162 Prof. Oliver Lodge on the Seat of the 
force by time and adventitious circumstances. 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 Kohl- 
rausch’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*. 
Fig. 4.—Ayrton and Perry’s Apparatus for measuring the Volta effect 
with all sorts of substances. 
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The substances are arranged on the lower platform, as, for instance, the 
metal and liquid shown in the figure at P and L. The platform, A B, 
is capable of rotation through 180° on its railway, R. 3 and 4 are 
carefully insulated gilt plates fixed to a bar which can be raised and 
lowered. The experiment consists in lowering these plates close to the 
surfaces to be tested, and connecting them with each other for a short 
time; then raise them, rotate the platform through 180°, lower again, 
and connect them with a quadrant-electrometer. 
* Ayrton and Perry, Brit. Assoc. Glasgow, 1876. No abstract printed. 
Part L., Proc. Royal Soc. 1877 or 1878, is a preliminary account. Part II. 
describes a metallic voltaic cell of magnesium and platinum and mercury, 
also some experiments on electrolytes of high resistance. Part I1T., Phil. 
Trans. 1880, is the complete account of their published electroscopic 
experiments. 
