229 
1916-17.1 On some Nuclei of Cloudv Condensation. 
-J 
source from which come the nuclei produced by this tube. The cause of 
the luminosity of these cracks may be worth investigating. 
A great number of tests were made with the tubes and with substances 
placed in them and heated to a temperature below that at which the tube 
was active. For instance, about 10 cm. of fine iron wire was coiled up into 
a length of 2 cm., and after the tube had been cleansed by heat was drawn 
by a magnet from the cold part of the tube into the cleansed part and 
heated to a temperature much under red heat. As was found in the early 
experiments, this gave a very great number of nuclei ; so dense was the fog 
Table III. — Nuclei produced by Heat and Chemical Action. 
4-3 
m 
CD 
H 
a 5 
- 4-3 
P 
o 
co Q 
N umber of 
Showers 
to clear at 
Number of Showers to clear at 
Higher Expansions. 
* 4-4 
O 
Substance used. 
rlA O 
Remarks. 
6 
£ 
?H p. 
4-3 pr 
m S 
8 
2 
4 
6 
8 
10 
12 
14 
16 
18 
20 
£ 
p.c. 
p.c. 
p.c. 
p.c. 
p.c. 
p.c. 
p.c. p.c. 
p.c. 
p.c. 
p.c. 
1 
Iron wire ' 
12 
28 
20 
22 
9 
7 
3 
2 
1 
9 
Much under red. 
2 
55 
8 
9 
3 
4 
3 
2 
1 
1 
2 
... 
... 
... 
I Effect of successive 
3 
4 
55 
55 
Hot 
6 
0 
3 
1 
3 
2 
6 
4 
5 
10 
4 
10 
3 
7 
3 
6 
1 
6 
4 
2 
- heatings all under 
J red. 
5 
? 5 
0 
0 
1 
4 
7 
6 
10 
8 
6 
5 
4 
3 
6 
55 ^ > 
Platinum wire . 
7 
13 
2 
_L 
Dull red. 
7 
6 
13 
7 
3 
X 
Red. 
8 
Phosphorus 
0 
0 
JL 
3 
6 
2 
1 
Air drawn quickly 
through. 
9 
Ver 
y den 
0 
se fog- 
3 minutes. 
]0 
Magnesium 
Tj 
0 
1 
9 
4 
2 
1 
9 
Dry air 30 minutes. 
11 
55 
55 
' o 
O 
0 
12 
9 
5 
3 
2 
1 
Moist air 30 minutes. 
12 
0 
1 
4 
2 
1 
it 2 ,, 
13 
Zinc 
o 
... 
... 
1 
2 
4 
4 
3 
2 
1 
15 3 „ 
14 
,, amalgamated 
0 
0 
10 
18 
• 
21 
7 
2 
1 
... 
... 
... 
... 
„ 30 „ 
in this case that it would have been difficult to test it for the size of the 
nuclei. A considerable quantity of filtered air was therefore added, till 
the condensation was thin enough for testing ; the result is given in test 
No. 1, Table III, where it will be seen that the air was first diluted with 
12 pumpfuls of filtered air, after which 28 showers at slow expansions 
of 8 per cent, and 20 showers at 2 per cent, were required to clear out the 
larger nuclei. When all these were disposed of there still remained large 
numbers of smaller nuclei, as the air gave 22 showers at 4 per cent., 9 at 
6 per cent., and others at higher expansions up to \ shower at 14 per cent. 
In tests Nos. 2, 3, 4, 5, and 6, Table III, are given the results of heating 
another piece of very fine iron wire 6 cm. long in the clear silica tube. It 
will be seen from test No. 2 that the effect of a temperature much under red 
was similar to that in test No. 1, the condensation being so dense at first that 
