78 Mr. Spitspury on a Single Galvanic Combination. 
a more delicate scale. Extraordinary as is the action evinced by 
the contact of an iron and steel wire, our curiosity was not a little 
increased, on finding that even two pieces of iron were capable 
of producing an equal, nay, a greater effect. As even the purest 
iron is, from the very nature of the methods employed to procure 
it, combined with a portion of carbon, the phenomenon in ques- 
tion might be attributed to its presence. If this supposition were 
correct, all metallic alloys would furnish similar results. 
To decide this question, a wire of brass, 4 inch diameter, was 
divided into two equal parts; one of these was connected with 
the one cup of the galvanoscope, and the other with the opposite 
cup. On making the connection between the two pieces of wire 
by nitric acid, the needle turned through a half circle. 
The laws, by which this singular phenomenon was regulated, 
were not at first sight very apparent. That they were not arbitrary 
or accidental, appeared evident; because, as often as the expe- 
riment was repeated with the same pieces of wire, the wire which 
was in the first instance positive, continued so throughout, and 
vice versa. After some ineffectual attempts, we succeeded in de- 
veloping them; that wire, which was the larger or exposed the 
greater surface to the action of the oxidating medium, was always 
positive ; the smaller wire of course negative*. Thus the same 
wire became alternately positive or negative, as a greater or less 
* The terms positive and negative are taken throughout this Paper in a sense contrary 
to the received one. By experiment it has been proved by CErsted, and also Mole, 
(Edinburgh Journal, Vol. V. 352), and we have verified it, that in a battery, composed of 
two unconnected plates of copper and zinc, the latter is negative and the former positive. 
As these simple batteries decompose water, in a similar manner with those of a compound 
series (it is true in a much smaller degree), but reverse the phenomena, will it not be 
better to consider henceforward compound batteries merely in the light of an assemblage 
of single pairs, whose active surfaces are those which are opposed and unconnected: con- 
sequently that the hydrogen is evolved in either species from the zinc side or negative, 
and the oxygen from the copper or positive? 
