PHYSICS: E. H. HALL 
Proc. N. a. S. 
TABLE 15 bis: GOLD. 
Kt = —0.934, K2 taken to be 0, and C2 = 0 
C, or 
C 
= —27 X 10-6 
Ci 
= —31 X 10-6 
C = —36 X 10-« 
(kf-^k). 
at 0° 
a 
at 100° 
Q 
(kf-^k) 
at 100° 
Q 
So 
(kf - k) 
at 100° 
0.01 
0 
0.08 
0.007 
0.5 
0.05 
0.007 
1 
0.02 
0.006 
0.10 
0 
0.51 
0.097 
0.5 
0.30 
0.097 
1 
0.13 
0.096 
0.20 
0 
0.99 
0.197 
0.5 
0.58 
0.197 
1 
0.25 
0.196 
0.40 
0 
1.95 
0.397 
0.5 
1.14 
0.397 
1 
0.49 
0.396 
Comparison of this with table 15 shows that ignoring the value of K2, 
small as it is, makes a good deal of difference in the values of 80 , though 
comparative little in the values of {kf -f- ^) at 100°, as calculated by means 
of equation (10). 
Uncertain as the values of {kf k) are, there is little room for doubt 
in most cases, if my theory is substantially sound, as to the direction of 
change of these values when the temperature is raised. Accordingly 
I have divided all the metals represented by the preceding tables into two 
groups, in the first of which {kf ^ k) is greater at 100° than at 0°, while 
in the second group the ratio in question is greater at 0°. 
For most of these metals Bridgman has determined the pressure -coeffi- 
cient of resistance at 0° and 100°. For magnesium the value at 0° only 
was found; for bismuth the highest temperature used was 75°. For all 
of the metals here considered except bismuth the coefficient in question is 
negative — that is, the resistance decreases with increase of pressure — 
but for bismuth it is positive. I shall make use of what Bridgman calls 
the average pressure-coefficient, the average value of the coefficient through 
a range of pressure from 0 kgm. to 12000 kgm. per square centimeter. I 
shall let TTo represent the value of this coefficient at 0°, and ttioo the value 
at 100°. 
In accordance with what has been said in the opening paragraphs 
of this paper we should, other things being equal, expect tt to decrease, 
numerically, with increase of {kf k) in metals for which tt is negative, 
and to increase with increase of {kf k) in metals for which tt is positive. 
Accordingly we might expect (ttioo — ttq) ttq to be, in general, a negative 
quantity for metals in which {kf k) increases with rise of temperature, 
and a positive quantity for metals in which {kf k) decreases with rise 
of temperature — bismuth of course requiring exceptional consideration. 
The table given below enables us to test the validity of this expectation. 
