292 DISCOURSE ON THE STUDY 



ences would be found to exist in their chemical 

 composition, all which proved fully justified in their 

 result before the essential value of this character was 

 acknowledged. This was no doubt in great measure 

 owing to the high importance set by the German 

 mineralogists on those external characters of touch, 

 sight, weight, colour, and other sensible qualities, 

 which are little susceptible, with the exception of 

 weight, of exact determination, and which are sub- 

 ject to material variations in different specimens of 

 the same mineral. By degrees, however, the neces- 

 sity of ascribing great weight to a character so de- 

 finite was admitted, especially when it was considered 

 that the same step which pointed out the intimate 

 connection of external form with internal structure 

 furnished the mineralogist with the means of re- 

 ducing all the forms of which a mineral is susceptible 

 under one general type, or primitive form, and af- 

 forded grounds for an elegant theoretical account of 

 the assumption of definite figures ab initio. 



(328.) A simple and elegant invention of Dr.Wol- 

 laston, the reflecting goniometer, gave a fresh im- 

 pulse to that view of mineralogy which makes the 

 crystalline form the essential or leading character, 

 by putting it in the power of every one, by the ex- 

 amination of even the smallest portion of a broken 

 crystal, to ascertain and verify that essential cha- 

 racter on which the identity of a mineral in the 

 system of Haiiy was made to depend. The appli- 

 cation of so ready and exact a method speedily led 

 to important results, and to a still nicer discrimin- 

 ation of mineral species than could before be at- 

 tained ; and the confirmation given to these results 



