20 EXPERIMENT STATION RECORD. 



Investigations into the physical composition of some Cape Colony soils, 

 C. F. JuRiTz {Reprint from Ann. lipt. So. African Atisoc. Adv. ScL, 1908, pp. 

 IS). — Detailed mechanical analyses of a large number of typical soils are re- 

 ported. These analyses were made for the purpose of ascertaining the physical 

 condition and properties of soils especially adapted to different classes of crops, 

 as well as the amount of moisture these soils are capable of retaining. The 

 method of mechanical analyis used is briefly outlined. 



The importance of mechanical analysis of soils, C. Eberiiart {Fiihling's 

 Landw. Ztg., 58 (190'J), No. 5, pi>. 176-188). — The importance of mechanical 

 analysis and the relative merits of different methods are discussed. 



A method for the determination of the external and internal soil surface, 

 F. ScHEEFFER (Joiir. Lundic, 57 ( IHO!)), No. 2, pp. 121-135, figs. 3; ahs. in Vlicin. 

 ZcnthJ., 1909, II, No. 11, p. 931). — The method proposed is based upon the de- 

 termination of hygroscopic water over sulphuric acid and the increase in 

 weight when the dried soil is Ivcpt over 9 per cent carbon tetrachlorid. Tests 

 of the method with satisfactory results on humus free soils are reported. 



Heat transference in soils, H. E. Patten ( U. 8. Dept. Agr., Bur. Soils Bui. 

 59, pp. 5), figs. 22). — The primary object of the investigations reported in this 

 bulletin " was to determine the relation between the heat conductivity and 

 moisture content of a soil with special reference to the importance of the 

 ' optimum water content,' " as explained in Bulletin 50 of the Bureau of Soils 

 (E. S. R., 19, p. S18). 



In the investigations reported with sand and soils of various kinds use was 

 made of a modification of Forbes's method, which " consists in measuring simul- 

 taneously the rate of temperature rise in a soil at regular distances from the 

 constant temperature heat source, and the difference of temperature gradient 

 which causes this rise." The special forms of apparatus used are described 

 and the complete data obtained are presented in tables and diagrams. 



A general result of the experiments was to show that a soil conducts heat 

 better and more quickly with a moisture content near but somewhat below that 

 recognized as the optimum. 



" The reason for this is that at the optimum water content we have the soil 

 grains formed into larger aggregates and the spaces between these aggregates 

 act as an air insulation against the passage of heat. As more water is added 

 some of these soil grain aggregates break up and their constituent grains now 

 serve to fill in the spaces between the larger aggregates, and the added water 

 gives still better contact between the soil crumbs and the small grains. Thus 

 the total effect is a better conduction of heat and a faster rise of temperature. 

 But when water is added to the soil over a certain percentage (which is different 

 for each soil) the temperature of the soil will rise more slowly, although heat 

 is being conducted by the soil better than at a lower moisture content. This 

 effect is produced by the high heat capacity of water, which is almost five times 

 that of a dry soil." 



" The practical value of the work lies in pointing out the nature of the soil 

 control which should be exercised in the planting of general farm crops to se- 

 cure a warm seed bed and good germination, in the handling of cranberry 

 marshes, and other special agricultural lines." 



The system water, calcium carbonate, carbonic acid, J. W. Leather and J. 

 Sen {Mem. Dept. Agr. India, Chem. Ser., 1 {1909), No. 7, pp. 117-131, pi. 1, 

 charts 6). — The solubility of minerals in the soils and rocks has been previously 

 shown to be greater in the presence of carbon dioxid than with ordinary water. 

 These tests, however, were generally made under conditions which are not as 

 they exist iu nature. From their work ou the concentrations of calcium car- 



