PHYSICAL ASTRONOMY. 



SECT. V. 



OF THE ATTRACTION OF SPHERES AND SPHE- 

 ROIDS. 



2QI. THE particles of matter being supposed 

 to attract with forces inversely as the squares 

 of the distances, the forces with which similar 

 solids attract particles similarly situated with 

 respect to them, are as any two homologous 

 lines, or any two similarly situated lines, in those 

 solids. 



This proposition is easily proved of pyramids, and 

 frusta of pyramids, of which the solid angle is 

 indefinitely small. From thence it is transfer- 

 red to all solids which can be resolved into the 

 same number of similar pyramids, that is, to all 

 similar solids. MACLAURIN'S Fluxions^ 629. 



. The same law of attraction being sup- 

 posed, a particle placed any where within a hol- 

 low shell of any thickness, contained between 

 similar and similarly situated surfaces, will be 

 in equilibria, or will be urged equally in all op- 

 posite directions. 



This 



