IN INCREASING THE INTENSITY OF ELECTRICITY. 54 
battery is moderately excited by diluted acid, and its poles, terminated 
by cups of mercury, are connected by a copper wire not more than a 
foot in length, no spark is perceived when the connexion is either formed 
or broken; but if a wire thirty or forty feet long be used instead of the 
short wire, though no spark will be perceptible when the connexion is 
made, yet when it is broken by drawing one end of the wire from its 
cup of mercury, a vivid spark is produced. If the action of the battery 
be very intense, a spark will be given by a short wire; in this case it is 
only necessary to wait a few minutes until the action partially subsides, 
or no more sparks are given; if the long wire be now substituted, a 
spark will again be obtained. The effect appears somewhat increased 
by coiling the wire into a helix; it seems also to depend in some mea- 
sure on the length and thickness of the wire. I can account for these 
phznomena only by supposing the long wire to become charged with 
electricity, which, by its reaction on itself, projects a spark when the 
connexion is broken*.” 
The above was published immediately before my removal from Al- 
bany to Princeton ; and new duties interrupted for a time the further 
prosecution of the subject. I have, however, been able during the past 
year to resume in part my investigations, and among others, have made 
a number of observations and experiments which develop some new 
circumstances in reference to this curious phenomenon. 
These, though not as complete as I could wish, are now presented 
to the Society, with the belief that they will be interesting at this time 
on account of the recent publication of Mr. Faraday on the same sub- 
ject. 
The experiments are not given in the precise order in which they 
were first made, but in that which I deem best suited to render them 
easily understood; they have, however, been repeated for publication 
in almost the same order in which they are here given. 
1. A galvanic battery, consisting of a single plate of zinc and copper, 
and exposing one and a half square feet of zine surface, including both 
sides of the plate, was excited with diluted sulphuric acid, and then 
permitted to stand until the intensity of the action became nearly con- 
stant. The poles connected by a piece of copper bell-wire, of the ordi- 
nary size and five inches long, gave no spark when the contact was 
broken. 
2. A long portion of wire, from the same piece with that used in the 
last experiment, was divided into equal lengths of fifteen feet, by making 
a loop at each division, which could be inserted into the cups of mer- 
cury on the poles of the battery. These loops being amalgamated, and 
dipped in succession into one of the cups while the first end of the wire 
* Silliman’s Journal, vol. xxii. page 408. 
