While examining the fine series of corundums brought from Burma by Mr. C. Barrington Brown, F.G.S., and comparing them with specimens obtained from Ceylon, Southern India, the United States. and other localities, I have been led to devote especial attention to the curious " parting-planes " which are sometimes found in crystals of this mineral, but which, in other cases, appear to be entirely wanting. In making these comparisons, I have had the great advantage of being able to refer to the fine collection of corundums in the British Museum (Natural History) at South Kensington, and have to gratefully acknowledge the advice and assistance which have been so freely afforded to me at all times by Mr. Fletcher and Mr. Miers.

In recent years, the respective provinces of Mineralogy and Petrography have become much more clearly defined than was formerly the case. We no longer include uncrystallised substances, like obsidian, taehylyto and coals among mineral species; and, on the other hand, we recognise the fact that many materials originally analysed and treated as homogeneous—such as lapis-lazuli, emery, and many similar materials—are really mineral aggregates or rocks, and thus come within the domain of the petrographer. This last advantage has been one of the most important of those which have resulted from the application of the microscope to the study of inorganic bodies.

In the course of some researches on the relation between the chemical constitution and the crystalline form of substances, I found it necessary to attempt an accurate determination of the densities of crystals.

Messrs. Playfair and Joule, in 1843, in the course of similar researches, determined the specific gravities of numerous salts by the use of an instrument which showed the actual volume of the solid investigated. This method was found to be subject to many errors, and they abandoned it for one which is the prototype of that ordinarily used in accurate work at present.

Argentina.--L. Brackebusch (Las Especies Min. de la Rep. Argentina), Anal. Soc. Cient. Argentina, 112, 1878; H. D. Hóskold, Mémoire général et spécial sur les mines, &c., duns la Rep. Argentina (Exposition de Paris, 1889), p. 126, analyses and maps; Catálogo oficial of the Argentine minerals at the Paris Exhibition, 58, 1889; Argentine Rep., Philadelphia Exhibition, 1876, pp. 197, 193; A. Sella, Nachr. d. k. Ges. d. Wiss. zu Göttingen, 317, 1891 (specific heat).

This new antimonate was found in the cinnabar mine of Tripuhy, near Ouro Preto, Minas Geracs, Brazil.

The occurrence of cinnabar at this locality has been known since 1810, and a short notice of it is given by Eschwogo in his Pluto Brasilensis, p. 456, which was published in 1883.