” in +the solar system, there is no question. Relatively speaking, this is quite +insignificant, for we cannot consider that as “waste material” which is +useful and,<span class="pagenum"><a name="Page_152" id="Page_152">[Pg 152]</a></span> indeed, essential to existence. For, consider first the +material in the Earth itself. Its total volume is 260,613,000,000 cubic +miles, but man only lives <i>upon</i> its surface of less than 200 million +square miles in extent, and he can not probe down as far as ten miles +below it, through the depths of ocean or by his deepest mine. Thus we are +left with over 258 thousand million of cubic miles that man, or plant, or +beast can never make direct use of. But without this 258 thousand million +cubic miles that he can never sow nor reap, the overlying platform on +which he dwells would be useless for retaining the air or the water by +which he lives. No less essential is the Sun; its vast bulk of</p> + +<p class="center">2,000,000,000,000,000,000,000,000,000 tons</p> + +<p>can, in no single unit, be counted “waste,” for it is from this that the +heat and light necessary for life on the Earth is derived. But the tonnage +of all the planets combined is but 0·13 per cent of the Sun alone; and a +wastage, if such it is, like this is insignificant from a material point +of view.</p> + +<p>There is a type of politician at the present day who is convinced that the +highest purpose to which land can be put is to build upon it; that being, +in general, the use giving the highest money return per square foot, +though the return does not always fall to the builder. It has taken not a +little agitation and popular pressure to enforce the truth that cultivated +land is also of use. But there are few who realize that land that is +neither<span class="pagenum"><a name="Page_153" id="Page_153">[Pg 153]</a></span> built upon nor cultivated is also essential. Our barren moors and +bleak hillsides, “wastelands” as we call them, are absolutely necessary as +collectors of the water by which we live. From them our springs take their +source; and they supply our cities with the first necessity of life.</p> + +<p>We find, then, in this universe so far as we can know it, that Space is +lavishly provided, Matter is lavishly scattered, Time is unsparingly drawn +upon, but Life in any form, and especially in its highest form, is, +relatively speaking, very sparsely given. That very circumstance surely +points to the overwhelming importance of conscious, intelligent Life, and +the insignificance of lifeless matter in comparison with it. We have to +exhaust arithmetic in computing the size, the mass, the output of heat and +light of our Sun, yet it is but the hearth-fire and lamp of terrestrial +life; and its amazing agglomeration of matter and energy is ungrudgingly +devoted to this humble purpose. Whatever view we hold as to the scheme of +the universe; whether with the unthinking we fail to recognize Thought and +Purpose behind its marvellous manifestations, or, with the thoughtful, +realize that only Infinite Thought could provide so wonderfully for the +bringing forth of thought in living material organisms, the conclusion +still remains: living intelligences are, by the direct testimony of the +universe itself, its noblest and most precious product.</p> + +<p><span class="pagenum"><a name="Page_154" id="Page_154">[Pg 154]</a></span>The plea is often made that as we find life adapting itself to a great +variety of conditions on this Earth, we must not set limits to its power +of adaption to the conditions of other worlds. But this plea is an +unthinking one. The range of conditions through which we find life on this +Earth is as nothing to the range given by the varied sizes and positions +of the different planets; and even on our Earth, life in the unfavoured +regions—the tops of mountains, the polar snows, the waterless deserts, +the ocean depths—is only possible because there are more favoured regions +close at hand, and there are, as it were, “crumbs that fall from the rich +man’s table.” A well-known littérateur in setting forth “a hundred ways of +making money” gave great prominence to the method of living as caretaker +in an empty house. But residing in an empty house does not, in itself, +supply the means of sustenance; these have to be furnished by the +wealthier man who employs the caretaker.</p> + +<p>Another plea for vague sentiment in this matter is that we cannot expect +that intelligent beings on other worlds would have the same form as man, +and if not the same form, then, that the same conditions of existence +would not hold good for them as for us. Both contentions are unsound. +Protoplasm is the physical basis of all the life that we know, whatever +its form; though these forms are to be counted by the million, and are as<span class="pagenum"><a name="Page_155" id="Page_155">[Pg 155]</a></span> +diverse as they are numerous. And everywhere and always, water is found +essential to protoplasmic life. Of life of any other kind we do not know +any examples; we have no instance; if such exist, then they are beyond our +ken.</p> + +<p>And neither anthropologist nor biologist would admit that the form of +intelligent life was an unrelated accident. Whether the form brought the +intelligence, or the intelligence the form, or both were evolved together, +the one reacting on the other, the human form and the human intelligence +are associated, and we feel this to be so of necessity. In 1891, Dr. +Eugene Dubois found in Java a molar tooth and a portion of a skull, and +later the thigh bone of the left leg, and two more teeth. Such as they +were, these relics appeared nearer in form to the corresponding fragments +of an average Australian than to those of an ape, and on this ground +intelligence was claimed for the creature of which they were the remains, +and it was given the name of Pithecanthropus, or Ape-Man. The discovery +aroused much discussion, but on all sides it was unhesitatingly assumed +that the difference between the form of Pithecanthropus and that of the +most similar ape was an index of its superior intelligence over the ape, +just in so far as that difference was in the direction of the modern human +form. The same remark applies to the recent discovery of very ancient +human remains in Sussex. Never at any time has it been <span class="pagenum"><a name="Page_156" id="Page_156">[Pg 156]</a></span>supposed that the +physical frame has followed any other path in the evolution of +intelligence than that which brought forth man. The flesh-eating animals +have attained efficiency in hunting and warfare by variation along many +types of form; the herbivora have been not less varied in the forms by +which as races they secured themselves from destruction; but Thought has +been associated with the development of one type or form only, and the +entire future of Thought on this planet rested neither with mammoth nor +cave-bear, but with the possessor of the erect stature, the upward look, +the differentiation of hand and foot, even in their crudest and earliest +stages.