The Extraction of Gold. 25 
be attended to. If the sand jis allowed to form a hard bank 
on the bed of the table the sulphides cannot settle into it ; 
on the other hand, if the sand is kept too loose, the motion 
of the table forms a wave which tends to throw the sulphides 
to the surface, and again exposes them to the risk of being 
carried off by the current of water. Numerous experiments 
were made to ascertain the form of stirrer best calculated to 
meet these requirements. That finally adopted is not unlike 
the prong of a sluice-fork, and is made of quarter-inch nail 
rod iron ; each stirrer being eighteen inches in length, with 
the end slightly curved. They are set about one and a half 
inch apart in rows, each row being fixed into an axle work- 
ing on gudgeons nine inches above the bottom of the table, 
on which the curved ends of the stirrers always rest, the 
axles allowing each row of stirrers to rise or fall with the 
table. The bed of the table is covered with light boiler 
plate to reduce the wear, as grooves, which impede the action 
of the stirrers, are soon formed in a wooden bottom. The 
sand and water are passed over a distributing board, which 
delivers them in an even sheet on to the sloping head, clear 
of the sand on the table. The suspending chains have regu- 
lating screws on each for the purpose of adjustipg the levels. 
The upper chains are fixed, but the lower ones pass over 
and are attached to a roller, by means of which the inclina- 
tion of the table can be altered at pleasure without disturb- 
ing the cross levels. When put to work the table is set 
with a slight inclination towards the head, and is gradually 
lowered whenever the sand at the head collects to over two 
and a half inches in depth. After working for a longer or 
shorter time, according as the sand operated on may be poor - 
in sulphides, or the contrary, the table will become loaded 
with them. The tailings should then be diverted to a spare 
machine, and clean water only allowed to run over the table. 
In a few minutes the bulk of the pyrites will have accumu- 
lated at the head, when the table must be stopped, the 
pyrites shovelled out, and the work resumed as _ before. 
Hitherto this machine has only been worked at the Good 
Hope mine ; the table used there bei ng a small one, two feet 
nine inches wide, with a bed seven feet long. Through this 
was passed the waste tailings from four head of stamps (7.e. 
from thirty-five to forty tons per week), and these were 
carefully sampled at short intervals before going on to the 
table and after leaving it, the samples being all filtered 
through close woven calico. The assay of these samples 
