422 Reflections on some Mineralogical System*. 



we could find nothing more proper to demonstrate the weak-, 

 ness and futility of the system of external characters ; but 

 it is not, in fact, worthy of attention. Let us take only two 

 instances. Mica is given as a mineral which has only a 

 single direction of cleavage; this supposes two faces termi- 

 nated by planes. But two planes are not sufficient to con- 

 tain a solid. What then terminates the other faces of mica? 

 This is what Hauy found in discovering other directions of the 

 laminae, by which he was led to determine the primitive form 

 and integral molecule of mica, which is a right quadrangu- 

 lar prism whose bases are rhombs. Consequently there are 

 three directions of the cleavage, and each of these three has 

 another parallel to it, whence result six parallel faces two 

 and two, or a parallelopiped. According to Werner, hya- 

 cinth has but two directions of cleavage. Haiiy found its 

 primitive form an octaedron with isoscele triangles, and con- 

 sequently its integral molecule a regular tetraedron, and four 

 directions of cleavage. Werner stopped his researches 

 where his senses abandoned him. Hauy has availed him- 

 self of all the means which a profound knowledge of the 

 different branches of the natural sciences has put in his. 

 power ; and in throwing a strong light on certain minerals, 

 he has rendered sensible the fissures which could not other- 

 wise- have been perceived. 



Some persons, indeed, have pretended to infer from what 

 Werner says respecting the property of cleavage, that he 

 also knew the form of the integral molecule, but having 

 perceived its futility as a principle of classification, he 

 abandoned the idea. Two notes (p. 28 and 127 of the 

 French translation), in his Treatise on External Characters, 

 nave been pointed out as announcing clearly his opinion. 

 I have been able to see nothing in the first, except that ani-. 

 mals and vegetables have different parts, which we call or- 

 gans, and that the separation of those parts destroys the 

 animal or vegetable, while we can divide a mineraj into as 

 many small parcels lis we please, without its ceasing to be the 

 same mineral. But jf we destroy its composition, then the 

 mineral is destroyed. Tt is not therefore doubtful that their 

 relations consist in their composition. In p. 31, there is the 

 following remarkable but just observation : " The systems 

 oft hose who have wished to arrange fossils by their external 

 characters* have already furnished a proof of the inconve- 

 nience 



* I have been assured by an old pupil and relative of Werner, that it wai 

 not originally his intention to form any system of mineralogy on external 



characters^ 



