ELECTROMOTIVE FORCES IN THE VOLTAIC CELL. 



471 



When he touches on theory he agrees with Thomson. Professor Clifton 

 has examined the Volta effects for the substances ordinarily used in 

 batteries with great care, and has probably elicited the maximum of 

 accuracy possible to his method. He gives the E.M.F. of numerous virgin 

 cells in which no current has circulated. 



Ayrton and Perry in 1876 devised in Japan a very ingenious but 

 somewhat unwieldy modification of Kohlrausch's method, and with the 

 help of students carried out a most extensive and laborious series of 

 determinations of metal /metal, metal /liquid, and liquid/liquid contacts. 1 



Pie. 1 — Ayrton and Perry's Apparatus for measuring the Volta effect with all sorts 



of substances. 



The substances are arranged on the lower platform, as, for instance, the metal and liquid shown 

 in the figure at v and l. The platform a b is capable of rotation through 180° on its rail- 

 way k. 3 and 4 are carefully insulated gilt plates fixed to a bar which can be raised and 

 lowered. The experiment consists iu lowering these plates close to the surfaces to be 

 tested, and connecting thern with each other for a short time ; then raise them, rotate the 

 platform through 180°, lower again, and connect them with a quadrant electrometer. 



On the appearance of Clifton's paper the year after, they issued a 

 strongly- worded claim 2 in respect both of priority and completeness, a 

 claim which seems to me well established, for their results are the most 

 comprehensive yet obtained, and the energy needed to devise, construct, 

 and use such an apparatus as the one they depict must have been 

 immense. A convenient summary of their numbers is to be found in 

 Everett's ' Units,' second edition. The main result achieved by them is the 

 experimental establishment of the summation law for all substances 



1 Ayrton and Perry : Brit. Assoc. Glasgow, 1876. No abstract printed. Part I. 

 Proc. Boij. Sac. 1877 or 1878 is a preliminary account. Part II. describes a metallic 

 voltaic cell of magnesium and platinum and mercury, also some experiments on elec- 

 trolytes of high resistance. Part III. Phil. Trans. 1880, is the complete account 

 of their published electroscopic experiments. 



- Ayrton and Perry : Letter published in 1877 by Meiklejohn, Yokohama. 



