Aggregations produced in Gases by Sadden Cooling, lol 
form found to be most suitable for these experiments is shown 
in fig. 5. 
Fte. 5. 
The tester used was the spiral tester of volume 3 c. c. 
The nuclei were produced in this by the " sudden " method 
of cooling, the temperature being that of liquid air. They 
were then driven into the evacuated spiral " oven " D of 
capacity 35 c.c 5 where they were kept for different lengths 
of time and at different temperatures. From this " oven " 
they were finally driven into the cloud-chamber by means of 
filtered air from the auxiliary reservoir E. 
The following table illustrates the rate at which the air 
nuclei disappear at atmospheric temperature and pressure. 
Table VI. 
Length of Time in the " Oven." 
Effect obtained. 
1 minute. 
3 minutes. 
10 „ 
20 „ 
14 hours. 
Tinted vain-cloud, 
Heavy shower. 
Thin shower. 
Several drops. 

TYe next compared the persistency of the nuclei at different 
temperatures. The " oven " could be maintained at any 
desired temperature up to 200° C. by hot glycerine. In 
order to have initially in the "oven" always the same 
number of nuclei the nucleated gas was driven into it at 
Phil. Mag. S. 6. Vol. 15. No. 90. June 1908. 3 E 
