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3- By cryftalization I underftand that power by which the in- 

 tegrant particles of any folid poffefling fufficient liberty of motion 

 unite to each other, not indifcriminately and confufedly, but ac- 

 cording to a peculiar uniform arrangement, fo as to exhibit in its 

 laft and moft perfed ftage regular and determinate forms. 



4. This power is now know^n to be poffeffed by all folid mineral 

 fubftances. 



5. The forms which cryftals, even of homogeneous fubftances, 

 exhibit, are often very numerous ; however in moft cafes they may 

 be reduced to a few primordial forms, which, as Abbe Hauy has 

 lately experimentally proved, are derived from certain original 

 forms appertaining to the minuteft particles of their concretion. 



6. The aflemblage of thefe ultimate particles into vifible aggre- 

 gates, fimilarly arranged, neceffarily requires that one of their 

 furfaces fhould be attradive of that particular furface of the other, 

 which prefents a correfponding angle, and repulfive of that which 

 prefcnts a dift'erent angle, otherwife the various regular rhom- 

 boidal and other polygon prifms and pyramids, which cryftals pre- 

 fent us, could never exift ; confequently the minuteft prifm, being 

 once formed, could never be prolonged if one end of fuch 

 prifms were not attradlive, and the other repulfive of the fame 

 given furface. 



7. Hence it has been obferved that cryftalization never takes 

 place in the middle of any folution. but always begins at the fur- 

 face 



