492 
Mr. Faraday on the 
on from these attenuated vapours, as it does in the denser 
states of the vapours experimented upon. There is, however, 
no good reason for supposing any difference in the force of 
aggregation of a solid body, dependent upon changes in the 
tension of the vapour about it ; and indeed, generally speak- 
ing, the method I have assumed for diminishing the tension 
of the vapour, namely, by diminishing temperature, would 
cause increase in the force of aggregation. 
Such are the principal reasons which have induced me to 
believe in the existence of a limit to the tension of vapour. 
If I am correct, then there are at least two causes, each of 
which is sufficient to overcome and destroy vapour when 
reduced to a certain tension; and both of which are acting 
effectually with numerous substances upon the surface of the 
earth, and retaining them in a state of perfect fixity. I have 
given reasons for supposing that the two bodies named, which 
boil at about 6oo° F. are perfectly fixed within limits of low 
temperature which we can command ; and I have no doubt, 
that, nearly all the present recognised metals, the earths, 
carbon, and many of the metallic oxides, besides the greater 
number of their compounds, are perfectly fixed bodies at 
common temperatures. The smell emitted by various metals 
when rubbed may be objected to these conclusions, but the 
circumstances under which these odours are produced, are 
such, as not to leave any serious objections on my mind to 
the opinions above advanced. 
I refrain from extending these views, as might easily be 
done, to the atomic theory, being rather desirous that they 
should first obtain the sanction or correction of scientific men. 
I should have been glad to have quoted more experiments 
