134 KANSAS CITY REVIEW OF SCIENCE. 



Again, considering that the Martial atmosphere is likely to be .105 that of the 

 earth, and is spread over .2828 the same amount of surface its density on the 

 surface of the planet is only .1379 that of the earth's surface atmosphere, giving 

 a pressure on the mercurial barometer of about 4.14 inches. The height of the 

 Martial atmosphere reduced to uniform surface density would be 2.694 times 

 that of the earth's atmosphere, or about 13.56 miles. The surface density of the 

 Martial atmosphere is only such as would be attained on the earth at the height 

 of 10.2 miles. 3 This implies a universal state of atmospheric tenuity on the sur- 

 face of Mars which has not been found compatible with any terrestrial life. The 

 simple difference in mass creates conditions which would render the surface of 

 Mars completely untenable by any human being ; and this consideration, it might 

 have been stated, applies as well to Mercury and the Moon. But this is no proof 

 that organic beings suited to such atmospheric pressure do not exist. Animals 

 are dredged from oceanic depths where the pressure as much exceeds the sea 

 level pressure as the atmospheric density of Mars falls below the terrestrial stand- 

 ard. Animals are adapted as they are because the conditions are as they are; 

 and we may feel assured that if the conditions were different, organic adaptations 

 would be different correspondingly. The conceivable range of adaptations is 

 limited only by the physical properties of inorganic matter. 



On the planet Jupiter, the mass so much exceeds that of the earth that all 

 the relative conditions are reversed. I have shown that atmospheric density is 

 nearly six and a half times as great as on the earth. Hence respiration would 

 only need to be six and a half times less active. On the contrary, the force 

 required to sustain the body against gravity would be more than two and a half 

 times as great, and all weights would be two and a half times as difficult to move. 

 This increased weight of the body and limbs would render comparatively less 

 efficient similar muscular efforts, while the gravitational resistances to be over- 

 come would be greater. A man sixteen and a quarter feet high would be barely 

 able to extend his arm at a right angle with his body. If ever the planet Jupiter 

 attains a habitable condition its organic beings will be limited in some such man- 

 ner as these numerical results imply. 



The apparent diameter of the Sun from Jupiter is only .2392 or ^l^- the same 

 from the earth; and the Sun's radiant energies in the forms of light, heat, actin- 

 ism and attraction, are only ^V of the same at the earth. Were the Sun's heat 



arm's length— would be 68 inches X "-5 = 42.5 feet; and the height of such a man on Mars would 



42.5 



be = 108.95 feet. 



.891 



1 

 3 If A = the height at which the density of the earth's atmosphere is — that at sea level, 



n 



then, since the density diminishes in a geometrical ratio as the height increases in an arithmet- 



1 1 



ical ratio, the height 27i will give a density of — ; the height 3A will give a density if — , and gen- 



n2 m 



1 1 



erally the height x h will give a density of — . But — = .1379, whence, of n == 2 and h = 2,705 miles, 



71.1; n^ 



X = 3.77 and x 7i = 3.77 X 2.705 = 10.2 miles. 



