Marvels of the Universe 



59 



at the surface of tfie earth, it will onlj' fall six feet at the surface of Mars It follows from this that 

 the atmosphere of Mars is arranged in a different manner from that of the earth. On the earth, at 

 a height of 3^ miles, half the atmosphere is left beneath us, and by an ascent of another 3^ miles 

 half the remaining atmosphere will be passed through, and so on. On Mars we should have to ascend 



MIDSUMMER ON MARS. 



Drawing of Mars, made by M. Antoniadi, on 1909 September 20 the day of the summer solstice of tfie Southern 

 Hemisphere — with the 3 3-inch refractor of the Meudon Observatory. The great bright region in the lower part of the disc is 

 " Aeria." one ofjthe red lands that whiten under a low sun. The black marking, in the form of a cornucopia, that borders 

 Acria is the Syrtis Major, and midway between Aeria and the polar cap is the large round island " Hellas " that also grows 

 white when near the edge of the disc. 



8| miles to reach the level of half pressure, and 17J miles to reach that of quarter pressure. If the 

 pressure at the surface of Mars was as great as it is on the earth, we should be looking down 

 through nearly three times the amount of atmosphere that we possess, and in all probability we 

 could not discern his surface at all. As it is, the surface markings on Mars are almost as distinct 

 as tho32 on the Moon, a clear proof that we are looking through a thin and shallow medium. We 



