502 THE CONSERVATION OF ENERGY 



In confirmation of these ideas as regards pressure, is the explanation 

 of the pressure and elasticity of gases given by Professors Clausius, 

 loule and others. Their investigations go to pi-ove that these properties 

 ai'e owing to the molecules of the gases moving in all directions with 

 great velocities, pressure being due to the momenta, masses and 

 number of molecules within, a given space, and elasticity to the vis 

 viva or energy of the molecules within the same space. 



A similar mode of action must be assumed for the luminiferous 

 ether ; that is to say, in still ether, as in still air, the constituent 

 particles are moving in straight lines with immense velocities, subject 

 to no actions except their impacts on each other and the atoms of 

 gross matter. These motions are to be carefully distinguished from 

 the ethereal waves, which correspond to the sound waves in air. 



"We can now explain forces of cohesion, and all kinds of tensile 

 forces. Without the assumption of the existence of ether, constituted 

 as above, such forces could not be explained. 



How these forces are produced, may be illustrated by the various 

 pneumatic phenomena, which may be classed under the popular idea 

 of suction. 



When the air in a receiver is rarified, the particles, having greater 

 space to move in, do not impinge the same number of times in a unit 

 of time against each other, nor against the sides of the vessel, their 

 velocity being supposed to remain unaltered ; hence the pressure is 

 less on the inside than on the outside, and there results an apparent 

 tension or attraction of the parts of the receiver towards the inside. 

 Similarly, if two flat surfaces are pressed together, the same phenomena 

 are witnessed ; in this case, it perhaps is possible that the air, instead 

 of being rarified, may be condensed ; in which case, the results would 

 be accounted for by supposing the velocities of the particles of confined 

 air to have been lessened to some extent. If the velocities of the 

 particles are unaltered, the elasticity is proportional to the density ; 

 if otherwise, it is not. 



Now, substitute for air the luminiferous ether, and for the flat 

 plates the sides of two atoms, and it becomes evident how they may 

 cohere. If this be the explanation of cohesion, we must assume all 

 atoms that are known to unite with others to have flat faces. The 

 luminiferous ether alone, in the present state of our knowledge, can 

 be supposed to consist of spherical atoms. 