</p> + +<p>Swift, in <i>Gulliver’s Travels</i>, conceived of a land where the intelligence +and conscience of Man dwelt in the form of the horse, and the human form +tabernacled the instincts of the beast. H. G. Wells, in his <i>War of the +Worlds</i>, attributed intelligence to monsters—half-cuttlefish and +half-anemone,—and the human form to their helpless, unresisting prey. +Both conceptions are as scientifically absurd as they are gross and +revolting; and if it were possible for the skeleton of creatures from +other worlds to be brought to us here, then biologists would as +confidently pronounce on their intelligence as they do on the extinct +forms of bygone ages—the nearer to the human form, the nearer to the +human mind. We have found the figures of reindeer, horse, and mammoth +scratched in outline<span class="pagenum"><a name="Page_157" id="Page_157">[Pg 157]</a></span> on a mammoth tusk; but though the artist has left no +other trace, we need no further evidence of his bodily form. Neither +horse, nor reindeer, nor mammoth made those rough outlines; they were +drawn by a man. More striking still, France yields us chipped flints by +the million, flints so slightly shaped that it is in dispute whether they +may not have been so broken by the action of torrents. But there are only +two theories about them; either they were so chipped by natural action, or +they were designedly so chipped by creatures resembling ourselves in head +and hand.</p> + +<p>The question that has been dealt with in this volume is a scientific one, +and the attempt has been made to treat it as such, and to argue from known +physical facts as to the conditions of worlds which we cannot visit. But +by many the question is generally discussed wholly apart from physical +facts at all, and it becomes one of sentiment and of religious sympathy. +Yet, curiously enough, the division between those who think that all +worlds must be inhabited and those who think that our own world stands +alone is not coincident with any line of theological divisions, but rather +cuts across all such. Some believers in Christianity argue that since God +has filled this world with Life, Life has been His purpose in the world, +and must therefore have been His purpose in all other worlds—they too +must be filled with Life in like manner. Other believers argue that this +world was the scene of the<span class="pagenum"><a name="Page_158" id="Page_158">[Pg 158]</a></span> Incarnation of Our Lord, and is therefore +unique in that respect; and that this uniqueness sets its stamp upon this +world in all respects. Opponents to Christianity are divided into the same +two classes, the one arguing that wherever there is matter the inevitable +course of evolution will produce life, and eventually intelligent life. +The other class are equally clear that all forms of life are special, the +result of the particular environment, and that it is unreasonable to +expect that any other world has had the same history as our own, or that +the same special conditions have prevailed elsewhere. In other words the +belief that there are other inhabited worlds has depended chiefly neither +on science nor on religious belief, but upon sentiment. There are some who +like to think themselves, and the race to which they belong, altogether +exceptional; others delight in finding themselves reflected wherever they +look. So far as Science has progressed and can return an answer to an +enquiry that exceeds so far the bounds of our direct observation, it +dissents from both orders of thought. The conditions of life are indeed +narrow, special, restricted; intelligent, organic life must, relatively +speaking, be a rarity in the universe, but we lack the information that +would enable us to affirm with any confidence that such life is only to be +found upon this world of ours. Heavy as the odds are against any +particular world being an inhabited one, yet when the limitless extent of<span class="pagenum"><a name="Page_159" id="Page_159">[Pg 159]</a></span> +space is considered, and the innumerable numbers of stars and systems of +stars, it seems but reasonable to conclude that though inhabited worlds +are relatively rare, the absolute number of them may be considerable; +considerable, if not at one particular moment of time, yet when the whole +duration of the universe is admitted.</p> + +<p>But there is a religious question connected with this enquiry; one that +goes down to the very roots of man’s deepest thoughts and aspirations. As +individuals our days on the Earth are as a shadow, and there is none +abiding; as individuals we pass and disappear; and though the race +remains, yet as far as science can guide us and enable us to penetrate the +future, the same lot awaits the race as well. Slowly but surely the water +of a planet will combine with its substance or disappear into its crust. +The cooling of the Sun, though it may be long delayed, would seem to be +inevitable in the sequel.</p> + +<p class="poem">“Oh, life as futile then as frail.<br /> +<span style="margin-left: 1em;"><strong><span class="spacer">·</span><span class="spacer">·</span><span class="spacer">·</span><span class="spacer">·</span></strong></span><br /> +What hope of answer or redress?<br /> +Behind the veil, behind the veil.”</p> + +<p>It is to this veil that we are now brought. It seems impossible to believe +that Life, so rare a fruit of the universe, intelligent Life, conscious +Life, to which the long course of evolution has been so manifestly leading +up all through the long ages, should have<span class="pagenum"><a name="Page_160" id="Page_160">[Pg 160]</a></span> no better destiny than a final +and hopeless extinction; that this Earth and all the efforts and +aspirations of the long generations of men should have no worthier end +than to swing, throughout the eternal ages, an empty, frozen heap of dust, +circling round the extinct cinder that was once its Sun. If we look +backward, we seem to discern clear signs of progress; if we look forward, +we discern nothing but the veil. Science is but organized experience, and +experience of the future we have none.</p> + +<p>There was a time when on this world there was no life; a time when life +began. How did it begin? Under what conditions?</p> + +<p>Of that great change—when non-living matter first became endowed with +life, became so endowed not by the action and intervention of other living +matter, but without it—we have no knowledge, no experience. And so long +as this continues to be the case, that change, the greatest physical +change that has yet taken place in the history of the universe, the first +change of the non-living into the living, is outside the reach of science; +it lies beyond its border. We may guess and speculate about it, but +speculation is not science; we may spin words about it with the utmost +skill of the dialectician, but metaphysics is not science; it can never +come within the scope of science until it has first come within the scope +of experience.</p> + +<p>There is, therefore, a veil behind us as well as<span class="pagenum"><a name="Page_161" id="Page_161">[Pg 161]</a></span> the one that encloses us +in front; and as hitherto Science has failed to pierce the veil of the +past, it is even less able to pierce the veil of the future; for of the +future we have no experience.</p> + +<hr style="width: 45%;" /> + +<p>Here, then, our enquiry must end, for it is an enquiry of physical +science; the search for living material organisms endowed with +intelligence. How life first came upon this Earth, or when, or where, is +beyond the power of science to determine. Yet it did come. There was a +time when there was no life here; none, not even the humblest form of it; +nor was there any hint or foreshadowing of it, still less of all its +infinities of form, and possibilities of development.