REVIEWS 53 



Arthur Keith. " Geology of the Piedmont Plateau Area of the Washing- 

 ton Quadrangle." Geologic Atlas of the U. S., Washington Folio, No. 70, 

 U. S. Geological Survey, igoi, pp. 2, 3. 



Keith describes and maps the geology of the Piedmont Plateau of the Washington 

 quadrangles. Igneous rocks of Archaean age are mapped under the following headings ; 

 biotite-granite, soapstone and serpentine (altering from peridotite and pyroxenite), 

 gabbro, meta-gabbro, diorite and meta-diorite (including granite, gneissoid granite 

 and schistose granite), and Carolina gneiss (including mica-gneiss, mica-schist, and 

 small bodies of granite, schistose granite, and diorite). In age these rocks rank in the 

 order named, the Carolina gneiss being the oldest. Also the relative areas of the 

 groups nearly correspond with their ages. 



T. Nelson Dale. "Structural Details in the Green Mountain Region, and 

 in Eastern New York." Bulletin of the U. S. Geological Survey, No. 

 195, igo2. 

 Dale sketches structural details in the Green Mountain district and in eastern 



New York, such as folds, cleavage, joints, and faults, some of them in the pre-Cambrian 



rocks. 



F. J. H. Merrill. " Metamorphic Crystalline Rocks of the New York 

 Quadrangle. Geologic Atlas of the U. S., New York City Folio, No. 83, 

 U. S. Geological Survey, 1902, pp. 3-5. 

 Merrill describes the metamorphic crystalline rocks of the New York quadrangle. 



Of these only one, the Fordham gneiss, is of pre-Cambrian age. The petfbgraphy of 



this gneiss is described. No opinion is expressed as to its sedimentary or igneous 



origin or as to its Algonkian or Archaean age. 



C. H. Smyth, Jr., and D. H.Newland. " Report on Progress Made During 

 1898, in Mapping the Crystalline Rocks of the Western Adirondack 

 Region." Eighteenth Annual Report of State Geologist for 1898 pub- 

 lished in Fifty-second Aftmial Report of the New York State Museum (for 

 1898), Vol. II, 1900, pp. 129-35. 



Smyth and Newland report progress in the mapping of the crystalline rocks of 

 the western Adirondack region. Inclusions of hornblende schists found in the more 

 acid gneisses of the region are believed to afford important evidence as to the origin of 

 the gneisses. Also light red granitoid gneiss has been found intrusive into a gray 

 gneiss, indicating, as before held, that all the gneisses are not of the same age. 

 Certain of the gneisses are found to be younger than, and intrusive into, certain schists 

 associated with the limestones. 



H. P. CusHiNG. " Recent Geologic Work in Franklin and S. Lawrence 

 Counties, N. Y." Nineteenth Annual Report of State Geologist for 1900, 

 published in Fifty -third Anmial Report of the New York State Museum, 

 Vol. I, 1902, pp. r 23-95. 

 Cushing discusses recent geological work in Franklin and St. Lawrence counties, 



N. Y., and concludes : 



I. That the Adirondack anorthosite is cut intrusively by an augite syenite, which 



is therefore younger. 



