390 Prof. Oliver Lodge on the Seat of the 
Here two alternative formule are given; it is a matter of 
opinion which shows the least divergencies from the column 
of observed values. 
The first is the one most naturally suggested by the theore- 
tical considerations of sect. 20, the 8 standing for Zn/O—Cu/O, 
or what is commonly called Zn/Cu. 
Electromotive Force of a Zinc-Platinum, Dilute Sulphuric- 
Acid, Cell, of Resistance 4 ohm, through which the specified 
currents are driven by two or three Grove’s; each plate 
exposing 53 square centimetres of surface on either side. 
H.M.F. reckoned positive when it helps the current on. 
Difference | Observed H.M.F. | E.M.F. cal- EMF. cal- 
Current, in | of potential | of cell (obtained | culated from inka 
amperes, | between ter- | by adding rC to | the empirical ae 2 ain 
C. minals, in the preceding formula ae 
volts. column). c= 4— 10. | ee 
"552 + °26 +°37 +°35 +102 
“44 + :30 +39 +°36 +1:05 
"936 + :12 +31 +31 + 89 
“SEs + 17 +°33 +°32 + 94 
1-88 + °15 +52 +°21 + 57 
1°52 + °33 +°63 +°25 + ‘69 
2-4 + °45 +°93 +°16 + -40 
20 + °24 +°64 +20 + °53 
2-4 — °30 +:18 +16 + -40 
1-96 — 09 +°30 + -20 + ‘55 
3°22 | — ‘60 +°04 +08 + 13 
2°72 — ‘35 +20 +:13 + :29 
4°16 —10 — 17 — 16 — 19 
3°36 — 63 +04 +06 + 08 
Here also are two alternative formule given, of which the 
first agrees best with the experimental results. Butit is very 
strange that the H.M.F. of this cell should be so low when the 
current is feeble : it is scarcely more than that of the copper 
cell. The only way I see of accounting for the error (if error 
it be) is that the platinum was put into the liquid after the 
copper plate, and it was sometimes found coated with a very 
thin evanescent film of copper when taken out. Theoretical 
considerations would suggest something more like the second 
formula as the probable H.M.F., the 1:2 being what is ordi- 
narily called Zn/Pt. 
22. I can now continue the quotation of the remainder of 
the preliminary notes with the certainty that they will be at 
any rate intelligible. I begin with statements intended to be 
true for substances of every kind, and then specialize them 
for the case of metals. 