</p> + +<p>Once Life was not, yet Life came, and now, life is abundant, but abundant +only in worlds quite exceptional in their conditions, and therefore few in +number; it is even conceivable that this Earth of ours may be unique. But +life as we know it, protoplasmic life, life dependent upon water, the life +of intelligence united to the material organism, is under sentence of +death. Has it any future beyond that veil? Is there any kind of life not +subject to these narrow limitations; not under the inexorable decree?</p> + +<p>To questions such as these Science has no reply to give; it is even more +helpless to answer them<span class="pagenum"><a name="Page_162" id="Page_162">[Pg 162]</a></span> than to determine how life first came; its +experience does not reach so far. Science can examine the present +conditions of physical life, but whether or no that life can undergo a +change greater than that which passed upon the old inorganic world, it +cannot determine. It has no experience.</p> + +<p>But if Science is dumb, if the utmost exertion of human energy and power +of research can throw no light on a future of which we have no experience, +we are not left without an answer. A voice has been heard, the voice of +the Son of God Himself:</p> + +<p>“I am the Resurrection and the Life. He that believeth on Me, though he +were dead, yet shall he live.”</p> + +<p>And accepting His word, the Church in all ages, and among all nations, +peoples, and tongues, has made reply:</p> + +<p>“<span class="smcap">I look for the resurrection of the dead and the life of the world to +come.</span>”</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><span class="pagenum"><a name="Page_163" id="Page_163">[Pg 163]</a></span></p> +<h2>INDEX</h2> + +<p class="index"> +Abbot, C. G., <a href="#Page_27">27</a>, <a href="#Page_34">34</a><br /> +<br /> +Albedo of Earth, <a href="#Page_54">54</a>, <a href="#Page_81">81</a><br /> +<span style="margin-left: 1em;">—— Jupiter, <a href="#Page_127">127</a></span><br /> +<span style="margin-left: 1em;">—— Mars, <a href="#Page_81">81</a></span><br /> +<span style="margin-left: 1em;">—— Moon, <a href="#Page_54">54</a></span><br /> +<br /> +<i>Albumin sol</i>, <a href="#Page_15">15</a><br /> +<br /> +Algol-type stars, <a href="#Page_35">35</a>, <a href="#Page_144">144</a>, <a href="#Page_145">145</a><br /> +<br /> +Antares, <a href="#Page_38">38</a><br /> +<br /> +Antoniadi, E. M., <a href="#Page_97">97</a>, <a href="#Page_104">104</a><br /> +<br /> +Archangel, climate of, <a href="#Page_87">87</a>, <a href="#Page_88">88</a><br /> +<br /> +Arcturus, <a href="#Page_35">35</a>, <a href="#Page_37">37</a><br /> +<br /> +Aristarchus, lunar crater, <a href="#Page_48">48</a><br /> +<br /> +“Astronomical unit,” <a href="#Page_21">21</a><br /> +<br /> +Atmosphere of, Mars, <a href="#Page_76">76</a><br /> +<span style="margin-left: 1em;">——, Moon, <a href="#Page_53">53</a></span><br /> +<span style="margin-left: 1em;">——, Sun, <a href="#Page_25">25</a></span><br /> +<span style="margin-left: 1em;">——, Venus, <a href="#Page_112">112</a></span><br /> +<br /> +<br /> +Barnard, E. E., <a href="#Page_89">89</a>, <a href="#Page_104">104</a><br /> +<br /> +Beer, <a href="#Page_60">60</a>, <a href="#Page_97">97</a>, <a href="#Page_98">98</a><br /> +<br /> +Bond, G. P., <a href="#Page_127">127</a>, <a href="#Page_128">128</a><br /> +<br /> +Brewster, Sir David, <a href="#Page_4">4</a><br /> +<br /> +<br /> +Calcium, <a href="#Page_12">12</a>, <a href="#Page_36">36</a><br /> +<br /> +Callisto, satellite of Jupiter, <a href="#Page_131">131</a><br /> +<br /> +Calory, <a href="#Page_26">26</a><br /> +<br /> +Campbell, W. W., <a href="#Page_145">145</a><br /> +<br /> +Carbon, <a href="#Page_11">11</a>, <a href="#Page_34">34</a>, <a href="#Page_38">38</a>, <a href="#Page_39">39</a><br /> +<br /> +Carbonic acid, <a href="#Page_11">11</a><br /> +<br /> +Cassini, <a href="#Page_59">59</a>, <a href="#Page_60">60</a>, <a href="#Page_130">130</a><br /> +<br /> +Ceres, minor planet, <a href="#Page_41">41</a>, <a href="#Page_120">120</a>, <a href="#Page_121">121</a>, <a href="#Page_122">122</a>, <a href="#Page_131">131</a><br /> +<br /> +Cerulli, V., <a href="#Page_104">104</a>, <a href="#Page_108">108</a><br /> +<br /> +Chromosphere, <a href="#Page_28">28</a>, <a href="#Page_29">29</a><br /> +<br /> +Cobalt, <a href="#Page_33">33</a><br /> +<br /> +Comet, Encke’s, <a href="#Page_119">119</a><br /> +<span style="margin-left: 1em;">——, Halley’s, <a href="#Page_119">119</a></span><br /> +<span style="margin-left: 1em;">——, spectra, <a href="#Page_38">38</a></span><br /> +<br /> +Copernican theory, <a href="#Page_1">1</a><br /> +<br /> +Copper, <a href="#Page_33">33</a><br /> +<br /> +Corona, <a href="#Page_40">40</a><br /> +<br /> +Coxwell, <a href="#Page_25">25</a>, <a href="#Page_75">75</a>, <a href="#Page_79">79</a><br /> +<br /> +Cyanogen, <a href="#Page_37">37</a>, <a href="#Page_38">38</a><br /> +<br /> +Czapek, F., <a href="#Page_11">11</a>, <a href="#Page_13">13</a><br /> +<br /> +<br /> +Darwin, Sir G. H., <a href="#Page_116">116</a><br /> +<br /> +Dawes, W. R., <a href="#Page_60">60</a>, <a href="#Page_63">63</a>, <a href="#Page_97">97</a>, <a href="#Page_99">99</a><br /> +<br /> +Denning, W. F., <a href="#Page_104">104</a><br /> +<br /> +Dispersion, anomalous, <a href="#Page_28">28</a><br /> +<br /> +Doppelmayer, lunar crater, <a href="#Page_52">52</a><br /> +<br /> +Dubois, Eugene, <a href="#Page_155">155</a><br /> +<br /> +<br /> +Eros, minor planet, <a href="#Page_57">57</a><br /> +<br /> +Europa, satellite of Jupiter, <a href="#Page_131">131</a><br /> +<br /> +Evans, J. E., <a href="#Page_107">107</a><br /> +<br /> +<br /> +Faculae, <a href="#Page_29">29</a>, <a href="#Page_30">30</a><br /> +<br /> +Fauth, P., <a href="#Page_50">50</a><br /> +<br /> +Flamsteed, lunar crater, <a href="#Page_52">52</a><br /> +<br /> +Fluorine, <a href="#Page_40">40</a><br /> +<br /> +Fraunhofer, <a href="#Page_33">33</a><br /> +<br /> +<br /> +Galileo, <a href="#Page_51">51</a>, <a href="#Page_59">59</a>, <a href="#Page_131">131</a><br /> +<br /> +Ganymede, satellite of Jupiter, <a href="#Page_131">131</a>, <a href="#Page_132">132</a><br /> +<br /> +Gay-Lussac, <a href="#Page_75">75</a><br /> +<br /> +<span class="pagenum"><a name="Page_164" id="Page_164">[Pg 164]</a></span>Glaisher, J., <a href="#Page_25">25</a>, <a href="#Page_75">75</a>, <a href="#Page_79">79</a><br /> +<br /> +Goodacre, W., <a href="#Page_49">49</a><br /> +<br /> +Green, N. E., <a href="#Page_60">60</a>, <a href="#Page_62">62</a>, <a href="#Page_63">63</a><br /> +<br /> +Greenwich Hospital School, <a href="#Page_107">107</a>, <a href="#Page_108">108</a><br /> +<br /> +“Gulliver’s Travels,” <a href="#Page_82">82</a>, <a href="#Page_156">156</a><br /> +<br /> +<br /> +Haeckel, E., <a href="#Page_12">12</a><br /> +<br /> +Halogens, <a href="#Page_36">36</a>, <a href="#Page_40">40</a><br /> +<br /> +“Harper’s Weekly,” <a href="#Page_93">93</a><br /> +<br /> +Helium, <a href="#Page_37">37</a><br /> +<br /> +Herschel, Sir J., <a href="#Page_54">54</a><br /> +<br /> +—— Sir W., <a href="#Page_20">20</a>, <a href="#Page_49">49</a>, <a href="#Page_59">59</a>, <a href="#Page_60">60</a>, <a href="#Page_61">61</a><br /> +<br /> +Hevelius, <a href="#Page_51">51</a><br /> +<br /> +Hippalus, lunar crater, <a href="#Page_52">52</a><br /> +<br /> +Hooke, R., <a href="#Page_59">59</a>, <a href="#Page_60">60</a>, <a href="#Page_130">130</a><br /> +<br /> +Huyghens, <a href="#Page_59">59</a><br /> +<br /> +Hydrocarbons, <a href="#Page_38">38</a><br /> +<br /> +Hydrogen, <a href="#Page_11">11</a>, <a href="#Page_36">36</a>, <a href="#Page_37">37</a>, <a href="#Page_38">38</a>, <a href="#Page_41">41</a>, <a href="#Page_81">81</a><br /> +<br /> +<br /> +“Inhabitant,” <a href="#Page_5">5</a><br /> +<br /> +“Inhabited” Worlds, <a href="#Page_2">2</a>, <a href="#Page_3">3</a>, <a href="#Page_4">4</a><br /> +<br /> +Io, satellite of Jupiter, <a href="#Page_131">131</a><br /> +<br /> +Iron, <a href="#Page_12">12</a>, <a href="#Page_33">33</a>, <a href="#Page_36">36</a><br /> +<br /> +<br /> +Jupiter, <a href="#Page_122">122-32</a><br /> +<br /> +——, belts, <a href="#Page_127">127</a>, <a href="#Page_129">129</a><br /> +<br /> +——, great red spot, <a href="#Page_130">130</a><br /> +<br /> +——, proper motion of spots, <a href="#Page_129">129</a><br /> +<br /> +——, satellites of, <a href="#Page_128">128</a>, <a href="#Page_131">131</a><br /> +<br /> +——, white spots, <a href="#Page_128">128</a>, <a href="#Page_130">130</a><br /> +<br /> +<br /> +Keeler, J. E., <a href="#Page_122">122</a>, <a href="#Page_125">125</a><br /> +<br /> +Kies, lunar crater, <a href="#Page_52">52</a><br /> +<br /> +Kirchhoff, <a href="#Page_33">33</a><br /> +<br /> +<br /> +Lacus Solis, <a href="#Page_97">97</a>, <a href="#Page_98">98</a>, <a href="#Page_99">99</a><br /> +<br /> +Langley, S. P., <a href="#Page_55">55</a><br /> +<br /> +Lilliputians, <a href="#Page_82">82</a>, <a href="#Page_83">83</a><br /> +<br /> +Linné, lunar crater, <a href="#Page_48">48</a><br /> +<br /> +Lockyer, J. N., <a href="#Page_60">60</a><br /> +<br /> +Lowell, P., <a href="#Page_65">65</a>, <a href="#Page_66">66</a>, <a href="#Page_67">67</a>, <a href="#Page_69">69</a>, <a href="#Page_71">71</a>, <a href="#Page_81">81</a>, <a href="#Page_97">97</a>, <a href="#Page_98">98</a>, <a href="#Page_99">99</a>, <a href="#Page_101">101</a>, <a href="#Page_103">103</a>, <a href="#Page_104">104</a>, <a href="#Page_105">105</a>, <a href="#Page_106">106</a>, <a href="#Page_108">108</a>, <a href="#Page_109">109</a>, <a href="#Page_110">110</a><br /> +<br /> +Lucifer, <a href="#Page_111">111</a><br /> +<br /> +<br /> +Mädler, <a href="#Page_46">46</a>, <a href="#Page_48">48</a>, <a href="#Page_60">60</a>, <a href="#Page_97">97</a>, <a href="#Page_98">98</a><br /> +<br /> +Maginus, lunar crater, <a href="#Page_46">46</a><br /> +<br /> +Magnesium, <a href="#Page_12">12</a>, <a href="#Page_36">36</a><br /> +<br /> +Manganese, <a href="#Page_33">33</a><br /> +<br /> +Mare Fecunditatis, <a href="#Page_47">47</a><br /> +<br /> +—— Humerum, <a href="#Page_52">52</a><br /> +<br /> +—— Nubium, <a href="#Page_52">52</a><br /> +<br /> +—— Serenitatis, <a href="#Page_48">48</a><br /> +<br /> +Mars, canals of, <a href="#Page_57">57-70</a>, <a href="#Page_78">78</a>, <a href="#Page_101">101</a>, <a href="#Page_102">102</a><br /> +<br /> +——, conditions of, <a href="#Page_71">71-95</a><br /> +<br /> +——, illusions of, <a href="#Page_96">96-110</a><br /> +<br /> +——, meteorology of, <a href="#Page_93">93-4</a><br /> +<br /> +——, oases of, <a href="#Page_65">65</a>, <a href="#Page_98">98</a>, <a href="#Page_99">99</a>, <a href="#Page_101">101</a><br /> +<br /> +——, thermograph of, <a href="#Page_91">91</a>, <a href="#Page_92">92</a><br /> +<br /> +——, winds of, <a href="#Page_77">77</a><br /> +<br /> +Mendeléeff, <a href="#Page_39">39</a><br /> +<br /> +Mercury, <a href="#Page_114">114-18</a><br /> +<br /> +Messier, lunar crater, <a href="#Page_47">47</a>, <a href="#Page_48">48</a><br /> +<br /> +Metabolism, <a href="#Page_10">10</a>, <a href="#Page_11">11</a>, <a href="#Page_14">14</a>, <a href="#Page_15">15</a>, <a href="#Page_38">38</a><br /> +<br /> +Millechau, <a href="#Page_104">104</a><br /> +<br /> +Milton, <a href="#Page_51">51</a><br /> +<br /> +Mira Ceti, <a href="#Page_150">150</a><br /> +<br /> +Molesworth, P. B., <a href="#Page_49">49</a>, <a href="#Page_104">104</a><br /> +<br /> +Moon, <a href="#Page_43">43-56</a><br /> +<br /> +——, “terminator” of, <a href="#Page_51">51</a><br /> +<br /> +Mont Blanc, <a href="#Page_25">25</a>, <a href="#Page_74">74</a>, <a href="#Page_80">80</a><br /> +<br /> +Mount Everest, <a href="#Page_75">75</a>, <a href="#Page_80">80</a><br /> +<br /> +<br /> +Nature of Vision, <a href="#Page_99">99</a><br /> +<br /> +Nebulae, spectrum of, <a href="#Page_38">38</a>, <a href="#Page_40">40</a><br /> +<br /> +Nebulium, <a href="#Page_40">40</a><br /> +<br /> +Negative elements, <a href="#Page_36">36</a><br /> +<br /> +Neison, E., <a href="#Page_48">48</a>, <a href="#Page_53">53</a><br /> +<br /> +Neptune, <a href="#Page_132">132</a>, <a href="#Page_141">141</a><br /> +<br /> +<span class="pagenum"><a name="Page_165" id="Page_165">[Pg 165]</a></span>Newcomb, S., <a href="#Page_93">93</a>, <a href="#Page_109">109</a><br /> +<br /> +Nicholson, J. W., <a href="#Page_40">40</a><br /> +<br /> +Nickel, <a href="#Page_33">33</a><br /> +<br /> +Nilosyrtis, “canal” on Mars, <a href="#Page_89">89</a><br /> +<br /> +Nitrogen, <a href="#Page_11">11</a>, <a href="#Page_37">37</a>, <a href="#Page_38">38</a>, <a href="#Page_39">39</a><br /> +<br /> +<br /> +Observatory, Chicago, <a href="#Page_44">44</a><br /> +<br /> +——, Harvard College, <a href="#Page_127">127</a><br /> +<br /> +——, Lick, <a href="#Page_122">122</a><br /> +<br /> +——, Paris, <a href="#Page_44">44</a><br /> +<br /> +Occultation, <a href="#Page_52">52</a>, <a href="#Page_53">53</a><br /> +<br /> +Organic Life, definition of, <a href="#Page_15">15</a><br /> +<br /> +Organism, living, <a href="#Page_6">6-19</a><br /> +<br /> +Organo-genetic elements, <a href="#Page_12">12</a>, <a href="#Page_38">38</a>, <a href="#Page_39">39</a><br /> +<br /> +Osmosis, <a href="#Page_15">15</a><br /> +<br /> +Oxygen, <a href="#Page_11">11</a>, <a href="#Page_36">36</a>, <a href="#Page_37">37</a>, <a href="#Page_38">38</a>, <a href="#Page_41">41</a><br /> +<br /> +<br /> +Periodic Law, Mendeléeff’s, <a href="#Page_39">39</a><br /> +<br /> +Phillips, T. E. R., <a href="#Page_104">104</a><br /> +<br /> +Phosphorus, <a href="#Page_12">12</a><br /> +<br /> +Photosphere, <a href="#Page_28">28</a>, <a href="#Page_33">33</a>, <a href="#Page_36">36</a><br /> +<br /> +Pickering, W. H., <a href="#Page_47">47</a>, <a href="#Page_48">48</a>, <a href="#Page_53">53</a>, <a href="#Page_109">109</a><br /> +<br /> +Pithecanthropus, <a href="#Page_155">155</a><br /> +<br /> +Planetary statistics, table of, <a href="#Page_72">72</a>, <a href="#Page_72">73</a>, <a href="#Page_135">135</a><br /> +<br /> +Platinum, <a href="#Page_36">36</a><br /> +<br /> +“Plurality of Worlds,” <a href="#Page_2">2</a><br /> +<br /> +Pollock, Master, <a href="#Page_109">109</a><br /> +<br /> +Potassium, <a href="#Page_12">12</a><br /> +<br /> +Poynting, J. H., <a href="#Page_86">86</a>, <a href="#Page_87">87</a>, <a href="#Page_89">89</a>, <a href="#Page_115">115</a><br /> +<br /> +Proctor, R. A., <a href="#Page_34">34</a>, <a href="#Page_77">77</a><br /> +<br /> +Prominences, <a href="#Page_29">29</a>, <a href="#Page_30">30</a>, <a href="#Page_37">37</a><br /> +<br /> +Protofluorine, <a href="#Page_40">40</a><br /> +<br /> +Protonilus, “canal” on Mars, <a href="#Page_89">89</a><br /> +<br /> +Protoplasm, <a href="#Page_11">11</a>, <a href="#Page_12">12</a>, <a href="#Page_13">13</a>, <a href="#Page_15">15</a>, <a href="#Page_38">38</a>, <a href="#Page_40">40</a>, <a href="#Page_154">154</a><br /> +<br /> +Pyramid, Great, <a href="#Page_45">45</a><br /> +<br /> +<br /> +Refraction, anomalous, <a href="#Page_28">28</a><br /> +<br /> +Reversing layer, <a href="#Page_36">36</a><br /> +<br /> +“Rice-grains,” of Sun’s surface, <a href="#Page_28">28</a>, <a href="#Page_29">29</a><br /> +<br /> +Ring Nebula in Lyra, <a href="#Page_40">40</a><br /> +<br /> +Rosse, Lord, <a href="#Page_55">55</a><br /> +<br /> +Ruskin, J., <a href="#Page_19">19</a><br /> +<br /> +<br /> +Saturn, <a href="#Page_132">132</a><br /> +<br /> +——, Rings of, <a href="#Page_138">138</a><br /> +<br /> +Schiaparelli, G. V., <a href="#Page_61">61</a>, <a href="#Page_62">62</a>, <a href="#Page_63">63</a>, <a href="#Page_64">64</a>, <a href="#Page_66">66</a>, <a href="#Page_97">97</a>, <a href="#Page_99">99</a>, <a href="#Page_107">107</a>, <a href="#Page_108">108</a>, <a href="#Page_116">116</a>, <a href="#Page_117">117</a><br /> +<br /> +Schooling, T. Holt, <a href="#Page_83">83</a><br /> +<br /> +“Scientia,” <a href="#Page_66">66</a><br /> +<br /> +“Semi-suns,” <a href="#Page_131">131</a>, <a href="#Page_132">132</a><br /> +<br /> +Serviss, Garrett P., <a href="#Page_17">17</a><br /> +<br /> +Singapore, climate of, <a href="#Page_87">87</a>, <a href="#Page_88">88</a><br /> +<br /> +Sinus Sabaeus, marking on Mars, <a href="#Page_97">97</a>, <a href="#Page_99">99</a><br /> +<br /> +Sirius, <a href="#Page_37">37</a><br /> +<br /> +Sodium, <a href="#Page_33">33</a>, <a href="#Page_36">36</a><br /> +<br /> +“Solar Constant,” <a href="#Page_26">26</a><br /> +<br /> +Spectroscopic binaries, <a href="#Page_144">144</a>, <a href="#Page_145">145</a><br /> +<br /> +Spectrum, <a href="#Page_53">53</a><br /> +<br /> +——, heat, <a href="#Page_55">55</a><br /> +<br /> +“Spurious” disc, <a href="#Page_103">103</a><br /> +<br /> +Stars, double, <a href="#Page_35">35</a><br /> +<br /> +——, multiple, <a href="#Page_35">35</a><br /> +<br /> +——, red, <a href="#Page_38">38</a><br /> +<br /> +——, spectra of, <a href="#Page_34">34</a>, <a href="#Page_38">38</a>, <a href="#Page_39">39</a><br /> +<br /> +Stefan’s Law, <a href="#Page_85">85</a><br /> +<br /> +Stoney, G. Johnstone, <a href="#Page_34">34</a><br /> +<br /> +“Streaming,” <a href="#Page_15">15</a><br /> +<br /> +Sulphur, <a href="#Page_11">11</a>, <a href="#Page_38">38</a><br /> +<br /> +Sun, <a href="#Page_20">20-32</a><br /> +<br /> +Sunspots, <a href="#Page_29">29</a>, <a href="#Page_30">30</a>, <a href="#Page_31">31</a>, <a href="#Page_38">38</a><br /> +<br /> +——, spectra of, <a href="#Page_37">37</a><br /> +<br /> +Swift, Dean, <a href="#Page_82">82</a>, <a href="#Page_156">156</a><br /> +<br /> +<br /> +Table Mountain, <a href="#Page_54">54</a><br /> +<br /> +Thermograph of Mars, <a href="#Page_91">91</a>, <a href="#Page_92">92</a><br /> +<br /> +<span class="pagenum"><a name="Page_166" id="Page_166">[Pg 166]</a></span>Titanium, <a href="#Page_36">36</a>, <a href="#Page_37">37</a>, <a href="#Page_38">38</a><br /> +<br /> +Tornadoes, <a href="#Page_31">31</a>, <a href="#Page_137">137</a><br /> +<br /> +“Twinkler,” <a href="#Page_114">114</a><br /> +<br /> +Tycho, lunar crater, <a href="#Page_46">46</a><br /> +<br /> +<br /> +Uranus, <a href="#Page_132">132</a>, <a href="#Page_140">140</a><br /> +<br /> +<br /> +Venus, <a href="#Page_57">57</a>, <a href="#Page_111">111-18</a><br /> +<br /> +Verworn, Max, <a href="#Page_7">7</a><br /> +<br /> +Very, F. W., <a href="#Page_55">55</a><br /> +<br /> +Vesper, <a href="#Page_111">111</a><br /> +<br /> +“Victoria,” hypothetical planet, <a href="#Page_83">83</a><br /> +<br /> +<br /> +Wallace, A. R., <a href="#Page_4">4</a><br /> +<br /> +“War of the Worlds,” <a href="#Page_104">104</a>, <a href="#Page_156">156</a><br /> +<br /> +Waste, <a href="#Page_151">151</a>, <a href="#Page_152">152</a><br /> +<br /> +Water, indispensable factor, <a href="#Page_15">15</a>, <a href="#Page_41">41</a><br /> +<br /> +Wells, H. G., <a href="#Page_104">104</a>, <a href="#Page_156">156</a><br /> +<br /> +Whewell, <a href="#Page_4">4</a><br /> +<br /> +Williams, A. Stanley, <a href="#Page_104">104</a><br /> +<br /> +Wolf, Max, <a href="#Page_40">40</a><br /> +<br /> +<br /> +Young, C. A., <a href="#Page_26">26</a>, <a href="#Page_33">33</a><br /> +</p> + +<p> </p> + +<p class="center">WILLIAM BRENDON AND SON, LTD.<br /> +PRINTERS, PLYMOUTH</p> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<div class="vertsbox"> +<p class="center"><span class="huge">Harper’s Library of Living Though</span></p> + +<p> </p> +<p class="center">ARTHUR HOLMES<br /> +<span class="huge">THE AGE OF THE EARTH</span><br /> +And Associated Problems. <i>Illustrated</i></p> + +<p>Gives us the result of the latest research into this field of enquiry. The +radioactive minerals are shown to be recording their own age with the +exquisite accuracy of a chronometer—their records checking physical, +astronomical, and geological methods of computation.</p> + + +<p> </p> +<p class="center">PROF. A. W. BICKERTON<br /> +<span class="huge">THE BIRTH OF WORLDS AND SYSTEMS</span><br /> +<i>Illustrated</i><br /> +<i>Preface by Prof. Ernest Rutherford, F.R.S.</i></p> + +<p>A graphic account of the formation of new stars from the collision of dead +suns or other celestial bodies. The theory throws light on many +astronomical problems, and with its conception of an immortal cosmos, is +of great philosophical importance.</p> + + +<p> </p> +<p class="center">PROF. SVANTE ARRHENIUS<br /> +<span class="huge">THE LIFE OF THE UNIVERSE</span><br /> +<i>2 Vols. Illustrated</i></p> + +<p>“We can thoroughly recommend these volumes. The information is accurate, +useful, and most suggestive. There are many for whom the first chapters of +Genesis are a subtle allegory covering the profoundest truths, and we are +grateful to the author for having set out this mass of facts.”—<i>The +Globe.</i></p> + + +<p> </p> +<p class="center">SIR OLIVER LODGE, F.R.S.<br /> +<span class="huge">THE ETHER OF SPACE</span><br /> +<i>Illustrated</i></p> + +<p>“This work by the great physicist will be found to possess an abiding +charm and an intellectual stimulation.”-<i>Observer.</i></p> + +<p>“Opens up new views into the nature of the universe. Precise and lucid, it +summarises our knowledge of the substance which fills all space and +penetrates all matter—the substratum of matter itself.”—<i>Birmingham +Post.</i></p> + +<p><br /><i>Please write for announcements and descriptive list:</i></p> + +<p class="center"><span class="smcap">Harper & Brothers</span>, 45 Albemarle Street, London, W.</p></div> + +<p> </p><p> </p> +<div class="vertsbox"> +<p class="center"><span class="huge">Harper’s Library of Living Thought</span></p> + +<p class="center"><i>Foolscap 8vo, gilt tops, decorative covers, richly gilt backs<br /> +Per Volume: Cloth 2s. 6d. net. Leather 3s. 6d. net.</i></p> + +<p> </p> +<p class="center">PROF. ARTHUR KEITH, M.D.<br /> +(Hunterian Professor Royal College of Surgeons)<br /> +<span class="huge">ANCIENT TYPES OF MAN</span><br /> +<i>Illustrated</i></p> + +<p>“The kind of book that only a master of his subject could write. It must +interest every thinking person.”<i>—British Medical Journal.</i></p> + + +<p> </p> +<p class="center">PROF. FREDERICK CZAPEK<br /> +<span class="huge">CHEMICAL PHENOMENA IN LIFE</span></p> + +<p>Discusses in clear, concise terms the great question—“Can life be +explained by physics and chemistry?” It deals with the life-processes of +plants, the molecular structure of protoplasm, organic synthesis in the +cell, the nature of ferments, and the subject of inheritance.</p> + + +<p> </p> +<p class="center">SIR A. TILDEN, F.R.S.<br /> +<span class="huge">THE ELEMENTS</span><br /> +Speculations as to their Nature and Origin<br /> +<i>Diagrams, &c.</i></p> + +<p>Points to the conclusion that the elements resulted from a change in some +primal essence, and discusses “whether all may not be suffering a slow +waste, which, in the long run, must lead back to the primal chaos.”