62 REVIEWS 



F. L. Ransome. "Ore Deposits of the Rico Mountains, Colorado. Ttventy- 

 second Anntial Report of the U. S. Geological Survey, Part II, 1900- 

 1901, pp. 229-397. 



Ransome describes the ore deposits of the Rico Mountains, Colorado, and inci- 

 dentally summarizes the geology of the area, referring the reader to a previous paper 

 by Cross and Spencer^ for further details. The Algonkian rocks consist of quartzites 

 and schists, exposed just north of Rico and in the canyon of Silver Creek. They 

 appear as fault blocks, in the heart of the dome, thrust up from below into the later 

 beds. 



Whitman Cross. " Geology of the Silverton Quadrangle, Colorado." From 

 Bulleti7i No. 182, U. S. Geological Survey, 1 901, by F. L. Ransome. 



Cross summarizes the geology of the Silverton quadrangle, Colorado, for Ransome's 

 bulletin on the economic geology of this quadrangle. Algonkian quartzites and 

 schists appear beneath the volcanics where the Animas River and the Uncompahgre 

 River and its tributaries cut through the volcanics. 



Irrigation. By F. H. Newell. New York: T. Y. Crowell & Co. 



Mr. Newell's book is written from the economic and social point 

 of view, and emphasizes the importance of irrigation as a national 

 problem. For this reason the general reader, as well as the person 

 directly concerned in' home-making in the arid West, will read the 

 work with interest. Guided by his extensive experience with problems 

 of irrigation, the author contrasts the present scanty occupation of the 

 western two-fifths of the United States with the possibilities for home- 

 making when the present water-supply shall have been properly con- 

 served. 



At the present time 7,300,000 acres are under irrigation, while the 

 natural water supply is sufficient for ten times that acreage. The success 

 already attained in this small fraction of the area abundantly justifies 

 the iiational expense already incurred, and becomes the basis for 

 urging national aid in bringing greater areas under irrigation. Cer- 

 tainly the addition of 60,000,000 acres, equivalent to two states the 

 size of Pennsylvania, to the present productive area of the public 

 domain is an expansion in the right direction. The fact that these 

 lands capable of irrigation are distributed, oasis like, through regions 

 which must always yield but scanty returns, and that these areas have 

 a calculable productivity equal to the best land in humid states, are 



'Whitman Cross and A. C. Spencer, "Geology of the Rico Mountains, Colo- 

 rado," Twenty-first Annual Report of the U. S. Geological Survey, Part II, 1899-1900, 

 pp. 1-165; summarized in Journal of Geology, Vol. X (1902), p. 910. 



