wae eS 
CHEMICAL SCIENCE IN AUSTRALASIA. 289 
used in America; but we believe there is only one mine in 
Australasia, the Waiorongamai, at Te Aroha, New Zealand, 
where any of them have been erected. Another furnace, the 
“Stetefelt,” works on the principle that a rapid oxidising and 
chloridising action can be produced by bringing the finely-divided 
particles, either with or without salt, in contact with an ascending 
column of hot air, and this again, although it has been worked 
successfully in America, has, we believe, been only tried at one 
place, St. Arnaud, in the colonies, where it was subsequently 
stopped. 
A furnace has been patented in the colonies by Mr. H. D. 
Meston, which consists of several floors communicating one 
with the other by slots, which can be opened or closed 
at pleasure. The ore is transferred from one shelf to a lower 
one through these slots from time to time, and the ore is stirred 
by revolving stirrers, the final roasting being performed in a 
reverberatory furnace. This would appear to possess the 
principal requirements for perfect and economical roasting. 
It is at present in operation at the Clyde Smelting Works, 
near Sydney, where it is stated to perform its work 
satisfactorily. 
So long as the gold is free from silver, or contains only a small 
proportion of that metal, but little difficulty is experienced in 
roasting, provided sufficient care is taken not to raise the heat 
too rapidly, and thus fuse or cake the material; but with silver 
the greatest care is necessary, because, in order to recover this 
metal, it is necessary to introduce salt at some time during the 
roast, preferably near the end, and a volatile chloride of gold is 
frequently formed, resulting, unless the greatest care is taken, in 
a loss of that metal. It would appear, however, that care and 
attention can overcome this difficulty, and the loss is comparatively 
slight where the process is thoroughly understood. After roasting, 
there are two distinct processes open, each of which has received 
a good deal of attention; these are respectively amalgamation 
and chlorination. 
Where amalgamation is employed, the roasted ore is ground in 
charges in some form of pan, and of these there are numerous 
adaptations. The objects of these pans are to provide as great a 
grinding surface as possible, and to have a complete circulation 
of the pulp. This circulation is generally secured by wings in 
the side of the pan diverting the flow of the current to the 
centre, but a pan has been patented in the colonies of late 
by Mr. G. C. Knapp which has an octagonal form, the mullers 
having, of course, only a circular rotation, and the circulation of 
the pulp in this machine is as perfect as it is possible 
to desire. Another pan, invented by Mr. C. Dubois, is 
closed at the top, and having a steam jacket below, 
it is claimed that the mercury is volatilised, and thus 
s 