</p> + + +<p> </p> +<p class="center">SIR WILLIAM RAMSAY, F.R.S.<br /> +<span class="huge">ELEMENTS AND ELECTRONS</span><br /> +<i>Diagrams</i></p> + +<p>The electron—“the atom of electricity”—is shown to be separable from +matter, and to be capable under certain circumstances of independent +existence. The book shows that the electron must be regarded as a kind of +“element” itself, with much stronger claims to “elementary” or +undecomposable characters than the bodies hitherto ranked as elements.</p></div> + + +<p> </p><p> </p> +<hr style="width: 50%;" /> +<p><strong>Footnotes:</strong></p> + +<p><a name="f1" id="f1" href="#f1.1">[1]</a> <i>Chemical Phenomena in Life</i>, pp. 62-3, by Dr. Frederick Czapek +(Harper’s Library of Living Thought). The reader is strongly recommended +to study this work in the present connection.</p> + +<p><a name="f2" id="f2" href="#f2.1">[2]</a> <i>Wonders of Life</i>, by Ernst Haeckel, Professor at Jena University, p. +130.</p> + +<p><a name="f3" id="f3" href="#f3.1">[3]</a> <i>Wonders of Life</i>, pp. 127-8.</p> + +<p><a name="f4" id="f4" href="#f4.1">[4]</a> <i>Chemical Phenomena in Life</i>, p. 58.</p> + +<p><a name="f5" id="f5" href="#f5.1">[5]</a> <i>Ibid.</i>, p. 22.</p> + +<p><a name="f6" id="f6" href="#f6.1">[6]</a> <i>Other Worlds</i>, by Garrett P. Serviss, pp. 63-4.</p> + +<p><a name="f7" id="f7" href="#f7.1">[7]</a> <i>Modern Painters</i>, by John Ruskin.</p> + +<p><a name="f8" id="f8" href="#f8.1">[8]</a> If this experiment could be carried out, it would be necessary to use +a spring balance. If the object were weighed in a pair of scales or by a +steelyard, the counterbalancing weights would be likewise affected in the +same proportion, so that the equilibrium would be undisturbed.</p> + +<p><a name="f9" id="f9" href="#f9.1">[9]</a> The movements of not a few double stars point to perturbations caused +by the attraction of unseen bodies. There are also a number of instances +known of “Eclipse” or “Algol-type” variable stars, in which the presence +of a dark companion is indicated by the diminution of the light of the +star at regular intervals.</p> + +<p><a name="f10" id="f10" href="#f10.1">[10]</a> <i>Proc. R. Soc.</i>, LXXX, 50, 1907.</p> + +<p><a name="f11" id="f11" href="#f11.1">[11]</a> <i>Nature</i>, LXXX, 158 (April 8th, 1909).</p> + +<p><a name="f12" id="f12" href="#f12.1">[12]</a> “Periodic Changes upon the Moon,” <i>Memoirs</i>, British Astronomical +Association, Vol. XIII, p. 88.</p> + +<p><a name="f13" id="f13" href="#f13.1">[13]</a> <i>The Moon</i>, by Philip Fauth, p. 156.</p> + +<p><a name="f14" id="f14" href="#f14.1">[14]</a> <i>Radiation in the Solar System: Its Effects on Temperature, and its +Pressure on Small Bodies</i>, by Dr. J. H. Poynting (<i>Phil. Trans. of the +Royal Society</i>, Vol. 202 A).</p> + +<p><a name="f15" id="f15" href="#f15.1">[15]</a> <i>Publ. of the Astron. Soc. of the Pacific</i>, Vol. II, pp. 286-8.</p> + + + + + + + + + +<pre> + + + + + +End of Project Gutenberg's Are the Planets Inhabited?, by E. Walter Maunder + +*** END OF THIS PROJECT GUTENBERG EBOOK ARE THE PLANETS INHABITED? *** + +***** This file should be named 35937-h.htm or 35937-h.zip ***** +This and all associated files of various formats will be found in: + https://www.gutenberg.org/3/5/9/3/35937/ + +Produced by Jonathan Ingram and the Online Distributed +Proofreading Team at https://www.pgdp.net (This file was +produced from images generously made available by The +Internet Archive/American Libraries.) + + +Updated editions will replace the previous one--the old editions +will be renamed. + +Creating the works from public domain print editions means that no +one owns a United States copyright in these works, so the Foundation +(and you!) can copy and distribute it in the United States without +permission and without paying copyright royalties. Special rules, +set forth in the General Terms of Use part of this license, apply to +copying and distributing Project Gutenberg-tm electronic works to +protect the PROJECT GUTENBERG-tm concept and trademark. Project +Gutenberg is a registered trademark, and may not be used if you +charge for the eBooks, unless you receive specific permission. If you +do not charge anything for copies of this eBook, complying with the +rules is very easy. You may use this eBook for nearly any purpose +such as creation of derivative works, reports, performances and +research. They may be modified and printed and given away--you may do +practically ANYTHING with public domain eBooks. Redistribution is +subject to the trademark license, especially commercial +redistribution. + + + +*** START: FULL LICENSE *** + +THE FULL PROJECT GUTENBERG LICENSE +PLEASE READ THIS BEFORE YOU DISTRIBUTE OR USE THIS WORK + +To protect the Project Gutenberg-tm mission of promoting the free +distribution of electronic works, by using or distributing this work +(or any other work associated in any way with the phrase "Project +Gutenberg"), you agree to comply with all the terms of the Full Project +Gutenberg-tm License (available with this file or online at +https://gutenberg.org/license). + + +Section 1. General Terms of Use and Redistributing Project Gutenberg-tm +electronic works + +1.A. By reading or using any part of this Project Gutenberg-tm +electronic work, you indicate that you have read, understand, agree to +and accept all the terms of this license and intellectual property +(trademark/copyright) agreement. If you do not agree to abide by all +the terms of this agreement, you must cease using and return or destroy +all copies of Project Gutenberg-tm electronic works in your possession. +If you paid a fee for obtaining a copy of or access to a Project +Gutenberg-tm electronic work and you do not agree to be bound by the +terms of this agreement, you may obtain a refund from the person or +entity to whom you paid the fee as set forth in paragraph 1.E.8. + +1.B. "Project Gutenberg" is a registered trademark. It may only be +used on or associated in any way with an electronic work by people who +agree to be bound by the terms of this agreement. There are a few +things that you can do with most Project Gutenberg-tm electronic works +even without complying with the full terms of this agreement. See +paragraph 1.C below. There are a lot of things you can do with Project +Gutenberg-tm electronic works if you follow the terms of this agreement +and help preserve free future access to Project Gutenberg-tm electronic +works. See paragraph 1.E below. + +1.C. The Project Gutenberg Literary Archive Foundation ("the Foundation" +or PGLAF), owns a compilation copyright in the collection of Project +Gutenberg-tm electronic works. Nearly all the individual works in the +collection are in the public domain in the United States. If an +individual work is in the public domain in the United States and you are +located in the United States, we do not claim a right to prevent you from +copying, distributing, performing, displaying or creating derivative +works based on the work as long as all references to Project Gutenberg +are removed. Of course, we hope that you will support the Project +Gutenberg-tm mission of promoting free access to electronic works by +freely sharing Project Gutenberg-tm works in compliance with the terms of +this agreement for keeping the Project Gutenberg-tm name associated with +the work. You can easily comply with the terms of this agreement by +keeping this work in the same format with its attached full Project +Gutenberg-tm License when you share it without charge with others. + +1.D. The copyright laws of the place