28 EXPERIMENT STATION EECOED. 



velocity of less than 2 meters per day, and that of the desert zone a still lower 

 velocity." 



Modern methods of water purification, J. Don and J. Chisholm {London, 

 1911, pp. XVI+368, figs. 96). — This booli attempts to discuss in an orderly 

 way the numerous and varied processes which have been recommended for the 

 purification of water and to consider how far their usefulness is determined 

 by the character of the water supply. Much of the information here assembled 

 has heretofore been available only in form of articles widely scattered through 

 periodical literature. The subjects treated are sources of supply, storage, 

 construction of reservoirs and care of filtered water, sand filtration, the man- 

 agement of sand filters, mechanical filters, purification by ozone, water-soften- 

 ing and household appliances, the testing of water, the problems of distribution, 

 and useful constants and data relating to water filtration and measurements. 



Sterilization of water by means of ultraviolet rays, Grimm and Weldekt 

 (Mitt. K. Priifimgsanst. Wasserccr. ii. Ahivasscr. Berlin, 1911, Xo. 14, pp. 

 8-5-102, fig. 1). — From a series of tests of the efficiency and cost of sterilization 

 of water by means of ultra-violet rays the authors conclude that clear water with 

 low bacterial content can be quickly and completely sterilized in this way, but 

 that cloudy and colored waters are not so readily sterilized. By prolonged 

 treatment the temperature may be raised sufficiently to bring about important 

 physical and chemical changes in the water. The process is costly as compared 

 with other methods of purification. 



A bibliography of 28 references to the subject is appended. 



Disposal of sewage on sewer farms, C. P. Jensen {Pacific Municipalities, 

 2h {1911), No. 6, pp. 23Jf-238; ahs. in, Engin. and Contract., 36 (1911), No. 7, p. 

 192). — A brief account is here glA'en of the disposal of the sewage of Fresno, 

 Cal., by irrigation. The city has a farm of 812 acres on which to dispose of 

 4,000,000 gal. of sewage per day. At the present time 600 acres of this farm is 

 used during the normal irrigation season and the sewage is disposed of during 

 the winter months on a large cattle ranch, but it is believed that the sewage 

 farm can be made to take care of the sewage during the entire year by ro- 

 tating it on 20-acre plats. 



The farm now yields sufficient income to pay the maintenance expenses of 

 settling tanks, sewer farm, and outfall sewers 5 miles long. It is believed that 

 in a few years it can be made to pay the total sewer maintenance charges. 

 The sewage is now used upon 200 acres of alfalfa, which, it is estimated, will 

 jdeld a net income of from .$12 to $15 per acre when two years old. 



SOILS— FERTILIZERS. 



Studies in soil physics, E. E. Free {Plant World, 1.', {1911), Nos. 2, pp. 29- 

 39; 3, pp. 59-66; 5, pp. 110-119; 7, pp. 164-116; S, pp. 186-190; al>s. in Jour. 

 Wash. Acad. Sci., 1 {1911), No. 4, pp. 121, 122).— In a series of five articles 

 the author presents his own view of some of the more salient points of soil 

 physics, emphasizing especially conceptions useful to the plant physiologist or 

 ecologist. The titles and main conclusions of the individual papers are as fol- 

 lows : 



"(1) The Physical Condition of Soils. — The range of physical conditions 

 possible to a soil is determined by its ultimate physical nature or character, 

 that is, by the nature, size, and number of the particles of which it is composed. 

 The physical condition, within this fixed range, is controlled by the moisture 

 content by virtue of the surface tension on the water films between the soil 

 grains. (2) Movements of Soil Water. — The capillary actions in the soil are 

 controlled by the forces of surface tension on the water films. Permeability is 



