Page:The Solar System - Six Lectures - Lowell.djvu/69



The number of molecules traveling at speed u is given by the equation,—

just as the probability of an error is given by the equation,

G = mean value of speed in metres per second. G'= mean value of speed in miles per second.

These speeds are got from the consideration that the energy, from which follows the temperature, is the same in the two gases; and, therefore, that

and, therefore, the speed of the molecule is inversely as the square root of the atomic weight.

So far theory. Now it is not a little interesting that observation supports this. That air still exists on Mars, oxygen, nitrogen, and carbonic acid,