254 liev. J. B. Emmett on the [April, 



sequently the expansion will proceed until this distance is 

 attained. The converse will take place by cooling. Q. E. D. 



Prop. V. 



The elastic force being constant, the change, produced in 

 equal volumes of different 

 gases by the same variation 

 of temperature, will be equal. 



Let A D be the radius of 

 a particle of a gas produced ; 

 let EFG be the curve whose 

 ordinates represent the force 

 of attraction at the distances 

 of their respective abscissse ; 

 these multiplied into the 

 density of the surrounding caloric give the density of the caloric 

 at those points ; therefore the pressure at B is as the area 

 EFGDB. Let the density of the surrounding caloric be 

 increased, and be to its former density as n : 1 ; represent this 

 by the curve HIK; then the area BE GD : area BHKD :: 1 : n 

 and area BHKD: area C I K D : : AC:AB; therefore, the 

 area B E G D : area C I K D : : A C : n A B. 



Let the area B E G D be equal to the area C I K D ; then A C 

 = n . A B or A C : A B : : n : 1 ; or the distance between the 

 particles will be as the change of temperature, force of attraction 

 being neglected. Q. E. D. 



Co?\ — If D be the density of caloric, or true temperature from 

 zero, the volume of a gas will be as D 3 , when the particles are 

 so distant that the compression of the caloric bears an insensible 

 ratio to its whole density. 



Scholium. 



Hence may be established a remarkable difference between 

 gases and vapours ; in the former great elastic force remains at 

 a temperature at which the latter become liquid or solid ; there- 

 fore in gases the deviation from the laws of expansion will be 

 much less than in vapours ; in the latter, there will be variations, 

 hereafter to be investigated, which will be the greatest in the 

 least volatile matters. 



Prop. VI. 



Heat will be evolved by the sudden compression of a gas or 

 vapour ; for by compression the calorific atmospheres of the 

 particles are diminished ; therefore, part of the heat which was 

 latent becomes sensible. Q. E. D. 



Cor. — Cold results from the sudden rarefaction of gaseous 

 matter. 



