G2 Prof. W. A. Norton on the Physical Constitution of the Sun. 



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

 has established that, when bodies are separated by considerable 

 distances, they tend toward each other by the attraction of gra- 

 vitation. But are we therefore to con-elude that the repulsive 

 action, so energetic at the near approach of the molecules, has 

 vanished altogether when they are a considerable distance apart ? 

 Is it not more probable that this force is confined 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 between the centres ? I have 

 elsewhere shown* that the force of gravitation cannot be the 

 attraction of cohesion operating at considerable or great dis- 

 tances. It is a force sui generis, entirely distinct from the forces 

 of molecular attraction and repulsion in operation at minute 

 distances and determining the constitution of bodies and their 

 mechanical properties, and operates in conjunction with, but in- 

 dependently 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 terrestrial 

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

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

 cesses of change in operation on its surface, we are at least en- 

 titled to assume the following as probable hypotheses : — 



1. That the sun exercises a repulsive action upon the mole- 

 cules of every gas or vapour that subsists at its surface, or is at 

 any time in any part of the region of space exterior to the sur- 

 face ; that this force is the sum of all the heat-impulses propa- 

 gated in sethereal waves from all the gaseous molecules posited 



* Philosophical Magazine, vol. xxxviii. p. 38. 



t It ought here to be stated that in my paper " On Molecular Physics/' 

 published in Sillirnan's Journal, vols, xxxviii., xxxix.,andxl., I have deduced 

 from the fundamental conception of a primitive molecule (or chemical 

 atom) adopted a force of molecular repulsion operating beyond the sphere 

 of the molecular or cohesive attraction, and reached the conclusion that 

 this force has its immediate origin in the physical change to which the 

 development of heat is in every instance due, viz. an inward or contractile 

 vibratory movement of the electric envelopes by which all atoms are con- 

 ceived to be surrounded as well as by ^ethereal atmospheres. It is accord- 

 ingly termed the molecular heat-repulsion. The repulsive energy of heat 

 in operation on any molecule is the sum of all the sethereal impulses de- 

 veloped by such movements of the envelopes of other molecules (whether 

 originating in the attraction exerted by the central atoms on their enve- 

 lopes, or in an external collision or pressure), and propagated to the mole- 

 cule. From the principle of interception of wave-force it results that the 

 external repulsive action exerted by a solid body is confined to the surface- 

 molecules; while a force of heat-repulsion is propagated to an indefinite 

 distance from all the molecules of a gas. 



