METALLIC WIRES BY ELECTRICITY. 463 
to the melting-point, is thus placed in very favourable cireum- 
stances for the absorption of oxygen and for its conversion into 
oxide. If metal therefore is reduced to powder by electricity 
exposed to the air, the greater part of it is found converted into 
oxide. At the time that the first careful experiments of this kind 
were instituted, Lavoisier’s theory of oxidation still admitted of 
controversy, and we find therefore that the greater number of 
those experiments were applied, as experiments on oxidation, to 
the solution of chemical problems, which now have no longer 
any interest*. Van Marum demonstrated the existence of me- 
tallic oxides, by reducing to powder metallic wires placed about 
one-eighth of an inch above sheets of paper, which latter were 
variously coloured by them. I prepared a few such figures with 
imperfect access of air, by confining the wires between two pieces 
of paper and pressing them together with a pound weight. In 
this manner, besides the colours produced by the oxides, pure 
metal was visible. It was particularly distinct with copper and 
cadmium, where between dark-coloured ramifications metallic 
veins were entangled, distinctly perceptible by their colour and 
lustre. It is, however, well-known that in irrespirable gases, 
and in vacuo, the powder to which the metals are reduced by 
electricity is also metallict. Thus the opinion is distinctly con- 
troverted, that the metals are oxidized by means of electricity, 
and their oxides scattered as powder. 
MEcHANISM OF INCANDESCENCE AND FUSION BY 
ELECTRICITY. 
Mechanism of Fusion. 
The marked effects produced by increasing discharges of elec- 
tricity upon metallic wires may be arranged, beginning with the 
weakest discharge, in the following order: the wire becomes 
warm ; is violently shaken; bends are produced in it; it is made 
incandescent; torn away from its fastenings; split into pieces ; 
melts; and is converted into powder. The mechanical and 
calorific effects alternate here with each other, but they often 
* Van Marum, Beschreibung. Erste Forts, p. 13. Cuthbertson, Nichol- 
son’s Journal, v. p. 136. Gilbert’s Annalen, vol. ii. p. 400. Singer, Elemente 
der Elektricitatslehre, Breslau, 1819, p. 122. 
+ Guyton-Morveau, Gilbert’s Annalen, vol, xxxii. p. 55. Van Marum, 
Beschreibung. Erste Fortsetzung, p. 26. 
