THE SEPARATION OF THE CRYSTALS 



409 



bearing, on which the bottom of the spindle rests, and also a form of roller 

 bearing, on which the hemispherical bottom of the spindle rests and rotates. 

 He attempted to restrain the oscillations of the machine by suspending a 

 weight to the spindle. This patent contains the germs of various later 

 successful types. 



Instead of attempting to restrain the rotating basket in rigid bearings, 

 all modern machines are so built as to be allowed to find their own centre 

 of oscillation. This very important advance is due to Bessemer, who 

 (patent 13202, 1850) described a machine suspended from a ball and socket 

 joint free to find its own centre of gyration. The spindle of Bessemer's 

 machine was extended below the bottom of the basket and carried a loose 

 wheel surrounded by a fixed curb. The object of this arrangement was to 

 restrain the amplitude of any oscillation which might arise from lack of 



FIG. 255 



balance in the load. Bessemer's patent also claimed the inverted type of 

 free machine, with the basket balanced on a ball and socket joint and under- 

 driven. In addition, he claimed the use of a rubber buffer between the 

 bushing and spindle, for the purpose of avoiding vibration and allowing 

 a certain freedom of movement. 



In a patent (13416, 1850) granted to Nind, as agent, the whole machine 

 is described as suspended by elastic rods, the lower end of the spindle 

 rotating in bearings surrounded by rubber buffers. 



The modern sugar centrifugal machine dates from Weston's patent 

 (3041 of 1867 ; U.S. patent 63770, 1867), and was developed by him when 

 engaged as an operating engineer in the Hawaiian Islands. His machine, 

 as shown in his patent, and from which the very latest machines only differ 

 in detail, combined freedom of oscillation with a solid stationary suspended 

 spindle supporting a hollow rotating spindle, to which is attached the per- 

 forated basket. His patent did not claim suspension, but only the special 

 means of suspension,* and he is in no wise to be considered the inventor of 



* A provisional patent issued to Johnson as agent (418 of 1852) mentions a hollow spindle, but gives no details. 



