• Section A. 



ASTRONOMY, MATHEMATICS, AND PHYSICS. 



ADDRESS BY THE PRESIDENT, 

 E. F. J. LOVE, M.A., F.R.A.S., F.P.S. (Lond.). 



THE THEORY OF THE VOLTAIC CELL. 



Exactly 107 years ago, Alessandro Volta, Professor of Physics at 

 Pavia, and Copley Medallist of the Royal Society of London, piled 

 up a succession of discs of tinfoil, copper, and moistened cloth — the 

 first voltaic battery — and in so doing set the scientific world a problem 

 which is still unsolved, albeit that its study has thrown a flood of 

 light on every branch of inorganic science and has even furnished the 

 biologist and physiologist with material for profitable meditation. 

 Chemists have seen in it the first faint adumbrations of the explana- 

 tion of chemical affinity ; electricians have fought for a century over 

 the conflicting suggestions which it has afforded respecting the nature 

 and origin of electromotive force ; thermodynamicists owe to it the 

 first and completest demonstration of the universal validity of their 

 fundamental principles ; of late years, metallurgists have begun to 

 seek in it the explanation of the obscure phenomena disclosed to them 

 by the microscope. (a) Even as an adjunct to business affairs, the 

 voltaic cell has played, and still plays, no mean part. So far from 

 being hurried off the stage by the advent of the dynamo, it has main- 

 tained its place alongside of that machine as an appliance which no 

 twentieth century electrical engineer can afford to discard ; the storage 

 battery for steady current production, the Clark, Hibbert, and Weston 

 cells for electromotive force standards alike have a far wider practical 

 usefulness to-day than the Daniell and Grove batteries of a genera- 

 tion ago — to say nothing of the original Volta pile — ever possessed. 



In the history of voltaic theory the names of five workers stand 

 oiit from the rest as of commanding importance. These are — in order 

 of time rather than of relative significance — Volta himself, Faraday, 

 liord Kelvin, von Helmholtz, and von Nernst. To these we owe suc- 

 cessive generalisations, often supposed to be irreconcilable, yet each 

 ultimately finding its place in a consistent and steadily growing body 

 of scientific doctrine. 



It is impossible to overrate the importance of Volta's original 

 contributions to the theory of the cell. The line of demarcation which 

 he drew between the two classes of conductors which we term " metalHc" 



(a) See Ewing and Rosenhain, Phil. Trans. CXCV. 



