SOILS — FEKTILIZEES. 619 



the agricultural development of peat lands, but more especially with reference 

 to the distillation products of peat. The third, or technical part, deals with 

 the methods of securing peat and with its utilization for fuel and for gas 

 manufacture. 



The average thorium content of the earth's crust, J. H. J. Poole {Phil. 

 Mag. and Jour. Sci., 6. scr., 29 (1915), No. 172, pp. 483-4S9; abs. in Beibl. Ann. 

 Pliys., 39 (1915), No. 11, p. 400).— Tests of the thorium content of 86 samples 

 of acid rocks, 48 samples of neutral rocks, and 56 samples of basic rocks showed 

 respective averages of 2.05X10°, 1.64X10-', and 0.56X10"', and a general mean of 

 1.05X10"'. The thorium content resembled the radium content in that it de- 

 creased in passing from acid to basic rocks, but no exact numerical relation 

 existed between the two. 



Soil formation and composition, J. W. Ames (Mo. Bui. Ohio Sta., 1 (1916), 

 No. 2, pp. 46-49)- — This is a brief discussion of the subject. 



The formation of humus by means of veg'etable compounds, A. Trusov 

 (Selsk. Khoz. i Lwsov., 246 (1914), Oct., pp. 233-245; abs. in Inteniat. Inst. 

 Affr. [Rome], Mo. Bui. Agr. Intel, and Flant Diseases, 6 (1915), No. 4, pp. 540, 

 54^).— Laboratory experiments on different organic substances forming humus 

 and the influence of chemical substances and temperature -thereon are reported. 



" The substances giving rise to the formation of humus are the nonoxiding 

 bases and acids. . . . The monosaccharids and disaccharids are transformed 

 into polysaccharids, which in their turn undergo subsequent dehydration, re^ 

 suiting in the decomposition of the molecule and oxidation with formation of 

 humus. In cases where oxidation does not take place, i. e., during the forma- 

 tion of ulmin and ulmic acid, the action is simply deliydration." 



With reference to the influence of temperature it is thought that the forma- 

 tion of humus is an intermediate stage in the carbonization of the material. 

 Experiments with aldehydes, ketones, and the series of polyatomic alcohols 

 showed that " aldehydes can only promote the formation of humus when associ- 

 ated with other compounds such as the polyatomic alcohols. Similarly ketones 

 alone do not lead to the production of humus unless associated with compounds 

 of other series." 



The author concludes " that the formation of humus should not be considered 

 as due to the disordered decomposition of molecules, but, on the contrary, to a 

 series of definite reactions, especially with associated compounds, such as the 

 aldehyde-alcohols, ketone-alcohols, etc." It is suggested " that the formation 

 of humus in nature takes place by an identical process, with the difference 

 that the micro-organisms of the soil play the role of the acids and bases." 



Relation between certain bacterial activities in soils and their crop- 

 producing' power, P. E. Bkown (U. S. Dept. Agr., Jour. Agr. Research, 5 (1916), 

 No. 18, pp. 855-869). — Ammouification, nitrification, and nitrogen fixation tests 

 made at the Iowa Experiment Station, using the soil-culture method, are re- 

 ported of a uniform loam soil of the Wisconsin drift area. Tliree series of field 

 plats, receiving rotation, liming, and manurial treatments, respectively, were 

 used in the work (E. S. R., 31, p. 121). 



The results obtained as a whole " show that . . . the ability of soils to bring 

 about the simplification of nitrogenous materials or the addition of nitrogen 

 may be considerably modified by various methods of soil treatment. Further- 

 more, they . . . [show] that certain bacterial activities in the soil may be 

 very closely related to the actual crop-producing ijower of the soil. The am- 

 monifying power of soils, their nitrifying power, or even, in certain cases, their 

 azofying power may, therefore, indicate the crop-producing power of soils or, 

 at least, their relative crop-producing power." 



