420 EXPERIMENT STATION EECOED, 



lected from 36 districts are reported and discussed, mainly with reference to 

 I)hysical and chemical composition. 



The improvement of lands and intensive exploitation of the soil, E. 

 Catzeflis {Bill. Union Agr. Egypte, 11 (1913), No. 101, pp. 2U-249; 12 {19U), 

 Nos. 102, pp. 11-17; 105, pp. 117-122). — This article discusses the economic 

 aspect of the physical, mechanical, and chemical improvement of the soils in 

 the northern part of the Egyptian Delta. 



A study of some physical properties of soils, R. Trnka (Internat. Mitt. 

 Bodenlc, 4 {1914), No. 4-5, pp. 363-387, figs. 3).— The results of studies of 

 methods of determining volume weight and porosity of soils ai"e reported. 



It is pointed out that methods of determining volume weight in which the 

 original soil structure has been disturbed are usually inaccurate, and it is con- 

 cluded that the method worked out by the author and A. Slavik of determining 

 A'olume weight by the water displacement of a clod in original condition which 

 has been given a waterproof coating by dipping in melted paraffin is more nearly 

 exact and more practicable. On the groinid that the determination of porosity 

 depends on the correct determination of volume weight and specific weight, it is 

 further concluded that the method of using a paraffin coated clod in natural 

 condition should also be applicable for determining porosity. 



An apparatus for accurately measuring water disi:)lacement is described. 



The adsorptive power of soils, P. Rohland {Internat. Mitt. BodenJc., 4 

 {1914), No. 4-5, PP- 393-404). — Substantially the same views are expressed in 

 this as in previous articles along the same line (E. S. R., 31, p. 514; 32, p. 318). 



On. osmosis in soils, C. J. Lynde and J. V. Dupej& {Jour. Amer. 8oc. Agron., 

 7 {1915), No. 1, pp. 15-19, fig. 1; Proc. and Trans. Roy. 8oc. Canada, 3. ser., 8 

 {1914). Sect. Ill, pp. 133-138, fig. 1). — This article reviews previous work on 

 osmosis in soils (E. S. R., 29, p. 124), and reports further experiments in 

 which a column of very fine soil was used as a semipermeable membrane and 

 a concentrated soil solution as the active solution. 



With a column of soil approximately 2.5 in. deep an osmotic pressure equal 

 to the pressure exerted by a column of water 11.5 ft, high was observed. " The 

 results indicate that the pressures observed are not due to the swelling of the 

 soil column . . . [but] are due to osmosis as follows: (1) The semipermeable 

 membranes used in investigations on osmotic pressure are colloids, (2) there 

 is strong evidence that the action of semipermeable membranes is one ,of 

 unequal absorption. One liquid is absorbed more readily than the other and 

 the movement is toward the liquid least absorbed." 



The consistency curves of mineral soils, S. Johansson and A. Atterbeeg 

 {Internat. Mitt. BodenJc, 4 {1914), No. 4-5, pp. 418-431, figs. 13).— In continua- 

 tion of work along the same general lines (E. S. R., 28, pp. 320, 620), studies 

 are reported of different mineral soils with reference to their consistencies 

 with variable water content. Twenty-five so-called consistency curves showing 

 the water content and the corresponding consistency are given and discussed. 



At approximately the middle of each curve is found a sharp knee and from 

 this the curve extends in both directions in the form of a hyperbola. The posi- 

 tion of this knee with reference to consistency varies for different soils, being 

 highest for the clays and lowest for the loams. To the left of the knee the 

 curve rises rapidly as it approaches the ordinate or consistency axis for the 

 heavy loams and clays, while for the lighter soils it is more nearly parallel to 

 the abscissa or water content axis. To the right of the knee the curve is the 

 longest for clays and the shortest for loams. 



These consistency curves indicate at what water content a soil is most 

 easily tilled. They show that most loams are tillable at all water contents 

 from zero to 14 or 20 per cent and that only the heaviest loams are not tillable 



