Mr. H. J. Brooke on the Crystalline Form of Beudantite. 349 



and of soda into two divisions, the sulphate and nitrate groups, 

 which must have a chemical significancy. The same division 

 of the salts in question has been made by M. Gerhardt, on 

 the ground that the nitrate class is monobasic and the sulphate 

 class bibasic. 



5. The application of liquid diffusion to the separation of 

 mixed salts, in natural and in artificial operations. 



6. The application of liquid diffusion to produce chemical 

 decompositions. 



7. The assistance which a knowledge of liquid diffusion will 

 afford in the investigation of endosmose. When the diffusi- 

 bility of the salts in a liquid is known, the compound effect 

 presented in an endosmotic experiment may be analysed, and 

 the true share of the membrane in the result be ascertained. 



But on the mere threshold of so wide a subject as liquid 

 diffusion, I must postpone speculation to the determination of 

 new facts and the enlargement of my data, of the present in- 

 completeness of which I am fully sensible. 



XLIV. On the Crystalline Form of Beudantite, 

 By H. J. Brooke, Esq., F.R.S.* 



IN a paper by Dr. Percy in the September Number of this 

 Journal, on the chemical constitution of Beudantite, it is 

 stated that its form is certainly very similar to, if not identical 

 with, that of cube-ore; that Levy maintained it to be an 

 obtuse rhombohedron with the vertical angle truncated ; and 

 that Descloizeaux, on the other hand, asserts that the crystals 

 are cubes similar in all respects to those of cube-ore from 

 Cornwall. It is clear from this statement that the crystals 

 examined by Descloizeaux were different in form from those 

 examined and described by Levy, which have only one of the 

 solid angles of the supposed cube truncated, the truncating 

 face being large in comparison with the size of the crystals ; 

 and instead of being bright, like the other faces, is of such a- 

 velvety dullness as scarcely to reflect any light. 



The composition seems therefore to have influenced the 

 form and character of the crystals of Levy's specimen, the 

 further distinction of which from those of cube-ore cannot, 

 however, on account of the imperfection of the faces, be made 

 out. 



* Communicated by the Author. 



