GEOLOGY AND MINERALOGY. 517 



Ing sketch-section sliews the position of the gravel-pit on the left bank of the Grand 

 Eiver, and its relations to the other deposits of the locality: 

 B 



A is the (Upper Silurian) Gypsiferous Limestone rock of the district ; B the drift 

 gravel ; and C the fresh-water deposits of the Grand River Flats. These latter 

 ■deposits, as already stated, belong to a more recent period ihan that of the true 

 Drift. 



ATTQITE AND HORNBLENDE. 



Eammelsbei'g has published a very valuable paper on the relations of Augite and 

 Hornblende, including the various species of these respective types. His analyses 

 «he-w that the oxygen ratio in the Hornblende type, instead of being as 4 : 9, is ac- 

 tually, as in the Augite type, as 1 : 2 — giving for each, the common formula 3 R 0, 

 2 Si 0^. In the aluminous hornblendes, he places the alumina with the silica ; or, in 

 other words, makes the two vicarious, as suggested by Bonsdorflf many years ago. 

 "When Fe'^ 0^ ia present, as in acmite, <fec., it is shewn to act the part of a base, 

 and thus to replace the oxides R 0. [There can be little doubt that acmite is to 

 a certain extent an altered mineral; and, very probably, the Fe'^ 0^ in these mi- 

 nerals, existed originally, in all cases, as Fe 0.]* 



WITHEEITE (carbonate OF BARTTA). 



Our attention has been recently attracted to a peculiarity, not hitherto noticed in 

 mineralogical works, in the blowpipe reactions of certain specimens of Witherite 

 (B a 0, C 0^) from one of the Cumberland localities. These specimens (of a yel- 

 lowish-white colour) became, after strong heating, pale greenish-blue. This arises 

 from the presence of a very small amount of oxide of manganese. A coloration of 

 this kind from the presence of manganese, can only occur — apart from the alkaline 

 carbonates — with carbonate of baryta. A blowpipe test by the author of this note, 

 founded on a similar reaction, is given in the fourth edition of Plattner's Probir- 

 kunst mit dem Lothrohre, p. 186. It is well known that if a manganese compound 

 be fused with carbonate of soda, an opaque greenish-blue glass or so-called " tur- 

 quoise enamel " will result. The fused bead is green whilst hot, and becomes 

 blue on cooling. If to a bead thus coloured, baryta be added, and the whole .be 



• The author is guilty of a somewhat remarkable oversight, when he states, in reference to 

 the crystallization of Wollastonite, that, " die selten deutlichen Krystalle dieses Minerals, 

 welche Brooke, Phillips, una von Kobell beschrieben haben, lassen zum Theil keine ungez- 

 wungene Vergleicliung su, und man hat bisher nioht gut vermocht, ihre Form auf die des 

 Augits zuruckzufiihren"— because, if the reader will refer to Dana's system of Mineralogy, 

 <4th ed., vol. 2, page 157,) he will find the crystal-relations of Wollastonite to Augite most 

 clearly pointed out ; and exactly in the same manner, moreover, as now shewn by Rammels- 

 berg. s- '''• ^' 



