AND CHEMICAL THEORIES OF GALVANISM. 
363 
the imaginary electro-motive force, since in the first case the electricity gene- 
rated is greatest when the conducting power of the fluid is least. 
Experiment II. 
Having made a small rectangular box divided into two equal compartments 
by a diaphragm of bladder, I introduced into one of them a disc of hard copper, 
and into the other an equal disc of soft copper. These discs being connected 
with the cups of the galvanometer, and the chambers filled with water, a con- 
siderable galvanic effect was produced, and the needle turned round as it does 
when the place of the hard copper was supplied with a disc of zinc. I then 
poured a little nitrous acid into the chamber containing the hard copper, and 
observed that the effect was diminished. By adding a little more acid the 
needle turned round several degrees in the opposite direction. This experiment 
completely overthrows the assumed principle that the galvanic effect increases 
with the conducting power of the fluid interposed between the metallic plates, 
since by increasing the conducting power of the fluid the effect was diminished, 
and by a proper increase was completely destroyed. It is a curious fact, that 
if nitric, sulphuric, or muriatic acid be used instead of the nitrous, the results 
will be quite the reverse. 
Having thus, I trust, satisfactorily shown that the electric theory is founded 
on false principles, I shall now very shortly examine the truth of the most ge- 
nerally received chemical theory of galvanism. 
3. Dr. Wollaston assumes that positive electricity is set at liberty by the 
combination of oxygen with one of the metals. This principle is frequently 
true, but in many cases it is totally false. This will be rendered obvious by 
the following experiments. 
Experiment III. 
Immerse two equal discs of zinc, connected by wires with the galvanometer, 
into the chambers of the rectangular box formerly used, and fill both com- 
partments with water ; no action will of course take place. Pour a little sul- 
phuric, nitric, or muriatic acids into one of the chambers, a considerable gal- 
vanic effect will be produced, and the needle will turn in the same direction as 
it does when copper is substituted for the plate of zinc immersed in the chamber 
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