as applied to Gases and Vapours. 517 



r being the mean value of a coefficient which is subject to small 



periodical variations only*. 



This coefficient, being the ratio of the vis viva of motion of a 

 peculiar kind to the whole vis viva impressed on the atomic atmo- 

 spheres by the action of their nuclei, maybe conjectured to have 

 a specific value for each substance, depending in a manner as yet 

 unknown on some circumstance in the constitution of its atoms. 

 It will afterwards be seen that this circumstance is the chemical 

 constitution. 



Let the entire atmosphere of an atom be conceived to be di- 

 vided into a great number of very acute pyramids meeting at the 

 centre, and having even numbers of faces, equal and opposite in 

 pairs; and let one of these pyramids, intersecting a spherical 

 layer whose distance from the nucleus is Rw and thickness 

 "Rdic, cut out a frustum, containing and surrounded by vortices. 

 Consider one pair of the faces of that frustum ; their length being 

 Udu, let their breadth be h and their distance asunder /. Then 

 they make with each other the angle at the apex of the pyramid 



their common area is hRdu j and the sum of the volumes of the 

 two triangular frusta of the spherical layer, included by diagonal 

 planes drawn between their radial edges, is 



fhRdu 



the sum of all such triangular frusta being the whole volume of 

 the spherical layer. 



The additional pressure due to the centrifugal force of vor- 

 tices, viz. 



v^p 



* As it has been represented to me, that I have, without stating sufficient 

 grounds, assumed the velocity of revolution w to be constant throughout 

 each individual vortex, I add this note to assign reasons for that supposition. 



First. Unless w, the velocity of revolution of a particle, is independent 

 of z, its radius vector, the atomic atmosphere cannot be in a permanent 

 condition. 



For if wis a function of 2, the external elasticity of a vortex will be a func- 

 tion of its diameter. If the whole atmosphere is in motion, vortices of dif- 

 ferent diameters must exist in the same spherical layer ; and if their ex- 

 ternal elasticities are different, their condition cannot be permanent. 



Second. Whatsoever may be the nature of the forces by which velocity 

 is communicated throughout the atmosphere, the tendency of those forces 

 must be to equalize that velocity, and thus to bring about a permanent 

 condition. 



