i6 IN STARRY REALMS. 



information will actually warrant. In the first place, the 

 most striking feature presented in Mr. Green's drawings, 

 as well as in every similar series of pictures, is the remark- 

 able white region near the pole of the planet. In the case be- 

 fore us it is the southern pole that is exposed to view. It 

 does not, however, appear that the white region is situated 

 quite centrally with reference to the axis. Mr. Green gives 

 good reasons for believing that the true south of the end 

 axis of rotation of Mars lies just within the eastern edge 

 of the white cap, as it appeared in September, 1877. The 

 phenomena of our own poles at once suggest an explana- 

 tion of the presence of these white regions on Mars. Can 

 it be that this planet, which resembles our earth in so 

 many other respects, resembles it also in the possession 

 of polar regions crowned with solid masses of peren- 

 nial snow and ice? Apart from the argument founded 

 on analogy, the strongest evidence that can be adduced in 

 support of the ice explanation of the white region arises 

 from the undoubted variability of size of the region over 

 which the white fields extend, corresponding with the 

 Martial season. 



The existence of an atmosphere surrounding the planet 

 has also been asserted, perhaps I might say demonstrated. 

 It is, however, certainly very much less ample than the 

 atmosphere enveloping this earth in its density and 

 extent. The most reliable indications of air around Mars 

 are afforded by the indistinctness of the planetary features 

 as they approach the margin by the gradual rotation of 

 the planet. In fact, Mr. Green speaks of the atmospheric 

 ring of bluish white surrounding the interior edge of the 

 disc. The atmosphere also sometimes contains masses of 



