658 REVIEWS 



age do not appear about the Adirondacks. The oldest Cambrian forma- 

 tion of this region is the Potsdam, a coarse, often pebbly, massive sand- 

 stone which was deposited in shallow water on the old land surface of the 

 present Adirondack region. This was succeeded by the Beekmantown 

 formation, composed generally of beds of sandy dolomite. In the Cham- 

 plain valley the Beekmantown is overlain by a considerable thickness of 

 quite pure marine limestones, which are very fossiliferous and known as 

 the Chazy formation. During Chazy time there was an elevation to the 

 "lovithwest of the Adirondacks, followed by a depression ; so that the Chazy 

 formation does not appear on that side of the Adirondacks, and the Beek- 

 mantown is succeeded unconformably by the thin band of pure limestone 

 known as the Lowville, which does not appear to the east and north of 

 the Adirondacks. The Chazy limestone on the northeast and the Low- 

 ville on the southwest are both overlain by marine fossiliferous limestones, 

 known as the Black River and Trenton formations. Through the invasion 

 of mud the Trenton limestones pass gradually into the Utica shale, which 

 is the youngest formation carefully described. Professor Cushing con- 

 cludes that "this submergence apparently completely overswept the old 

 Adirondack island," and "the whole of New York State would seem to 

 have been submerged, and that for the last time in its geologic history." 



C. S. Prosser 



Corundum and the Peridotites 0} Western North Carolina. By 

 Joseph Hyde Pratt and Joseph Volney Lewis. (Vol. I, 

 N. C. Geological Survey, Raleigh, 1905.) Pp. 464, 45 plates 

 and maps, 35 figures. 



The North Carolina Geological Survey has heretofore published only 

 "Bulletins" and "Economic Papers" of rather a preliminary nature. 

 This volume is the first of a series of more elaborate reports on special 

 subjects. It treats of the peridotites and associated basic magnesian 

 rocks of North Carolina, and describes incidentally similar occurrences 

 elsewhere in the world. The geology of the state, the petrography of 

 the rocks, their alteration and their origin are discussed in the first part 

 of the work. Then follow chapters on corundum, its physical and chemi- 

 cal properties, varieties, and uses; its occurrence and distribution; its 

 alteration, its origin, and the method of mining and milling. The last 

 chapter treats of chromite and other minerals of economic value which 

 occur in the corundum-peridotite belt. 



E. W. S. 



