and on the Construction of Voltaic Batteries, 69 



to the quantity of metals used, and arises, I conceive, from the 

 application of a principle which I believe is quite novel in the 

 construction of voltaic batteries, namely, that of diminishing 

 the metallic surfaces as the fluid in its onward passage accu- 

 mulates; thus acquiring increased force in proportion to the 

 smallness of the substance to which it is restricted." It was 

 in the absence of the information that would have been de- 

 rived from the promised communication from Mr. Mullins, 

 or of precise information from any other source, that the fol- 

 lowing experiments were begun, having for their immediate 

 object to determine what proportions should be preserved be- 

 tween the zinc and copper in any voltaic combination, and to 

 trace the existence and nature of the principle of action alluded 

 to in the above extract from the paper of Mr. Mullins. 



Before the invention of your constant voltaic battery we 

 possessed no instrument upon whose regularity of action we 

 could depend, for either the establishing (by even an approxi- 

 mation to the truth) or the demonstrating of many of the laws 

 of voltaic electricity. The battery of Wollaston, or modifica- 

 tions of it, either as an elementary or a compound one, had ge- 

 nerally been employed in such investigations. But you have 

 shown that there is an uncertainty and variableness in its ope- 

 ration, of so great an amount as should surely preclude its 

 employment in experiments intended to decide upon the fun- 

 damental laws of the science. 



It is, perhaps, to this circumstance mainly, or as much so 

 as to that of our possessing no common standards of compari- 

 son in the majority of instances, that we owe the conflicting 

 statements of the fundamental laws of the phenomena of gal- 

 vanism which pervade the various treatises upon it. Of such 

 conflicting statements we have one recent instance, among 

 very many, in which the previously admitted law of the con- 

 ductibility of wires of different lengths is called in question by 

 E. Lenz *, who substitutes in its place another law, of which 

 the expression is, that " their conductibilities are in an inverse 

 ratio to their lengths," in contradiction to that formerly held 

 of their conducting power being "inversely as the square root 

 of their lengths." I would submit that many other such laws 

 are not yet decided, since it has not been shown generally in 

 what way provision was made to guard against the irregular 

 operation of the exciting battery employed, or that experi- 

 menters generally were aware that such irregularities pre- 

 vailed, or at least, prevailed to so great an extent as has now 

 been shown. 



* Scientific Memoirs, part ii. p. .'120. [See also p. 1 1 of the present Num- 

 ber. — ElHT.'J 



