402 W. A. Norton— Physical Constihition of the Su. 



point between this attraction and the inner repulsion. This 

 occnrs in the welding of iron. 



Other evidences of an effective repulsion in operation be- 

 tween the molecules of bodies in contact, or in close proximitv, 

 are cited in treatises on Physics ; although it is not always dis- 

 tinctly recognized that the sphere of its action lies entirely with- 

 out that of the effective molecular attraction. Now what is tLe 

 range of this effective repulsion between bodies. It obviously 

 extends only to a small distance. Cavendish's well-known ex- 

 periment has established that, when bodies are separated by con- 

 siderable distances they tend toward each other by the attrac- 

 tion of gravitation. But are we therefore to conclude that tlie 

 repulsive action, so energetic at the near approach of the mole- 

 cules, has vanished altogether when they are a considerable 

 distance apart Is it not more probable that this force is con- 

 fined to the surface molecules, and disappears at moderate 

 distances, in comparison with the attraction of gravitation 

 which is the result of the action of the entire masses on each 

 other, because it decreases according to the inverse squares of 

 the distance between the surfaces instead of the distance be- 

 tween the centers. I have elsewhere shoAvn* that the force ot 

 gravitation cannot be the attraction of cohesion operating at 

 considerable or great distances. It is a force sui generis, entirely 

 distinct from the forces of molecular attraction and repulsion 

 in operation at minute distances, and determining the constitu- 

 tion of bodies and their mechanical properties ; and operates 

 in conjunction with, but independently of, these molecular 

 forces, f 



In view of the concurrent testimony that we have now seen 

 is afforded by the two departments of Cometary, and Terrestnai 

 Physics, it will be admitted that, in attempting to gain a new 

 insight into the physical constitution of the sun, and the pro- 



* Philosophical Magazine, vol. xx: 



