1821.] Causes of Calorific Capacity, Latent Heat, S,x. 259 



a like excess of temperature to produce precisely the same 

 effect, which is another fact well known to philosophers. 



After the whole of the body is thus liquefied, the superadded 

 increments of temperature will produce a corresponding increase 

 in the temperature of the fluid in the same manner as it did in 

 the solid state before the liquefaction. If the temperature be 

 now continually augmented, the body will at length arrive at the 

 other limit of its fluidity. Every increment of temperature from 

 this point will serve only to generate a further disunion of the 

 particles ; and, therefore, for the same reasons as I have already 

 given in the case of liquefaction, the temperature of the body, if 

 there be any thing of a similarity in the disunitable parts, will 

 remain stationary until the whole fluid be evaporated, which is 

 conformable to experience. 



Since the decomposition or division of the particles of water, 

 alcohol, &c. to form vapour, produces an apparent diminution of 

 temperature, the recomposition or union of the divided parts, or 

 what is called the condensation of the vapour, must, under equal 

 circumstances, produce an equivalent augmentation of tempera- 

 ture ; for the temperature of every body, as I have stated, is 

 measured by the momentum of its particles individually ; and, 

 therefore, when two or more unite, if they form the union in a 

 similar way to what they did the disunion, an increase of indivi- 

 dual momentum, and, therefore, of temperature, must be the 

 consequence. And, for like reasons, the union resulting from 

 the conversion of a fluid into a solid will be attended with an 

 increase of temperature. In either of these cases it does not 

 follow, however, that the chunge of state is the effect of a mere 

 union only in the parts ; probably a disunion in the first instance 

 may contribute to it. For instance, in the solidification of a 

 fluid, if some of the particles of the fluid consist of atoms having 

 a less adaptation the one for the other than they have for certain 

 parts of the other particles, those particles may still remain entire 

 as long as the temperature continues sufficiently intense ; 

 because then the said atoms come in contact with, and fly off, as 

 a part of their respective particles, from the particles for which 

 they have this superior adaptation, with a force too great for the 

 adaptative force of union to overcome. But as soon as the tem- 

 perature is diminished enough, the greater adaptation takes 

 effect, and the atom separates from the one, and forms a union 

 with the other particle ; especially if, as may probably be the 

 case, the two particles come in contact when they are both moving 

 nearly parallel and towards the same parts ; for then the collision 

 would-be the least able to resist the separation in one case, and 

 the union in the other. No sooner is an atom thus lost than 

 the deprived particle has its motion and the intensity of its colli- 

 sion diminished, which only expose it to the further depreda- 

 tions of the contiguous particles. The very next collision, 

 therefore, probably deprives it of another atom. By this second 



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