286 STATE AND PROGRESS OF 
In the earlier machines this motion was imparted to the balls 
by cones, against which the centrifugal force so acted as to 
produce the rotatory motion desired, and it acted well so long as 
the balls preserved their spherical form, but if any small flat 
surface became worn, or if fine matter accumulated in the machine, 
the balls ceased to rotate. In the present arrangement the balls 
cannot stop, and the true spherical form is preserved. 
The result of experiments with the first mill made on the new 
plan is that the hardest quartz can be rapidly reduced to the 
finest powder, and the inventor has supplied us with the following 
figures, derived from actual experiments, as illustrative of the 
work performed :— 
Power required to work a four feet diameter 
mill ‘en ta sf ... 6 horse-power. 
Quantity passed through wire screen, with 
1600 holes to square inch, per hour de De Wibs 
Weight of heaviest piece in mill Se. el etewite 
Total weight of mill_... Bc i. © -Setons’ 
A plant is now being erected at the Britannia Mine, near 
Forbes, which wili afford an excellent guide as to the actual 
working results of the machine. There are several incidental 
advantages which are claimed for this mill. The whole grinding 
pan can be replaced at the same cost as replacing a false bottom. 
The wearing parts are all castings. The mill requires no founda- 
tions, and can be set to work a few hours after arrival at a mine, 
and can easily be moved from place to place. 
The refractory gold ores, in the majority of cases, carry a certain 
amount of free gold in them, and are thus generally subjected to 
the processes to which we have alluded before undergoing further 
treatment. They are sometimes, however, taken direct from the 
battery for concentration without the intervention of any method 
of amalgamation, or, at times, passed through a system of pan 
amalgamation, which will be alluded to further on, without being 
concentrated at all. 
In concentration there is a wide field for inventors, and to 
this subject a good deal of attention has been directed. Until 
comparatively lately concentration was performed on blanket 
tables, in buddles of various form, or on end blow, percussion, or 
shaking tables only ; but of late the Frue Vanner and Triumph 
Concentrator have been somewhat extensively introduced, doing 
their work very completely, but working at a comparatively slow 
rate, wo vanners being required for each #ve heads of stamps. 
A patent has been taken out by Mr. G. C. Knapp and 
Mr. T. E. Fuller for a concentrator known as the ‘‘ Champion,” 
which, while working on a similar principle to the Triumph, has 
different mechanical arrangements, and the belt is shorter and 
wider. This concentrator comes under the head of belt 
