232 EXPERIMENT STATION RECORD. 



"It is to be confessed that tlie present investigation gives support to the view that 

 the nitrates are largely lost to the surface soil during the late autumn months, but 

 whether this occ-urs in normal seasons to the extent here indicated is very doubtful." 

 The origin of nitrates in caverns earth, W. H. Hess (Jour. Geol, 8 (1900), 

 pp. JJ9-1S4; (ihx. in Tech. Quart., 14 (1901), No. 1, Rev. Chem., p. ^).— Analyses and 

 other data are cited to show that "the nitrates are not derived from the excrement 

 of bats, as popularly supposed, but have their origin in the oxidation or nitrification 

 of organic matter in the surface soil through the agency of bacteria, and the subse- 

 quent leaching of the nitrates so formed downward into caverns, where they slowly 

 accumulate with other salts as the water escapes by evaporation." 



Nitrates in cave earths, H. W. Nichols [Jour. Geol, 9 (1901), No. 3, pp. 236- 

 243). — An argument to disprove Hess's hypothesis above referred to. 



Soil solutions: Their nature and functions, and the classification of alkali 

 lands, F. K. Cameron (V. S. Dept. Agr., Dlrhion of Soil. '< Bui. 17, pj). .'?9).— This 

 bulletin ' discusses the nature and function of soil solutions, including tlie mutual 

 effect of electrolytes, hydrolysis, role of iron, calcium, carbon dioxid, and organic 

 matter in the soil, some possible functions of hydrous silicates, acidity of soils, sup- 

 posed poisonous action of heavy metals, soil analyses, and absorption by soils; the 

 classification of alkali lands, including the fonnation of alkali, methods of analysis, 

 limitations of the classification, and descriptions of Pecos, Fresno, Salt Lake, Billings, 

 and modified types of alkali; and occasional occurrence of alkali in humid regions — 

 in Maryland, Florida, and various other localities. 



As regards the nature and functions of soil solutions, the following general con- 

 clusions are drawn: 



"(1) The mineral, and to a large extent the organic, components of the soil are 

 electrolytes, and soil solutions are mainly solutions of electrolytes. 



" (2) The hypotheses of electrolytic dissociation and hydrolysis in aqueous solution 

 give rational explanations for many phenomena hitherto regarded as inexplicable or 

 exceedingly obscure. 



"(3) The rational procedure in the chemical investigation of the soil, from the 

 point of view of its relation to crop culture, is to study the soil solution and in what 

 manner it is modified l)y contact with the solid and gaseous components of the soil." 

 The classification of alkali as "black" or "white," depending upon the presence 

 or absence of sodium carbonate, is condemned as "inadequate in view of our pres- 

 ent knowledge of alkali phenomena." A classification based "on chemical grounds, 

 considering alkali conditions or the result of the action of aqueous solutions of cer- 

 tain soluble salts" is tentatively proposed. Four classes of alkali are considered, 

 the predominating features in the formation of which are, (1) the action of the 

 sodium chlorid on gypsum, resulting in the formation of sodium sulphate and calcium 

 chlorid, typified in alkali soils of the Pecos Valley, New Mexico; (2) the action of 

 sodium chlorid on calcium carbonate resulting in the formation of sodium carbonate 

 and calcium chlorid as occurring typically about Fresno, Cal. ; (3) the simultaneous 

 action of sodium chlorid upon gypsum and calcium carbonate resulting in the forma- 

 tion of only small quantities of soluble carbonates, a very common form typified in 

 the alkali of the Salt Lake Valley, Utah; and (4) the interaction almost exclusively 

 of soluble sulphates, not a common class, occurring typically about Billings, Mont. 

 Modifications of the types described are more or less frequently found. 



A number of cases of the occurrence of soluble salts in the soils of a humid region 

 are cited as evidence ' ' that the essential differences between conditions obtaining in 

 the soils of humid and arid regions are rather those of degree than of kind; that 

 the fundamental forces at work are in reality the same, and that the study of the phe- 

 nomena presented in one area can and should be of the greatest value in interpret- 

 ing those of another area." 



^See U. S. Dept. Agr. Rpt. No. 64 (E. S. R., 12, p. 522). 



