62 H. J. Grayson : 



Guided by this knowledge, confirmed by niicioscopical evidence 

 from tlie examination of a variety of powders, it was decided to 

 carry on the process of separation of the three finest grades of 

 emery, obtained by the decantation method of separation, to a 

 greater degree of refinement, the method adopted l>eing essentially 

 as follows : — 



A circular upright glass jar, about 10 inches high by 5 inches 

 wide, was roughly graduated into one-inch spaces. With this jar, 

 the syphon and attachments shown in Fig. 1, Plate XI., were used. 

 The attachments include a glass tube of about 5 m/m. bore, bent 

 as indicated; the short arm being longer than the depth of the 

 vessel used Avith it. The longer arm is extended as required with 

 rubber tubing; it must be more than twice the length of the short 

 arm, and retained at a length convenient so as to maintain a 

 constant pressure at the outfloAv. Various sized jets to control the 

 overflow of the syphon are required. A convenient series of these 

 jets, which are not difficult to make and adjust, should permit of the 

 whole of the Avater being withdraAvn from the container during 

 intervals of about 10, 20, 40 and 60 minutes. 



It should be noted that the short arm of the syphon passes through 

 a large circular piece of cork, which acts as a float upon the surface 

 of the water in the graduated container, and also serves to regulate 

 the depth of the intake tube. The bent syphon and its attachments 

 are suspended and counterpoised by means of a cord, pulleys and 

 Aveight, as shown in the figure, the outfit being completed with over- 

 flow receptacles.! 



Before using this outfit with the particular grade of abrasive 

 it is proposed to refine, the rate of flow from the syphon should first 

 be adjusted. If the required grade is one of 20 minutes, the water 

 level in the container should be lowered one inch in two minutes. 

 Generally it is better that the time should exceed rather than fall 

 short of the interval for which the adjustment is made. Everything 

 being in readiness, the container is filled to the upper graduation 

 mark Avith thoroughly mixed emery and water and allowed to settle 

 for about 2| minutes, before the float is lowered upon its surface or 

 the syphon clamp removed. On releasing the latter the water level 

 should fall to wathin about one inch from the bottom of the con- 

 tainer. The inlet tube is prevented from descending too near the. 

 surface of any sediment on the bottom of the container by inserting 

 3 pins or bits of Avire tripod-Avise into the under surface of the float 



1 The overflow vessel must be placed well below the syphoti outlet and not as shown in the 

 fl:jfure, which was thus drawn for convenience of reduction. 



