ANNALS 



OP 



PHILOSOPHY. 



NOVEMBER, 1824. 



Article I. 



On the Use of Gold Leaf as a Test of Electromagnetism. By 

 the Rev. J. Camming, Professor of Chemistry in the University 

 of Cambridge. 



(To the Editors of ihe Annals of Philosophy .) 



GENTLEMEN, Cambridge, Sept. 31, 1824. 



In the instrument which I constructed between three and 

 four years since for the detection of minute quantities of electro- 

 magnetism, the test employed was the action of the connecting 

 wire on a magnetised needle ; I have lately applied to this pur- 

 pose the reverse principle, viz. the action of a magnet upon the 

 connecting wire by making a slip of gold leaf a part of the circuit. 

 The instrument is readily constructed by substituting for the two 

 slips of gold leaf in Bennet's electrometer a single slip suspended 

 from the wire of the upper plate, and resting upon the metallic 

 base. 



Though not so delicate a test of electromagnetism as the 

 galvanoscope above alluded to, yet with even a feeble power, I 

 find it to be very sensible to the action of a small horse-shoe 

 magnet ; and it may, perhaps, be considered as an advantage 

 peculiar to this instrument, that it exhibits the magnetic action 

 of the closed circuit by a modification of the same apparatus 

 which is used for detecting the electric action of the circuit 

 when open. I am, Gentlemen, very truly yours, 



J. Gumming. 



New Series, vol. viii. y 



