200 Prof. Faraday on Electric Induction — 



with in like manner, not the slightest signs of any of these eifects 

 were produced. There is reason, from principle, to believe that 

 an infinitesimal result is obtainable, but as compared to the water 

 wire the action was nothing. Yet the wire was equally well and 

 better insulated, and as regarded a constant current, it was an 

 equally good conductor. This point was ascertained by attach- 

 ing tlie end of the water wire to one galvanometer, and the 

 end of the air wire to another like instrument ; the two other 

 ends of the wires were fastened together, and to the earth con- 

 tact; the two free galvanometer ends were fastened together, 

 and to the free pole of the battery : in this manner the current 

 was divided between the air and water wires, but the galvano- 

 meters were affected to precisely the same amount. To make 

 the result more certain, these instruments were changed one for 

 the other, but the deviations were still alike ; so that the two 

 wires conducted with equal facility. 



The cause of the first i-esults is, upon consideration, evident 

 enough. In consequence of the perfection of the workmanship, 

 a Leyden arrangement is produced upon a large-scale ; the cop- 

 per wire becomes charged statically with that electricity which 

 the pole of the battery connected with it can supply* ; it acts 

 by induction through the gutta percha (without which induction 

 it could not itself become charged, Exp. Res. 1177), producing 

 the opposite state on the surface of the water touching the gutta 

 percha, which forms the outer coating of this curious arrange- 

 ment. The gutta percha across which the induction occurs is 

 only 0*1 of an inch thick, and the extent of the coating is enor- 

 mous. The surface of the copper wire is nearly 8300 square 

 feet, and the surface of the outer coating of water is four times 

 that amount, or 33,000 square feet ; hence the striking character 

 of the results. The intensity of the static charge acquired is 

 only equal to the intensity at the pole of the battery whence it 

 is derived ; but its quantity is enormous, because of the immense 

 extent of the Leyden arrangement ; and hence when the wire is 

 separated from the battery and the charge employed, it has all 

 the powers of a considerable voltaic current, and gives results 

 Avhich the best ordinary electric machines and Leyden arrange- 

 ments cannot as yet approach. 



That the air wire produces none of these effects is simply 

 because there is no outer coating correspondent to the water, or 

 only one so far removed as to allow of no sensible induction, 

 and therefore the inner wire cannot become charged. In the air 

 wire of the warehouse, the floor, walls, and ceiling of the place 

 constituted the outer coating, and this was at a considerable 

 distance ; and in any case could only affect the outside portions 

 * Davy, Elements of Chemical Philosophy, p. 154. 



