88 Scientific Intelligence. 



No. TIT. Hydrography of Virginia ; by N. C. Grover and 

 R. H. Bolster. Pp. 234, with 10 plates and 1 text-figure. This 

 Bulletin discusses the drainage basins of the prominent rivers of 

 Virginia, — namely, the Potomac, the James, the Roanoke, and 

 New River. A drainage map of the state showing gaging and 

 rainfall stations is given, and a large amount of data are pre- 

 sented for the individual rivers. 



6. La Sierra cle Cordoba : Constitution geologica y JProductos 

 minerales de aplicacion / by W. Bodenbender. Rep. Argen- 

 tina An. d. Ministerio d. Agric. Sec. GeOl., Tom. T, Num. II, 1905. 

 8°, 150 pp. — The Sierra de Cordoba lies between 21° and 23° S. 

 and 63^° and 65° W. in Argentina with a general north and south 

 direction and is composed of several ranges, some of whose 

 peaks have altitudes from 6-8000 feet. The memoir is devoted 

 first to a general geological description of the area, aided by a 

 geological map. Then follows a list of occurrences of minerals, 

 of which a large number of species are mentioned. The rocks 

 are then treated and brief petrographic descriptions of the 

 different kinds are given, both of the crystalline schists and 

 igneous rocks. The sedimentary rocks are conglomerates, sand- 

 stones, etc., of Cambrian and supposedly Silurian age and of the 

 Permian-Triassic, with argillaceous beds of the Pampas terrane. 

 The work concludes with a brief account of the economic min- 

 eral deposits. It is illustrated by a considerable number of half- 

 tone cuts of photographs illustrating various features of interest 

 in the mountain region. The work is more or less general and 

 preliminary in character, yet contains in compact form a great 

 deal that is of interest and importance concerning a little known 

 region. l. v. p. 



7. Contributions from the Geological Department of Colum- 

 bia University. Vol. xii, Nos. 107, 108. Vol. xiii, Nos. 109-114. 

 — These include numerous geological papers, published by gen- 

 tlemen connected with Columbia University in various journals 

 and society transactions, and now collated, in convenient form 

 for binding, in sequence with similar volumes previously dis- 

 tributed. 



8. The Constitution of the Silicates. — In a paper on the 

 Chemical Constitution of the Feldspars, presented to the Vienna 

 Academy in 1903, Professor Tschermak undertook to throw 

 light on the chemical composition of the feldspars, especially with 

 reference to the particular type of silicic acid present. From 

 the slow decomposition of the mineral by hydrochloric acid a 

 hydrated silicic acid is separated which, when exposed to the air, 

 rapidly loses water for a number of days, but finally passes into 

 a condition where the further loss is very slow, except upon 

 ignition. By determining the amount of water present at the 

 point named, the author believes that he establishes the constitu- 

 tion of the silicic acid present. For anorthite, for example, the 

 loss of water by ignition was found to be 23-41, while the acid 

 H 2 Si0 3 requires 22*98. The conclusion is reached, therefore, 



