86 EXPERIMENT STATION RECORD. [VoL 87 



on the flatter lands in order to cover the land without waste. ... It is 

 important for the irrigated farm to have a moderate proportion of cultivated 

 crops. . . . Small, direct ditches which carry the water to the point of appli- 

 cation will save water as compared with broad, shallow ones, which expose the 

 water to evaporation and percolation loss." 



A further cooperative study of the relation of proper irrigation to bacterial 

 count is reported by T. D. Beckwith. It was found " that the bacterial counts 

 vary with soil moisture. . . . Irri.iration, by increasing the amount of soil 

 moisture, stimulates bacterial growth." 



The drainage of irrigated shale land, D. G. Miixeb and L. T. Jessup (C7. S. 

 Dept. Agr. Bui. 502 {1911), pp. 40, pls. 9, figs. /2).— This bulletin contains in- 

 formation on the drainage of those irrigated lands of the Rocky Mountain States 

 that are underlain by shale. 



" Outcroppings of shale and lands immediately underlain by shale . . . ar« 

 found in northern New Mexico, in southeastern Arizona, in large areas of Colo- 

 rado, in the eastern portion of Utah, in the extreme eastern part of Idaho, in 

 Wyoming, Montana, and In the western parts of Nebraska and the Dakotas." 

 Three different ways by which the movement of seepage water takes place in 

 shale are " (1) over the top of the undisturbed and impervious strata, (2) be- 

 tween the layers, and (3) through joints, faults, and cleavage planes. . . . The 

 source of the seepage water is deep percolation, resulting from irrigation and 

 from seepage losses from canals and laterals. . . . 



"The drainage of shale lands can not be accomplisheil by ordinary methods 

 of drainage, due to the movement of the water through the shale under pres- 

 sure and also to the extreme retentlveness of the overlying adobe soil. The 

 three essential factors for successful drainage of shale lands are (1) proper 

 location of drains, (2) sufficient depth, and (3) relief welKs. Drains must be 

 so located as to tap the contributing shale features, such as ridges, points, 

 knolls, etc. . . . The amount of .shale reached and the amoiuit of water de- 

 veloped are augmented by increasing the depth of the drains. These depths 

 never siiould be less than 6 ft, and generally depths of 7 and 8 ft. and greater 

 are essential to success. 



** A system of drainage in many of the shales will be incomplete and un- 

 successful without relief wells. The area of influence of relief wells Is small ; 

 this necessitates that they be closely spaced — in many cases 5 or 6 to 100 ft. of 

 trench. The most eflicient depth for the wells has been found to range from 

 6 to 20 ft. below the bottom of the tile drain. The major portion of the water 

 developed by most of the drainage systems in shale comes from the relief wells. 

 A diameter of 2 in. has been found to be sufficient for the relief welLs, and in 

 most of the shales they have been lnstalle<l with the soil auger. Frequently, 

 however, hard strata require the use of a churn drill. 



" For trenches in shale ranging from 6 to 7 ft. in depth, and with labor at 

 25 cts. per hour, unit costs for excavating, laying tile, and back filling, together 

 ^\^th the cost of Installing the relief wells, have ranged from 12 to 25 cts. per 

 linear foot of trench. This does not Include the cost of any material for the 

 drains. The acreage costs of drainage of the lands referred to in this bulletin 

 have rangeil from $13 to $100 per acre for the area actually affected." 



Rural sanitation in the Tropics, M. Watson (London: John Murray. 1915. 

 pp. XVI+S20, pis. 45, figs. 2).— This book deals with swamp and soil drainage 

 and oiling as antimalarial measures, tropical water supplies, sewage disposal, 

 and general rural sanitation as practiced in British Malaya, Italy, India, Sn- 

 matra, Hongkong, and the rhilippine Islands, Panama, British Guiana, and 

 Barbados. 



