620 EXPERIMENT STATION" EECORD. 



servative at the lower depths (15 cm. and 30 cm.) in the heavy clay soil in- 

 vestigated. The moisture at 3 cm. falls as low as 1 per cent and that at 30 

 cm. rises to as much as 32 per cent. The average moisture of the soil from 

 the surface to 30 cm. in the driest weeks of the year is 6.5 per cent, in the 

 wettest is 29 per cent. At its minimum water content the clay soil contains 

 nbout one-fourteenth of the annual supply of water furnished it by the normal 

 rainfall. 



"The weekly rate of atmospheric evaporation ranges from a minimum of 

 173 cc. to a maximum of 1,084 cc. — the annual total being 31,447 cc, in terms 

 of loss from a porous cup atmometer. This is equivalent to a loss of 345 cc. 

 per square centimeter from a free water surface. The ratio of evaporation to 

 rainfall is as 9.3 is to 1. 



" The ratio of evaporation to soil moisture fluctuates from a minimum 

 amount to a maximum which are in the proportion of 1 to 10, The ratio of 

 evaporation to soil moisture at the foot of the Santa Catalina Mountains is 9,7 

 times the same ratio for their summit. The annual amplitude of moisture con- 

 ditions at the Desert Laboratory is as great, therefore, as that which exists 

 in the most arid portion of the year between localities which are 5,000 vertical 

 feet apart." 



Effect of forests on run-off, J. C. Stevens (Jour. Electricity, 32 (1914), 

 Nos. 3, pp. 49-51, figs. 2; 4, PP- 73-75; 5, pp. 93-95; 6, pp. 116, 117, fig. 1; 7, pp. 

 135-137, figs. 3; 8, pp. 166, 167, fig. 1; 9, pp. 190, 191, figs. 4).— In a somewhat 

 detailed discussion of the effects of forests on run-off, in which he deals with 

 several watersheds as examples, the author reaches the conclusion " that uni- 

 formity of stream flow is influenced, practically in total, by factors entirely 

 independent of forests, and if forests have any influence at all on this feature, 

 it is very insignificant. The tendency they 6o possess, though almost infini- 

 tesimal, would be in a helpful direction in some cases, in others in a harmful 

 direction.'' 



Note on the chlorin content of rain water at Tortugas, Fla., R. B. Dole 

 (Jour. Wash. Acad. ScL, 4 (1914), ^o. 1, pp. 3, 4; ahs. in Chem. Ahs., 8 (1914), 

 Ao. 4, p. 767). — A chlorin content of 2.9 parts per million of water was found. 



Water, E. P. Wightman (Pop. Sci. Mo., 84 (1914), A'O. 3, pp. 218-226) .—The 

 more important facts regarding the composition, properties, and importance in 

 the economy of life of water in gaseous, liquid, and solid forms are summarized 

 in this article. 



Ground water and wells, H. Hofer von Heimhalt (Grundwasser und 

 Quellen. Brunswick, 1912, pp. XI-\-135, figs. 51). — The author has attempted in 

 this work to present a hydrogeological text-book to serve as a guide in dealing 

 with both the theoretical and practical sides of problems relating to ground 

 water and wells. The principal topics discussed are the physics, chemistry, and 

 biology of water supplies relative to quality and judgment; soil water from the 

 infiltration of atmospheric precipitation; ground water, its origin, movement, 

 and relation to streams and lakes ; shape, grade, and variations of ground water 

 level ; ground water strata ; influence of pumping on ground water ; rock water ; 

 wells and their yield ; dependence of quality of water on geological conditions ; 

 pollution of ground water and wells and means of protection ; and water sup- 

 plies for villages. 



North Dakota waters, E. F. Ladd (North Dakota Sta. Rpt. 1912, pt. 3, pp. 

 449-483). — This article notes the dangers from contamination of water sup- 

 plies, discusses such subjects as solids and organic matter in water, boiler and 

 antifoaming compounds, and purification of water, warns against the use of 

 so-called household and faucet filters, and gives analyses of a large nuuibpr of 

 waters from wells and other sources in North Dakota. 



