plage 
XX. On the Sustaining Voltaic Battery, in reference to some 
Observations of Professor Daniell zx the April Number of 
the Philosophical Magazine, 1842. By F. W. vr Mo.eyns, 
Esq., late M.P. for Kerry, M.A., F.G.S., 5c.* 
To the Editors of the Philosophical Magazine and Journal. 
GENTLEMEN, 
pD° me the favour to insert in your forthcoming Number, 
the following observations on a paragraph in the letter 
of Professor Daniell, published in the Philosophical Magazine 
for April 1842. Absence from this country prevented my ad- 
verting to it before. 
After setting forth the difference between the principles of 
the constant battery and M. Becquerel’s voltaic combination, 
Mr. Daniell proceeds :—“ But, of course, the principles of the 
construction are independent of form and materials, and are 
capable of application to flat, square and equal surfaces of the 
two metals as well as to concentric arrangements. They admit 
also of the employment of different metals and of different 
electrolytes. They are not changed by placing the zinc on the 
outside instead of the znside of the copper, nor even by altering 
the name of the constant battery to that of the sustaining bat- 
tery.” Now, as the designation “ Sustaining ” was given by me 
to my battery, upon its introduction in 1836, and distinguishes 
it fully as much as the term “ Constant” does Prof. Daniell’s ; 
and as it might be inferred from the above extract that the 
principles of the two batteries are not only identical, but that 
the “ Sustaining ” isa mere modification of the “ Constant,” 
I feel myself called upon to protest in the strongest manner 
against the correctness of such a conclusion. 
It is incorrect, because, assuming Prof. Daniell to have 
truly stated his own principles, there is not one principle in 
my combination similar to his, and this difference in principle 
is supported by the very wide difference in construction. A few 
sentences will show the distinction. 
ist. My battery is no¢ constructed “on the principle of a 
central disposition of the active metal with regard to the con- 
ducting surfacet,” but on the very different principle of cir- 
cumferential disposition, which offers the advantages of proxi- 
* The publication of this letter is urged upon us by the author as an act 
of justice which it would be unfair in us to refuse. 
r. De Moleyns alleges that we “have published papers containing in- 
jurious remarks and insinuations,” and that “ it becomes a point of justice 
to afford him an opportunity of protecting himself from the conclusions 
which would be drawn were he to remain silent”.—Eb. 
* See Daniell’s Chemical Philosophy, sect. 737-705. 
