42 ELECTRICITY IN MOTION. 



at a quadruple distance a quadruple force ; in the same manner a 

 separation of nine degrees is probably derived from an intensity 

 twenty. ievcn times as great as at one. In Lane's electrometer the 

 magnitude of a shock is determined by the quantity of air through, 

 which it is obliged to pass between two balls, of which the distance 

 may be varied at pleasure j and the power of the machine may be 

 estimated by the frequency of the sparks which pass at any given 

 distance. It app<ars from Air. Lane's experiments, that the 

 quantity of electricity required for a discharge is simply as the 

 distance of the surfaces of the balls, the shocks being twice as fre. 

 quent when this distance is only -^ of an inch as when it is T f r . 

 Air. Yolta says, that the indications of Lane's and Henley's elec. 

 troraeter agree immediately with each other ; but it seems difficult 

 to reconcile this result with the general theory. Sometimes the 

 force of repulsion between two balls in contact is opposed by a 

 counterpoise of given magnitude, and as soon as this is overcome, 

 they separate and form a circuit which discharges a battery ; 

 whence the instrument is called a discharger. 



It must be confessed that the whole science of electricity is yet 

 in a very imperfect state : we know little or nothing of the inti. 

 mate nature of the substances and actions concerned in it : and we 

 can never foresee, without previous experiment, where or how it 

 will be excited. We are wholly ignorant of the constitution of bo. 

 dies, by which they become possessed of different conducting pow 

 ers ; and we have only been able to draw some general conclusi- 

 ons respecting the distribution and equilibrium of the supposed 

 electric fluid, from the laws of the attractions and repulsions that 

 it appears to exert. There seems to be some reason to suspect, 

 from the p! aenomcna of cohesion and repulsion, that the prcs. 

 sure of an elastic medium is concerned in the origin of these 

 forces ; and if such a medium really exists, it appears nearly re. 

 lated to the electric fluid. The identity of the general cause o^ 

 electrical and galvanic effects is now doubted by few ; and in this 

 country the principal phenomena of galvanism are universally 

 considered as depending on chemical changes ; perhaps, also, time 

 may shew, that electricity is'very materially concerned in the essen. 

 tial properties, which distinguish the different kinds of natural 

 bodies, as well as in those minute mechanical actions and affections 

 which are probabry the foundation of all chemical operations ; 

 but at present it is scarcely safe to hazard a conjecture ou a sub" 



