150 Notices respecting New Books. 



have space between them ; and since every bodv can com- 

 nnmiiate tlie power of expansion to a bodv of a lower tem- 

 perature, tliat is, can give an expansive n)otion to its parti- 

 cles, it is a jirobable inference ihai its own particles arc 

 possessed of n^olion ; but as there is no change in the po- 

 sition of its parts as long as its temperature is uniforiTi, the 

 motion, if it exist, nui^t be a vibratorv or undulatorv mo- 

 tion, or a motion of the particles round their axes, or a 

 motion of particles round each other. 



'* Tt scents possible to account for all the phoenomena of 

 heat, if it be suppost d that in solids the particles are in a 

 constant state of vibratory motion, the particles of the 

 hottest bodies ntoving with the greatest velocity anil through 

 the greatest space; that in fluids and elastic fluids, besides 

 the vibratory motion, which must be conceived greatest in 

 the last, the particles have a motion round their own axes, 

 with dilferent velocities, the paiticles of elastic fluids mov- 

 ing with the greatest quickness ; and that in ethereal sub- 

 stances the particles move round their own axes, and se- 

 parate from each other, penetrating in right lines through 

 space. Temperature may be conceived to depend upon 

 the velocities of the vibrations ; increase of capacity, on the 

 motion being performed in greater space; and the dnviinu- 

 tion of temperature, during the conversion of solids into 

 fluids or gases, may be explained on the idea of the loss of 

 vibratory motioti, in consequence of the revolution of 

 particles ^round their axes, at the moinent when the body 

 becomes fluid or aeriform, or from the lo'is of rapidity of 

 vibration in consequence of the motion of the particles 

 through creater space. 



'* If a specific fluid <^f heat be admitted, it must be sup- 

 posed liable to most of the aftections which the particles of 

 common matter are assumed to possess, to account for the 

 phaenomena ; such as losing its motion when combining 

 with bodies, producing motion when transmitted from one 

 body to another, and gaining projectile motion wiien 

 passinc: into free space : so that many hvpothej^cs must be 

 adopted to account for its mode of agency, w hich renders 

 this view of the subject less simple than the other. Very 

 delicate experinnents have been made, which show that 

 bodies when heated do not increase in weight- This, as 

 far as it goes, is an evidence against a specific subtile elastic 

 fluid producing the calorific expansion ; but it cannot be 

 considered as decisive, on account of the imjierfection, of 

 our instruments : a cubical inch of inflammable air requires 

 a good balance to ascertain that it has any sensible weight j 



and 



