132 Mr. J. J. Waterston on the Expansion 



lines of a few bodies computed and laid down as above, chiefly from 

 the observations of Regnault. The parallelism of certain lines 

 (as those marked W), and the convergence of others to the same 

 point in the axis of temperature, is well marked out. 



1 E 



§ 29. It would be well if the constants g, 7, and -or r were 



fully determined for the various bodies in a state of purity where 

 it is practicable. They are supplementary to specific gravity and 

 boiling-point; and when tabulated both numerically and gra- 

 phically, would perhaps carry us a step further on the road that 

 connects the physical with the chemical. 



The description of a body with regard to its quantitative phy- 

 sical characteristics embraces : — (1) specific gravity, (2) boiling- 

 point, (3) constants of its chart line, (4) constitution of a 

 gaseous volume in volumes or fractional parts of a volume of its 



constituents: [e.g. HO* = 9, which at once exhibits its chemical 

 constitution and specific gravity in the gaseous or vaporous form ; 



so also H *N* = 8 - 5 (ammonia), OS F =32 (sulphurous acid), 

 O^S° = 40 (sulphuric acid), 0*N = 22 (protoxide of nitrogen), 

 Oa^[2- = i5 (binoxide of nitrogen), &c. 



A fractional index to a symbol as showing that in the act of 

 chemical union what was a single molecule has separated into 

 two or more, is demanded by the dynamical theory of gases; and 

 we cannot have a distinct idea of the potential nature of the 

 dynamic convulsion or evolution of a dynamic integral that 

 accompanies chemical union without keeping both the symbolic 

 letters and their indices united in idea. No other indices can 

 be substituted ; for although others may define the chemical 

 constitution, they do not define the molecular constitution, 

 which involves the antecedent separation as well as consequent 

 union. 



MM. Deville and Troost have by heat alone separated S into 



S ¥ ; we are therefore justified in entertaining the idea of the ulti- 

 mate molecule as an integral part of a gas or vapour being 

 capable of subdivision. How far this may go, it would be im- 

 proper to limit, as the forces at the command of the chemist are 

 so insignificant in comparison to the heat and pressure with 

 which the elements of matter have to contend in the body of the 

 sun or even below the surface of our planet. But it is daily 

 becoming more manifest that the elementary molecule, although 

 minute beyond conception, is to be studied as a microcosm essen- 

 tially dynamical in its internal constitution, its apparent statical 

 condition being simply the antagonism of transcendant vis viva 

 potents.] (5) molecular volume ; (6) other points with reference 



