152 Proceedings of Royal Society of Edinburgh. 
[sess. 
Commercial Bismuth-Lead Couple , No. 1 and No. 2, one junction 
at 0° C. ; the other at pt.° 
No 1 . 
No. 2. 
EMF of couple in 
C.G-.S units. 
Temperature pt. ° 
in degrees of plat, 
thermometer. 
EMF of couple in 
C.G-.S. units. 
Temperature pt.° 
in degrees of plat, 
thermometer. 
-579100 
+ 100*1 
-664150 
+ 100 
-458330 
+ 84-0 
- 533680 
+ 83*0 
-334700 
+ 66*3 
-388400 
+ 63-2 
-212460 
+ 46*2 
-287060 
+ 48-8 
-100400 
+ 24*1 
-136130 
+ 25-9 
-64720 
+ 15*6 
-80600 
+ 15*6 
-40720 
+ 9-1 
-45050 
+ 9-1 
+ 11870 
- 7*0 
+ 37150 
- 8-2 
+ 53090 
- 28*5 
+ 113070 
- 28*4 
+ 64580 
- 44*4 
+ 153140 
- 43-0 
+ 63600 
- 52-1 
+ 168800 
- 51-0 
+ 52480 
- 64*2 
+ 184340 
- 61*6 
+ 47810 
- 70-8 
+ 189780 
- 68-9 
+ 29640 
- 87*9 
+ 190120 
- 81*0 
+ 2700 
- 102*2 
+ 200110 
- 99*7 
-35570 
- 119-5 
+ 192340 
- 115-0 
-70960 
- 135*2 
+ 174830 
- 132-6 
-105760 
- 153-3 
+ 153910 
- 152-0 
-130870 
- 165*3 
+ 140310 
- 163*2 
-159240 
- 178-7 
+ 117460 
- 177-4 
- 167740 
- 186-9 
+ 108890 
- 184-7 
- 187370 
- 195-5 
+ 87350 
- 195*5 
t is the absolute temperature ; the formula holds throughout nearly 
the whole range of temperatures experimented with, viz., from 
- 69° C. to + 242*5° C. At the two highest temperatures, 219° C. 
and 242*5° C., there is a slight deviation from the parabolic form 
of the curve. 
In Plate I., the values of a and b are 0*0126 and -0*000034 
respectively. The formula holds from the lowest temperature at 
which the experiment was carried out, viz., -74° C., till about 
24° C. After that the curve deviates altogether from the para- 
bolic form. 
The fact that E can be represented by such a temperature curve 
suggests another way of expressing the results. For, consider the 
variation of E with the temperature, viz., 
— = a + 2 hi 
dt 
