250 
DR. HAROLD A. WILSON ON THE 
Hence Rq 
_ 1 320 _ 
1+15x00038 
1248'8 ohms, 
,,, _ IL"" __6^6_ — 1629° on the platinum scale used. 
— T> 1 '2 4 9 X 0 • 0 0 3 1 2 9 ^ 
ItQa 
(2) Balancing resistance at 18° C. for wire 0-2 millim. in diameter and about 
13 centims. long, 694 ohms. 
Ditto when just melting, 4000 ohms. 
Hence Rq 
_ 6 94_ 
1 + 1 8 x 0 0038 
= 650'4 ohms, 
.u — _-isjj)-!-._ 
— 6 5 0-4 X 0 -00 3 1 2 9 
1647° on the platinum scale used. 
The mean of these two results, 1638°, was taken to lie the melting-point of platinum 
on the platinum scale used. The correction to the centigrade scale at the melting- 
point of platinum is therefore 1820 — 1638 = + 182°. 
The correction at other temperatures was calculated from this by means of a 
paraliolic difference formula as used liy Callendar and Griffiths, 
t — pt = 
^(l066 
t 
1066 ’ 
where t = temperature centigrade, pt — temperature on platinum 
A = a constant. 
The constant A is given hy the equation 182 = A 
A = 151. The following table gives the values of the 
1 \ 1A.2 0 
" 10 6 6’ 
correction 
temperatures :— 
scale used, 
which gives 
at several 
Temperature. 
! 
Correction. 
Temperature on 
platinum scale. 
° G. 
o 
1066 
0 
1100 
5 
1200 
22 
1300 
10 
1400 
62 
1500 
87 
1600 
114 
1700 
143 
1800 
176 
1820 
182 
1066 
1095 
1178 
1260 
1338 
1413 
1486 
1557 
1624 
1638 
A curve was plotted from these numbers giving 
temperature on the platinum scale. Tlie following 
correction taken from this curve :— 
the correction in terms of the 
talde gives some values of the 
