Aggregations produced in Gases by Sadden Cooling. 753 
Comparing the above with Table II. it will be seen that 
the effects obtained in methane are very similar to those 
obtained in air. 
III. The Effect in Mixtures. 
In the hope of getting further light on the origin of the 
nuclei we performed a series of experiments on mixtures of 
gases of varying proportions. Three mixtures were tried, viz., 
air and carbon dioxide, air and ethylene, and air and water- 
vapour. The apparatus shown in fig. 4 was devised to mix 
the gases in known proportions. 
Ym. 4. 
M 
\fw: 
Tc TapS Fig JI 
The apparatus consists of two large glass globes of 1J litres 
capacity connected together by a glass tube. The tube F 
leads to tap S in fig. 2. Enough concentrated sulphuric acid 
is introduced to fill one globe. By means of a three-way 
tap A the globe B can be connected to a water-pump or to 
the atmosphere as desired. The mixing of the gases is 
effected thus : — The globe B is connected to the pump and 
the sulphuric acid is drawn into it to within a centimetre of the 
tap, which is then closed. Grlobe C is now exhausted through 
the tap D ; fsee fig. 2) to a pressure of about 4 cm. and air 
let in through P until the pressure falls a definite amount. 
Carbon dioxide is then admitted and, finally, more air until 
the pressure is atmospheric. The proportions of the con- 
stituents are determined from their respective partial pressures. 
Some thirty minutes are taken over this process to allow the 
oases to mix thoroughly. In order to diminish any 
