46 TlMEHRI. 
to the inch, and over a series of copper plates covered 
with mercury, arranged in terraces so that the particles 
of gold stick on to these plates where they become 
amalgamated with the mercury. Cross channels or riffles 
traverse the terraces and intercept the coarser auriferous 
mineral, and the stream at last falls into a frame consisting 
of a long shallow box fitted with inclined trays, to which 
a movement is given by mechanical means, causing the 
heavier mineral refuse to travel up stream while the 
lighter particles flow to waste. 
The auriferous mineral is ground finer in contact with 
mercury by being fed into a circular iron cistern, over 
the bottom of which segments of iron are dragged — by 
which means, the mineral and mercury are rubbed 
together and the gold amalgamated. 
It may be safely assumed that the method adopted in 
Queensland in 1886 is an improvement on the Californian 
Milling, described in the Reports under notice.* 
Mr. ATTWOOD'S paper embodied in the fifth report 
gives ample instruction for sampling auriferous quartz. 
[* Most of the Gold quartz of California contains in addition to the 
free gold, a large proportion of the metal so intimately associated with 
pyrites ("sulphurets ") that a separate process, is required to extract it. 
The recent method, known as Chlorination, as described by Mr. Durden, 
late A6ting Secretary of the State Mining Bureau, is as follows : — 
After as much gold as possible has been extracted by amalgamation 
with mercury the remaining material is passed on to "concentrators" 
which separate the auriferous pyrites from the worthless rock. The 
pyrites are then roasted in a reverberatory furnace, dampened and 
placed in false-bottomed tubs coated with asphaltum, and then 
subjected to the continued action of chlorine gas, by which means 
the gold is converted into a soluble chloride, which is subsequently 
washed out thoroughly with water from the insoluble residue. From 
this solution, the metal is precipitated by proto-sulphate of iron, and is 
then melted into bars.— Ed.] 
