400 
PROFESSOR C. H. LEES: THERMAL AND ELECTRICAL 
closed by a cork through which the leads passed, and the whole placed in a hypso- 
meter with the lower 11 centims. of the tube exposed to the steam. Owing to the 
uncertain behaviour of the shellac on which t he insulation of the coils depended in 
the presence of moisture at this temperature, the coils were well dried by being kept 
at 100° C. for about an hour and a half before the following measurements were 
taken:— hm 
3 40 compensating leads 
3 42 lower coil 
3 44 upper ,, ... 
3 46 „ „ ... 
3 48 lower ,, ... 
3 50 compensating leads 
07223 ohm (apparent). 
3 - 87 4 ohms 
3-878 
3-878 
55 
55 
3-876 
0‘1219 ohm 
5 5 
55 
Barometer 76"78 centims. at 15°"5 C. = 76"63 centims. at 0° C. at sea-level in 
latitude 45°. 
From these measurements we conclude that the resistances of the coils at a 
temperature of 100°"2 3 C. are :— 
Upper coil . . 3’878 — 0"122 = 3"756 apparent ohms = 3"715 true ohms. 
Lower ,, . . 3’875 — 0 - 122 = 3753 ,, ,, = 3-712 ,, ,, 
Although the slight excess of the resistance of the upper coil over that of the lower 
coil is not proportional to that of either coil, it is so small in amount that it will be 
sufficient in defining the platinum temperature scale for the coils used and in reducing 
it to the standard hydrogen scale to use the means of the observed resistances at each 
temperature. 
We thus have for the platinum temperature t v corresponding to a resistance It of 
either coil 
K • / • / V /I 
(19) 
t P = — 100°-23 = 102-3(11-2-734), 
0-980 
and as the basis of the connection between the platinum and hydrogen scales the 
following :— 
Temperature t H on hydrogen scale. Resistance. 
82°"9 C. absolute = —190°"1 C. 0726 ohm. 
273°-0 C. # „ = 0° C. 2-734 ohms. 
373°-23 C. „ = 100°-23 C. 3714 „ 
In order to compare the platinum used with that used by other experimenters, the 
“ fundamental constants” of Callendar are calculated as follows :— 
“Fundamental coefficient” 
3-714-2734 
2-734 x 100-23 
“ Fundamental zero ” =- 
0-00358 
0-980 
274-0 
0-00358. 
— 279°-3. 
* Chappuis, ‘ Travaux et Memoires du Bureau International,’ VI., p. 108. 
