MARS AND VENUS 311 



the sharp retreating figure of the globe in that high 

 latitude. 



After thus carefully setting out his facts, Mr. Lowell 

 proceeds to his theorizing somewhat as follows : 



1. According to the molecular theory and the math- 

 ematical analysis by Clerk Maxwell, the molecules of 

 hydrogen possess velocities of about seven miles a second, 

 which is slightly higher than the critical, or parabolic, 

 velocity at the earth's surface, and very much higher 

 than this same velocity at the surface of Mars. Now, 

 Doctor Johnstone Stoney has suggested that a logical 

 consequence of this molecular pecularity should be that 

 small bodies like the moon would, because of their feeble- 

 ness of attraction, gradually lose these swifter-moving 

 molecules and, in the course of years or centuries, become 

 denuded, not only of a large part of their original atmos- 

 phere, but more particularly of their original supplies of 

 water, of which mineral hydrogen is an indispensable 

 constitutent. As scientists in general concede this de- 

 duction of Doctor Stoney, and as the dead moon is uni- 

 versally believed by them to be devoid of both air and 

 water, or practically so, the inference is that Mars, 

 though more slowly, is following the moon's example and 

 gradually deteriorating into a desert planet at the end 

 of a protracted period of exalted biological development. 

 Mars, then, Mr. Lowell concludes, is an arid planet, and 

 to its inhabitants, if any, water must be at a very high 

 premium. 



2. Water is essential to life. There being no 

 oceans, the streams too must be dried up. The alter- 

 native is presented of death from thirst, or of recourse 

 to the only fresh water supply remaining, to wit, the 

 polar snows. 



3. Naturally this necessity prompted to the Mar- 

 tians the canal idea. Of course the system now in evi- 

 dence was not constructed in a day; it was the result, 

 rather, of slow growth, developing painfully in inverse 

 ratio to the failing sources of supply. 



