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ART. IIl.—On the Changes which take place in the Electricity 
- of the Simple and Compound Galvanic Circles, by increasing 
or diminishing the distance of the Zinc and Copper Plates from 
each other. By K. T. Kump, Esq. Lecturer on Chemistry, 
Member of the Royal Physical Society, &c. &c. 
WHEN a fine metallic wire is made to complete the circuit be- 
tween the poles of a galvanic battery consisting of a few large plates, 
the circulation of the electricity along the wire, in a few minutes 
raises its temperature to.a red heat, and if the quantity of electri- 
city generated be too great to pass along the wire, the heat will be- 
come so intense as to cause it to take the liquid form. If the 
plates composing this battery be cut so as to form a battery of 
smaller sized plates, presenting, however, the very same extent of 
surface to the action of the liquid, we shall find that in this ar- 
rangement the quantity of electricity will be quite unable to raise 
the temperature of the wire to a red heat. 
This is a fact that has been well ascertained, but never perfect- 
ly accounted for ; and it was for the purpose of investigating its 
eause that the following experiments were performed. 
-. Experiment [.—Having procured a glass jar, eighteen inches 
in height, and six in diameter, into the bottom of which a small 
hole was perforated, to admit of a wire passing through it, a plate 
of copper, and one of zinc, was then prepared, nearly the size of 
the internal diameter of the jar, so as to slip easily into it. To the 
centres of each of the plates, a copper wire was then soldered. 
The zinc plate was lowered into the bottom of the jar ; the cop- 
per wire, which was attached to the centre of its under surface, 
passing through the -hole made for this purpose in the bottom of 
the jar. The apparatus was then rendered tight by cement. A 
mixture of muriatic acid and water, in the proportion of one of 
acid to sixteen of water, was now poured into the jar until it was 
quite filled. The extremity of the wire coming from the zinc plate 
which was at the bottom of the jar, was then connected, by means 
of mercury, with a needle apparatus: the extremity of the wire 
coming from the copper plate, was in like manner connected with 
the needle apparatus, so as to form a continuous metallic wire 
passing below a magnetised needle; and thus to complete the gal- 
vanic circuit whenever the copper plate was immersed in the jar. 
The apparatus being thus prepared, the copper plate, by means 
of its wire, was brought in contact with the liquid, in a sloping di- 
rection, and very gradually, until the whole of it was immersed to 
the depth of the sixteenth of an inch, leaving nearly eighteen inches 
of liquid between the two plates. The instant this was done, the 
simple galvanic circle was completed, and the needle indicated that 
a current of electricity was passing along the wire, sufficient to 
cause a deviation of between four and five degrees. The copper 
