278 PROCEEDINGS OF SECTION B. 
Sulphide Concentrates. 
Lead, per cent. ...| 60 55 66 66 69 67 65 64 
SilversiOz7. Vass.) 21 19 19 22 21 2320 19 
Zinc, percent. ...| 8 9 8 | 8 8 7 76} 10 
The chief end that the metallurgist in charge had to keep in 
view was the output. He was not asked simply to smelt the ores, 
but was also required to vary the charges in such a way as to keep 
the weekly returns of silver and lead nearly even. The silicious 
kaolin ores are the chief source of silver, and a glance at the assays 
given above will show how these vary in value and composition, 
and, as pointed out previously, not daily but hourly. 
The indicator of the daily output was the assay of a small 
sainple of lead, called the ‘dip sample,” taken directly from the 
“well” of the furnace once every twelve hours, and, as the assay 
showed a rise or fall in silver, the charge was changed accordingly. 
For instance, if the “ dip assay” showed a drop in silver, and the 
returns were not good enough for the part of the week which had 
elapsed, it was often necessary to sacrifice a nice, economical 
charge on the furnace, and replace some low grade basic ore by 
the silicious and troublesome kaolin ore to raise the value of the 
bullion, and, correspondingly, the week’s output. Or the reverse 
condition might have to be considered. It is simply impossible 
for the mine to regulate the assay value of the ore (which is the 
sole thing the mine part of the organisation looks at), because in 
the kaolin stopes the faces may be ‘all or part in low grade ore for 
some hours, perhaps days ; and without any change in the appear- 
ance of the ore, the assays suddenly rise or fall. “In a large mine 
such as the Broken Hill Proprietary, where the demand made by 
the furnaces is great and imperative, it is impossible to keep the 
ore stored in the stopes until the assay value is known, and usually 
the ore is in the smelter bins, and probably in the furnace, before 
the underground manager knows its value. This is not an advan- 
tage, especially if we regard it from the metallurgist’s point of 
view, who is asked to keep the return steady, otherwise it is 
seldom that any absolutely useless ore is sent to the furnaces for 
the want of the assays or means to store it underground. One 
needs to see and know the tremendous ore body of the Proprietary 
Mine to quite grasp this assertion ; but if I say that all the ore 
carries silver, whether the lode is 300 feet wide or 3 feet, it will 
be readily understood that, with constant experience of the pecu- 
liarity of the ore, the underground manager can judge very closely 
from his previous results what the average value of the ore will be 
each day ; but it is to be clearly understood that there is no abso- 
lute guide to the ores’ value except experience of the ore body’s 
idiosyncracies, when assays are not available at once, nor any 
