54 Self-sustaining Voltaic Battery. 
heres somewhat to dense metallic plates? The thickness of the 
adhering film may be extremely small, but its resistance may be 
quite considerable, for the raititatig of airs is almost incompara- 
ble to that of metals. We know that a battery has penetrated 
over 3,000 miles of iron wire, and when a battery of 2,000 pairs 
had the poles parted only the least distance that could be man- 
ipulated, then the galvanic action could not be exhibited. 
it remains now only to notice the electrolytic changes, with 
reference to continued action. e generated sulphate of zine 
alters the conditions of action, not only by saturating the acid 
and water, but the dissolved sulphate itself is an electrolyte, and 
therefore may coat the conducting plate with zinc, and deterio- 
rate it just as was shown would result from the salts of the other 
base metals. Porimsiely, there is not so much danger of the 
ate becoming wholly coated with zinc as with the other base 
metals, for the deposited zinc is rapidly removed by its great ten- 
dency to become salt, in which it is assisted by the close prox- 
imity of the uncoated portions of conducting plate, forming good 
local circles with it. Should there be no “portions of the plate 
bare to reduce the counter-tension generated by the resolution of 
the deposited zinc, then we should have the tension acting 
against the battery current. This probably can never happen, 
yet the plate is often made nearly inefficient by the reduced zinc, 
when the acid is mostly saturated. 
The acidulated water or sulphate of hydrogen is peste 
by a far less tension than decom posés sulphate of zinc; it is only, 
therefore, when the quantity of sulphate of hydrogen ‘ecoriell 
proportionately small, ad causes the tension to rise a its in= 
creased resistance, that the sulphate of zine is decom 
But it is unquestionable that that force which is ihe result of 
the combination of the elements of sulphate of zinc, cannot of 
itself undo that combination ; yet while the battery is working, 
zine is constantly being deposited and re-dissolved. In consider- 
ing this action of the galvanic current, which is ap rently so 
anomalous to the exhibition of every other known force, | have 
concluded that we should look for some additional force acting 
conjointly with the current, rather than for a moment admit the 
absurdity of an * electro-motive force,” with its supposed capa- 
city of acting infinitely without expending itself. Such an addi- 
tional force I Conceive ean be found in the attraction of the mat- 
ter of the conduc ting plate for the heavy element of the electrolyte. 
If the conditions | under which the deposition of the zine takes 
place be considered, it must appear that it is the attraction which 
makes the determination. In the first place the deposition is 
nothing when the proportion of sulphate of zinc about the plate 
is small in comparison to the sulphate of hydrogen; but as the — 
proportion of sulphate of zinc increases, the decomposition tion of it 
