348 NOTICES OF THE MEETINGS (Jan. 20> 
equally good conductor. This point was ascertained, by attaching 
the 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 contact; 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 galvanometers 
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 results is, upon consideration, evident 
enough. In consequence of the perfection of the workmanship, a 
Leyden arrangement is produced upon a large scale: the copper 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 arrangement. The gutta 
percha across which the induction occurs, is only 0.1 of an inch 
thick, and the extent of the coating is enormous. 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 33000 
square feet. Hence, the striking character of the results. The 
intensity of the static charge acquired is only equal to the in- 
tensity 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 con- 
siderable voltaic current, and gives results which the best ordi- 
nary electric machines and Leyden arrangements 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 con- 
stituted the outer coating, and this was at a considerable distance ; 
and in any case could only affect the outside portions of the coils 
of wire. I understand that 100 miles of wire stretched in a line 
through the air, so as to have its whole extent opposed to earth, is 
equally inefficient in shewing the effects, and there it must be the 
distance of the inductric and inducteous surfaces (1483), combined 
with the lower specific inductive capacity of air, as compared with 
gutta percha, which causes the negative result. The phenomena alto- 
* Davy, Elements of Chemical Philosophy, p. 154. 
