760 Messrs. Owen and Hughes on Molecular 
be subjected to an intense electric field. This chamber was 
a glass tube about 10 cms. long and 3 cms. in diameter. Inside 
was a closely fitting brass tube of nearly the same leugth, 
which in turn surrounded a thick brass rod coaxial with it. 
There was thus left an annular space about 5 mm. wide between 
the brass tube and the central rod. Most of the gas driven 
into the tube was located in this space. After remaining in 
this space for one minute under the action of different electric 
fields, the nucleated air was driven into the cloud- chamber. 
The effect was found to be the same whether the electrodes 
were both earthed or at potential-differences of 230, 1000, or 
4000 volts. 
This proves the nuclei to be uncharged. 
VI. Discussion of Results. 
The additional investigations published in this paper have 
not furnished evidence necessitating a change in the views 
expressed in the previous paper. Still much remains obscure 
and difficult to account for completely. We restate our 
explanation of the effects as follows : — 
When the temperature of the gas falls sufficiently, and not 
too slowly, molecular aggregations are formed, most probably 
of those slowly moving molecules whose kinetic energy is less 
than their mutual potential energy. On the kinetic theory, 
this means of course that the aggregations approximate more 
to the liquid phase than to the gaseous. Possibly the effects 
may be regarded as pointing to incipient liquefaction taking 
place in the gas at a temperature well above the real liquefying 
temperature. 
The number of molecular aggregations is increased to a 
remarkable degree by increasing the suddenness of cooling. 
We find this difficult to explain, possibly it may be connected 
with the irreversibility of the phenomenon as evidenced by 
their persistency. 
It has already been stated that the nuclei are of considerable 
size. This does not necessarily mean that smaller nuclei are 
not produced under the same circumstances, for such aggre- 
gations might be produced but, owing to smaller stability, 
have disappeared before the expansion can be made. 
The more rapid disappearance of the nuclei at higher 
temperatures is readily explained by the more vigorous 
bombardment of the aggregations by the molecules of the 
heated gas. 
The results in C0 2 are interesting as they suggest a 
fundamental difference between evaporation from the liquid 
