ANNALS 



OF 



PHILOSOPHY. 



APRIL, 1824. 



Article I. 



On Expansions, particularly on those of Glass and Mercury. 

 By Mr. Crichton. 



(To the Editor of the Annals of Philosophy.) 



SIR, Glasgow, March 10, 1824. 



A thorough acquaintance with the various laws which 

 regulate the expansive powers of different bodies, is of such 

 acknowledged importance in all experimental researches, that 

 the most eminent scientific men of this and other countries have 

 their names identified with some correction, or new determina- 

 tion, in this branch of knowledge. 



So late, however, as 1818, when MM. Dulong and Petit insti- 

 tuted the experiments detailed in their well-known prize memoir, 

 published in the 7th volume of the Annales de Chimie et de 

 Physique, those gentlemen, though in possession of determina- 

 tions by Roy, Smeaton, Deluc, Lavoisier, Laplace, and many 

 others, nevertheless deemed it expedient to try anew what the 

 expansions were of glass and mercury, as these were to form the 

 basis of all their after investigations. 



They begin with finding the absolute dilatation of mercury. 

 Their method of doing this is so ingenious, that very general 



reliance seems to be placed on the number they assign, — • for 



the dilatation of mercury in thermic unit from the temperature 

 of freezing, to that of boiling water. 



MM. Dulong and Petit next proceed to ascertain the appa- 

 New Series, vol. vii. r 



