460 RIESS ON THE INCANDESCENCE OF 
wires, when taken red-hot from the fire, if they have not been 
previously oxidized on the surface, will become heated until 
they melt, and that melted copper by the absorption of oxygen 
is converted into a pulverulent state. The experiments described 
above show that the fusion of these two metals by means of 
electricity is materially affected by the absorption of oxygen, and 
that probably the same takes place with the other metals. This 
is confirmed by the fact established by different observers, that 
even platina is fused much more readily by electricity in the 
open air than in an exhausted vessel. 
Electrical fusion is a very complicated phzenomenon, and it is 
impossible to arrange the metals in the order of the powers of 
the current of discharge necessary to produce their fusion, be- 
cause the same amount of fusion cannot be attained in each 
metal. Silver, and particularly copper, is only to be obtained 
in fine globules; brass and German silver cannot be obtained 
in globules at all. We could therefore only take as a standard 
the size of the fused portions, which is dependent upon many 
contingencies. In general it must be borne in mind that in all 
the metals fusion takes place after the shivering to pieces, and 
that in those metals which become incandescent without melting 
the shivering to pieces occurs after the first appearance of visible. 
incandescence by daylight. For this last phenomenon the laws 
have been developed above. 
Residue of Charge after Fusion. 
Van Marum* remarked, that a certain charge of the battery 
was necessary to melt a given length of wire, but that only a 
part of the accumulated quantity of electricity was consumed in 
producing fusion ; that portion which remained behind in the 
battery being considerably larger than was usual on other occa- 
sions. 
I have endeavoured in the following experiments to determine 
the amount of this residuary portion: the experiments were 
made with the battery used in the beginning. 
Experiment 42.—A platina wire (radius 0:02089, length 15 
lines) was fixed in the connecting circuit, and when it had been 
destroyed it was replaced by a precisely similar one. On the 
discharge of different quantities of electricity the following ap- 
pearances were observed :— 
* Beschreibung, &c. Erste Fortsetzung, p. 13. 
