Electrical Tension without Metallic Contact. 285 



trials I found the following arrangement produce the effects 

 I had anticipated. 



Two plates, one of copper and the other of zinc, 4 inches in 

 diameter, were attached to the insulated glass pillars of my mi- 

 crometer electrometer (Phil. Trans. IS^O, p. 185) ; the plates 

 were carefully approximated to about y^oth of an inch apart : 

 when thus adjusted, a copper wire was attached to each of the 

 plates, and also to the discs of the electroscope, which are fixed 

 at about one-eighth of an inch apart ; the leaf of the electro- 

 scope was raised so as to allow it to swing clear of the two discs, 

 and when not excited, to remain equidistant from each : thus ar- 

 ranged, the apparatus is ready for the experiment. With one 

 hand the experimentalist holds a Zamboni's pile so as to have 

 one of its terminals within about an inch of the brass plate or 

 cap of the electroscope, and with his other hand he separates 

 the plates ; immediately on separation the terminal of the pile is 

 brought into contact with the cap of the electroscope, and the 

 leaf will be attracted as follows : — if touched by the — termi- 

 nal of the pile, the leaf of the electroscope will be attracted to 

 the disc in connexion with the zinc plate, and if by the + ter- 

 minal, the leaf will be attracted to that in connexion with the 

 copper plate, which are precisely the same results as follow 

 the separation after actual contact. 



In this experiment we certainly have decided signs of elec- 

 trical tension without any metallic contact. 



Clapham Common, ^ ^™' ^^'^^ „ 



September 24, 1844. John P. Gassiot. 



XL VIII. A description of an exterisive series of the Water Bat- 

 tery ; mith an Account of some Experiments made in order 

 to test the relation of the Electrical and the Chemical Actions 

 which take place before and after completion of the Voltaic 

 Circuit. By John P. Gassiot, Esq..^ F.R.S. * 



1. IN a paper, which I communicated to the Royal Society 

 -*- in 1839, and which was honoured by insertion in the 

 Transactions of the following yearfj I described a series of 

 experiments made with some powerful voltaic batteries, for 

 the purpose of determining the possibility of obtaining a spark 

 before the completion of the voltaic circuit. I was therein en- 

 abled to establish a few facts respecting polar tension, or rather 



* From the Philosophical Transactions for 1844, part i. p. 39; having 

 been received by the Royal Society December 7, 1843, — read January 25, 

 1844. 



[f Noticed in Phil. Mag. S. 3. vol. xvi. p. 594.] 



