20 EXPERIMENT STATION RECORD. 



of extremely soluble salts . . . that solids immersed in a fluid may retain 

 about or upon their surfaces a layer of the fluid which is restrained by them, 

 from moving, or is compelled to move with them, in such a manner as to 

 become an integral part of a compound system of solid and fluid." The bearing 

 of this theory on the suspension of solids such as fine soil particles in liquids 

 or dust particles in air, on the retention by filters of the soluble substances in 

 solutions, and on the flocculation of suspended particles as in case of silt and 

 sea water, is explained. It is shown that the adherent film of water greatly 

 increases the etfective cross-section of a particle of silt, for example, and cor- 

 respondingly reduces the force required to maintain it in suspension. " When 

 the turbid water of a stream commingles with the salt water of the sea there 

 begins at once a reduction of the thickness of water films about the suspended 

 sediment, which increases their effective specific gravity and at the same time 

 increases the surface tension, causing flocculation, which carries to the bottom 

 both the silt and a portion of the salts which initiated flocculation and final 

 precipitation." 



Some phases of soil investig'ation, T. F. Hunt (Penn. Dcpt. Agr. Bill. 169, 

 pp. Ji5-52). — This article points out the importance of (1) a soil survey, (2) 

 cooperative plat tests of fertilizers and cultural niethods on difi'erent types of 

 soil, and (.'>) a study of factors affecting plant growth on different soil types. 

 Roles of the soil in limiting plant activities, B. E. Livingston {Plant 

 World, 12 {1909), No. 3, pp. 49-53). — The dependence of plant activities upon 

 the physical properties of the soil, especially those properties controlling or 

 modifying the movement and supply of soil water with its dissolved substances, 

 is discussed. 



Observations and researches on soil temperature, II, S. de Grazia {Ann. 

 R. 8taz. Chim. Agr. Hpcr. Roma, 2. ser., 2 {1907-8). pp. 333-3.',7, i)ls. 2; /S7«.?. 

 Sper. Agr. Hal., .'il {1908). No. 9-11, pp. 689-703. pis. 2; aft.s. in Chcm. Zenthl.. 

 1909, I, No. 6, p. Ji59). — This is a continuation of work previously reported 

 (E. S. R., 20, p. 620), but dealing with the infiuence of soil temperature on the 

 growth of certain plants during the early stages of their growth. 



The observations were made 10, 17, 24, and 31 days after sowing. In normal 

 conditions of soil, humidity, temperature of the surrounding air, and for soil 

 temperature between 10 and .15° C. the observations show that potatoes, corn, 

 wheat, and hemp during the first stages of growth are responsive to small 

 increases of soil temperature, even as small as 0.5°. The various species are 

 differently influenced ; corn and potatoes in comparison with hemp and wheat 

 show the effects for a longer time, beginning with germination. The beneficial 

 effect of such increases of temperature is shown in a notably more rapid devel- 

 opment of both stems and roots, especially the latter. 



Nitrification and denitrifi.cation in soils, S. von Bazarewski {Bcitriigc cur 

 Kenntnis dcr Nitrifikation und Denitrifikation im Boden. Inaug. Diss. Gottin- 

 gen, 1906, pp. So, pi. 1 ; rev. in Neues Jahrh. Min., Geol. u. PaldontoL, 2 {1908), 

 No. 2, Rcf., p. 186; Jour. Soc. Chem. Indus., 28 {1909), No. 3, p. 153; Chcm. 

 Zenthl., 1909, I, No. //, pp. 309, 310). — The conclusions drawn from the investi- 

 gations reported in this article are briefiy as follows: 



Nitrifying bacteria are most abumlant in the top soil to a depth of 10 cm., 

 but are rare at a depth of 50 cm. because of the fact that humus and oxygen are 

 necessary to their life and growth. Following the growth of green manuiing 

 plants there is an increase of nitrifying organisms in the deeper layers of the 

 soil. The most favorable temperature for nitrification in soils appears to be 

 about 25 to 27° C, that is, about 10° lower than in pure cultures in artificial 

 media. The small amount of soluble organic substances in soils does not inter- 

 fere with nitrification, but i)erhaps exerts a beneficial iuflueuce since an addi- 



