116 SCHIAPARELLl's LATEST VIEWS REGARDING MARS. 



they must occupy the poles of rotation of the phiuet, or at least must 

 be fouud very uear to them. Consequently they were given the name 

 of polar caps or spots. And not without reason is it conjectured that 

 these represent upon Mars that immense mass of snow and ice which 

 still to-day prevents mivigators from reaching the poles of the earth. 

 We are led to this conclusion not only by the analogy of aspect and of 

 place, but also by another important observation. - - - 



As things stand, it is manifest that if the above mentioned white 

 polar spots of Mars represent snow and ice they should continue to 

 decrease in size with the approach of summer in those places and 

 increase during the winter. Now this very fact is observed in the 

 most evident manner. In the second half of the year 181»2 the south- 

 ern polar cap was in full view; during that interval, and especially in 

 the months of July and August, its rapid dimimition fiom week to week 

 was very evident even to those observing with common telescopes. 

 This snow (for we may well call it so), which in the beginning reached 

 as fiir as latitude 70^ and formed a cap of over 2,000 kilometers (1,L*00 

 miles) in diameter, progressively diminished, so that two or three months 

 later little more of it remained than an area of perhaps 300 kilometers 

 (180 miles) at the most, and still less was seen in the last days of 1802. 

 In these months the southern hemisphere of Mars had its summer, 

 the summer solstice occurring upon October 13. Correspondingly the 

 mass of snow surrounding the northern pole should have increased; 

 but this fact was not observable, since that pole was situated in the 

 hemisphere of Mars which was opposite to that facing the earth. The 

 melting of the northern snow was seen in its turn in the years 1882, 

 1884, and 1886. 



Theseobservationsof the alternate increase and decreaseof the i)olar 

 snows are easily made even with telescopes of moderate power, but 

 they become much more interesting and instructive when we can follow 

 assiduously the changes in their more minute particulars, using larger 

 instruments. The snowy regions are then seen to be successively 

 notched at their edges; black holes and huge fissures are formed in 

 their interiors; great isolated pieces many miles in extent stand out 

 from the i)rincipal mass and, dissolving, disappear a little later. In 

 short, the same divisions and movements of these icy fields present 

 themselves to us at a glance that occur during the summer of our own 

 arctic regions, according to the descriptions of explorers. 



The southern snow, however, presents this peculiarity: The center 

 of its irregularly rounded figure does not coincide exactly with the pole, 

 but is situated at another point, which is nearly always the same, and 

 is distant from the pole about 300 kilometers (180 miles) in the direc- 

 tion of the Mare Erythricum. From this Ave conclude that when the 

 area of the snow is reduced to its smallest extent the south pole of 

 Mars is uncovered, and therefore, ])erhaps, the problem of reaching 

 it upon this planet is easier than upon the earth. The southern snow 



