482 EXPERIMEXT STATION RECORD. [Vol.41 



60 cycle induction motor using current at 440 volts. In the tests it was found 

 that all the units exceeded the required efficiency of 81 per cent at 90 ft. head. 



"As a whole the efficiency tests of this plant illustrate the recent very 

 remarkable advance in centrifugal pump design from the standpoint of 

 efflciencj', and give reason to believe that it is not too much to expect that in 

 the case of large units, working under reasonably high heads, 85 per cent 

 efficiency may be obtained where the character of the installation is such as to 

 warrant the extra expense of a pump designed for the special conditions under 

 wiiich it is to operate. Such efficiency can only be obtained by the use of small 

 running clearances in the impeller at the wearing ring, which prevent leakage 

 from the discharge back to suction ; and the water seal preventing air leakage 

 into the suction passage around the shaft must be perfectly air-tight. Wear is 

 to be expected in the course of time in the wearing rings, and the glands can 

 not be maintained in perfect condition after a loiig period of use, so that to 

 maintain the high efficiency found when the installation is new it will be 

 necessary to renew from time to time the wearing rings and the bronze sleeves 

 on the shaft." 



Transforming canal losses in terms of depth to quantity, P. A., Cxjppee 

 (Engin. Neics-Rec, 81 {191S), No. 5, p. 220, fig. i).— Graphic data are given 

 showing the seepage loss in irrigation canals in second feet per thousand feet 

 length of canal for wetted perimeters from to 100 ft. for a loss of 1 ft. in 

 depth over the wetted canal area in 24 hours. 



Computing' the lateral pressure of saturated earth, A. G. Husted {Engin. 

 Neios-Rec, 81 (1918), No. 10), pp. J,41, 442, figs. £).— The author proposes a 

 method of computing the lateral pressure of saturated earth which is based on 

 the usual diy earth formula but takes account of the separation of hydrostatic 

 from earth pressure and allows full hydrostatic pressure. Thus, the vertical 

 earth pressure is obtained by adding the total weight of earth above the plane 

 of saturation to the net weight of earth below the plane of saturation ; the 

 lateral earth pressure is obtained by multiplying this vertical pressure by tan * 

 (45° — -J 02) in which 02 = the angle of repose of earth under water; and the 

 total lateral pressure is obtained by adding the hydrostatic pressure to this 

 lateral earth pressure. 



Inexpensive cypress lath subirrigation plan {Okla. Agr. Col., Ext. Div. Circ. 

 72 {1918), pp. Jf, figs. 5). — This circular gives brief instructions for the use of 

 cypress lath in the construction of subirrigation laterals. 



Agricultural drainage, T. .1. Evans {Florence, Ala.: Author, 1918, pp. S5, 

 figs. 2). — This pamphlet is a prospectus of a more elaborate work on the sub- 

 ject to be issued later. Its purpose is to secure the opinions of professional men 

 and to interest those contemplating drainage projects. 



Synopses of drainage laws, J. S. Smith et al. {Columbia, ]\Io.: E. W. Stephens 

 Pub. Co., 1918, pp. 365). — This handbook contains a brief outline of the drainage 

 laws of each of 24 States. 



Farm drainage {Ann. Rpt. Dept. Agr. Prince Edimrd Island, 1917, pp. 35-If8, 

 pis. 3). — This report deals with the underdrainage of agricultural lands with 

 special reference to conditions on Prince Edward Island. It is estimated that 

 there are 200,000 acres on the island that could be profitably drained. Under 

 average conditions it is estimated that drainage costs about $30 per acre. 

 Features of drain construction are discussed. 



Use of dynamite i^ .viiximalarial drainage operations, J. K. Hoskins and 

 W. E. Hardenburg {Pub. Health Rpts. [U. S.], 33 {1918), No. 47, pp. 2052, 

 2053).— It was found that in antimalarial drainage work with dynamite the 

 best results were obtainei! in mucky areas where the mud was so deep and soft 

 that hand excavation became slow and difficult. 



