598 EXPERIMENT STATION RECORD. 



formations passed through by each well-. Then follow in order a discussion of the 

 geology and physiography of the valley, of the area in which pumping underground 

 water for use in irrigation is profitable, and of the origin of the salts in well waters 

 and their effects on vegetation. The quantity of underground water is estimated in 

 various ways, and the cost of pumping is discussed. 



The valley fill, at least to a depth of several hundred feet, consists of river debris, 

 wash from near-by hillsides, and chemical precipitates in more or less impervious 

 layers, which serve in many cases to confine the underground water under some pres- 

 sure. The valley till is saturated With water more or less impregnated with various 

 salts derived from Salt River. 



The quantitative estimate of the underflow indicates a volume of flow of 148,196 to 

 287,760 acre-feet per year. At this rate something less than 96 pumping plants, 

 each supplying 200 miner's in. or 5 cu. ft. per second, could be operated continuously. 



"The cost of pumping in Salt River Valley varies from 5.4 to 13.8 cts. per acre-foot 

 per foot of lift, or a cost per acre-foot of pumped water of $2.50 to something like f>5. 

 The volume of underflow is large, but not inexhaustible by the operation of pumps. 

 It is capable of extended development, but there is danger that a greater draft will 

 be made upon it than is consistent with the maintenance of the water level within 

 practicable pumping distance." 



A report on the establishment of tide-gauge work in Louisiana, G. D. Har- 

 ris (Geol. Survey La. Bui. 3, pp. 28, pis. 8, figs. 5). — This is an account of the estab- 

 lishment of a tide-gauge station near the Gulf Coast for the purpose of determining 

 mean tides, as the basis for establishing reliable bench-marks through southern Lou- 

 isiana. The data secured will be of special value in the drainage of marsh lands 

 along the Gulf, as it will show not only the mean-tide levels, but the height of 

 extreme tidal waves from which the lands must be protected if they are to be used 

 for agriculture. 



It is the intention to determine by a long series of tide-gauge readings the elevation 

 of a few seacoast bench-marks with great accuracy, and from them run a line of 

 precise levels along the Southern Pacific Railroad and establish at intervals of, say 

 every 5 miles, permanent bench-marks, and thereby give the true height of the 

 same above sea level. All local lines can then be referred to one datum plane. Fairly 

 reliable bench-marks many miles from the railroad will very soon be left by local 

 engineers and the mapping of the region will be greatly facilitated. The results 

 secured will be of scientific value also in the study of laws of tidal action. A detailed 

 description of the station established at Weeks Island is given. 



A study of rock decomposition under the action of water, A. S. Cushman 

 (U. S. Dept. Agr., Office Public Roads Circ. 38, pp. 10, figs. 3) . — This is a discussion of 

 laboratory methods of testing the decomposition of rock under the action of water, 

 describing a new method now being used. 



Manual for Iowa highway officers, A. Marston, C. F. Cuktiss, and T. H. Mac- 

 doxali) {Ames: Iowa Highway Com., 1905, pp. 102, pis. 20, figs, 8). — The legislature 

 of Iowa on April 13, 1904, created the State highway commission, whose duties are 

 to devise plans for improvement in the highways of the State, to disseminate informa- 

 tion on the subject of good roads, and conduct demonstrations in road construction. 



It is provided that the State College of Agriculture and Mechanic Arts shall act as 

 a highway commission, and the board of trustees of the college has intrusted this 

 work to the engineering and agricultural departments. The manual is issued by 

 this commission. It contains a general discussion of the value of good roads, and 

 the topography of the State with reference to road materials and construction. The 

 State of Iowa has at present about 100,000 miles of public roads, not over 1,000 

 miles of which have been surfaced with either gravel or stone. Most of the roads of 

 the State are made on section lines, but the commission recommends the abandon- 



