Their y of Cryfialliz ;twn. 4T 



forms has limits, which ca". be determined by theory, ac- 

 cording to the laws, to which the ftructure of cryilals is fub- 

 je£ted. 



The fol'd of the primitive form, obtained by means of the 

 operation above explained, may be fubdivlded in a direction 

 parallel to i's different faces : all the enveloping matter is 

 equally divifible by fe£tions paral'el U the faces of the pri- 

 mitive form. It thence foliows that the part? detached by 

 the help of all chef? feclions are fimilar, and differ only in 

 their bulk, which continues to decreafe in proportion as the 

 divifion is carried flill farther. We, however, muft except 

 thofe which are near to the faces of the fecondary folid ; for, 

 thefe faces not being parallel to thofe of the primitive form, 

 the fragments which have one of their facets taken in the 

 fame faces cannot entirely refemble thofe detached towards 

 the middle of the cryftal. Tor example, the fragments of the 

 hexaedral prifm (fig- 1), the external facets of which make 

 part of the bafes or of the planes, have not, in that refpefr, 

 the fame figure as thofe fituated nearer the centre, and of 

 which the facets are all parallel to the feclions p/ut t 

 I q y v, &c. But theory, as I fhall fliew, removes all the 

 embarraffment which, on the firft view, arifes from that 

 diverfity, and reduces the whole to an unity of figure. 



But the divifion of the cryftal into fmall fimilar folids has 

 a term beyond which we mould come to particles fo fmall, 

 that they could no longer be divided without analyfing them; 

 that is to fay, without deftroying the nature of the fubftance. 

 I flop at that term ; and I give to the corpufcula we fhould 

 infulate, if our organs and inftruments were fufficiently 

 delicate, the name of integral molecule. It is very probable 

 that thefe moleculae are thofe which were fufpended in the 

 fluid in which the cryftallizarion was effected. But my 

 readers may judge for themfelves. We may, however, 

 with truth, affert, that, by the afiiftance of thefe moleculae, 

 theory reduces to fimple laws the different metamorphofes of 



cryftals, 



