274 Prof. Oliver Lodge on the Seat of the 
Numbers obtained from unsatisfactory oxides and hydrates 
like those of aluminium, arsenic, and bismuth, are not likely 
to be useful for our present purpose. J know of no better 
data yet available however. 
It is now easy to write down a Volta series obtained by 
pure calculation from heats of combustion. We can then 
see how far it agrees with the results of direct experiment. 
The principle on which I determine which of the preceding 
numbers to select is simply to choose Thomsen’s when it refers 
to the simplest oxide, and in other cases to take what one can 
get. Metals about which there is obvious uncertainty, as for 
instance sodium, aluminium, bismuth, &ec., are omitted. 
Calculated Volta Series. 
Lithium and waaae 3°0 Nickel . |. 0 4 p= Bale 
Potassium. = 2°95 Lead Meer eS 
Calemm, Ge: 2 ss 284 Thallium’ “> aoe 
AMO Pepihice: WOae aati eO. Copper .. >“)sieaagel! 
Tron. 2.4 Oe Eee aot: Mercury. <2 geeaaa 
BPs) ken. Ree (he) Ceal eet eee Palladium: <2 canes 
Cadmium) “2 oe. (sales Silver .< . Selle 
Cobaltse te owe 1°38 
To compare this series with those obtained by experiment, 
we may as well take zinc as the metal of reference, and write 
down the Volta effect between it and the other metals, first as 
abstracted from the above table, and then as found by different 
observers. Strictly, one ought first to subtract Peltier forces 
from the observed numbers before comparing them with 
theory; but these forces are too small to make any appreciable 
difference. hole a 
Volta Effects in Air. 
Comparison between Theory and Experiment. 
Observed by 
Calculated Pellat. Ayrton and Perry.| Clifton. 
Metal pair. | from heats of 
oxidation. Udine Using 
Clean.) Scratched.| commer- mal- 
5 eamated 
cial zinc 
ine. 
Zine :— a 
4 Bihar ee eee, See 0 39 25 3h) 28 46 
ead .22.020.. “70 or °65 “15 “aul 20 35 
Irons es. il er |) -4 56 ‘70 60 74 75 
Nickel « ...... 53 47. 63 
Copper trn..e 1:04 or fl 86 75 89 "85 
Mercury 1:18 aif 1:06 1-20 1:07 
Silver cess. PT L-oralb8)|. ol 1-12 Ma 
IP Latinum ee oa keene ae rs -98 11S 
