Biographical Memoir of M. Haiiy, 



In minerals, on the contrary, wliere no apparent motion takes 

 pilace ; where the molecules, once placed, remain in their place 

 until a violent cause separates them from each other ; where 

 matter, in a word, is persistent, it would seem at first sight that 

 it is of it ; or, in other words, of the chemical composition, that 

 the essence of the being must consist. But, on further reflec- 

 tkitt, 'We come to understand, that, if the matters themselves are 

 diflferent, they can only be so through the form of their mole- 

 cules. It is further conceived, that these particular forms of 

 the molecules, and of the different combinations which they 

 form, must necessarily result from determinate total forms. It 

 is even found, that, if ihere be any thing in mineralogy that can 

 represent the individual, it is these total forms, when they pre- 

 sent a regular whole, a crystal, in short ; since at least, at the 

 moment when this crystal is formed, all the molecules which 

 constitute it must have contributed to a common movement, 

 and grouped themselves according to a law which was impressed 

 upon them by all. Now, nothing proves that, in this common 

 movement, there could have been involved molecules of another 

 nature which occurred accidentally within the same sphere of ac4^ 

 tion ; or that elements or atoms identical in their nature, at the 

 moment when they contracted their first union, could have 

 grouped themselves into different crystalline molecules ; and that 

 what the mind conceives as possible, experience makes known 

 as real. It is therefore manifest, that, in these two cases, che- 

 mical analysis would only give imperfect ideas of the mineral, 

 and would not be in accordance with its most apparent pro- 

 perties. 



Such are, without doubt, the views, of which M. Haiiy did 

 not perhaps render a very exact account to himself, but which 

 iti soine degree guided his genius, or his scientific instinct, and 

 which induced him to give the chief rank to crystallization in 

 all his determinations of mineral species. 



It may be said, that all the discoveries and observations 

 made of late years, even those which have been considered as 

 objections to this fundamental rule, are rather confirmations of it. 



What we have just said, for example, of the crystallizing 

 power, and of the power which it has of drawing foreign mole- 

 cules along with the essential molecules, is so true, that it in- 



