32 



MINERALOGICAL SYSTEMS. 



fimilar paffages when producing the various forms of cryfiak; 

 ami the primitive of the table before us muft be the primitive of 

 thecr^ftal under examination. In a word it is t!ie moftfimple 

 form ; and firft impreffions greatly llrengthen the illufion. If 

 perfuafion was the fole obje^ of philofophy, De L'Ifle would 

 have been a powerful phiiofopher; but philofophy mufl con- 

 vince, demonftrate, and wreft confent, however violently op- 

 pofed. An enemy mufl not therefore be able to make ufe of 

 the fame arms, or adduce the fame proofs to eftablifli a con- 

 trary opinion. Ncverthelefs fuch would be cafe with Mr. 

 . tnd miY be De L'llle's tables and the application of them ; For it is an in- 

 eftabiXfaUhood.^^"^^^^^'^ ^'*^» ^^^^ by a feries of arbitrary troncations we 



, may pafs infenfibly from any given form to any other. Grounded 

 on this principle, and feconded by Mr. de L'lOe's ingenuity, 



. any form may become primitive, and any other deduced from 

 it. Now as t))e combinations are infinite, a multitude of tables 

 may be conltru<5ted, forms of the fame fpecies may be dif- 

 perfed in different tables: the moft fimple of each table will 

 be the primitive, therefore forms of the fame fpecies will have 

 different primitives. But when by the fame principle both 

 fides of thequeftion can be proved, nothing is proved. 



To fay the mofl fimple form mull. be the primitive is an il- 

 lufion, for we know not what is the moft fimple for nature. 

 Wilh our feeble organs and confined fenfes we can form no 

 judgment of Jimple, when the operations of nature are in 

 quefi;ion. Nature embraces the entire univerfe, her laws are 

 fimple; but the combina,tions made according to thofe laws 

 are unbounded, therefore complicated. 



Let us not forget, however, that the idea of troncations, 

 and the idea of taking the mod fimple form for the primitive, 



,.are fo, natural that they muft have been the firft to prefent 



; themfelves to the man who was opening the carreer: " Often, 

 fays^the Abbe Hauyi (vol. I. page 14) a more compound form 

 only diff(^rs from a more fimple one by certain little faces which 

 may be produced by feftions, either at the folid angles, or on 

 the edges of the fimpler form,** and in a note he fays, " this 

 was the obfervation which gave the celebrated Rom^ de L'Ifle 

 the idea of his fyflem of troncations, that he might fuccef- 

 fively deduce from each other the different varieties of cryftaU 

 line forms alTumed by the fame fubflance." 



Mr. 



On the njoft 



fiiijple form. 



TEe <>ftfm of 

 troncatipns is 

 the moft ob- 

 Tious. 



