294 
MR. C. T. R. WILSON ON CONDENSATION OF WATER VAPOUR 
had been used with the other ^ases. This was unfortunately broken immediately 
afterwards and the apparatus made to replace it was much smaller, having a capacity 
of only 8 cub. centims., tlie length of the expansion chamber being 4 centims., and 
that of the piston 5 centims. The pressure required to balance the weight of the 
piston was about 2 millims. of mercury. The volume of the gas is, therefore, smaller, 
and the rate at which it expands slower than in the former machine. 
Expansion Ptequlred to Produce Pain-like Condensation in Nitrogen. 
Date. 
B. 
t°C. 
TT. 
Pi- 
Pi- 
P2- 
P2- 
II 
fL 
cC 
October 6. 
754 
13 
11 
681 
1423 
390 
1132 
1-257 
November 19 
765 
17-5 
15 
562 
1310 
289 
1037 
1-263 
„ 19 ... . 
764 
17 
14 
546 
1294 
276 
1024 
1-264 
„ 19 ... . 
764 
17 
14 
540 
1288 
275 
1023 
1-259 
November 30 ... . 
772 
11 
10 
610 
1370 
321 
1081 
1-267 
Mean 
1-262 
The number of drops appeared to be small in nitrogen. 
Expansion Required to Produce Cloud-like Condensation in Nitrogen. 
Date. 
B. 
fC 
TT. 
Pi- 
Pi- 
P-2- 
P 2 - 
P 1 /P 2 — 
October 6. 
754 
13-5 
12 
765 
1506 
350 
1091 
1-380 
November 21 .... 
775 
15-0 
13 
713 
1473 
307 
1067 
1-380 
„ 21 ... . 
775 
15-0 
13 
709 
1469 
304 
1064 
1-381 
Mean 
1-38 
The colour pheuomena were exactly like those observed in air. 
Measurements were made of the expansion required to produce the sensitive tint. 
Date. 
Q 
0 
V^l 
October 6. 
13-5 
1-417 
November 28. 
11-5 
1-434 
28 
n .. 
11-5 
1-430 
jMean 
1-4-27 
The observations of November 28 were made with the smaller machine, those of 
October G with that which had been used for the experiments on the other gases. 
