490 
Mr. Faraday on the 
bear a high temperature without appreciable loss by volatili- 
zation, as platina, gold, iron, nickel, silica, alumina, charcoal, 
&c. ; and, consequently that, at common temperatures, no 
portion of vapour rises from these bodies or surrounds them ; 
that they are really and truly fixed ; and that none of them 
can exist in the atmosphere in the state of vapour. 
But there is another force, independent of that of gravity, 
at least of the general gravity of the earth, which appears to 
me sufficient to overcome a certain degree of vaporous elas- 
ticity, and, consequently, competent to the condensation of 
vapour of inferior tension, even though gravity should be 
suspended ; I mean the force of homogeneous attraction. 
Into a clean glass tube, about half an inch in diameter, in- 
troduce a piece of camphor ; contract the tube at the lamp 
about four inches from the extremity ; then exhaust it, and 
seal it hermetically at the contracted part ; collect the cam- 
phor to one end of the tube ; and then, having placed the tube 
in a convenient position, cool the other end slightly, as by 
covering it with a piece of bibulous paper preserved in a moist 
state by a basin of water and thread of cotton ; in this way, 
a difference in temperature of a few degrees will be occa- 
sioned between the ends of the tube, and after some days, or 
a week or two, crystals of camphor will be deposited in the 
cooled part ; there will not, however, be more than three or 
four of them, and these will continue to increase in size as 
long as the experiment is undisturbed, without the formation 
of any new crystals, unless the difference of temperature be 
considerable. 
A little consideration will, I think, satisfy us that, after the 
first formation of the crystals in the cooled part, they have 
