LOWELL. — TEMPERATURE OF MARS. 667 



Similarly for Mars it is 



and as the whole mass of the earth's atmosphere over any space di/dz = 

 4.5 that of Mars at a similar point, and r/i = .38^, we have 



1 = ^-^ Ts' 



whence as J. = 30 inches of barometic pressure, Ai = 2.5 inches. 



Boiling Point on Mars. 



Owing to the less amount of the Martian air and the smaller gravity 

 at the surface of the planet the boiling point of water is greatly re- 

 duced, being probably in the neighborhood of one hundred and eleven 



degrees Fahrenheit. If the whole mass of air be -^ of the earth's, 



4.0 



while gravity is .38 of ours, the pressure is 



dlir/i = .09 of the earth's, 

 whence the boiling point is 44° C. or 



79 + 32 = 111° F. 



For the same reason sublimation takes place more freely at identical 

 temperatures there. Proportionally, therefore, there would be more 

 water- vapor in the air. 



We may summarize the results for Mars : 



Mean Temperature . . . . 48° F. or 9° C. 



Boiling point of water . . . . 1 11 ° F. or 44° C. 



Amount of air per unit surface . 7 in. or 177 mm. ; § of the earth's. 



Density of air at surface . . . 2.5 in. or 63 mm. ; yVof " " 



The look of the surface entirely corroborates the temperature result 

 of this investigation. 



'to-- 



Januart 14, 1907. 



