IN INCREASING THE INTENSITY OF ELECTRiriTY. 541 



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 pei'ceptible 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 

 pliaenomena only by supposing the long wire to become charged with 

 electricitj^, 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 phaenomenon. 



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 zinc 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 

 la.«t 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 Joiunal, vol. xxii. page 108. 



