Existence of a Limit to Vaporization. 349 



which case it would immediately cause the entire condensation 

 of the vapour. 



The preceding experiments may be made with iodine, and 

 many other substances ; and indeed there is no case of distinct 

 crystallization by sublimation* which does not equally afford 

 evidence of the power of the solid matter, to overcome a posi- 

 tive degree of tension in the vapour from which the crystals 

 are 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, dependent 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 in- 

 crease 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 re- 

 duced to a certain tension ; and both of which are acting ef- 

 fectually 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 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, car- 

 bon, and many of the metallic oxides, besides the greater 

 number of their compounds, are perfectly fixed bodies at com- 

 mon temperatures. The smell emitted by various metals when 

 rubbed may be objected to these conclusions, but the circum- 

 stances 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 ac- 

 quire their fixed point at, or somewhat below, common tem- 



* Calomel, corrosive sublimate, oxide of antimony, naphthaline, oxalic 

 acid, &c. &c. 



peratures. 



