ON THE FORMATION OF- CRYSTALS'. « 191 



produced in his other experiments. But on the whole, he 

 thinks they feem to eftablifh, 1. That the contact of one me- 

 tallic fubftance with another generally produces electricity. 

 2. That the quantity and quality of the electricity fo produced, 

 is various, according to many circumftances which feem to 

 occur in the products of it, or in a great meafure to influence 

 it. 3. And that thefe circumftances are, the various nature of 

 the metallic fubftances, their various degrees of heat, the 

 ftate of the atmofphere, the hand of the operator, &c. each 

 of which caufes has its ihare in the refult. 



VI. 



On the Formation of Ciyjlak, defcribing a Method of producing 

 them large and regular. ByCiT. Le Blanc *. 



IT had long fince been remarked, that the fame fait is On the caufes 

 f ufceptible of cryftallizing under feveral different forms. C. °* cryftalliza- 

 Hauy has demonftrated, that all thefe fecondary forms are 

 owing to different arrangements of the farrie integrant mole- 

 cule ; he has fhewn that thefe effects are not the effect of 

 what is termed chance, but that they proceed from laws 

 fufficiently fimpte, which may eafily be determined. Here 

 he has flopped ; he has not yet thought proper to publifli the 

 ideas which he has given in his courfe [of lectures] relative to 

 the caufes which difpofe the integrant molecules to follow fuch. 

 or fuch a law in their mutual arrangement, Thefe are the 

 caufes which Cit. Le Blanc inveftigates in his obfervations on 

 the growth of cryftals. He has been long engaged in thefe 

 inquiries, and the memoir which he has read to the Ihftitute 

 is a continuation and fequel of that which he read to the Aca- 

 demy of Sciences, of which an extract was inferted in the 

 Journal de Phyfique, November 1788, p. 374. He has dif- Cryftalsof ex- 

 covered, by his perfevering and ingenious obfervations, that traordinary fize 

 we may confiderably vary both the bulk and form of the ' 



cryftals at pleafure, by caufing them to be formed and to 

 grow under certain circumftances, and he has long iince en- 



* Communicated to the French National Inflitute, and abridged 

 in the Bulletin des Sciences, whence the aboye is translated. No. 

 50, An. iO. 



rtched 



