His first draft of a theory 399 



COR. i. Let a fluid of the above-mentioned kind be spread uniformly through 

 infinite space except in the hollow globe BDE, and let 

 the sides of the globe be so thin that the force with which 

 a particle placed contiguous to the sides of the globe 

 would be repelled by so much of the fluid as might be 

 lodged within the space occupied by the sides of the 

 globe should be trifling in respect of the repulsion of the 

 whole quantity of fluid in the globe. 



If the fluid within the globe was of the same density 

 as without, the particles of the fluid adjacent to either 



the inside or outside surface of the globe would not press against those surfaces 

 with any sensible force, as they would be repelled with the same force by the 

 fluid on each side of them. But if the fluid within the globe is denser than 

 that without, then any particle adjacent to the inside surface of the globe will 

 be pressed against by the repulsion of so much of the fluid within the globe as 

 exceeds what would be contained in the same space if it was of the same 

 density as without, and consequently will be greater if the globe be large than 

 if it be small. Consequently the pressure against a given quantity (a square inch 

 for example) of the inside surface of the globe will be greater if the globe is 

 large than if it is small. 



If the particles of the fluid repel each other with a force inversely as their 

 distance, the pressure against a given quantity of the inside surface would be 

 as the square of the diameter of the globe. So that it is plain that air cannot 

 consist of particles repelling each other in the above-mentioned manner. 



If the repulsion of the particles was inversely as some higher power of the 

 distance than the cube, then any particle of the fluid would not be sensibly 

 affected except by the repulsion of those particles which were almost close to 

 it, so that the pressure of the fluid against a given quantity of the inside surface 

 would be the same whatever was the size of the globe, but then the elasticity 

 [would] be in a greater proportion than that of the power of the density. 



If the repulsion of the particles is inversely as some less power than the cube 

 of the distance, and the density of the fluid within the globe is less than it is 

 without, then the particles on the outside of the globe will press against it, and 

 the force will be greater if the globe is large than if it be small. 



If the density of the fluid within the globe be greater than without, then 

 the density will not be the same in all parts of the globe, but will be greater 

 near the surface and less near the middle, for if you suppose the density to be 

 everywhere the same, then any particle of the fluid, as d, would be pressed with 

 more force towards a, the nearest part of the surface of the sphere, than it would 

 [be] in the contrary direction. 



If the repulsion of the particles is inversely as the square of the distance, I 

 think the inside of the sphere would be uniformly coated with the fluid to a 

 certain thickness, in which the density would be infinite, or the particles would 



