106 



Profs. Dewar and Fleming on the 



equal purity. The antimony and bismuth were prepared for 

 us by Mr. George Matthey, to whom our thanks are espe- 

 cially due for valuable assistance in this matter. The other 

 alloys used were taken as found in commerce. The iron was 

 a sample of the softest annealed transformer iron obtainable. 

 As regards the manganese-steel, two samples of Hadfield's 

 12-per-cent. manganese-steel were used, one in its ordinary 

 non-magnetic condition, and one of the same composition but 

 which had been rendered sensibly magnetic by heating it to 

 a full red-heat. It will be seen that this operation quite 

 appreciably alters its thermo-electric value. The carbon used 

 was a carbon filament from an incandescent lamp. 



In the following Tables the values of the electromotive force 

 of a thermo-couple formed of the metal and two chemically 

 pure lead wires are given in C.G.S. units, as determined from 

 a particular Clark cell, for stated temperatures. The sign 

 4- before the value of the E.M.F. signifies that the lead wire 

 in connexion with that end of the metal which is at 0° C. is 

 higher in potential than the other lead wire ; and the sign — 

 that the reverse is the case. The curves in the appended 

 chart are plotted from these tables. 



No. 1. 

 Platinum-Lead Couple. 



One junction at 0° C. ; the other at pt°. 



E.M.F. 



of Couple 

 in C.G.S. units. 



Temperature pt° 

 in degrees of 



StandardPlatinum 1 

 Thermometer. 



E.M.F. 



of Couple 

 in C.G.S. units. 



Temperature pt° 



in degrees of 



Standard Platinum 



Thermometer. 



-29630 

 -25370 

 -21920 

 -18200 

 -14670 

 -11750 



- 8910 



- 8850 



- 6830 



- 4920 



- 4760 



- 2830 



- 2810 



- 2050 



- 2080 



+ 99°9 

 + 90-3 

 + 81-2 

 + 71-0 

 + 61-1 

 + 51-0 

 + 41-7 

 + 41-0 

 + 33-2 

 4- 25-4 

 + 24-6 

 + 15-6 

 + 15-5 

 + 12-3 

 + 11-6 



-f 1090 

 + 1530 

 + 2800 

 + 4530 

 -f 4980 

 -f 4750 

 + 4150 

 + 3520 

 + 1010 

 - 4150 

 -12040 

 -19220 

 -24690 

 -26590 

 -30930 



- 60 



- 9-8 



- 21-9 



- 389 



- 56-7 



- 64-9 



- 80-7 



- 90-2 

 -109-3 

 -1351 

 -1611 

 -181-0 

 -192-8 

 -196-3 

 -205-6 



