CONDUCTIVITIES OF METALS AND ALLOYS AT LOW TEMPERATURES. 401 
The temperature on the platinum thermometer corresponding to 
82 0, 9 C. absolute on the hydrogen thermometer is 
0-726-2734 
2-734 x 0-00358 
— 205°-2. 
— 190°T C. or 
The 8 of the difference equation 
is then given by 
15-1 
190 \ 
100 /’ 
or 8 = 
15-1 
5-51 
2-74. 
( 20 ) 
The platinum wire is, therefore, nearly identical in properties with that used as a 
standard by Dewar and Fleming,'"' the fundamental constants of which Callendar 
has calculated,f and appears to be rather less pure than that used by me in the 
determination of the heat conductivities of some substances which are electrical 
insulators at low temperatures.^ 
The connection between the two temperature scales (20), and between the 
conductivities according to the two scales, 
Jc u = l' P y , i.e. y = kp {1 + 8 (0'01—£ b /50,000)}, .... (21 ) 
c(t n 
is shown in the following table§ :— 
Table of Connection between Temperatures and Thermal Conductivities on the 
Platinum Scale used and the Hydrogen Scale. 
in- 
o 
100 
o 
100 
0-973 
90 
90-2 
0-978 
80 
80-4 
0-984 
70 
70-6 
0-989 
GO 
60-7 
0 • 995 
50 
50-7 
1-000 
40 
40-7 
1-006 
30 
30-6 
1-011 
20 
20-4 
1-016 
10 
10-2 
1 -022 
0 
0 
1-027 
- 10 
- 10-3 
1-033 
20 
- 20-7 
1 • 038 
- 30 
- 3U1 
1-044 
- 40 
- 41-5 
1-049 
- 50 
- 52-1 
1-056 
^H* * * § 
C 
kn/h- 
o 
- 60 
o 
- 62-6 
1-060 
■ 70 
- 73-3 
1-066 
- 80 
- 84-0 
1-071 
- 90 
- 94-7 
1 -077 
- 100 
- 105-5 
1 • 082 
- 110 
- 116-3 
1-088 
- 120 
- 127-2 
1-093 
- 130 
- 138-2 
1 ■ 099 
- 140 
- 149-2 
1-104 
- 150 
- 160-3 
1-110 
- 160 
- 171-4 
1-115 
- 170 
-182-6 
1-121 
- 180 
- 193-8 
1-126 
- 190 
-205-1 
1-132 
-200 
-216-4 
1-137 
* ‘ Phil. Mag.,’ 40, p. 100 (1895). 
t ‘Phil. Mag./ 47, p. 213 (1899). 
\ ‘Phil. Trans.,’ A, 204, p. 451 (1905). 
§ Compare CALLENDAR, ‘Phil. Mag./ 47, p. 214 (1899). 
VOL. CCVIII.—A. 3 F 
