HYDRAULIC METHOD 



two glass tubes, one (F) bent down 

 so as to conduct the overflow into 

 the receiving vessels, and the other 

 (H), termed the " piezometer," for 

 the purpose of regulating the flow 

 by the height attained therein by 

 the column of water. 



The standardisation of the 

 apparatus consists principally of 

 altering the size of overflow- open- 

 ing F, until with a piezometer 

 pressure of 5 cm., 100 c.c. of water 

 will pass over in one minute. 



The use of the lower conical 

 portion of the elutriator is twofold : 

 viz. {a) to secure a gradual decrease 

 in the velocity of the rising cur- 

 rent; {U) to produce an agitation 

 among the soil particles for the 

 purpose of disintegrating any 

 aggregates. The object of the 

 cylindrical portion is to secure a 

 uniform speed in the rising current. 

 For uniform currents there is a 

 fairly definite determinable rela- 

 tionship between the speed of the 

 current and the maximum size of 

 the particles carried out of the 

 apparatus. 



68, Procedure. — The " air-dry fine 

 earth," freed from stones and 

 gravel by sifting (see above), is 

 treated with hydrochloric acid 

 as in the preparation of the 

 sample for the sedimentation 



-'-"- J 



Fig. 15.— Mayer's modifi. 



cation of Schone's 



elutriator. 



