THE SEPARATION OF THE CRYSTALS 



413 



copper or brass sheet would be forced against the inner surface of the shell, 

 sealing its perforations. 



In the earlier machines the discharge of the sugar was effected by lifting 

 it in scoops over the lip, and the discharge through the bottom of the basket 

 appears for the first time in Wes ton's patent, though previously Gordon 

 (2213, of 1867) had patented a machine in which the whole bottom was 

 lowered. Considerable labour is expended in scraping the sugar from the 

 wall of the basket, and to obviate this Sillem (898 of 1858), Green (1332 of 

 1859) an d Merril (1178, 1867) all patented the use of scrapers which were held 

 against the wall of sugar whilst the machine was still revolving. Although 

 patented again by Weston (1937, 1883) as a " plough " in a very practical 

 form, this system does not seem to have come into use till many years later. 



FIG. 258 



FIG. 259 



The Roberts-Gibson discharger (patent 5675, 1910) is shown in Fig. 258. 

 To avoid damaging the screen, these devices should be used with a renew- 

 able hard wood tip, as was also pointed out by Weston. 



The self-discharging basket of Watson, Laidlaw & Co., Ltd., is shown in 

 Fig. 259. This is contained in Laidlaw's patents (4498, 1894 ; 8766, 1895 ; 

 5750, 1902). In this machine the massecuite is fed on the cone whilst the 

 basket is in motion, at a speed sufficient to project the material against the 

 side. When the massecuite dries, the slope of the wall is insufficient to retain 

 the sugar, even before the basket has come to rest. 



The Centrifugal Spindle. The spindle shown in Fig. 256, representing 

 very closely the original Weston patent, remained a standard pattern for 

 many years. Certain modifications are mentioned below. Laidlaw's 

 patent (6081, 1891) introduced the double wedge-shaped buffers, shown 

 also in Fig. 256, which serve to give a more uniformly distributed pressure 

 in different positions of .the basket. Later, the buffer assumes a conical 



