^14 Biographical Memoir ofM. Hauy. 



stratioBs of his theory. He read a course of lectures to them 

 on the subject. MM. de Lagrange, Lavoisier, de Laplace, 

 Fourcroy, Berthollet, and de Morveau, went to the college of 

 the Cardinal Lemoine to hear the lectures of the modest regent 

 of the second class, who was quite confused at seeing himself 

 the teacher of men, whose scholar he would scarcely have ever 

 dared to call himself. In a doctrine so new, and yet already 

 almost complete, the most able men were in fact but scholars. 

 Perhaps no doctrine of so comprehensive a nature was ever pre- 

 sented, which, from the commencement, possessed such clearness 

 and developement, as that exhibited and illustrated by M. Haiiy. 

 He had even invented modes of calculation which were essential 

 to his subject *, and had previously represented, by formulae 

 which were peculiar to himself, all the possible combinations of 

 crystallography. 



One cannot learn better than on this occasion what distin- 

 guishes those solid works of genius, on which eternal edifices 

 >are founded, from those more or less happy ideas which present 

 themselves for a moment to certain minds, but which, for want 

 of being cultivated, produce no lasting fruits. 



Six or seven years before Haiiy, Gahn -f-, a young Swedish 

 chemist, who was afterwards professor at Abo, had also remarked, 

 in breaking a crystal of pyramidal spar, that its nucleus was a 

 rhomboid similar to Iceland spar. He had communicated this 

 observation to his master, the celebrated Bergmann, a man of su- 

 perior mind, and one who might have been thought capable of eh- 

 citing all its consequences. But in place of repeating it on different 

 crystals, and of thus discovering, by experiment, within what 

 limits the fact might be generalized, Bergmann gave himself up 

 to hypotheses, and from the first step ran wide of the subject. 



* See his memoir on an analytical method for resolving the problems relative to 

 the structure of crystals^ in the volume of the Academy for 1788, p. 13. ; and 

 on the manner of reducing to the theory of the parallelopiped that of all the other 

 primitive forms of crystals, in the volume of 1789, p. 519. 



I Sec in the first volume of the Nova Acta of the Academy of Upsal, 

 printed in 1773, p. 150, Bergmann's memoir, entitled, Crystallorum formee e 

 spatho ortcB. It is reprinted in Bergmann's works, Leipsic edition, and La- 

 metherie inserted a translation of it in the Journal dc Physique of 1792, t. xl. 



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