formed by single metallic Plates and Fluids . 401 
fluids and solutions of sulphuret of potash, in such a manner 
that the opposite sides of every plate may be undergoing diffe- 
rent chemical changes ; the mode of alternation being regular. 
The same metals that act in the second class, may be used in 
the third class ; and the order of their powers is similar. The 
pile may be erected in the same manner as the pile with zinc in 
the first class; the cloths moistened in acid being separated 
from those moistened in solution of sulphuret, by a third cloth, 
soaked in solution of sulphate of potash. 
Three plates of copper, or silver, arranged in this manner, 
in the just order, produce sensible effects ; and twelve or thir- 
teen series are capable of giving weak shocks, and of rapidly 
producing gas and oxide in water; the wire connected with the 
oxidating end of the apparatus evolving hydrogen; and the 
wire attached to the end acting on the sulphuret, depositing 
oxide when composed of silver, and generating oxygen when of 
gold. 
V. In all the single metallic piles constructed with cloths, the 
action is very transient : the decomposition of the acids, and of 
the sulphurets, is generally completed in a few minutes ; and, 
in consequence, the Galvanic influence ceases to be evolved. 
The arrangement of all the different series may, however, (by 
means of an apparatus constructed after the ideas of Count 
Rumford,) be made in such a manner as to give considerable 
permanency to their effects. This apparatus is a box, covered 
with cement incapable of conducting electricity, and composed 
of three pieces of mahogany, each containing grooves capable 
of receiving the edges of the different plates proper for com- 
posing the series. One half of these plates must be composed 
of horn, or glass, and the other half of metallic substances ; and 
MDCCCI. 3 F 
