METHODS OF MECHANICAL ANALYSIS 9 



them and lead to erroneous results. In this case unboiled 

 soil must be used, and the matter retained by the sieves 

 lightly rubbed under water with the finger, or a caoutchouc 

 pestle, till the water ceases to become turbid. 



The finer groups of soil constituents, which pass through 

 the sieve with narrowest meshes, are separated by elutriation. 

 The methods which have been employed are very numerous. 

 Some are based on the fact that when soil has been shaken 

 up with water the larger particles are the first to subside ; 

 in others the separation is effected by the successive use of 

 streams of water of different velocities, the feeblest current 

 removing only the finest particles. 



A simple method of analysis, sufficing only to give a general 

 idea of the character of the soil, is that recommended by 

 Schloesing; it is employed in France, Belgium, and Italy. 

 Full details will be found in Schloesing, Chimie agricole, 

 1885, 80 ; Grandeau, Traite d' Analyse, 1897, 252 ; and Wiley, 

 Agricultural Analysis, i. 200. The coarser ingredients, 

 ' Pebbles ' and ' Gravel,' are separated by sieves with 5 mm. 

 and i mm. meshes, the separation of these in a clean state 

 being aided by water. 



The fine soil and water which has passed through the i mm. 

 sieve is allowed to stand twenty-four hours, the clear water 

 is then decanted, and the remaining soil and water evaporated 

 till the mass assumes the condition of a stiff paste, which is 

 then carefully kneaded by the fingers till it has a perfectly 

 uniform composition. Water is determined in a portion of 

 this paste, and two other portions, each representing about 

 10 grams of dry soil, are taken for a duplicate analysis. Each 

 portion is placed in a porcelain capsule 9-10 cm. diameter, 

 15-20 cc. of water added, and the whole stirred with the 