where you are located also govern +what you can do with this work. Copyright laws in most countries are in +a constant state of change. If you are outside the United States, check +the laws of your country in addition to the terms of this agreement +before downloading, copying, displaying, performing, distributing or +creating derivative works based on this work or any other Project +Gutenberg-tm work. The Foundation makes no representations concerning +the copyright status of any work in any country outside the United +States. + +1.E. Unless you have removed all references to Project Gutenberg: + +1.E.1. The following sentence, with active links to, or other immediate +access to, the full Project Gutenberg-tm License must appear prominently +whenever any copy of a Project Gutenberg-tm work (any work on which the +phrase "Project Gutenberg" appears, or with which the phrase "Project +Gutenberg" is associated) is accessed, displayed, performed, viewed, +copied or distributed: + +This eBook is for the use of anyone anywhere at no cost and with +almost no restrictions whatsoever. You may copy it, give it away or +re-use it under the terms of the Project Gutenberg License included +with this eBook or online at www.gutenberg.org + +1.E.2. If an individual Project Gutenberg-tm electronic work is derived +from the public domain (does not contain a notice indicating that it is +posted with permission of the copyright holder), the work can be copied +and distributed to anyone in the United States without paying any fees +or charges. If you are redistributing or providing access to a work +with the phrase "Project Gutenberg" associated with or appearing on the +work, you must comply either with the requirements of paragraphs 1.E.1 +through 1.E.7 or obtain permission for the use of the work and the +Project Gutenberg-tm trademark as set forth in paragraphs 1.E.8 or +1.E.9. + +1.E.3. If an individual Project Gutenberg-tm electronic work is posted +with the permission of the copyright holder, your use and distribution +must comply with both paragraphs 1.E.1 through 1.E.7 and any additional +terms imposed by the copyright holder. Additional terms will be linked +to the Project Gutenberg-tm License for all works posted with the +permission of the copyright holder found at the beginning of this work. + +1.E.4. Do not unlink or detach or remove the full Project Gutenberg-tm +License terms from this work, or any files containing a part of this +work or any other work associated with Project Gutenberg-tm. + +1.E.5. Do not copy, display, perform, distribute or redistribute this +electronic work, or any part of this electronic work, without +prominently displaying the sentence set forth in paragraph 1.E.1 with +active links or immediate access to the full terms of the Project +Gutenberg-tm License. + +1.E.6. You may convert to and distribute this work in any binary, +compressed, marked up, nonproprietary or proprietary form, including any +word processing or hypertext form. However, if you provide access to or +distribute copies of a Project Gutenberg-tm work in a format other than +"Plain Vanilla ASCII" or other format used in the official version +posted on the official Project Gutenberg-tm web site (www.gutenberg.org), +you must, at no additional cost, fee or expense to the user, provide a +copy, a means of exporting a copy, or a means of obtaining a copy upon +request, of the work in its original "Plain Vanilla ASCII" or other +form. Any alternate format must include the full Project Gutenberg-tm +License as specified in paragraph 1.E.1. + +1.E.7. Do not charge a fee for access to, viewing, displaying, +performing, copying or distributing any Project Gutenberg-tm works +unless you comply with paragraph 1.E.8 or 1.E.9. + +1.E.8. You may charge a reasonable fee for copies of or providing +access to or distributing Project Gutenberg-tm electronic works provided +that + +- You pay a royalty fee of 20% of the gross profits you derive from + the use of Project Gutenberg-tm works calculated using the method + you already use to calculate your applicable taxes. The fee is + owed to the owner of the Project Gutenberg-tm trademark, but he + has agreed to donate royalties under this paragraph to the + Project Gutenberg Literary Archive Foundation. Royalty payments + must be paid within 60 days following each date on which you + prepare (or are legally required to prepare) your periodic tax + returns. Royalty payments should be clearly marked as such and + sent to the Project Gutenberg Literary Archive Foundation at the + address specified in Section 4, "Information about donations to + the Project Gutenberg Literary Archive Foundation." + +- You provide a full refund of any money paid by a user who notifies + you in writing (or by e-mail) within 30 days of receipt that s/he + does not agree to the terms of the full Project Gutenberg-tm + License. You must require such a user to return or + destroy all copies of the works possessed in a physical medium + and discontinue all use of and all access to other copies of + Project Gutenberg-tm works. + +- You provide, in accordance with paragraph 1.F.3, a full refund of any + money paid for a work or a replacement copy, if a defect in the + electronic work is discovered and reported to you within 90 days + of receipt of the work. + +- You comply with all other terms of this agreement for free + distribution of Project Gutenberg-tm works. + +1.E.9. If you wish to charge a fee or distribute a Project Gutenberg-tm +electronic work or group of works on different terms than are set +forth in this agreement, you must obtain permission in writing from +both the Project Gutenberg Literary Archive Foundation and Michael +Hart, the owner of the Project Gutenberg-tm trademark. Contact the +Foundation as set forth in Section 3 below. + +1.F. + +1.F.1. Project Gutenberg volunteers and employees expend considerable +effort to identify, do copyright research on, transcribe and proofread +public domain works in creating the Project Gutenberg-tm +collection. Despite these efforts, Project Gutenberg-tm electronic +works, and the medium on which they may be stored, may contain +"Defects," such as, but not limited to, incomplete, inaccurate or +corrupt data, transcription errors, a copyright or other intellectual +property infringement, a defective or damaged disk or other medium, a +computer virus, or computer codes that damage or cannot be read by +your equipment. + +1.F.2. LIMITED WARRANTY, DISCLAIMER OF DAMAGES - Except for the "Right +of Replacement or Refund" described in paragraph 1.F.3, the Project +Gutenberg Literary Archive Foundation, the owner of the Project +Gutenberg-tm trademark, and any other party distributing a Project +Gutenberg-tm electronic work under this agreement, disclaim all +liability to you for damages, costs and expenses, including legal +fees. YOU AGREE THAT YOU HAVE NO REMEDIES FOR NEGLIGENCE, STRICT +LIABILITY, BREACH OF WARRANTY OR BREACH OF CONTRACT EXCEPT THOSE +PROVIDED IN PARAGRAPH 1.F.3. YOU AGREE THAT THE FOUNDATION, THE +TRADEMARK OWNER, AND ANY DISTRIBUTOR UNDER THIS AGREEMENT WILL NOT BE +LIABLE TO YOU FOR ACTUAL, DIRECT, INDIRECT, CONSEQUENTIAL, PUNITIVE OR +INCIDENTAL DAMAGES EVEN IF YOU GIVE NOTICE OF THE POSSIBILITY OF SUCH +DAMAGE. + +1.F.3. LIMITED RIGHT OF REPLACEMENT OR REFUND - If you discover a +defect in this electronic work within 90 days of receiving it, you can +receive a refund of the money (if any) you paid for it by sending a +written explanation to the person you received the work from. If you +received the work on a physical