274 HISTORY OF MINERALOGY. 



to us, as mineralogists, all chemical compounds are 

 minerals. 



The defect of the principle of the natural-history 

 classifiers may be thus stated : in studying the 

 external characters of bodies, they take for granted 

 that they can, without. any other light, discover the 

 relative value and importance of those characters. 

 The grouping of species into a genus, of genera into 

 an order, according to the method of this school, 

 proceeds by no definite rules, but by a latent talent 

 of appreciation, a sort of classifying instinct. But 

 this course cannot reasonably be expected to lead 

 to scientific truth ; for it can hardly be hoped, by 

 any one who looks at the general course of science, 

 that we shall discover the relation between external 

 characters and chemical composition, otherwise than 

 by tracing their association in cases where both are 

 known. It is urged that in other classificatory 

 sciences, in botany, for example, we obtain a natu- 

 ral classification from external characters without 

 having recourse to any other source of knowledge. 

 But this is not true in the sense here meant. In 

 framing a natural system of botany, we have con- 

 stantly before our eyes the principles of physiology; 

 and we estimate the value of the characters of a 

 plant by their bearing on its functions, by their 

 place in its organization. In an unorganic body, 

 the chemical constitution is the law of its being; 

 and we shall never succeed in framing a science of 

 such bodies, but by studiously directing our efforts 

 to the interpretation of that law. 



