51 
the copper ; the copper is not at all oxydated, but rather 
preserved, the current in the liquid passing from the zinc 
to the copper ; but if we associate copper with platina also 
in dilute sulphuric acid, the copper is oxydized, and dis- 
solved in like manner as the zinc in the former experiment, 
the current passing from the copper to the platina. And 
if, instead of a single pair of elements, we use a battery 
of considerable intensity, we may, by connecting a plate of 
copper with the copper or platina terminal, and a plate of 
zinc with the zinc terminal (£ e. making the copper the 
anode and the zinc the cathode), we may reverse the ordi- 
nary electrical condition of the two metals, causing the 
copper to be oxydated and dissolved, and the zinc to give 
off hydrogen. In like manner, as the voltaic current may 
reverse or diminish the electro-motive forces of metals, so 
also it can increase them. If we place two plates of copper 
in a solution of sulphate of copper, and in the first instance 
simply connect them, we have no action ; but if we connect 
them as though in voltaic series, with a pair of copper and 
zinc plates, we shall find the two copper plates acting as 
voltaic elements, one plate being oxydated and dissolved, 
and the other having copper deoxydized and precipitated 
on it. On examining the current circulating in such double 
combination, we find the intensity not materially altered by 
the combination of the two copper plates. Thus in the com- 
pound battery each plate communicates its own degree of 
intensity to the plate in the next cell, in the series with 
which it is in connexion, in addition to the intensity which 
such next plate would of itself possess in a single combi- 
nation. We may, therefore, understand how the intensity 
accumulates in a compound battery. 
We have, however, learnt that in a single pair of elements 
the current passes from the zinc to the platina, (i e. in the 
liquid ;) the zinc, therefore, in an unclosed circuit, appears 
VOL. III. D 2 
