THE NEW GOLD-SAVING MACHINE.

Otago Witness, Issue 1893, 2 March 1888, Page 12

THE NEW GOLD-SAVING MACHINE.

A machine named " The Hydraulic Syphon Amalgamator," recently patented by Afessre D. W. M'Arthur, C.E., and W. G. Johnston, ironmonger, of Hokitika, is (says the West Coast Times) likely to prove au important factor in gold saving. It is entirely self-acting, and can be utilised for crushed ore or other tailings.

A small working model is now at view at the rear of Messrs Johnston and Co.'s premises, Re veil street. Owing to the difficulty of obtaining the necessary fittings in Hokitika many of the mechanical details are unavoidably omitted. Yet, despite these shortcomings, a very fair outline of the idea is conveyed. The model referred to is constructed of pieces of bent glass tubing, with rubber joints, and represents an inverted syphon. Those required for practical use will be made either of sheet iron or other metals. The lower cavity contains quicksilver through which water, sand, and tailings (aided by their own specific gravity and the requisite pressure) freely pass, the gold alone being retained. Attached to the cud of the syphon, and tangentially so placed, is a cylindricalshaped tank, which is intended to trap any fugitive amalgam that may escape from the cavity above mentioned. The entry to the tank being near the bottom, while the exit is immediately above on the same side, imparts to the tailings a spiral rotary motion which, by the aid of a small quantity of live silver previously placed in the bottom, likens the contents to a quicksand, readily enabling metallic substances to gravitate to the bottom, and thus effectually providing against loss of either quicksilver or amalgam. In the plan already registered the various items connected with the machine are described in detail — viz., gauge taps, pressure valves, man-hole, a regulating telescope slide whereby the pressure may be adjusted according to circumstances, also particulars re size and shape of the mercury chamber, &c., &c, &c. Although the latter items are not shown in the model, the main principle (in a small degree) sufficiently demonstrates what machines of a larger capacity should be capable of performing. Heavy black sand and pebbles freely pass through the quicksilver, which is kept in a state of constant agitation or friction so indispensable in promoting amalgamation. Though stones or even heavier substances may be passed through the silver barrier, their passage not being essential can be easily prevented by an ordinary grating. A machine properly constructed on the above lines will doubtless prove of material importance in connection with beach dredging, as it will do away with extensive staging, hoppers, tables of green baize, copper plates, &c, &c, not to mention the wear and tear they necessarily entail. In addition to the model is a sketch plan showing how the machine can be applied to ordinary sluicing claims, and may be briefly described as follows — viz. : A represents an open tail-race, B is a grating situated about midway ; under this is an excavation in which the syphon is fixed in readiness to receive all the sludge water and fine tailings. Cis an iron shoot, placed at the end of the grating, and at a sufficient angle to allow the large stones to slide down by their own momentum, entering the tail-race at the point D in conjunction with the discharged tailings from the syphon, proceeding thence in their regular course to the end of the boxes. The patentees, from their knowledge and experience of the large percentage of loss of fine gold, have for some time past given the subject their combined study, and in referring to the matter instanced the fact of the Government Sludge Channel at Kumara, from which an average yield of something like 300oz of gold per annum is obtained. What is lost in excess of even that amount is probably considerable, as no gold-saving means other than the primitive stone blocked bottoms are used.

The Humphrey's Gully Company, Mont dOr, Greenland, and other large sluicing claims doubtless experience a proportionate loss of fine gold. In the first-named claim several plans have been tried, among others the drop box and American side grizzly, but as these (especially when many are used) tend to deprive the tail-race of a large proportion of the water required to carry off the tailings, it was found expedient (in the instance mentioned) to use only one in lieu of three, as originally intended. Upon closely examining the gold saved, however, it was found to be rather of that medium sample said to be travelling along the bottom of the boxes, while the great bulk of the fine flour gold is admittedly buoyed up midway, and, unable to find a resting place, is hurried along in the force of the current until reaching the end, when it is finally deposited on the tailing heap. Henoe the more practical way to overcome the difficulty appaars as above stated — viz., to force the entire body of tailings (minus stones) through any effective gold extractor capable of receiving them, whether it be the machine already described (which certainly seems a most feasible, not to say simple one), or by any better plan that ingenuity or experience may devise. A large size working model, in glass, of the syphon amalgamator is now being made in Melbourne, and will be exhibited at the Victorian Exhibition. Mr Park has also volunteered to give the new gold-sawr n trial at his works at the Arahura, where dredging is now in active operation. As a proof that the syphon will probably be in demand on a small as well as a large scale, many old experienced blacksanders, including Mr Foster, who have seen the model working, have expressed themselves sufficiently in its favour to be quite willing to purchase machines as soon as ready— a wish that will doubtless be gratified as soon as arrangements can be completed for their manufacture. The public will then have an ample opportunity of criticising its merits.