1^6 Ati Attnnpt to arrange the 



tions of the pyramids to the prifm, and reverfed together witii- 

 out the intermediate part. In fact, the varieties appear to 

 be almoft innumerable. 



After I had made the above arrangement, I received the 

 32d Number of the Journal iles ISihies, from which I beg 

 leave to fubjoin the following extracts : 



'* The primitive form of the cryftals of oxydated tin ap- 

 peared to me to be that of a cube performing the function of 

 a parallelopipedcn ; fo that the decrement? which produce the 

 fecondar^' forms have,' in regard to the two oppolite faces of 

 the cube, which muft be confidcret as the Lafes, an action 

 different from that which takes pl:)ce in regard to the other 

 four faces that reprefent the planes of the prifm." (p. 576.) 



*' One of the rareft varieties of this kind is that reprefented 

 fig. 7 *, and which is the feventh of Rome de Lifle, T. III. 

 p. 422. We give it the name oi dijiiqu^ oxyd of tin; 

 that is to fay, with two ranges of facets. It has altogether 

 tliirty-fix faces ; four of which M M are ^•ertical, and on 

 each fide eight inferior oblique z., -z'y and eight fupcrior 

 oblique 0. i. If, as ufual, we denote the edges of the bafe of 

 the cubic nucleus by B, and the angles by A, we fliall have, 



as the indicating fign of this variet}', M (AB'B^) BA, in 

 which the intermediary decrenjent is referred to the facets 

 ^■, z.', the decrement B to the facets 5 .s, and the decrement 

 x\ to the facets 0,0. The following is the indication of the 

 principal angles: incidence of M to M 90^, of 2; to z 116'^ 20', 

 of £; to 2' ijS'' 30 , of i- to 5 120", of to J 150''. Quantity 

 of the angle 7Z 118'^ 4'." {Suite de l Ext rait du Traite df 

 Mi7icrahgie de C. Hauv, p. 578.) 



_ From the preceding extracts it appears that Ilauy has fup- 

 pofed the cube to be the nucleus or primitive form of the 

 oxidated tin cryftals. I have again carefully examined the 

 crvltalfc in my own collc6lion, aud, according to the indi- 



* Fig. 23 is a tracing from Haiiy's fig. 7, referred to l-.erc, and is the 



iauie cryftal as reprefented llg. iS. 



calions 



