The Frue vanner will, as a rule, act well when the pulp is sufficiently fine.  It is really a adaptation of an old and simple apparatus used in China and India for washing gold dust from the sands of rivers.  The original consisted of an endless band of strong cloth or closely woven matting, run on two horizontal rollers placed about seven feet apart, one being some inches lower than the other.  The upper is caused to revolve by means of a handle.  The cloth is thus dragged upwards against a small stream of water and sand fed to it by a second man, the first man not only turning the handle but giving a lateral motion to the band by means of a rope tied to one side.

Chinamen were working these forerunners of the Frue vanner forty years ago in Australia, and getting fair returns.

The Frue vanner is an endless indiarubber band drawn over an inclined table, to which a revolving and side motion is given by ingenious automatic mechanism, the pulp being automatically fed from the upper end, and the concentrates collected in a trough containing water in which the band is immersed in its passage under the table; the lighter particles wash over the lower end.  The only faults with the vanner are—­first, it is rather slow; and secondly, though so ingenious it is just a little complicated in construction for the average non-scientific operative.

Of pan concentrators there is an enormous selection, the principle in most being similar—­i.e., a revolving muller, which triturates the sand, so freeing the tiny golden particles and admitting of their contact with the mercury.  The mistake with respect to most of these machines is the attempt to grind and amalgamate in one operation.  Even when the stone under treatment contains no deleterious compounds the simple action of grinding the hard siliceous particles has a bad effect on the quicksilver, causing it to separate into small globules, which either oxidising or becoming coated with the impurities contained in the ore will not reunite, but wash away in the slimes and take with them a percentage of the gold.  As a grinder and concentrator, and in some cases as an amalgamator, when used exclusively for either purpose, the Watson and Denny pan is effective; but although successfully used at one mine I know, the mode there adopted would, for reasons previously given, be very wasteful in many other mines.

There is considerable misconception, even among men with some practical knowledge, as to the proper function of these secondary saving appliances; and sometimes good machines are condemned because they will not perform work for which they were never intended.  It cannot be too clearly realized that the correct order of procedure for extracting the gold held in combination with base metals is—­first, reduction of the particles to a uniform gauge and careful concentration only; next, the dissipation, usually by simple calcination, of substances in the concentrates inimical to the thorough absorption of the gold by the mercury; and lastly, the amalgamation of the gold and mercury.