DESCRIPTION OF TH? APOPHYILITE. 27v5 



forty-eight faces. It will be easy to perceive the connexion 

 of this type with the crystal that includes only its elements, 

 from the identity of the letters marking the corresponding 

 faces on the twopolyedrons, fig. 5 and 6*. 



Among the various forms of integrant particles, that are Integrant pa^ 

 rectangled parallelopipedons, 1 know no one, that does not 

 differ perceptibly from that of the apophyllite in the ratio 

 of its dimensions, which alone is sufficient to show, that 

 this mineral substance ought to be considered as a distinct 

 species. On this subject I think it may not be amiss, to 

 repeat what I have said elsewhere : it is not simply in the ^^,^ di-,tin- 

 nuniber and positions of the natural junctures, that the guishing spe- 

 geometrical character consists, which I employ to distin- *^'"** 

 guish one species from another, but also in the comparative 

 dimensions of the forms of the particles. Hence arises a 

 system of crystallization, which accords only with the sub- 

 stance possessing this form, unless it be a limit capable of 

 belonging to several minerals, as the cube, regular tetra- 

 edron, &c. ; in which case it is necessary to add an auxiliary 

 physical character to that derived from the form of the par- 

 ticles, that the species may be determined unequivocally. 

 The analyses I have mentioned tend equally to establish an 

 essential distinction between the apophyllite and all other 

 minerals, and thus the results of chemistry and mineralogy 

 with respect to this substance fully satisfy the two condi- 

 tions enunciated in my definition of a species, considering 

 this as an assemblage of natural bodies, the integrant par- 

 ticles of which are similar in form, and composed of the 

 same principles united in the same proportions. *' Mine- 

 ralogy will have attained perfection, when we find through- 

 out that cojiformlty between the operations of two sciences, 

 which should continually assist each other ; and the agree- 

 ment of which, as they investigate nature by very diirerent 

 paths, must doubly confirm the trutl/sthey disclose." 



* Fig. 6 represents the ten 'aces of the elementary crystal : fig. 5 

 shows only the twenty four faces of the compltte crysral, supposed to 

 be seen in front; but it is ewsy to conceive in iinaglnation xh« other 

 twenty fo'or, which are on the bick pan. 



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