14 PHYSICAL CONSTITUTION OF SOIL 



in height and 45 mm. in diameter ; this cylinder is united 

 at its lower end to a brass cup-shaped funnel, crossed by 

 an horizontal axis furnished with four wings ; this churn is 

 separated from the cylinder by a wire screen with meshes 

 0-8 mm. in diameter. The churn is worked by any convenient 

 motor power ; about 500 revolutions per minute is the speed 

 required when separating the two finest groups of particles, 

 for the other separations a smaller velocity will suffice. The 



FIGURE 2. 



lower end of the brass funnel is fixed into a conical test- 

 glass, which is in connexion with the water supply. The 

 water is supplied from a reservoir maintained at a constant 

 level. The lever opening the water tap moves over a graduated 

 arc, on which are marked the positions of the lever which 

 yield supplies of water giving the required velocities in the 

 glass cylinder. 



The apparatus being half filled with water, and the churn 



