348 Mr. Faraday on the 



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 

 the power of diminishing the tension of the vapour of cam- 

 phor, below that point at which it could have remained un- 

 changed in contact with the glass, or in space : for the vapour 

 of the camphor is of a certain tension in the cooled end of the 

 tube, which it can retain in contact with the glass, and there- 

 fore it remains unchanged ; but which it cannot retain in con- 

 tact with the crystal of camphor, for there it is condensed, and 

 continually adds to its mass. Now, this can only be in con- 

 sequence of a positive power in the crystal of camphor of at- 

 tracting other particles to it ; and the phaenomena of the ex- 

 periment are such as to show, that the force is able to over- 

 come a certain degree of elasticity in the surrounding vapour. 

 There is therefore no difficulty in conceiving that, by dimi- 

 nishing the temperature of a body and its atmosphere of va- 

 pour, the tension of the latter may be so far decreased, as at 

 last to be inferior to the force with which the solid portion, 

 by the attraction of aggregation, draws the particles to it; in 



which 



