1912.] PUBLIC DOCUMENT — No. 31. 115 



A NEW METHOD FOR THE APPROXIMATE 

 MECHANICAL ANALYSIS OF SOILS. 



G. E. STONE AND G. H. CHAPMAN. 



According to the best authorities, and giving the definition 

 used by the authors of Bulletin No. 24 of the United States De- 

 partment of Agriculture, '^ The mechanical analysis of a soil 

 consists in the separation of the soil particles into groups de- 

 pendent upon the size of the grains, and in the determination of 

 the percentage by weight of the particles constituting each group. 

 The limits of these groups are arbitrarily chosen with reference 

 to the ease in making the separation, and to the importance of 

 the particles of any gi^Tn size in determining the physical char- 

 acteristics of the soil." 



Many methods have been devised at dift'erent times by investi- 

 gators, but the whole matter was somewhat hazy on account of 

 each one using his own measurements for grading the soil par- 

 ticles, etc., until the present method of centrifugal analysis was 

 devised by the authors of the bulletin previously noted. Since 

 that time the methods described therein have been made use of 

 by the United States Department of Agriculture and the experi- 

 ment stations in general, where absolutely accurate results are 

 desired for all characters of soils. 



The chief objection to the methods heretofore devised has been 

 the length of time necessary to carry through an analysis, even 

 of the simplest soil. 



In the work of this station there have arisen many occasions 

 when it would have been of great advantage to know approxi- 

 mately the composition of a soil, more particularly of those used 

 in greenhouses and market gardening. With a large amount of 

 other routine station work always on hand it was found impos- 

 sible to devote the time necessary to make an analysis of the soil 

 samples by the ordinary centrifugal, or as we shall hereafter 



