IN VOLTAIC ELECTRICITY AND ELECTRO-MAGNETISM. 
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bined or voltaic when connected plates are immersed in a conducting liquid, 
is derived from the experiments of M. Becquerel, combined with the following. 
M. Becquerel found that if one end of a metallic wire be heated by a spirit 
lamp, it becomes positive, whilst the cold end is negative. If a platina wire 
be placed on the cap of a gold-leaf electrometer, and the projecting end heated 
and then touched with a piece of heated glass or moistened paper so as to re- 
move the positive electricity, the gold-leaves will immediately diverge by nega- 
tive electricity. It becomes then an important question to ascertain if the free 
electricity thus developed, changes its character and becomes voltaic. This 
was accomplished by the next experiment. 
Exp. II. Having connected two slips of platina by copper wires with the cups 
of a galvanometer, I heated the end of one of the pieces, and immersed both, 
parallel to one another, in diluted nitric acid, when only a slight effect was pro- 
duced on the needle. I then substituted iron for platina, and repeated the ex- 
periment, when a powerful effect was produced. With copper, the effect was 
somewhat less. With zinc, the effect was considerable : but with antimony 
and bismuth scarcely any effect could be observed. But what is most remark- 
able is the fact, that in all the cases the cold metal is positive and the hot 
negative; or in other words, the cold metal has the same relation to the hot, 
that zinc has to copper in an ordinary voltaic arrangement. This experiment 
demonstrates that the free electricity developed by heat has no connexion 
with that developed by voltaic action : since the effects of heat in developing 
free electricity in platina is much greater than in iron ; whereas the voltaic- 
electricity developed in iron is much greater than that developed in platina, 
and both of an opposite character. Since this portion of free electricity deve- 
loped by heat does not become voltaic, it is exceedingly improbable that the 
electricity developed by the contact or pressure of metals should by immersion 
in a liquid acquire this character. 
4. In both theories of voltaic electricity it is admitted that the zinc is posi- 
tive, and the copper negative. The analogy between common and voltaic elec- 
tricity seems to me to have been pushed too far. I have carefully sought for 
the proof of this principle, but have been unable to find any. We have already 
shown that the experiments of M. Parrot are quite conclusive against the 
truth of the experiments of Volta. Again: in the dry pile of De Luc, free posi- 
