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The character of the included rock fragments suggests that the ice 

 moved from the southeast. Intercalated slate beds indicate recessions 

 of the ice. Whether they represent temporary retreats or long inter- 

 glacial epochs is not known. Two conglomeratic beds below the prin- 

 cipal tillite are of probable glacial origin, though it is not certain that 

 they were deposited directly by the ice. H R B 



Geology of the Lake Pleasant Quadrangle, Hamilton Co., N.Y. By 

 William J. Miller. New York State Museum, Bull. No. 

 182, 1916. Pp. 75, pis. 10, figs. 4, map 1. 



The Lake Pleasant Quadrangle lies in the south central Adirondacks. 

 The Grenville series of meta-sediments and intrusives outcrops" over 

 most of the region and is cut by a network of normal faults. Two 

 small areas of Paleozoic strata are preserved by the dropping of fault 

 blocks. The maximum thickness of this section is 500 feet. The 

 formations preserved are: Potsdam sandstone, Theresa beds, Little 

 Falls dolomite, Black River (Lowville) limestone, Trenton limestone, 

 and Canajoharie (Trenton) shale. 



The normal syenites of the region grade into basic syenites, also into 

 granitic syenites and granites. The basic phases are attributed to the 

 assimilation of dark Grenville gneisses. Pure differentiation has been 

 the principal factor in the production of the silicic phases. Transitions 

 from gabbro into basic syenite are described as due to assimilation by 

 the gabbro. H. R. B. 



Geology and Underground Waters of the Northern Llano Estacado. 

 By Charles L. Baker. Bull. Univ. Texas, No. 57, 1915. 

 Pp. 225, pis. 10, maps 3. 



For half a century or more the Llano Estacado has been famous for 

 its stock-raising. Recently there has been a serious attempt to utilize 

 the ground water for purposes of irrigation. The supply of shallow 

 water is found to be insufficient to irrigate all the land that it underlies. 

 Conservation is therefore of first importance, but unless dry farming 

 proves more successful than in the past this region will always be chiefly 

 a stockman's country. 



Previous geologic work is largely confirmed by the present study. 

 The strata represented are the Permian red-beds, the Upper Triassic 

 Dockum group, comprising the Tecovas and Trujillo formations, marine 

 beds of upper Comanchean age, possibly some Cretaceous rocks, and 

 imperfectly known Miocene and later Cenozoics. H R B 