medium, you must return the medium with +your written explanation. The person or entity that provided you with +the defective work may elect to provide a replacement copy in lieu of a +refund. If you received the work electronically, the person or entity +providing it to you may choose to give you a second opportunity to +receive the work electronically in lieu of a refund. If the second copy +is also defective, you may demand a refund in writing without further +opportunities to fix the problem. + +1.F.4. Except for the limited right of replacement or refund set forth +in paragraph 1.F.3, this work is provided to you 'AS-IS' WITH NO OTHER +WARRANTIES OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO +WARRANTIES OF MERCHANTIBILITY OR FITNESS FOR ANY PURPOSE. + +1.F.5. Some states do not allow disclaimers of certain implied +warranties or the exclusion or limitation of certain types of damages. +If any disclaimer or limitation set forth in this agreement violates the +law of the state applicable to this agreement, the agreement shall be +interpreted to make the maximum disclaimer or limitation permitted by +the applicable state law. The invalidity or unenforceability of any +provision of this agreement shall not void the remaining provisions. + +1.F.6. INDEMNITY - You agree to indemnify and hold the Foundation, the +trademark owner, any agent or employee of the Foundation, anyone +providing copies of Project Gutenberg-tm electronic works in accordance +with this agreement, and any volunteers associated with the production, +promotion and distribution of Project Gutenberg-tm electronic works, +harmless from all liability, costs and expenses, including legal fees, +that arise directly or indirectly from any of the following which you do +or cause to occur: (a) distribution of this or any Project Gutenberg-tm +work, (b) alteration, modification, or additions or deletions to any +Project Gutenberg-tm work, and (c) any Defect you cause. + + +Section 2. Information about the Mission of Project Gutenberg-tm + +Project Gutenberg-tm is synonymous with the free distribution of +electronic works in formats readable by the widest variety of computers +including obsolete, old, middle-aged and new computers. It exists +because of the efforts of hundreds of volunteers and donations from +people in all walks of life. + +Volunteers and financial support to provide volunteers with the +assistance they need are critical to reaching Project Gutenberg-tm's +goals and ensuring that the Project Gutenberg-tm collection will +remain freely available for generations to come. In 2001, the Project +Gutenberg Literary Archive Foundation was created to provide a secure +and permanent future for Project Gutenberg-tm and future generations. +To learn more about the Project Gutenberg Literary Archive Foundation +and how your efforts and donations can help, see Sections 3 and 4 +and the Foundation web page at https://www.pglaf.org. + + +Section 3. Information about the Project Gutenberg Literary Archive +Foundation + +The Project Gutenberg Literary Archive Foundation is a non profit +501(c)(3) educational corporation organized under the laws of the +state of Mississippi and granted tax exempt status by the Internal +Revenue Service. The Foundation's EIN or federal tax identification +number is 64-6221541. Its 501(c)(3) letter is posted at +https://pglaf.org/fundraising. Contributions to the Project Gutenberg +Literary Archive Foundation are tax deductible to the full extent +permitted by U.S. federal laws and your state's laws. + +The Foundation's principal office is located at 4557 Melan Dr. S. +Fairbanks, AK, 99712., but its volunteers and employees are scattered +throughout numerous locations. Its business office is located at +809 North 1500 West, Salt Lake City, UT 84116, (801) 596-1887, email +business@pglaf.org. Email contact links and up to date contact +information can be found at the Foundation's web site and official +page at https://pglaf.org + +For additional contact information: + Dr. Gregory B. Newby + Chief Executive and Director + gbnewby@pglaf.org + + +Section 4. Information about Donations to the Project Gutenberg +Literary Archive Foundation + +Project Gutenberg-tm depends upon and cannot survive without wide +spread public support and donations to carry out its mission of +increasing the number of public domain and licensed works that can be +freely distributed in machine readable form accessible by the widest +array of equipment including outdated equipment. Many small donations +($1 to $5,000) are particularly important to maintaining tax exempt +status with the IRS. + +The Foundation is committed to complying with the laws regulating +charities and charitable donations in all 50 states of the United +States. Compliance requirements are not uniform and it takes a +considerable effort, much paperwork and many fees to meet and keep up +with these requirements. We do not solicit donations in locations +where we have not received written confirmation of compliance. To +SEND DONATIONS or determine the status of compliance for any +particular state visit https://pglaf.org + +While we cannot and do not solicit contributions from states where we +have not met the solicitation requirements, we know of no prohibition +against accepting unsolicited donations from donors in such states who +approach us with offers to donate. + +International donations are gratefully accepted, but we cannot make +any statements concerning tax treatment of donations received from +outside the United States. U.S. laws alone swamp our small staff. + +Please check the Project Gutenberg Web pages for current donation +methods and addresses. Donations are accepted in a number of other +ways including including checks, online payments and credit card +donations. To donate, please visit: https://pglaf.org/donate + + +Section 5. General Information About Project Gutenberg-tm electronic +works. + +Professor Michael S. Hart was the originator of the Project Gutenberg-tm +concept of a library of electronic works that could be freely shared +with anyone. For thirty years, he produced and distributed Project +Gutenberg-tm eBooks with only a loose network of volunteer support. + + +Project Gutenberg-tm eBooks are often created from several printed +editions, all of which are confirmed as Public Domain in the U.S. +unless a copyright notice is included. Thus, we do not necessarily +keep eBooks in compliance with any particular paper edition. + + +Most people start at our Web site which has the main PG search facility: + + https://www.gutenberg.org + +This Web site includes information about Project Gutenberg-tm, +including how to make donations to the Project Gutenberg Literary +Archive Foundation, how to help produce our new eBooks, and how to +subscribe to our email newsletter to hear about new eBooks. + + +</pre> + +</body> +</html> diff --git a/35937-h/images/circle.jpg b/35937-h/images/circle.jpg Binary files differnew file mode 100644 index 0000000..3909fed --- /dev/null +++ b/35937-h/images/circle.jpg diff --git a/35937-h/images/thermo.jpg b/35937-h/images/thermo.jpg Binary files differnew file mode 100644 index 0000000..8054272 --- /dev/null +++ b/35937-h/images/thermo.jpg diff --git a/35937-h/images/thermo_tmb.jpg b/35937-h/images/thermo_tmb.jpg Binary files differnew file mode 100644 index 0000000..9aab627 --- /dev/null +++ b/35937-h/images/thermo_tmb.jpg diff --git a/35937-h/images/title.jpg b/35937-h/images/title.jpg Binary files differnew file mode 100644 index 0000000..5655b78 --- /dev/null +++ b/35937-h/images/title.jpg |
