MINERAL CONSTITUENTS 



125 



applied by Nobel in his apparatus given in figure 66. This was not 

 very satisfactory and the same principle was applied somewhat dif- 

 ferently by Scheme in his elutriator. The apparatus consists of a 

 conical glass tube, as shown in figure 67. The sample, after 

 thorough disintegration and passing through sieves to remove, the 

 coarser material, is placed in the tube and a current of water allowed 



Fio. 65. Bottle for Subsidence Method of mechanical analysis. By forcing air into the 

 bottle through A, the water with the suspended particles ia forced out through B to the level 

 of C. 



to enter at G. It is evident that the size of the particles carried 

 upward and through the outlet tube will depend upon the rate of 

 flow of the water, and by regulating this the separations are made. 

 There are some inaccuracies in this method caused by counter-cur- 

 rents in the elutriation cylinder and the tendency of the particles 

 to collect into grannies. In order to overcome this, Hilgard devised 

 his churn elutriator. 



