METALLIC WIRES BY ELECTRICITY. 475 
of metal be used, and the experiment frequently repeated, by the 
oxidation of its surface. The discharge of a battery produces 
in the first experiment oxidation and fusion in the balls between 
which the spark passes. The discontinuous discharge has also, 
as we have seen, the effect of detaching and fusing particles 
of metal; and when pieces of metal are used, the presence of 
metallic particles in the spark is quite intelligible. This how- 
ever by no means proves the necessity for such particles in 
every electric spark, and the opinion concerning the nature of 
the electric spark which is founded upon these facts, although 
supported from different quarters in modern times, offers so 
many difficulties, that its complete establishment can only be 
effected by more extended researches than have hitherto been 
made. 
4 RY. 
