216 Proceedings of the Royal Society of Edinburgh. [Sess. 
Hall Effect . — This was measured in magnetic fields of strengths varying 
from 2000 to 22,000 units, at temperatures of 13-3° C. and 99-8° C. 
Temperature of Plate = 13-3° C. 
Temperature of Plate = 99-8° C. 
Field. 
R x 10 7 . 
Field. 
R x 10 7 . 
2,250 
+ 6-60 
1,950 
4-965 
4,050 
4-8-75 
5,500 
+ 6T0 
6,400 
4-8-83 
8,450 
4-6T7 
9,500 
4-9*00 
15,000 
4-6-26 
14,850 
17,300 
+ 8 95 
19,000 
4-6-06 
+ 8-70 
22,600 
4-5-73 
22,600 
+ 8-01 
The coefficient R is positive ; it decreases with increasing field, very 
slightly at first, but more rapidly as the field approaches 20,000 units. 
Increase of temperature produces a very marked increase in the 
value of R. 
Temperature coefficient of R in field of 6,400 units = +0*0052. 
„ „ „ 22,600 „ =+0*0046. 
Copper. Thickness of plate = 0-063 mm. 
Thermomagnetic Temperature and Potential Effects . — These were 
measured in magnetic fields of three different strengths, and at three 
temperatures, viz. 43*9° C., 70-7° C., and 125’8° C. 
Temperature of Plate 
= 43-9° C. 
Temperature of Plate 
= 70-7° C. 
Temperature of Plate 
= 125-8° C. 
Field. 
S x 10 7 . 
Q x 10 4 . 
Field. 
SxlO 7 . 
Q x 10 4 . 
Field. 
SxlO 7 . 
«C 
X 
I — 1 
© 
7,850 
-2'04 
+ 1-61 
7,900 
-1-75 
+ 1-53 
7,700 
-1-74 
+ 1-48 
13,550 
-2-20 
+ 1-67 
13,650 
- 1-84 
+ 1-53 
13,000 
- 1-80 
+ 1-47 
21,400 
-2-27 
+ 1*69 
21,400 
-1-86 
+ 1-55 
21,150 
-1-74 
+ 1-47 
The effects are of opposite signs, S being negative and Q positive. 
The values of S and Q are only slightly affected by the strength of the 
magnetic field. 
Increase of temperature causes a diminution in the numerical values of 
both S and Q, and the rate of diminution decreases as the temperature rises. 
Temperature coefficient of S in field of 21,000 units for range — 
43 9° C. to 70-7° C.= -0-0068. 
„ „ „ „ 70-7° C. to 125-8° C.= -0 0012. 
„ „ Q „ 43-9° C. to 70-7° C. = - 0-0031. 
70-7° C. to 125-8° C. = -0-0009. 
