THE 

 LONDON, EDINBURGH and DUBLIN 



PHILOSOPHICAL MAGAZINE 



AND 



JOURNAL OF SCIENCE. 



[FOURTH SERIES.] 



SEPTEMBER 1853. 



XXII. On the Fourth Law of the Relations of the Elastic Force, 

 Density, and Temperature of Gases. By Prof. Potter, A.M.* 



WHEN matter is in the gaseous state, it possesses three 

 principal properties which are common to every species 

 of gas, namely elastic force, density, and temperature ; these all 

 depend on the quantity of caloric contained in the gas, arising 

 from the peculiar affinity existing between the dense matter and 

 the caloric of the gas. 



There are consequently three laws of the relations of the above 

 properties of gases, which we may expect to have been discovered 

 in an approximate form only in the first instance. The first is 

 the law of Boyle and Mariotte for the relation of the elastic 

 force and volume (or density) when the temperature is constant ; 

 the second is the law of Dalton and Gay-Lussac for the relation 

 of the volume and temperature when the elastic force is constant ; 

 the third, that for the relation of the elastic force and tempera- 

 ture when the density is constant, is given by Amonton's law, 

 which consists of the two previous laws compounded into one. 



The above laws are independent of any consideration of the 

 quantity of caloric in the gas ; but we have important problems 

 which require the knowledge of a fourth law for their solution, 

 giving the relation of the volume and temperature ivhen the quan- 

 tity of caloric is constant. An hypothetical law was assumed by 

 Poissonf in order to obtain a solution of the problem of sound, 

 which was adopted in another form by Laplace J. 



* Communicated by the Author. 



f Journal de VEcole Poly technique, vol. vii. p. 363. " Et generalement 

 si une couche d'air eprouve une condensation tres petite et designee par y, 

 entre deux autres couches d'air, la temperature de la premiere devra s'elever 

 del!6°y." 



X Mecanique Celeste, vol. v. p. 125. 

 Phil. Mag. S. 4. Vol. 6. No. 38. Sept. 1853. M 



