M. HenrJci on the Theory and Application of Electricity, 165 



tricity of the same kind, the free electricity of any conductor 

 is diffused over its surface and forms a layer of inconsiderable 

 thickness. But, on the one hand, if the electricity were thus 

 forced towards the surface, there must be something which 

 forces, consequently electricity, in the interior of the conductor, 

 and again the repelled particles must exert an equal but op- 

 posing action, inasmuch as they cannot escape into any sur- 

 rounding non-conductor. Thus an equilibrium would be 

 formed betwetMi all the electrical particles, which could only 

 consist in an equality of their mutual pressure. In fact, we 

 only find this condition in aeriform bodies which are confined 

 in any given space (as in porous bodies, which have no at- 

 traction for them); moreover, in a solid body heated through- 

 out and surrounded by a bad conductor of heat, we find no 

 trace of a distribution of this heat over the surface. 



It is difficult to understand what is the nature of the re- 

 pulsion supposed to exist between the particles of like elec- 

 tricities. When repulsion occurs between two such particles, 

 both must evidently separate from one another, consequently 

 a fluid consisting of such particles must be expansible, and 

 vice versa compressible. The mathematical theory of electri- 

 city hitherto adopted requires, however, that the electricities 

 should be incompressible fluids. This assumption is how- 

 ever by no means supported by analogy. In ponderable bo- 

 dies we find a repulsion of the ultimate molecules in gases 

 only, /. e. in remarkably compressible bodies alone; in liquids, 

 properly so called, which are always to a certain extent com- 

 pressible, we find an attraction of their particles. 



The ordinary view of the electrical principle is conse- 

 quently not capable of explaining the action of electrified bo- 

 dies at a distance, which is produced as if their free electricity 

 existed only at the surface, and altogether we must consider 

 it merely of use as a means of handling electrical phaenomena, 

 and as enabling us to treat the same mathematically. 



2. The current from an electrical machine produces gal- 

 vanic (magnetic, thermal, chemical, &c.) effects, just as the 

 current from a galvanic series. We can, without difficulty, re- 

 duce two currents, one originating in each manner, to exactly 

 the same galvanic action. In this case the electrical particles 

 must have the same quantity of motion in both. 



But what a marked difference exists in their tension ! and 

 yet, according to the dualistic hypothesis, the separation and 

 reunion of the electricities in the conducting circles of each 

 must take place with equal energy if the above-mentioned 

 conditions are to be fulfilled. Hence it appears natural that 

 there should exist different kinds of electricity, just as there 



