SOILS FERTILIZERS. 119 



guidance as to crops that may succeed, or are not likely to do so; (4) to throw 

 light on the manurial requirements of the soils." 



The authors are of the opinion as a result of their experience in such work 

 that the geological formation affords the best basis for a soil survey, although 

 admitting that considerable difficulty is encountered where the fonnation is 

 obscured by drift. 



Mechanical analysis is considered the most important of the various deter- 

 minations made in the course of soil analysis, and it is believed that " for 

 agricultural purposes the size of the soil particles is more significant than 

 their actual composition."' This is emphasized by the controlling influence of 

 the size of particle upon available water supply and tillage. 



Of the chemical determinations the total carbonate is considered as perhaps 

 most important. " The amount and nature of the organic matter is important, 

 and it is necessary to know whether free acid is present or not. Like calcium 

 carbonate, humus modifies the properties of the finest particles." 



Soil surveys and soil analyses, A. D. Hall and E. J. Russell (Jour. Agr. 

 Set., Jf (1911), Xo. 2, pp. 182-223). — This article is based upon a survey of the 

 soils of southeast England (E. S. E., 25, p. 818), and discusses the value, 

 methods, and purposes of a soil survey, giving particular attention to the 

 relative value of mechanical and chemical analysis (see also above) as illus- 

 trated by typical examples of the soils of this particular area. 



" Since our present conventional methods of chemical analysis fail to char- 

 acterize the soil with sufficient completeness we recommend that for purposes 

 of a survey a large number of soils should be submitted to mechanical analysis, 

 including the determination of organic matter and of calcium carbonate, and 

 then a carefully chosen representative set, not necessarily more than a half 

 or even a quarter, should be analyzed chemically. 



" Up to a certain point . . . the mechanical analysis should form the basis 

 of the survey because it alone takes account of those physical functions — 

 the regulation of the water supply and therefore of the temperature, of the 

 air supply, ease of cultivation, etc. — that play so large a part in determining 

 the value of a soil. 



" But on the other hand mechanical analysis is restricted in its application 

 and gives useful indications with one only of the well-defined chemical types 

 Into which soils may be divided. In one area four chemical groups are rec- 

 ognizable : (1) Chalk soils, (2) acid humus or peat soils, (3) neutral humus 

 soils, (4) mineral soils, i. e., sands, loams, and clays. It is to this last group 

 alone that mechanical analysis can be applied with any degree of usefulness, 

 but since agricultural soils belong so largely to this group the method is really 

 applicable in by far the great majority of cases." 



The interpretation of the results of both mechanical and chemical analysis 

 are discussed at some length. 



Soils of the Eastern United States and their use, XIX-XXIII, J. A. Bon- 

 steel (U. S. Dept. Agr., Bur. Soils Circs. ^1, pp. 16; 42, pp. 14; U, i>p. 19; 45, 

 pp. 14; 46, pp. 20). — These circulars deal respectively with the following soil 

 types, as surveyed and mapped by the Bureau of Soils : 



Circular 41, The Wabash Clay, of which a total area of 419,915 acres in 23 

 areas in 9 States has been surveyed and mapped. 



Circular 42. The Trinity Clay, of which a total of 570,434 acres in 20 surveys 

 in 3 States has been surveyed and mapped. " The Trinity clay is a black, tena- 

 cious, heavy clay found in the alluvial bottom lands of the main streams which 

 flow through the black Cretaceous prairies of Alabama, Mississippi, and Texas 

 and to a considerable distance along the lower courses of such streams as have 

 their headwaters in the prairie sections. . . . The greater proportion of the 



