GALVANISM. 



331 



GALVANISM. 



THE investigation of the mechanical phenomena of material substances has 

 been, in modern works, conducted by resolving these effects into two principal 

 divisions ; those in which the bodies exhibiting them are at rest, and those in 

 which they are in motion. As applied to solid bodies, these divisions have 

 been respectively denominated STATICS and DYNAMICS ;* and, as applied to 

 fluids, HYDROSTATICS and HYDRODYNAMICS. Electricity being assumed to be 

 a physical agent, having the properties of an elastic fluid, and capable, like 

 the grosser solids and fluids, of being maintained in a state of equilibrium by 

 the mutual action and reaction of antagonist forces, or of moving in definitfe di- 

 rections, and forming currents of greater or less intensity, the analysis of its 

 effects would naturally be conducted by means of the same classification ; 

 and, accordingly, that division of the science in which the electric fluid is con- 

 sidered in a state of equilibrium or repose, and in which the physical conditions 

 on which such equilibrium depends are investigated, would be denominated 

 ELECTRO-STATICS, while that in which the effects of currents of electricity are 

 considered, would be called ELECTRO-DYNAMICS. 



REST being in its nature more simple than MOTION, and the cases of forces 

 mutually destructive of each other's influence, and therefore productive of equi- 

 librium, being more simple than those in which motion ensues from the com- 

 bined action of forces differing from each other in various respects, it was nat- 

 ural that, in every part of physics, the principles of statics should be first es- 

 tablished and understood. Such has been accordingly the course which the 

 progress of discovery has taken in other branches of natural philosophy, and 

 electricity is not an exception to it. All the phenomena which have been hith- 

 erto adverted to in this notice belong properly to ELECTRO-STATICS. In all of 

 them the electric fluid is contemplated in a state of equilibrium ; or if its mo- 

 tion be occasionally considered, it is only in sudden and momentary changes 

 from one state of equilibrium to another. Thus, when a Leyden jar is char- 



* The terms STEREO-STATICS and STEREO-DYNAMICS would be preferable. 



