
TRANSACTIONS OF THE SECTIONS. 17 
about half that of a zinc and platinum element in the same liquid. Mr. Joule in 
1841 gave (in his paper on the heat of electrolysis) the key to the explanation of all 
such difficulties, by pointing out that the heat must be generated in different quan- 
tities by the electrical evolution of equal quantities-of hydrogen at equal surfaces of 
different metals. The author of the present communication, reasoning on element- 
ary mechanical and physical principles, from Faraday’s experiments, which show 
that a zinc diaphragm in a trough of dilute sulphuric acid exercises no sensible 
resistance to the continued passage of a feeble electric current, demonstrated that a 
feeble continued current, passing out of an electrolytic cell by a zinc electrode, must 
generate exactly as much more heat at the zinc surface than the same amount of current 
would develope in passing out of an electrolytic cell by a platinum electrode, as a xinc- 
platinum pair working against great external resistance would develope in the resistance 
wire by the same amount of current. A series of experiments, commenced for illus- 
trating this conclusion, were described and a few of the conclusions stated. It was 
found that in two equal and similar electrolytic cells in the same circuit, which dif- 
fered from one another in one of them having its exit electrodes of zinc, and the 
other of platinum, very sensibly more heat was developed in the former than in the 
latter, verifying so far the conclusion stated. By separating the two electrodes by 
means of porous diaphragms, it was found that, at least with low strengths of cur- 
rent, more heat was developed at the negative than at the positive electrode, when 
both electrodes were of zinc; while when both were of platinum, much more heat 
was found at the positive electrode than was found at the negative, for all strengths 
of current, which gave sufficient thermal effects to be tested in this respect. The last- 
mentioned result, which had not been anticipated by the author, appears to be in 
accordance with experimental conclusions announced by De la Rive. 
Many other results of a remarkable nature were obtained in a series of experi- 
ments on the heat evolved in different parts of various electrolytic and chemical 
electromotive arrangements, but much difficulty had been found in interpreting 
them correctly on account of initial irregularities depending on “ polarization,” 
which often appeared to last as long as the experiments could be continued without 
introducing other sources of disturbance, and which produced marked effects on the 
observed thermal phenomena. 
This communication was brought forward principally for the purpose of calling 
attention to what may be done if experimenters can be induced to undertake re- 
searches on the evolution of heat in all parts of a galvanic battery or of any electro- 
thermal apparatus, but partly also on account of the novelty of some of the results 
which have been already obtained by the author. 
On the Mutual Attraction between two electrified Spherical Conductors. 
By Professor W. Tuomson, .A., F. RSL. & #. 
In a previous communication by the same author at the last Oxford Meeting of 
the Association, the attraction of a single electrified sphere, influenced by the presence 
of another, on any external electric point, was shown to be the same as that due to 
a converging infinite series of electric points in determinate positions within it, to 
which the name of “ electrical images’”’ was given. Hence it is concluded that the 
attraction of one sphere upon the other is equal to that of one infinite series of 
electrical images upon another, and is immediately expressible algebraically by a 
«< double series.”” Another method by which a single series is obtained to express the 
required attraction, had been alluded to at the previous Cambridge Meeting, and worked 
out to numerical results, which were published in November 1845, in the first Number 
of the Cambridge and Dublin Mathematical Journal. It was not until 1849 that 
the author found a way of reducing the double series to a single one, and so suce 
ceeded in arriving at the same form of result by the two methods. Detailed accounts 
of both methods, with all the formule for completely working out the solution, 
including the case of contact for which the series is not convergent, were commu- 
nicated by letter to M. Liouville in the month of July of that year, and, not having 
as yet been published, are now laid before the British Association. Similar methods 
are applicable to determine the whole force experienced by either of two electrified 
1852. 2 
