378 Reviews — Brief Notices. 



2. Ferberite in Colorado. — The rare mineral ferberite occurs in 

 workable quantities in Boulder County, Colorado. An exhaustive 

 account is given by Messrs. Hess & Schaller (Bulletin 583, "United 

 States Geological Survey, 1914). The end members of the wolframite 

 series are ferberite, FeW0 4 , and hiibnerite, MnW0 4 ; wolframite is 

 an isomorphous mixture of these two compounds. The ferberite of 

 Boulder County occurs in beautifully developed, though small 

 crystals, some of a wedge shape, others of almost cubic habit ; also 

 massive and in blades. They are black, almost metallic, and opaque 

 in thin sections. All known analyses of the wolframite group are 

 tabulated and criticized, and an appendix contains an elaborate 

 crystallographic discussion. 



3. Bulletin 577 of the United States Geological Survey contains 

 a very full description of the geology of the phosphate deposits north- 

 east of Georgetown, Idaho, by Messrs. B. W. Richards and G. R. 

 Mansfield. The phosphate - bearing rock is an oolitic sediment 

 associated with limestones, and probably of Permian age : near the out- 

 crops it seems to have undergone secondary enrichment by weathering. 

 Average samples generally show about 32 per cent of phosphoric 

 acid, and the amount of rock available is estimated at more than 

 2,500,000,000 tons. The geological structure of the district is very 

 complicated, including an overthrust which has carried Carboniferous 

 rocks for a distance of some 12 miles over Cretaceous and Eocene 

 strata : consequently in places the phosphate beds are buried too 

 deeply to be worked. No satisfactory explanation of the origin of 

 the phosphatization is forthcoming. 



4. In the Bulletin of the Geological Society of America, vol. xxv, 

 pp. 277-320, 1914, Mr. Charles Schuchert describes his work on the 

 Medina and Cataract formations of New York and Ontario. It is shown 

 that the Cataract formation of Ontario, formerly ascribed to the Clinton, 

 is really equivalent to the typical Medina of New York, while the 

 Brassfield Beds of Ohio are of about the same age. The variations 

 are due to deposition in marine areas with only limited connexion, 

 encroaching from different directions. The Medina is essentially 

 a sandstone facies, while the others are calcareous. The second part 

 of the paper contains an historical review of research on these rocks, 

 together with full descriptions of sections and lists of fossils. — B. H. B. 



5. North American Geology. — The valuable Bibliography of North 

 American Geology has appeared for 1913. It is compiled and indexed 

 by J. M. Nickles and is a model of what such publications should be. 

 It includes all papers on the North American Continent and adjoining 

 islands, as well as Panama and the Hawaiian Islands. There are 

 1,357 items. 



6. Potash in the Texas Permian. — The impossibility of securing 

 shipment from Germany of potash has led the Texan Bureau of 

 Economic Geology to investigate the sources of supply in that State. 

 The results are highly satisfactory, and Mr. J. A. TJdden has issued 

 a detailed report in the Bull. TJniv. Texas, 1915, No. 17. 



7. Rhodesia. Museum, Department of Geology. — Owing to the 

 departure of Mr. Macgregor for England in February, 1915, a detailed 

 account of the progress of the Geological Department during the past 



