On Mr. Beimel's Electrometer. 415 



did not appear to have the slightest effect on its external 

 characters. 



It is totally impossible to investigate the quantity of oxy- 

 gen in ammonia by direct experiments on the amalgam of 

 its base; I shall hereafter proceed to relate sonie experi- 

 ments made in order to ascertain it. The whole of our 

 knowledge of the base of anmionia, that problematical and 

 yet in every respect highly interesting substance, consists 

 almost entirely in our being assured of its existence under 

 certain circuntstances. 



[To be continued.] 



LXII. On Mr. Bennet's Electrometer. 

 By Ez, Walker, Esq. 



To Mr. Tilloch. 



Dear Sir, — x do not remember to have seen any further 

 account of ihe properties of Mr. Hennet's Electrometer, 

 than what the inventor has given us in the Philosophical 

 Tran'^actions for 1786, which relates mostly to its extreme 

 sensibility, in distinguishing small quantities of electricity. 

 This instrument, however, has other properties, which 

 merit ihe attention of electricians. 



An excited surface being brought near the top of this 

 instrument, but not so near as to produce as park, the p^old- 

 leaves will diverge in the same state of eleccricity as the 

 excited surface ; but as soon as it is removed, the gold- 

 leaves will collapse, and instantly diverge again in a con- 

 trary state ; and these changes will take place every time 

 that the excited surface is moved to and from the cap of 

 the instrument. 



There is no work on electricity with which I am ac- 

 quainted, that takes notice of these phasnomena, nor was 

 it till after I had made many experiments that I could forni 

 any lliing like an explanation. 



But after 1 found that there is a positive and a negative 

 point, at every interruption of an electric circuit, or that 

 the top plate of the instrument is negative, at the same 

 time that the gold-leaves are positive, the phaenomena no 

 longer ajipeared inexplicable. 



Place a slip of leaf-gold, about half an inch long and 

 one-tenth of an inch broad, upon the top of the instrument, 

 and let one end of it be fixed to the plate, with paste, gum- 

 water, or varnish ; then, if a glass tube, excited by rubbing 

 it with silk, be brought near the lop of the electrometer, 



th» 



