1820.] Mathematical Principles of Chemical Philosophy. 141 



both of which are absurd. The phenomenon must remain inex- 

 phcable, unless we admit that the two glasses can be brought 

 into perfect contact. 



There has been much speculation respecting caloric, or that 

 which produces the phenomena of heat ; there are at present 

 two principal hypotheses ; according to one, the immediate 

 cause of the phenomena of heat is supposed to be motion, and 

 the laws of its communication precisely the same as those of 

 motion ; and this motion is supposed to be of a vibratory or 

 undulatory nature, or a motion of the particles round their 

 axes, or round each other (Davy's Elera. Chem. Philos. p. 94); 

 according to the other, caloric, or the matter of heat, is supposed 

 to be a real ethereal, or highly subtile elastic fluid, capable of 

 insinuating itself into the interstices between the particles of all 

 matter. Of these, the first appearing totally untenable, it will 

 be requisite to examine the grounds on which it appears objec- 

 tionable before the principles which are intended to be esta- 

 blished are advanced ; and here we must particularly observe 

 that no analogy between the phenomena of heat and those of 

 undulatory motion has ever been proved ; the only sort of vibra- 

 tory or inidulatory motion with which matter is known to be 

 attected is that which produces sound, or which is communicated 

 to solid matter, by those vibrations of the air by which sound is 

 produced ; and the phenomena which hence arise are by no 

 means analogous to those of heat. It is possible to imagine 

 other sorts of vibratory motion, and to suppose them capable of 

 producing different eflfects ; but in strict philosophical research, 

 nothing can be admitted which has not been proved to exist ; 

 besides, this motion, if there be such, can never be rendered 

 perceptible to any of our senses ; the assumption of it, there- 

 fore, ought not to be allowed, unless some physical cause be 

 assigned which must produce it; now there certainly is no 

 power or force inherent in matter by which any vibration what- 

 ever can be produced among the particles of matter; for the only 

 force whose existence has been proved is centripetal, and the 

 only effect of this is to cause the particles from a state of rest to 

 tend to each other's centres in right lines, with an accelerated 

 motion, till perfect contact is attained, when all motion what- 

 ever ceases : in addition, such motion, at least in solids and 

 liquids, must meet with great and constant resistance, especially 

 from the force of cohesion in the former ; consequently when a 

 solid has attained the temperature of the surrounding medium, 

 the vibration of its particles must be continually diminishing; 

 and in order that it may preserve the uniform temperature to 

 which it is exposed, it must constantly be absorbing heat, or 

 have the motion which is lost in consequence of the resistance 

 which opposes it renewed; and, therefore, a solid can never 

 attain the precise temperature of the surrounding medium, but, 

 however long it may be exposed to it, it will always excite the 



