Prof. Grove's Remarks on a Letter of Prof. Daniell. 335 



in his papers, Phil. Trans., 1836, p. 117 etseq., he proceeds to 

 explain his constant battery as dependent upon the removal 

 of that hydrogen by causing it to deoxidate copper: in a 

 subsequent publication (Phil. Trans., 1839) he abandons this 

 view, and considers the deposition of the copper as " a primary 

 result of electrolytic action." This would altogether alter 

 the theory of his battery and of mine. I do not think it is a 

 matter of great consequence which theory be adopted ; each • 

 has many peculiar difficulties, each tends to many similar 

 conclusions, and either may lead to equally successful experi- 

 mental results. Theory is valuable as a means not as an end, 

 and that theory of the voltaic battery is in my opinion the 

 best which best collates the observed phaenomena and which 

 leads to the discovery of the best voltaic combinations. But 

 although I would hesitate, without more conclusive experi- 

 ments, in ascribing this superiority to either of these theories, 

 there is another principle of the voltaic battery enounced by 

 Mr. Daniell, as to which, so far from agreeing with him, I must 

 take leave (with every respect for his scientific attainments) 

 to differ toto ccelo : it is as to the relative extent of surface to 

 be given to the metals of voltaic combinations. Mr. Daniell 

 has in the Phil. Trans, for 1836, p. 128, and in several subse- 

 quent papers, stated that the best theoretical form for a voltaic 

 combination is when the generating metal is arranged with 

 regard to the conducting one as the centre of a sphere to its 

 periphery, and recommends a rod within a cylinder as the 

 nearest practical approximation to such an arrangement ; fol- 

 lowing the authority of Mr. Daniell, I first constructed my 

 batteries of this form, but very soon abandoned it (see Phil. 

 Mag. forOct.1839, p. 288) ; and 1 am now convinced, by three 

 years' experience and by repeated experiments, corroborated 

 by the experiments of others, that this is by no means the best 

 form of arrangement, as regards ceconomy either of space, 

 time, or material. I believe the old arrangement of equal sur- 

 faces to be sufficient for most practical purposes ; but the relative 

 size may be considerably modified according to the nature of 

 the electrolytes, the conducting power of the metals, and other 

 circumstances. I cannot enter more fully on this point without 

 writing a paper especially on this subject. 



P.S. Since the above was written I have received a paper 

 of Mr. Daniell's just printed, Phil. Trans. 1842, part ii., for 

 which I have to thank the author : it contains a series of ex- 

 periments on my battery, and with a voltameter of my con- 

 trivance. In this paper I see Mr. Daniel alters many of his 

 opinions upon the relative size of the plates in voltaic com- 

 binations. 



