450 abstracts: geology and engineering 



other parts of southern New Mexico and western Texas but some of 

 them are local or present peculiarities. The Tertiary rocks consist of 

 thick accumulations of agglomerate, tuff, and ash and thin sheets of 

 various kinds of lava. 



The principal mineral resource is underground water, which occurs in 

 large quantities in the deposits underlying the plain, and is pumped for 

 irrigation. It is supplied by percolation from Mimbres River and by 

 local rains. Tests of five wells by A. T. Schwennesen gave yields 

 ranging from 122 to 603 gallons per minute, or from 14.5 to 88 gal- 

 lons per minute for each foot of drawdown. 0. E. M. 



GEOLOGY AND ENGINEERING.— Contributions to the hydrology 

 of the United States, 1915. Nathan C. Grover. U. S. Geologi- 

 cal Survey Water-Supply Paper No. 375. Pp. 131, 9 plates, 31 

 text figures. 1916. 



This volume includes the following papers: 



Ground water for irrigation in the Sacramento Valley, California. Kirk 

 Bryan. Sacramento Valley, 150 miles long, 40 miles wide, and con- 

 taining more than 3,000,000 acres of agricultural land, is remarkable 

 for its great supply of ground water, the rapid recharge of this supply 

 in the rainy season, and the large area in which the water table stands 

 close to the surface. More than 80 per cent of the valley has a depth 

 to water of less than 25 feet. In 1913, water was drawn from wells 

 at 1664 pumping plants for the irrigation of 40,859 acres. 



Ground water in Paradise Valley, Arizona. O. E. Meinzer and A. J. 

 Ellis. Paradise Valley affords an example of "stream escape," in 

 contrast to "stream capture." Cave Creek, entering this valley 

 from the side, formerly discharged through it, but built up its alluvial 

 fan until it found an exit through a pass in the opposite mountain wall. 

 It now crosses the valley and still furnishes most of its ground-water 

 supply. 



The relation of stream gaging to the science of hydraulics. C. H. Pierce 

 and R. W. Davenport. This paper emphasizes the modernness of 

 stream gaging as a science and coordinates it with the science of hy- 

 draulics and the still more comprehensive science of hydrology. The 

 evolutio n of stream gaging to its present status has involved in a high 

 degree that balancing of practice against abstract theory which has 

 made hydraulics to so large an extent an empirical science. The im- 

 portance of analytical studies and of utilizing the established facts 

 of the science of hydraulics in the practice of stream gaging is illus- 

 trated by examples. Stream gaging, or, in a broad sense, hydrometry, 



