276 Mr, Exley's Application of 



Or thus : let one of the atoms be increased in its absolute 

 force in any ratio; then the force between it and every 

 other atom in the vessel is increased in the same ratio : but 

 the repulsion between it and contiguous atoms, and, con- 

 sequently, between all contiguous atoms, is increased in 

 that ratio : therefore, the equilibrium continues ; that is, 

 a variation in the absolute force produces no change of 

 equilibrium, and their tendency to separate remains as 

 before. The truth of the proposition is manifest, when the 

 sphere of repulsion only is changed. 



Def. 1 . A single group of atoms is a collection of two or 

 more tenacious atoms, such, that all their centres are within 

 the sphere of repulsion of some one of them, as in fig. 4. 



Def. 2. A double group of atoms is two tenacious atoms, 

 or two single groups, or one atom or single group connected 

 by a third atom or single group, such that the connecting 

 atom or group displaces the greatest part of the ethereal 

 and electric atoms between the two atoms or groups which 

 it connects, and the parts of their atmospherules on the 

 contiguous sides, as in tig. 5 and 6. 



Cor. 1. Considering a single group as one atom, there 

 will be always in equal volumes of different gases an equal 

 number of atoms, the pressure being given. 



For, 1st, when the tenacious atoms are distinct, and 

 separate, and of the same kind ; this follows from the 2nd 

 and present propositions; since, being in the gaseous form, 

 they are kept apart by intervening ethereal matter ; and, 

 since they are of the same kind, they will be uniformly 

 arranged in the vessel ; therefore, on the other hand, if 

 two gases of two given sorts occupy equal volumes, and 

 contain an equal number of tenacious atoms, the centres 

 will be equi-distant ; therefore, the separating forces (by 

 this and the preceding proposition) will be equal ; and 

 hence, they will sustain the same, pressure ; therefore, when 

 the pressure is given, the number of atoms is equal. 



2nd. It is manifest from the same propositions, that a 

 single group will occupy a volume equal to that occupied 

 by a single tenacious atom ; for, since the centres of all the 

 atoms in the group are within the sphere of repulsion of 

 one of them, the centre of gravity of the group may be 

 considered as the centre of a single atom, and the contout* 



