400 Mr . Davy's Account of Galvanic Combinations , 
little mixture of the fluids, or chemical action between them, 
will take place : and an alternation of twelve series of this kind, 
forms a battery capable of producing sensible effects. 
III. The second class of Galvanic combinations with single 
plates is formed, when plates, or arcs, composed of a metallic 
substance capable of acting upon sulphurated hydrogen, or upon 
sulphurets dissolved in water, are formed into series, with por- 
tions of a solution of sulphuret of potash, and water, in such a 
manner that one side of every plate, or arc, is in contact with 
water, whilst the opposite side is acted on by the solution of 
sulphuret. Under these circumstances, when the alternation is 
regular, and the number of series sufficiently great, Galvanic 
power is evolved ; and water, placed in the circuit with silver 
wires, is acted on ; oxide being deposited on the wire connected 
with the side of the plate undergoing chemical alteration, whilst 
hydrogen is evolved from the side in contact with water. 
Silver, copper, and lead, are each capable of forming this com- 
bination. Plates made from either of those metals, may be ar- 
ranged with cloths, (moistened, some in water, and others in 
solution of sulphuret of potash,) in the following order, metal, 
cloth moistened in sulphuret of potash, cloth moistened in water, 
and so on. 
Eight series will produce sensible effects ; and the wire from 
the top of the pile produces oxide. 
Copper is more active, in this class of batteries, than silver ; 
and silver more active than lead. 
IV. The third and most powerful class of Galvanic batteries, 
constructed with fluids and single metals, is formed, when me- 
tallic substances oxidable in acids, and capable of acting on 
solutions of sulphurets, are connected, as plates, with oxidating 
