312 PROCEEDINGS OF SECTION B. 
The dust accumulating in the first large chamber was removed 
every night and added to the ore on the cooling floor. The dust 
from the drying floor flues was removed at greater intervals, and 
was leached in shallow charges by itself. If it were to be removed 
daily it could be sent to the vats mixed with the ordinary stuff on 
the cooling floors. The roasted ore was not allowed to remain 
long in the hot-ore hopper, but was quickly removed to the cooling 
floor, where it was left in a pile, about 3 feet high, until quite 
cool; this we found to take nearly a week. From the cooling 
floor the roasted ore was taken by a short tramway to Division III. 
III. The Leaching Mill. This comprised :— 
Three ore vats, 16 feet diameter, 7 feet deep. 
Three precipitating vats, 10 feet diameter, 9 feet deep. 
Two square tanks for wash-water precipitation. 
Two square tanks for storing precipitates. 
One square cement sump for solution. 
One No..5 gun-metal lined Blake pump. 
Two stock solution vats. 
Wrought-iron pressure tank. 
. Johnson’s filter press. 
10. Cast-iron tank for making sodium sulphide. 
11. Two wrought-iron tanks for storing sodium sulphide. 
See Ce OU Co 
Fresh water was supplied by gravitation from a dam above the 
mill. The steam boiler in the crushing mill furnished the steam 
required, but was too small for other requirements. Had the mill 
been run at its full capacity a separate boiler would have been 
necessary for the leaching mill. 
The vats were made from a local timber, known as beech or 
white cedar, and were constructed exactly as recommended by 
Stetefeldt. They were provided with ejectors for circulating extra 
solution, and were well tarred with coal tar, as were also the 
launders and all ironwork. The stock solution vats were fitted 
with cast-iron pipes for heating the solution by steam. These 
large vats must not be left empty for any hours or they begin 
to leak, however well made they may be. ‘The ore was charged 
into the vats dry, water being introduced from the bottom to 
saturate the charge while filling proceeded. ‘The tailings were 
sluiced out when there was sufficient water to spare for the purpose. 
The extra solution was made up on the charge. The solutions 
were stirred by hand with a long wooden rabble during precipita- 
tion. The precipitates settled rapidly, and were run off daily. 
The lead was not precipitated separately. When sutlcient preci- 
pitates had accumulated they were pressed in the filter press and 
dried. The pressure was produced by steam. <A brick drying 
chamber heated by steam was built for drying the precipitates, 
but it was too slow ; so the drying was done in a kind of oven, 
