\^9^f\ Existence of a Limit to Va^orizatign, , ^il 



formed. The same power, or the force of aggregation, is also 

 illustrated in crystallizing solutions ; where the solution has a 

 tendency to deposit upon a crystal, when it has not the same 

 tendency to deposit elsewhere. 



It may be imagined that crystallization would scarcely go 

 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, dependant upon changes in the tension of the 

 vapour about it ; and indeed, generally speaking, 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 retain- 

 ing them in a state of perfect fixity. I have given reasons for 

 supposing that the two bodies named, which boil at about 600° 

 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 per- 

 fectly fixed bodies at common temperatures. The smell emitted' 

 by various metals when rubbed may be objected to these con- 

 clusions, 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 upon 

 the subject, and especially relative to such bodies as acquire 

 their fixed point at, or somewhat below, common temperatures^ 

 Captain Franklin has kindly undertaken to make certain experi- 

 ments for me in the cold regions to which he has gone, and 

 probably when he returns from his arduous undertaking, he may 

 have some contributions towards this subject. 



