84 PROF. COOKE AND DR. CARPENTER. 



" When two molecules come within a certain distance 

 of each other, a mutual action takes place between them ; 

 which may be compared to the encounter of two billiard- 

 balls." 



In a recent paper, Professor J. P. Cooke ex- 

 plains the theory of molecular vibrations in the 

 following words : 



% 



" Conceive what a molecular storm must be raging 

 about us, and how it must beat against our bodies, and 

 every other exposed surface. The molecules of our 

 atmosphere move on an average nearly four times slower 

 than those of hydrogen under the same conditions ; but 

 as they weigh about fourteen and a half times more than 

 the hydrogen molecules, they strike with equal energy. 

 Do not think the effect of the blows insignificant, be- 

 cause the molecular projectiles are so small ; for they 

 make up by their number for their small size. Consider, 

 for example, that a cubic yard of air contains over two 

 pounds of molecules, which are vibrating with an aver- 

 age velocity of sixteen hundred feet a second, equivalent 

 to that of a cannon-ball of equal weight rushing at the 

 same tremendous rate. If the movements of the mole- 

 cules were all turned to one direction, instead of opposite 

 vibratory directions, even the massy pyramids could not 

 withstand this destructive violence. In the midst of 

 this molecular tornado, our preservation depends on the 

 beating of the storm in opposite directions ; and so pre- 

 cisely counteracting, that we are wholly unconscious of 

 the tumult of molecular forces." 



These molecular vibrations are discovered by 

 the microscope continually taking place to such an 

 extent, that Dr. Carpenter cautions microscopists 

 not to mistake them for vital forces. The vibra- 



