206 On the Limits of Vaporisation. [1830. 



the development of their result. Four years have since 

 elapsed, during which, the effects, if any, have been accumu- 

 lating, and it is the object of this brief paper to give an account 

 of them. 



The point under consideration originally was, whether there 

 existed any definite limit to the force of vaporization. Water 

 at 220 sends off vapour so powerfully, and in such abundance 

 as to impel the steam-engine; at 120 it sends off much less; 

 at 40, though cold, still vapour rises ; below 32, when the 

 water becomes ice, yet the ice evaporates ; and there is no cold, 

 either natural or artificial, so intense as entirely to stop the 

 evaporation of water, or in the open air prevent a wet thing 

 from becoming dry. 



The opinion of many, among whom were the eminent names 

 of Sir H. Davy and Mr. Dalton, was, that though the power 

 of evaporating became continually less with diminution of tern-' 

 perature, it never entirely ceased, and that therefore every 

 solid or fluid substance had an atmosphere of its own nature 

 about it and diffused in its neighbourhood ; but which being 

 less powerful as the body was more fixed, and the existing 

 temperature lower, was, with innumerable substances, as the 

 earths, metals, &c., so feeble as to be quite insensible to ordi- 

 nary or even extraordinary examination, though in certain cases 

 they might affect the transmission of electricity ; or, rising into 

 the atmosphere, produce there peculiar and strange results. 



The object of my former paper was to show that a real and 

 distinct limit to the power of vaporization existed, and that at 

 common temperatures we possess a great number of substances 

 which are perfectly fixed. The arguments adduced, were drawn 

 first from the power of gravity, as applied by Dr. Wollaston, 

 to show that the atmosphere around our globe had an external 

 limit, and then from the power of cohesion ; either of these 

 seemed to me alone sufficient to put a limit to vaporization, and 

 experiments upon the sufficiency of the latter force were de- 

 tailed in the paper. 



The conclusion was, that although such substances as ether, 

 alcohol, water, iodine, &c. could not as such be entirely de- 

 prived of their vaporizing force, by any means we could apply 

 to them, but, if in free space or in air, would send off a 

 little vapour, yet there were other bodies, as iron, silver, copper, 



