94 Traces of Unity in the Various 



ibility. In the decomposition and composition which 

 the terminal points proceeding from the conductors of 

 an electrical machine develope when immersed in dif- 

 ferent chemical media, we get the production of chemical 

 affinity by electricity, of which motion is the initial 

 source. Lastly, motion may be again reproduced by the 

 forces which have emanated from motion ; thus the 

 divergence of the electrometer, the revolution of the 

 electrical wheel, the deflection of the magnetic needle, 

 are, when resulting from frictional electricity palpable 

 movements reproduced by the intermediate modes of 

 force, which have themselves been originated by motion." 

 Without parallax, or relative change of position, 

 motion is unproduceable, probably unimaginable. Mo- 

 tion, in short, has to do very obviously with ponderable 

 matter. Nor is a different conclusion arrived at when 

 heat is made the starting point of enquiry. At any rate 

 the difficulty is to realize heat except as motion in a 

 direction opposed to that of the attraction of cohesion, 

 and made known by its action on certain nerves of 

 sensation. With certain not unintelligible exceptions in 

 which the question is complicated by the introduction 

 of crystallization, polarization, dessication, &c., a body 

 expands when heated and shrinks on cooling. This is 

 all. The heat doing this work may be regarded as a 

 communicable repulsive force ; as a thing it is unknown. 

 Certain changes of ponderable matter, for which changes 

 heat is the generic name these are all that are known. 

 Even the notion of latent heat must be discarded with 

 as little compunction as phlogiston. That heat will 

 produce electricity is seen in the discovery of Seebeck, 

 that when dissimilar metals are soldered together, or 

 made to touch, and then heated at the point of contact, 

 a current of electricity flows through the metals in one 



