Mr Sankey on the action ofCaloricy Sfc, 17 



Art. II. — Theory/ of the Action of Caloric in producing the 

 Expansion of Fluids and Solids, with a Formula for the 

 Modulus of Gravity. By W. S. Sankey, Esq. A. M., of 

 the University of Dublin, and Extraordinary Member of 

 the Royal Medical Society of Edinburgh. Communicated 

 by the Author. 



In estimating the relative effects of caloric on the expansion 

 of fluids, as manifested by the increase of their altitudes in 

 thermometers, &c. it appears to me that some circumstances 

 connected with the essential character of the fluid state, as 

 distinguished from every other state of bodies, have been very 

 generally overlooked. This increased altitude or rise of the 

 fluid is, I think, usually referred almost exclusively to the 

 expansion of the fluid in a direction perpendicular to its base, 

 and that solely in consequence of the distance between each 

 parallel stratum of the fluid being increased by the fresh in- 

 troduction of caloric. In this view the relative heights of the 

 fluid at different temperatures will be considered as propor- 

 tional to the expansive power exerted by the caloric upon the 

 fluid, and, therefore, as such will be taken as a fair estimate of 

 that power. It is obvious, however, to any one who will give 

 the subject a moment's reflection, and take into consideration 

 the nature of fluids, that, although this may hold true as to 

 solids, it is not equally the case in respect to bodies in a state 

 of fluidity. For it is clear that the same power which the ca- 

 loric exerts in increasing the distance between the minute par- 

 ticles in the perpendicular direction will operate no less for- 

 cibly in increasing the distance between the particles in a di- 

 rection parallel to the base. Now, considering the fluid as 

 consisting of a number of parallel strata, it is obvious that the 

 effect of this increased distance between the minute particles 

 in each stratum will be to drive off" and eject, for want of 

 room, one or more atoms from each stratum, or else to dimi- 

 nish the bulk of each atom. This latter does not appear very 

 consonant to the idea which we form of an ultimate atom, nor 

 to the eff^ects of caloric itself, considered as a general expan- 

 sive power. At all events, we would not expect this to take 



NEW SEEIES. VOL. I. NO. I. JULY 1829. B ^ 



