1910-11.] 
Isopiestic Expansibility of Water. 
467 
Distances 
1-0 
[ 
Near C. 
Near F. | 
from top 
Normal 
2-2 
4-0 
5-0 
6-5 
of Dilato- 
of Dilato- 
in cm. = 
Position. 
meter. 
meter. 
r 
150 
150 
90 
210 
210 
140 
300 
300 
220 
230 
240 
350 
350 
270 
400 
400 
320 
300 
450 
450 
380 
Temperature 
in < 
degrees C. 
l 
500 
550 
500 
550 
420 
470 
325 
15 
... 
600 
700 
600 
520 
1 570 
450 
200 
800 
660 
350 
30 
900 
740 
1000 
860 
750 
450 
15 
1040 
920 
1100 
990 
100 
1150 
400 
l 
1200 
1100 
In this Table, the first column is to be compared directly with each of 
the remaining columns. It must be remembered that only two thermo- 
elements could be inserted at once, and, as the important question was a 
comparison of the other temperatures with the temperature in the normal 
position, one thermoelement was kept fixed there and the other varied. 
In the calculation we are concerned with the temperature of the contents 
of the bulb AB when the temperature given by the thermoelement in the 
normal position was T x (say). Now the normal position of the bulb was 
such that the lower end B was always about 4 cm. from top of oven. The 
bulb was slightly wider towards end B. I proceeded, therefore, as follows : 
I ascribed to the upper two-thirds of the bulb the temperature T 1? and to 
the remaining third the temperature T 2 (say), 4 cm. from the top. 
Let T 3 be the average temperature of whole bulb ; then T 3 = |T X + JT 2 , 
where, from table of temperatures, 
T 2 may be taken as T 1 — 80 ; from T 3 = 0° to T x = 600°, 
and T 2 may be taken as T 3 — 150 ; from T x = 600° to T x = 1000° ; 
i.e. T 3 = T x — 25 (approx.) between 0° and 600°, 
and T 3 = T 1 — 50 (approx.) between 600° and 1000°. 
This full correction had to be applied only in those cases in which 
the lower surface of the liquid was at B when the temperature T x was 
registered. 
In several cases, however, the liquid level was below B, in other cases 
above B, for the temperature T 1 . 
