Geology and Natural History. 71 



ton. 433 pp., 4to, 72 plates, 18 figures. U. S. Geological Sur- 

 vey, Professional paper 32. — The area covered by the discussion 

 in this volume embraces nearly all of South Dakota, Nebraska 

 and Kansas, and extends westward to central Wyoming and 

 Colorado. Over most of the region the rolling plains of the 

 eastern portion rise gradually and uniformly to the westward. 

 The geological structure is comparatively simple for the most 

 part, with the exception of the Black Hills region in South 

 Dakota and portions included of the Big Horn and Laramie 

 Ranges in Wyoming and Colorado. The geological features are 

 very fully presented in the first half of the present volume, the 

 descriptions being based upon work by numerous geologists 

 in the past, supplemented by that of Mr. Darton and his assist- 

 ants. Numerous excellent views from photographs, and also 

 geological maps and sections, accompany the text. The chief 

 interest of the investigation, however, lies in the question of 

 water supply, which in many parts of the region is very deficient 

 and must be supplemented where possible by artesian wells. 

 Great numbers of these have already been sunk, many of them 

 with excellent results, and the study that Mr. Darton has made 

 so carefully of the region gives promise that still more will be 

 accomplished in the future. Although the rocks of Cambrian, 

 Ordovician, Carboniferous and Jurassic age are believed to 

 underlie the entire area, almost no wells exist lower than the Cre- 

 taceous, and the water horizon of the Dakota sandstone is the 

 most widely extended and the most useful. The author states 

 that over a thousand deep wells have been sunk east of Missouri 

 River most of which are from 500 to 1000 feet in depth and yield- 

 ing a large supply of flowing water, most of which is used for 

 irrigation. The aggregate flow from these wells is estimated to be 

 about 7,000,000 gallons a day. From the Fox Hills-Laramie for- 

 mation the supply is much more limited. The Tertiary deposits 

 also yield useful wells, particularly in the Denver basin. Finally, 

 the alluvial deposits of the Quaternary afford large quantities of 

 water from limited depths (5 to 50 feet), while the tubular wells 

 in east South Dakota and east Nebraska bring the water of the 

 glacial drift mainly at the base of the till. 



The great pressure under which the water exists is a point of 

 much interest and shows that it must owe its origin to an altitude 

 some thousands of feet above. Several wells in eastern South 

 Dakota, for example, show surface pressures over 175 pounds to 

 the square inch, and two are a little over 200 pounds ; the latter 

 indicating a pressure of 780 pounds at the bottom of the well. 

 The theoretical hydrostatic pressure is, however, much dimin- 

 ished by the leakage of water to the east and south. . Full 

 details are given in the volume in regard to existing wells, and 

 the work closes with a chapter upon the Economic Geology of 

 the region, that is, the supplies of coal, oil, gas, salt, etc. 



3. Origin of the Channels surrounding Manhattan Island, 

 New York ; by W. H. Hobbs. Bull. Geol. Soc. America, xvi, 



