284 STATE AND PROGRESS OF 
GOLD. 
Free milling gold ores include all those ores in which the gold 
is in a free state, associated generally with quartz as a gangue, 
but occasionally also with porous ironstone or gossan. In the 
majority of cases, however, where gold occurs under the latter 
condition, it is coated by a film of oxide of iron, which prevents 
proper amalgamation, and is also, in many cases, of a very fine 
nature ; these characters would transfer the ore from this class 
to that of class No. 2. 
The treatment of ores of class No. 1 has, from the earliest 
times, consisted of crushing and amalgamation, and although 
many new systems of crushing have been tried from time to 
time, no machine has yet been introduced which will compete 
with stamps when a large quantity of ore has to be dealt with. 
‘The primitive battery crushing of the early days has, however, 
given place in the better managed mines to plants in which all 
the points which promote rapid, efficient, and economical work 
are considered ; and although we still find batteries supplied 
from some foundries built upon the old systems and employing 
the old patterns, there is a decided tendency at present to erect 
thoroughly capable machines, and to study what really are the 
best methods of treating the ore. 
Perhaps the chief point of difference to be noted in batteries is 
that some employ light stamps, with a high drop, while others 
use heavy stamps, 8 or 9 cwt., with a drop of 6in., or, in some 
cases, even less. It will be evident that one advantage of the 
latter form is that the battery can be worked at a higher speed, 
since those with a low drop will not take the same time to fall 
as those in which the drop is higher. Another point in which 
a great difference presents itself in the efficiency of different 
machines, is to be found in the method of feeding the stone to the 
battery. In many cases, even now, the stone, as it is brought 
from the mine, is roughly spalled by hand, and fed into the mill 
whenever the feeder has time or inclination to attend to the 
work ; and thus at times we hear the stamps striking direct on 
the dies, having nothing to crush, while at others there is so 
much stone in the battery that the stamps have a large part of 
their fall cut off, and are, moreover, crushing stone on stone 
instead of, as intended, directly on the dies. The more improved 
batteries of the present day are supplied with ore crushers (stone 
breakers), which reduce the stone to about one and three-quarter 
inch metal, and this is fed into the boxes by means of improved 
self-feeders, such as the Challenge Ore Feeder, which can be 
regulated so as to furnish a regular supply of ore to the mill. 
There is a good deal of prejudice against ore-feeders at some 
mines even now, and no doubt, in certain cases, they have not 
worked satisfactorily ; but the fault has been, not in the feeders 
