CONDUCTION, OR CONDUCTIVE DISCHARGE. 85 



which the induction throws them ; and thus it is that ordinary insulation and con- 

 duction are closely associated together, or rather are extreme cases of one common 

 condition. 



1325. In ice or water we have a better conductor than spermaceti, and the phe- 

 nomena of induction and insulation therefore quickly disappear, because conduction 

 quickly follows upon the assumption of the inductive state. But let a plate of cold 

 ice have metallic coatings on its sides, and connect one of these with a good elec- 

 trical machine in work, and the other with the ground, and it then becomes easy to 

 observe the phenomena of induction through the ice, by the electrical tension which 

 can be obtained and continued on both the coatings (419. 426.). For although that 

 portion of power which at one moment gave the inductive condition to the particles 

 is at the next lowered by the consequent discharge due to the conductive act, it is 

 succeeded by another portion of force from the machine to restore the inductive state. 

 If the ice be converted into water, the same succession of actions can be just as easily 

 proved, provided the water be distilled, and (if the machine be not powerful enough) 

 a voltaic battery be employed. 



1326. All these considerations impress my mind strongly with the conviction, that 

 insulation and ordinary conduction cannot be properly separated when we are ex- 

 amining into their nature ; that is, into the general law or laws under which their 

 phenomena are produced. They appear to me to consist in an action of contiguous 

 particles dependent on the forces developed in electrical excitement ; these forces 

 bring the particles into a state of tension or polarity, which constitutes both induction 

 and insulation ; and being in this state, the continuous particles have a power or ca- 

 pability of communicating their forces one to the other, by which they are lowered, 

 and discharge occurs. Every body appears to discharge (444) ; but the possession 

 of this capability in a greatei' or smaller degree in different bodies, makes them better 

 or worse conductors, worse or better insulators ; and both induction and conduction 

 appear to be the same in their principle and action (1320.), except that in the latter 

 an effect common to both is raised to the highest degree, whereas in the former it 

 occurs in the best cases, in only an almost insensible quantity. 



1327. That in our attempts to penetrate into the nature of electrical action, and 

 to deduce laws more general than those we are at present acquainted with, we should 

 endeavour to bring apparently opposite effects to stand side by side in harmonious 

 arrangement, is an opinion of long standing, and sanctioned by the ablest philoso- 

 phers. I hope, therefore, I may be excused the attempt to look at the highest cases 

 of conduction as analogous to, or even the same in kind with, those of induction and 

 insulation. 



1328. If we consider the slight penetration of sulphur (1241. 1242.) or shell-lac 

 (1234.) by electricity, or the feebler insulation sustained by spermaceti (12/9. 1240.), 

 as essential consequences and indications of their conducting power, then may we 

 look on the resistance of metallic wires to the passage of electricity through them as 



