426 Prof. Norton on Molecular Physics. 



this compression of the molecular atmospheres, should, then, be 

 a source of heat. Thus chemical combination of two particles 

 in which they are drawn into close union, collision of bodies, 

 external pressure, and friction are different sources of heat. 

 The disturbance of the electric equilibrium of contiguous mole- 

 cules may also give rise to the evolution of heat — by reason of 

 the increased repulsion exerted by the excess of electric sether 

 accumulated upon certain of the molecules, or upon one side of 

 them, or of a discharge of the sether occurring from one molecule 

 to another. 



Propagation of Heat. — Primarily the heat-pulses are developed 

 in the universal sether associated with the atoms of bodies. 

 These pulses may be conveyed outward through the universal 

 sether posited between the atoms, and in this way be freely trans- 

 mitted through substances ; or they may be more or less taken 

 up or absorbed by the electric atmospheres of the molecules which 

 they encounter. Such absorbed pulses may be given out again 

 or radiated in their original form, or they may pass on to conti- 

 guous molecules through the electric sether that pervades the in- 

 terval between them. It is probably in this latter mode chiefly 

 that heat is conducted from particle to particle of a substance, 

 though the pulses that are given out by any particle to the sur- 

 rounding universal sether may.be in part propagated onward, 

 absorbed by the particles they encounter, and partially propa- 

 gated onward again in the same manner to the next particles. 



The flow of heat from one particle to 'another of a substance 

 tends to disturb the electric condition of the particles ; for the 

 repulsive action of the heat-pulses in the atmosphere of one 

 particle tends to urge away a portion of the electric aether from 

 the contiguous side of the next particle in the line of propaga- 

 tion, and so to induce a negative electric state upon that side, 

 and a positive state on the further side. This disturbance of the 

 electric equilibrium of contiguous molecules may give rise to a 

 discharge of the electric sether from the one to the other, and a 

 consequent more ready propagation of the heat-pulses from the 

 one to the other. Upon this idea there is a close analogy 

 between the conduction of heat and the conduction of electricity 

 in the galvanic current, both depending upon the facility with 

 which an electric polarization of contiguous particles is deter- 

 mined. The origin of this propagated polarization in the one 

 case is the addition of repulsive pulses to the atmosphere of a 

 molecule, and in the other the accumulation of an excess of the 

 repulsive electric sether around a molecule or upon one side of 

 it, A confirmation of these views is afforded by certain pheno- 

 mena of thermo-electric currents, from which it appears that the 

 conduction of heat is in reality attended with the disturbance of 



