tfB' M*. Faraday on the [DeC; 



that th^ Whol6 canilot be distinctly trcLfced at t)ne view. The 

 best age of the moon I have found to be between eight and 

 twelve days after conjunction. 



About the S parts are similar appearances, but more compli- 

 cated, for which reason I have not yet obtained a complete 

 outline ; they run through Sarmatia to the W of Mare Caspium 

 and towards Paludes, to which they seem to be joined ; forming 

 in their course several spaces, which have the appearance of 

 small lakes. There are similar appearances between S Extremus, 

 Ponti Euxini, and Mare Caspium. 



Article VIII. 



On the Existence of a Limit to Vaporization, By M. Faraday, 

 FRS. Corresponding Member of the Royal Academy of 

 Sciences at Paris, &c.* 



It is well known that within the limits recognised by experi- 

 ment, the constitution of vapourf in contact with the body from 

 which it rises, is such, that its tension increases with increased 

 temperature, and diminishes with diminished temperature ; and, 

 though in the latter case we can, with many substances, so far 

 attenuate the vapour as soon to make its presence inappreciable 

 to our tests, yet an opinion is very prevalent, and I believe 

 general,! that still small portions are produced; the tension 

 being correspondent to the comparatively low temperature of 

 the substance. Upon this view, it has been supposed that eveiy 

 substance in vacuo, or surrounded by vapour or gas, having no 

 chemical action upon it, has an atmosphere of its own around it ; 

 and that our atmosphere must contain, diffused through it, 

 minute portions of the vapours of all those substances with 

 which it is in contact, even down to the earths and metals. I 

 believe that a theory of meteorites has been formed upon this 

 opinion. 



Perhaps the point has never been distinctly considered ; and 

 it may therefore not be uninteresting to urge two or three 

 reasons, in part dependant upon experimental proof, why this 

 should not be the case. The object, therefore, which I shall 

 hold in view in the following pages, is to show that a limit exists 

 to the production of vapour of any tension by bodies placed in 

 vacuo, or in elastic meaia, beneath which limit they aire perfectly 

 fixed. 



♦ From the PhUosophical Transactions for 1826. 



+ By the term vapour, I mean throughout this paper that state of a body hi which it 

 is permanently and indefinitely clastic. 



X See Sir H. Davy's paper on ElcQUical Phenomena exhibited in Vacuo. Philoj, 

 Trans. 1822, p. 70. 



