MAES. 



525 



server about 25 J. Around this pole was a 

 coronet of apparently glittering snow. Lord 

 Kosse had estimated the diameter of this 

 snowed surface in July, three months before, 

 at 1,000 miles ; at the beginning of the oppo- 

 sition, in October, it did not exceed 560 miles; 

 and it diminished continually during the two 

 months of observation : thus, from Martial 

 latitude 74 S., in July, the snow had receded 

 to 8 S. in October, this pole having been all 

 the time in sunshine. N"o appearance of snow 

 was then seen about the north pole. In 1864 

 the opposition was later in our year by about 

 seven weeks at the end of November; the 

 south pole was tilted toward the observer 

 only about 6, and the snow had been longer 

 in sunshine. Only a small ellipse of snow 

 could then, and that not invariably, be de- 

 tected. But now there were sure indications 

 of snows in two situations on the northern as- 

 pect of the planet. The appearance reached 

 the latitude of about 50, constituting an unin- 

 terrupted arctic zone in the latter part of the 

 southern Martial summer, and toward the 

 close of the northern winter. Fifty degrees of 

 north latitude then free from great tracts of 

 snow, would be a result fairly matching the 

 average climate of our northern zones toward 

 the end of February. Mr. de la Rue's draw- 

 ings, April, 1856, showed northern and south- 

 ern snow masses, the northern not then reach- 

 ing the pole, which was toward the sun ; and 

 the equatorial interval between the two was 

 105 a fact leading to the conclusion that 

 the temperature is not much lower than that 

 of the earth, upon which the interval may be 

 taken at about 120. 



The surface of the planet, generally free 

 from the appearance of snow, offers a great 

 variety of distinct outline, which separates 

 bright from dusky or shaded parts. In general, 

 an undulated outline is traced along the inter- 

 tropical regions, mostly south of the equator ; 

 from this a large tract of bright surface spreads 

 toward the north, while south of it the surface 

 is mostly greenish gray, or appeal's in half- 

 lighted spaces. Calling the gray parts sea, 

 and the bright land, it would follow that upon 

 Mars water prevails in the southern and land 

 in the northern hemisphere. The tint of the 

 supposed land is that of a soft red, like the 

 diffused air-tints of a hazy sunset, -or that given 

 by Indian red, faint. As seen in the observa- 

 tions of 1864, the larger masses of supposed 

 land had the same color as when previously 

 observed, though then more faint, in part at 

 least, through increased distance; but the seas 

 were at that time gray and shadowy, without 

 the very distinct greenish hue noticed in 1862. 

 In his opening address before the British Asso- 

 ciation, at the meeting of 1865, Professor Phil- 

 lips, whoso remarks in his previous papers 

 would bear the interpretation that he consid- 

 ered the red color of the continental parts of 

 Mars as due to some quality of the land itself, 

 distinctly avowed the opinion already given as 



that of Huggins and Joynson, declaring that 

 " enough is ascertained to discountenance the 

 notion of his redness being due to a peculiarity 

 of the soil." In any case, the redness is, as a 

 rule, hardly traceable over any part of the 

 smaller and less distinctly bordered lands of 

 the south. One broad dark surface appeared 

 about the equator in longitude 20, communi- 

 cating by an apparent channel (a long narrow 

 strait, running K E. and S. W. DAWES), 

 with the north polar region, which also pre- 

 sents for the most part apparently a water sur- 

 face. 



Are there, then, in fact, snows? land? 

 water? any thing, indeed, beyond effects of a 

 vast and diversified stratum of cloud ? The an- 

 swer is: the facts go to show a distinct and 

 steady melting away of snows. Then there 

 must be water, and an atmosphere having 

 aqueous vapor. Besides, the characteristic out- 

 lines noted upon the planet's surface are too 

 permanent for cloud. Of land and water sur- 

 faces on the body of the planet, as one may see 

 by looking from a high mountain on land and 

 ocean, the water surfaces must appear the more 

 obscure. Unlike the earth, Mars appears to 

 have more land than water surface, the land 

 being mostly collected in a broad band, includ- 

 ing the intertropical spaces and the northern 

 temperate region, while seas surround the poles, 

 and cover a large proportion of the south tem- 

 perate zone. 



But how account for a climate on this more 

 distant planet not greatly differing from that 

 of our earth, when the mean quantity of sun- 

 shine reaching the former should by theory be 

 only the (f) 2 of that affecting the latter? 

 Two suppositions present themselves : the flow 

 of internal heat may be greater; or the waste 

 of heat from the surface may be much less. In 

 fact these two conditions may coexist: di- 

 rectly considered, the second is probably the 

 more important in the case ; and yet it appears 

 requisite to suppose a greater communication 

 of heat from the interior of the planet, in order 

 to maintain in the atmosphere, and with the 

 limited ocean-surface of Mars, the greater quan- 

 tity of vapor, to the presence of which the re- 

 taining of the sun's heat should be due. For 

 Prof. Tyndall has shown that an atmosphere 

 charged with vapor is to its planet as the 

 "clothing" or "jacket" to a steam cylinder; 

 it keeps in the heat; and in case of an atmos- 

 phere holding vapor, the deeper and denser 

 the stratum of the latter, the greater the effect. 

 The vapor, while it admits freely the sun's ra- 

 diant heat, possesses in proportion to its extent 

 in height and the percentage of it present, a 

 greater power of arresting the outflow into 

 space both of the planet's central heat and that 

 it receives from the sun. Possibly the atmos- 

 phere of Mars may be peculiar in quality ; if so, 

 spectrum analysis may yet indicate that fact. 

 Many independent observations go to show that 

 this planet's atmosphere is extensive, but also 

 that it is not always loaded with clouds. 



