Reviews — Indian Geological Survey. 275 



replacement of the carbonate of lime by silica and ferrous carbonate ? 

 Considering the fact that the imprisoned substance contains an excess 

 of carbonate of lime and very little ferrous cai'bonate, but in other 

 respects corresponds to the analysis of the Cleveland ironstone, are we 

 not justified in accepting the evidence as going far to prove that the 

 original deposit was really siliceous and aluminous limestone, and that 

 not only ferrous carbonate, but ferrous silicate in solution, has taken 

 the place of carbonate of lime, as Dr. Sorby maintains, and that 

 co-incidentally silica in solution has passed from the mass of calcareous 

 and siliceous mud which surrounded the original, nearly pure lime- 

 stone concretions, and was then deposited in concentric layers ? " 



IV. — Indian Geological Survey. 



TMIIE Memoir on "The Geology of Northern Afghanistan", by 

 JL Mr. H. H. Hayden, Director (Mem. Geol. Surv. India, 

 vol. xxxix, pt. i, 1911), contains observations made "during 

 a short tour undertaken primaiily for the investigation of economic 

 questions ". The author describes the physical features and main 

 geological structure of the country, and deals with a varied series 

 of rock-formations. The age of the oldest, " Metamorphic and 

 Crystalline Series," is practically undetermined, but it includes 

 limestone, yielding ruby and rarely sapphire, and this may be of 

 Devonian age. There is evidence of Lower Palaeozoic rocks, of 

 Devonian, Carboniferous, Permo-Carboniferous (Fusulina limestone), 

 Triassic, Jurassic, Cretaceous, Tertiary, and Pleistocene. The facts 

 gathered by the author, and previously by C. L. Griesbach (1880-8), 

 lead to the conclusion that the " country is divisible into two strati- 

 graphical provinces, one of which is represented only in Eastern 

 Afghanistan, while the other comprises by far the greater part of the 

 country and embraces most of the northern and western districts. 

 The affinities of the former province are with the Himalayan area, 

 whereas those of the latter are with "Western Asia and also to some 

 extent with Europe. The mutual separation of the two provinces 

 seems to have taken place towards the end of the Carboniferous 

 period". The memoir is illustrated by a geological map and many 

 striking views of stratigraphical and rock features, including a 

 recumbent fold, overthrusts, dome-structure, unconformities, etc. 



V. — United States Geological Survey. 



BULLETIN 433, 1910, consists of a report on the "Geology and 

 Mineral Resources of the Solomon and Casadepaga Quadrangles, 

 Seward Peninsula, Alaska", by Mr. P. S. Smith. In this work 

 we have descriptions, with geologic and topographic maps, of 

 portions of Seward Peninsula on the borders of Norton Sound in 

 Western Alaska. A small and useful geologic map of the entire 

 peninsula is also given, and this shows a pre-Ordovician series of 

 gneisses, limestone, and schists, the Kigluaik group ; a series of 

 unfossiliferous schists, and of limestones which yield Ordovician 

 and possibly Silurian fossils; and a newer limestone "from which 

 Carboniferous or Upper Devonian fossils have been obtained ". There 

 are also andesites of uncertain age, granites of later date, some late 



