304 Prof. Oliver Lodge on the Seat of the 
known what is the effect of mixing media, and so passing 
gradually from one to the next. | 
We have given several Volta series; and, for the sake of 
completeness, I will now give some Peltier series for a few 
substances according to the experiments of Professor Tait at 
different Centigrade temperatures. Jxpressing each number 
as a function of the temperature, we are able to give an infi- 
nite number of Peltier series in one table. The range of 
temperature over which this table may be interpreted -is from 
—18° to 400° or so, provided the metals do not begin to melt. 
Non-metallic substances have not yet been introduced into 
such series: much experimental work remains to be done 
before they can be. The metals used by Tait were not 
chemically pure. 
True Contact E.M.F. or Peltier Series. (Microvolts.) 
Metals. At any Temperature 2° C. |At 10° C.) At 100° C. 
MOM ig aee he eae eeesee hemes —4760— 3-94¢+ 04877? | —4795 | —4667 
iardiiPlatimuma. -ecae.ece — 718— ‘54¢+:007527 | — 722 — 697 
Sonn elatimumas eee + 168+ 363¢+:0117 + 205 + 641 
Vinemesiim, 20). cere sar — 618+ -36¢+°00952? | — 613 | — 487 
German Silver ............ +83104+2617¢+ 0512 | +357 +6439 
Gadi GL aees Sea - — 73l—1446¢—-0429027 | — 880 | —2606 
ZING jes oatres Shisiea aan chars ee — 643— 8957-0247? — 735 —1778 
Dilivelesi cee mst aoueeae skeet — 590— 626¢—-015?? — 654 | —13866 
AVOAG? pact eees Nees ee scenes: 0 0 0 
Copper ssid. seni sase02 — 874— 3:96¢—-00952? | — 415 | — 865 
ee lence, Se een erate Soe + 118— 1:08¢—-00552? | + 107 | — 45 
PN arMeYANUTTY, ee. eat oer + 211— °31¢—-00392? | + 207 + 141 
paleo RSs: +1718+16°15¢+ 0362 | +1883 | +8693 
othetical* Mercur 
Leis y \ +1800+ 46¢ —-0072 | +1845 | +2190 
To find the E.M.F. of a junction at a specified temperature 
we have only to subtract the numbers in the above table, 
inserting the value of the temperature. Thus a junction of 
zinc and copper at 10° has an E.M.F’. of 320 microvolts, act- 
ing from copper to zinc; and a unit current sent across such 
a junction from copper to zinc, or from zinc to copper, absorbs 
or generates heat at the rate of 320 microwatts, and the current 
gains or loses energy at the same rate. Clerk-Maxwell says 
that the force is one microvolt, and that it acts from zinc to 
copper (‘ Hlementary Hlectricity,’ p. 149, note) ; but he only 
means, I suppose, that the H.M.F’. of a zine-copper circuit 
with one junction a degree hotter than the other is a micro- 
* This row of numbers is little better than a guess from some curves 
given in Wiedemann’s Elektriceitdét. A more probable deduction from 
some quite new experiments of C. L. Weber (Wied. Ann. November 
1884), gives, for mercury, 1181+5°68¢+ 00527. (Cf note to sect. 27.) 
