394 ACTUAL WORKING IN ORIGINAL RESEARCH. 



the specific gravities of each of the pure metals is also a 

 nearly definite and characteristic number. 



Chemists partly detect and distinguish the various 

 elementary substances, as well as their compounds, by 

 means of the different degrees in which they possess par- 

 ticular properties, and they determine the amounts of 

 those substances by means of their different atomic and 

 molecular weights, and combining proportions. In qua- 

 litative analysis, although the degrees of the properties 

 of substances are rarely actually measured, they are esti- 

 mated by the eye, and employed as qualitative tests : for 

 instance, a precipitate of chromate of lead is distin- 

 guished from one of chromate of baryta by its greater 

 degree of yellowness ; one of sulphate of barium from one 

 of sulphate of calcium by its greater degree of insolubility 

 in water ; a salt of strontium from one of calcium by the 

 greater degree of redness which it imparts to a flame, 

 &c. &c. 



In these, and a multitude of other ways, quantitative 

 research, and mathematical, arithmetical, and geometrical 

 methods, are of immense use in physical and chemical dis- 

 covery. We know, for instance, a priori, from geometrical 

 considerations, that a molecular chemistry of one dimen- 

 sion only cannot be true, and that any true molecular 

 theory of physics or chemistry must admit of three 

 dimensions. 1 



Millions upon millions of measurements remain to 

 be made in every single science. All our tables of con- 

 stants remain to be completed, and the old ones re- 

 constructed, by the aid of more refined methods and 

 instruments, and a very great number of new ones formed. 

 Nearly all our tables of physical and chemical phenomena 



1 See Geometric Chemistry. By Henry Wurtz, 1876, U.S.A. 



