A NEW GOLD-SAVING MACHINE.

Otago Witness, Issue 2103, 14 June 1894, Page 16

A NEW GOLD-SAVING MACHINE.

(From Our Riverton Correspondent.) Mr T. M. Baldwin, of the National Bank, has been at Orepuki for some weeks practically testing a gold-saving appliance, of which he is the inventor and patentee. Ib is the first machine thafc I have seen or heard of that is at all capable of treating large quantities of washdirt, and after a careful examination of the gold-saving portion of the machine — which is now fixed to treat the tailings from Cooper's claim, where two f aceß are being worked — I feel certain that it will treat any quantity of washdirt that may be desired. Where there is nothing but fine gold, as in this district, one appliance with a tube box, say 12in in'diameter, will treat all the stuff that can be washed down the tail 'race by three Government heads of ■water, after all the boulders and b bones have been screened cut of the tail race, as is usual heie. The following is a rough description of the machine, which I think any practical miner will understand. Of course, in ground sluicing, where all the rough stones can be screened out of the tail race, the revolving cylinder is not required, as the whole of the stuff is run over a perforated zino plate, the stuff that goes through the plato going direcbly inbo the tube box. The machine for separating and screening the gravel consists'of a fixed cylindrical case of sheet iron of any length or diameter that may be required to put the desired quantity of stuff through, inside of which a cylinder fixed with the necessary pitch revolves at something like 20 revolutions per minute. The cylinder contains what may be called three screens, the inner most one, say, of 18in diameter, which Mr Baldwin estimates would take four heads of water with all the washdirfc they could cairy, is composed of iron bars |in by -Jin set on edge longitudinally | of an inch apart, the next of 6iri of copper wire netting mesh, and the outer one, of still greater diameter, of perforated zinc, such as that used for meat safes. The- water carrying the washdirfc either out of a tail race or dredge buckets is directed inbo the inner cylinder, which separates all the large stones, delivering them into a box, to be discharged where required, the smaller material passing through the bars on to the second I screen, which also delivers what does not pass through it into another box, where it can either be discharged into the tailings or carried along boxes with the usual appliances for saving coarse gold. Of course the end of the inner cylinder projects beyond the end of the second, and the second beyond the third, so that the material from each can be discharged inbo separate boxes. The fine stuff that passes through the zinc screen which contains all the fine gold so difficult to save is directed through an opening in the outside case into a round box (which I call the tube box) about 12in in diameter, into the bottom of which is fixed a large number of copper tubes a quarter of an inch in diameter, and 3in in length, through which the material passes down on to the quicksilver. These tubes are fixed at a slight angle, which causes the quicksilver to revolve. The quicksilver, o: which Mr Baldwin uses 751b in the machine now at work, is contained in a pan set 6in or Bin below the tube box. The silver pan ia of greater diameter than the tube box, which allows the Band to boil up over the edge. The pan is fixed so that the distance of the silver below the tubes can be regulated by a screw which lessens or increases the pressure of the material on the quicksilver, which is the crucial point in the working of the machine, as Mr Baldwin contends that if every particle of the dirb containing the gold is brought into direct contact with the silver the gold must be saved. And there is not the slightest doubt that his invention thoroughly attains that object.

It appears to me that, with the silver constantly moving and the washdirt forced into contact with it in such small quantities, all the gold which it is possible to save in quicksilver must be saved. If the machine should fulfil the expectations of the inventor — which I see no reason to doubt — it will create a revolution in gold mining, as it will save an immense quantity of extremely fine gold that none of the present appliances make the slightest pretence of saving. Ifc will be especially serviceable on our sea beaches, where the gold is thinly distributed through large quantities of gravel and sand, which I feel certain will pay handsomely if the whole of the gold can be saved, while putting through large quantities of stuff. It may appear that such thin material ss perforated zinc would not stand the wear and tear of gravel passing over it, bub whether it is on account of some inherent quality in the zinc itself or on account of it 3 smoothness there appears to be actually no friction, as one sheet after being fixed in a tail race for nearly two months showed little or no sign,s of wear and tear.