AIK WATER — SOILS. 525 



salt solution, respectively, is the same as for the water and solution without tlu^ soil, 

 providing no surface mulch is formed. 



"(5) The rate of evaporation gradually decreases with increase in concentration. 



"(6) The diminution of evaporation with increasing concentration is much less 

 than the corresponding diminution in vapor pressure. This is due to the fact that 

 the atmosphere is never vajior free, and that the diffusion of water vapor is retarded 

 by the surrounding air. 



"(7) The diminution of evaporation of soils containing solutions of 'alkali' salts is 

 much greater than can be accounted for through the influence of the lower vapor 

 pressure, and is due to the formation of a mulch at the surface of the soil through the 

 crystal lizati(^n of the salts." 



A study of the physical properties of clay as related to soil 

 structure, V. H. Davis iA(/r. student, 7 {1900), No. i, p2>. lo-IS).-~ 

 This i.s iin abstract of a thesis presented to the faculty of the Ohio 

 State University in li»()(). Tests of the tensile strength of wet ground 

 brick and clay from the university campus by a modihcation of G. E. 

 Ladd's method and of the breaking strength of dry Ijrick of the same 

 material are reported. It Avas found that the tensile strength of a wet 

 substance ha\'ing no inhercMit plasticity, such as the ground brick used 

 in these experiments, was practically independent of the size of the par- 

 ticles. With a substance naturally plastic, like the clay, the tensile 

 strength increases as the size of the particles decreases. A great differ- 

 ence was found in the breaking strength of the wet and dry substances. 

 The conclusion is drawn '"that fineness of particles accompanies plas- 

 ticity and is essential to it, but is not in itself a cause of plasticity, and 

 that the real cause is yet to be determined."" 



The moisture of the soil under the pine forest of the Khrenov 

 estate, G. ^Iouoso\' {Srl.sk. KI(o.z. i Lyosor., I'.Xj {lUUO), JIar.., pp. 

 JiSl-519). — The forest is situated on dune hills. The moisture was 

 determined at the depths (»f 10 cm., 25 cm., 50 cm., 1 meter, 1^ meters, 

 and 2 meters. The author's results corroborate those obtained b}^ 

 Visotski, who arrived at the following conclusions: (1) The upper sur- 

 face of the soil dries out most where it is most open, as, for instance, 

 on black fallow, and k>ast under forest; (2) the soil as a whole dries 

 out most under virgin soil covered with grass, next under forest, and 

 least under l)lack fallow; and (3) the subsoil dries out most under forest, 

 next under virgin soil, and least under black fallow. 



In addition the author found that: (1) The subsoil under forests in 

 the spring is more moist than in the open, and only later on does it 

 dry out more than under the latter; (2) the soil is not in all cases more 

 moist under forests than imder treeless areas. There are certain sandy 

 soils covered with pines in which the upper layers, except in the early 

 spring, are drier than in treeless areas. — p. fireman. 



The air, II. Blucuer {Die Luft. litre Znmmmoisetzuug luul Untersnchung, ihr Ein- 

 fluns unci ihre Wlrkiingini, sowie ihre lechnlsche Aasnutzung. Leipsic: Olto Wigand, 1900, 

 pp. XII-^322,figs. -?^).— ^This book treats of the constituents and impurities of air, 

 its physical projierties, including the meteorological phases of the subject; physical. 



