170 ANNUAL OF SCIENTIFIC DISCOVERT. 



in glass or other brittle bodies ; melted as in metals, or chemically 

 separated, as in compound bodies. These various actions are the 

 equivalents of the electric force, and are its correlated forms. 



The energy, in that particular form we call electricity, has, in 

 each of these cases of discharge, been expended. As a cause, it 

 has acted, and as such has disappeared. Its further existence 

 must be sought for in its effects. The mechanical and chemical 

 separations, the heat and the light, are all so many evidences of 

 the electric force and exact measures of it. 



That all these changes are the results of molecular displace- 

 ments seems plain from the effects. When passed through a 

 thick plate of glass, the discharge pulverizes, along its track, the 

 glass to an impalpable powder. A violent separation of particle 

 from particle iuis taken place, as if the molecular spaces were filled 

 with an explosive substance. A blow from a hard body, or from a 

 fluid that would drive the particles before it and leave a clear open- 

 ing. Each particle is so disrupted from the adjacent ones as to break 

 up the cohesion, while none are thrown off except at the surface, 

 where there is no force to counteract the explosive action. The 

 pulverized atoms must occupy more space, and naturally press 

 outward in the direction of least resistance. The burr on both 

 sides of a card merely indicates the strong molecular repulsion 

 acting from -within outward. The imprisoned air in bodies of 

 loose texture will have its influence ; but the double burr will be 

 produced in their plates of wax, in which air cannot be present in 

 sensible quantity. When a tree is riven by lightning, the splinter- 

 ing is caused by the repulsive energy acting along the line of dis- 

 charge. If the fibres of the wood, when the fracture takes place, 

 had been changed to gunpowder or gun-cotton, and exploded, the 

 results would closely represent those effected by electricity. So 

 when a body is melted by the discharge, the heat in producing 

 liquidity certainly acts upon the molecules. But it is unreasonable 

 to suppose that the heat is developed by the discharge merely on 

 the surf;\ce, and then passes inward by the slow process of con- 

 duction. On the contrary, it flashes into intense energy, at the 

 fc^ame instant, among all the particles of the mass. The inconceiv- 

 able rapidit}^ of the change caused by electricity, leaves no time 

 for conduction. 



That chemical affinity is a molecular force, no one, it is pre- 

 sumed, will doubt. But the very intimate relations of the chemi- 

 cal and electric forces, so mucli so as to induce in some minds a 

 belief of their identity, will hardly permit us to assign a molecular 

 character to one and not to the other. The light which pervades 

 the atmosphere for some distance around the point where lightning 

 strikes the earth, does not seem, from the cases the writer has 

 witnessed, to be a gleam or reflection from the brighter track of 

 the spark, but rather a light produced in the air, for some distance 

 around, by molecular disturbance, the same in kind, but less in 

 degree, as that which rivals sunlight along the central path. A 

 green tree, at which the writer happened to be looking the mo- 

 ment it was struck, was covered from top to bottom with a dift'iised 

 flame, in the midst of which the central stream of fire gleamed in 



