Vol. 6, 1920 
PHYSICS: E. H. HALL 
153 
TABLE 17 
{A) (B) 
MetaIvS in which (kf -^ k) Increases Metals in which (kf -^ k) Decreases 
WITH Rise oe Temperature with Increase of Temperature 
TTO 
TTIOO 
(tTIOO TTo) TTO 
TTO 
TTlOO 
(TriOO TTo) -r- TTe 
Co 
—0.06873 
—0.06726 
—16.9% 
Ag 
— O.O5333 
— O.O5336 
+0.9% 
Ni 
— O.O5I47 
— O.O5I58 
+7.5% 
Al 
—0.05382 
— O.O5377 
-1-3% 
Pd 
— O.O5I9O 
— O.O5I86 
-2.1% 
An 
—0.05287 
— O.O5292 
+ 1.7% 
Pt 
— O.O5I87 
— O.O5I84 
-1.6% 
Bii 
+O.O4223 
+ O.O42O2 
+9.4% 
St 
— O.O592O 
— O.O595I 
+3.4% 
Cd 
— O.O5894 
— O.O5927 
+3.7% 
Zn 
— O.O547O 
— O.O5454 
-3.4% 
Cu 
— O.O5I83 
— O.O5I77 
-3.3% 
Mean —2.2% 
Mg2 
Mo 
— O.O555 
— O.O5I29 
—0.06127 
—1.6% 
Ta 
— O.O4II5 
— O.O4I23 
+7.0% 
W 
— O.O5I23 
— O.O5I26 
+2.4% 
Mean +2.1% 
1 For bismuth, because tt is positive and the highest temperature for tt was 75°, we 
use (tTo TTts) -j- TTO. 
2 Bridgman did not find ttioo for magnesium. 
Iron does not appear in this table, for the reason that, as table 12 shows, 
it should go into Section (A) under some conditions, but into Section (B) 
under other conditions. Its value of (xioo — tto) -^ ttq is about 4%. 
This value, if put into Section (A), would make the mean value there 
— 1.3%; put into Section (B), it would make the mean there + 2.3%. If 
{kf -r- k) for iron is greater than 10% at 0°C., which seems likely, iron 
belongs to vSection (B). 
Thallium and aluminium should go into Section (A) if (kf -^ k) in them 
is less than 1% at 0°C; but this is improbable. 
It is to be observed that for each section of table 17 the average value 
of (ttioo — TTo) TTo comcs out with the sign it should have according to 
the predictions of the dual theory of electric conduction, as used in this 
paper, a minus sign for Section {A) and a plus sign for Section (B). This 
can hardly be pure accident. 
Under Hypothesis (B) 
All of the equations and all the tables of this paper, thus far, are based 
upon or are consistent with "hypothesis (A)." If hypothesis (B) is 
adopted instead, equation (8) is changed in the manner already described 
and the result in equations (13) to (19) is to replace 1.5 by 2, 4 by 4.5, 
and 6.5 by 7, in the parenthesis (1.5 — q), (4 ^ — q) and (6.5 — q). 
The resulting tables, for cobalt and bismuth, the only metals for which 
the calculation has been made, are given in Tables 18 and 19 (below) . 
By comparison of these two tables with the corresponding ones obtained 
by the use of hypothesis (A) we see that no radical difference in the re- 
