364 



THE POPULAR SCIENCE MONTHLY.— SUPPLEMENT. 



has been, is, or will be, inhabited — are demon- 

 strated in the third of the essays above mentioned. 

 That essay presents the view toward which the 

 present writer had been gradually led — from the 

 Brewsterian theory which he accepted until 1871, 

 through the Whewellite, toward which he had 

 inclined until 18*73, when finally the intermediate 

 theory seemed pressed upon him by overwhelm- 

 ing weight of testimony. 



Our present purpose is to show more particu- 

 larly how this theory accords with what is known 

 respecting the planet Mars. We wish also to 

 show how both the lines of reasoning which had 

 been before employed, one pointing to the Brew- 

 sterian theory, the other to the Whewellite theo- 

 ry, converge in the case of Mars upon this inter- 

 mediate theory. 



In the first place, we saw, in considering the 

 conditions which favor belief in the existence of 

 life in the planet Mars, that he presents the clear- 

 est possible evidence of being one in origin and 

 structure with our own earth. We cannot tell 

 what the nature of the soil of Mars may be, but 

 its generally ruddy tinge— so well marked that, 

 though the telescope shows an almost equal part 

 of the surface to be greenish in hue, the red pre- 

 vails, giving to the planet as seen by the naked 

 eye its obvious red color — seems to show that it 

 resembles the red sandstone of our own earth. 

 This, we know, is one of the older geological 

 formations, and if we could safely compare ter- 

 restrial with Martian geology, or, let us say, ge- 

 ology with areology, we might almost be tempted 

 to find in the present prevalence of a tint belong- 

 ing to one of the earlier of our terrestrial forma- 

 tions an argument in favor of the theory that 

 Mars passed through fewer stages of development 

 during its life-bearing condition than our earth, 

 and that thus the later formations of our earth's 

 surface are wanting in the surface of Mars. This 

 reasoning would not be very safe, however; it 

 implies a resemblance in details which is unlikely, 

 the observed rule of Nature seeming, so far as we 

 can judge, to be similarity in generals, variety in 

 details. We may well believe that the ruddiness 

 of the soil of Mars is due to the same general 

 cause as the ruddiness of our red sandstone — the 

 general prevalence of certain organisms ; but 

 neither the actual character of this particular for- 

 mation, nor its position in the terrestrial series 

 of strata, can be safely predicated of the ruddy 

 formation constituting the chief part of the visi- 

 ble land-surface of Mars. Few will now suppose 

 with a French writer, that the ruddiness of Mars 

 is due to the color of vegetation there. A cer- 



tain support is given to the idea by the circum- 

 stance that the degree of ruddiness is variable, 

 and is somewhat greater during the Martian sum- 

 mer than in spring and autumn. In this sense, 

 we may say of the summer of Mars with the poet 

 Wendell Holmes : 



" The snows that glittered on the disk of Mars 

 Have melted, and the planet's fiery orb 

 liolls in the crimson summer of its year." 



But the ruddiness of the planet's summer — 

 which will be well marked this year, for on Sep- 

 tember 18th, only eleven days after its time of 

 nearest approach and greatest splendor, it will 

 be midsummer's day for the southern half of 

 Mars — can be otherwise and better explained 

 than by supposing that the Martian forests glow 

 with fiery foliage during the summer days. We 

 can see, as the summer proceeds, the white mists 

 which had hidden the planet's lands and seas 

 breaking up, and the features of the surface be- 

 ing gradually revealed with more and more dis- 

 tinctness. It is to the disappearance of these 

 mists and clouds, not to the red leaves of Mar- 

 tian trees, that the change in the planet's color 

 must most probably be referred. 



We have less reason for doubt as to the na- 

 ture of the greenish markings. The spectro- 

 scope, as we have already explained in " Life in 

 Mars," shows that the air of Mars is at times 

 laden heavily with the vapor of water. We can 

 no longer, therefore, follow Whewell in doubting 

 the real nature of the green parts of the planet, 

 or refuse with him to accept the explanation of 

 the white polar markings long since advanced by 

 Sir W. Herschel. Undoubtedly wide seas and 

 oceans, with many straits, and bays, and inland 

 seas, exist on Mars. Snow and ice gather in the 

 winter-time about his polar regions, diminishing 

 gradually in extent as summer proceeds, but 

 never entirely disappearing. 



Thus we are not left doubtful as to the gen- 

 eral resemblance of Mars, so far as the structure 

 of his surface is concerned, to the earth on which 

 we live. lie has a surface of earth, probably in 

 large part formed by deposition at the bottom of 

 former seas and subsequently raised above the 

 sea-level by subterranean forces, or rather caused 

 to appear above the surface by the effects of the 

 gradual shrinkage of the planet's crust. Of the 

 existence of Vulcanian energy we have unmis- 

 takable evidence in the fact that lands and seas 

 exist, for a continent implies the operation of 

 Vulcanian forces. The shapes, too, of the out- 

 lines of the lands and seas indicate the existence 

 i of mountain-ranges, and these, too, of consider- 



