REVIEWS 445 



northeast to southwest across the area, and along the southern and 

 southwestern border. On the northwest they are in extended and 

 comparatively broad belts, but in the eastern portion they appear in 

 many small and separated exposures, associated with some quartzites 

 and much greater amounts of characteristic gniesses, but greatly 

 broken up by igneous intrusions. The quartzites thus far known are 

 in small quantity, but such as they are, they are found principally in 

 the eastern portions of the area, where the limestones are thinnest 

 and most scattered. From the presence of the quartzites it is inferred 

 that clastic sediments must have been present in larger amounts than 

 has heretofore been realized. On the east it has not been proven 

 that sediments form synclines pinched into the underlying gneissoid 

 rocks. On the contrary they seem to constitute low, dipping, flat 

 monoclines. 



Conunent. — The complex geology of the Adirondack crystalline 

 rocks is being rapidly worked out by Kemp, Smyth, Gushing, and 

 others. The frequent brief papers issued by these geologists in nearly 

 all cases report some important advance in the solution of their prob- 

 lem. The precise relations of these advances to the general problem 

 may not be clear to the average geological reader, too busily engaged 

 to follow the subject closely, and for such the general summary of 

 Adirondack geology given by Kemp ' will be of value. 



In a previous comment^ on Adirondack geology the state of 

 geological knowledge, as indicated by the literature on the subject 

 then available, was briefly summarized by the writer, and here atten- 

 tion will be called only to later developments. One of the most 

 interesting of these is the extension of the areas of pre- Cambrian 

 sedimentary and associated rocks, and the corresponding contraction 

 in the area of the great Adirondack gabbro. This was formerly 

 supposed to occupy the great central area of the Adirondacks with 

 the pre- Cambrian sediments and the associated gneisses around its 

 periphery. Recent work seems to show that the area is occupied by 

 gneisses, with narrow limestone belts, cut through on the east by a 

 number of immense intrusions of gabbro. Another advance is the 

 discovery of greater quantities of clastic sediment than have before 



' Pre-Cambrian Sediments in the Adirondacks, by J. F. Kemp : Vice Presiden 

 tial address published in Proceedings of tlie A. A. A. S., Vol. XLIX, 1900, pp. 

 157-184. 



^JouR. Geol., Vol. VII, pp. 410-41 1. 



