l 2 c 20 Geological Society, 



a single cavity in which the expansible fluid within had communi- 

 cated a polarizing structure, similar to that around the cavities in 

 the diamond. He believes, therefore, that the softness must have 

 been that of semi-indurated gum ; and that the diamond was de- 

 rived from the decomposition of vegetable matter, as is admitted to 

 have been the case with amber. The crystallized condition of the 

 diamond is not to be considered as decisive against this inference, 

 since the mineral called mellite has a distinct crystallized form, 

 while its composition and locality attest a vegetable origin *. 



A notice " On the Occurrence of the Bones of Animals in a 

 Coal-mine in Styria," by Professor Anker, of Joanneum in Gratz, 

 was then read. 



March 13. — A paper, entitled "Geology of the Environs of Bonn," 

 by Leonard Horner, Esq. F.G.S. F.R.S. &c, was read. 



The district described by the author lies on both sides of the 

 Rhine, — the Siebengebirge, or Seven Mountains, constitute the 

 chief feature ; and the highest point in the group, the Oelberg, is 

 1369 English feet above the level of the sea. It possesses peculiar 

 interest to the geologists of England, as being the nearest point 

 where volcanic phenomena, approaching in character to those of 

 modern times, can be seen. 



The lowest stratified rock is grauwacke, which seems to belong 



* [As the subject of the origin of the diamond was discussed in our pages 

 some years ago, we annex an historical remark or two to the above abstract 

 of Sir D. Brewster's paper. In the communication to the Royal Society 

 of Edinburgh, alluded to in the abstract, it was argued that the original 

 compressible state of the diamond could not have arisen from the action of 

 heat, on account of "the nature and recent formation of the soil in which 

 it is found." Mr. Brayley, when discussing the arguments in favour, re- 

 spectively, of the vegetable and the mineral origin of this gem (in a notice 

 headed " Origin of the Diamond" published in the Phil. Mag. and Annals, 

 N.S., vol. i. p. 147 — 149, and signed E. W. B.), observed, that the disco- 

 very, subsequently to Sir D. Brewster's researches, of a diamond in a ma- 

 trix of brown ironstone occurring in beds subordinate to chlorite slate in 

 the Brazils, and the information, also subsequently promulgated, that the 

 diamonds of Southern India are found in an ancient breccia, removed Sir 

 David's objection on this point. Mr. Brayley inferred, therefore, since, for 

 aught that had been advanced to the contrary, the compressible state once 

 possessed by the diamond might have resulted from the action of heat, that 

 the optical characters discovered by Sir D. Brewster, did not necessarily 

 refer its origin to the vegetable kingdom. 



In the paper read before the Geological Society, however, Sir D. Brew- 

 ster shows, in a direct manner, by comparing the optical characters of the 

 diamond with those of other crystallized substances, that the original soft 

 or pasty state of the former could not have been produced either by igneous 

 fusion or by aqueous solution. The evidence now adduced on this point 

 is therefore quite independent of the geological situation of the gem; and 

 it would appear to be impossible to refer it to any other than a vegetable 

 origin, as originally suggested by the author of the paper. 



We observe that Dr. Thomson's statement of the geological situation of 

 the diamond (Inorg. Chem. vol. i. p. 156.) is derived from the above-cited 

 notice in the Phil. Mag. and Annals. — Edit.] 



