154 Prof. Oliver Lodge on the Seat of the 
TABLE OF CONTENTS, 
Chapter I. Historical and Critical. Page 
1. Short historical sketch of the views and methods of the early period 154 
2. Commencement of the modern period.. §..-. «..0..+5>seetwun 159 
3. Summary of the work done by the more modern experimenters— 
Hankel, Ayrton and Perry, Clifton, Pellat ..............5. 160 
4, Experimental inquiry into, and general discussion of, the etfect of 
atmosphere on Volta effects.— Pfaff, De la Rive, Brown, Thomson, 
Pellat,;Schulze=Berge; Vion Zam 27. oii ois a 0» lotus e 'yokl vale 167 
5. Views of Exner. Papers of Knott'and Hart .......\.. eee 179 
6. Account of other papers bearing on the subject; and views of 
Banaday: 050.450 60k idle Wye ac PRE ectincane fo o/a elke ra ah one eae 184 
1. The subject chosen for the present discussion illustrates 
in a remarkable way the need for such conversations. It is 
scarcely credible, at the present rate of progress, that eighty- 
four years after the discovery of the voltaic pile, opinion 
should still be utterly divided as to the seat of the main H.M.F. 
in it. I venture to hope that it may now be decided, and a 
substantial agreement arrived at with respect to it. My busi- 
ness is to open the discussion; but it so happens that for some 
seven or eight years I have believed myself to see more or 
less clearly to the root of this particular matter, and a labori- 
ous review of the literature of the subject has only strengthened 
my conviction. Having, therefore, strong and definite views 
I can hardly help letting them appear; and without assuming 
prematurely that these views are agreed with, they may yet 
serve as a link with which to connect the facts and the mul- 
tifarious observations thereon. 
In the course of my reading on the subject I have found 
only two great and epoch-making papers, that of Volta in 
1801, and that of Sir William Thomson in 1851. The other 
contributions are some of them keen, like those of Faraday 
and Clerk Maxwell; some of them laborious, like those of 
Hankel and Ayrton and Perry ; but none contain anything 
essentially and powerfully new except those two: unless, 
indeed, we include in the subject the immensely important 
phenomena of Seebeck and of Peltier, and Faraday’s funda- 
mental law of electro-chemical decomposition. 
Volta* showed that when two metals were put into contact 
and separated, the insulated one was charged with electricity 
sufficient to make gold leaves diverge. fie also stated that 
the contact force between any two metals was independent of 
intermediate metals, so that the metals could be arranged in 
a definite numerical series ; and he gave the first series of the 
kind:— Zn——~ Pbs—~Sn\— Fe— Cu Ag. 
5 1 i 2 3 
* Volta, Gehler’s Worterbuch, iv. p, 616. See also a carefully edited 
version, Annales de Chim, 1 ser. xl. p. 225 (1801). 
