ON THE LIMITS OF VAPORISATION. 



BY M. FARADAY, F.R.S., 



Director of the Laboratory of the Royal Institution, &c. &c. 



T WAS induced some time since to put together a few remarks 



and experiments on the existence of a limit to vaporisation, 

 which were favoured with a place in the Philosophical Transac- 

 tions for the year 1826. When the experiments there men- 

 tioned were published, I arranged some others bearing upon 

 the same subject, but which required great length of time for 

 the developement of their result. Four years have since 

 elapsed, during which, the effects, if there had been any, have 

 been accumulating, 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 vaporisation. 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 tem- 

 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, Sec., 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 shew that a real and 

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

 common temperature, we possess a great number of substances 



