C—3.

In the West Coast mining district attention is being given to dredging areas in Marlborough, also on the Karamea, Mokihinui, Waimangaroa, Orowaiti, Buller, Grey, Teremakau, Hokitika, and Totara Bivers and adjacent flats, Boss Flat, and other places. For several of these new dredges are in course of construction, and the machinery of one dredge in Otago has been bought for removal to the West Coast. That a number of claims have been put on the market in consequence of the feverish excitement which has taken hold of a portion of the community goes without saying. How far several of them are justifiable has yet to be proved, and in this, as in other branches of mining, the unexpected often happens. When the Hartley and Biley Dredging Company was put on the market some difficulty was experienced in getting shares taken up, but the phenomenal returns which this medium-sized dredge has obtained—amounting very recently to 1,187 oz., valued at £3 15s. per ounce ( = £4,451 55.), for a single week's work—has caused quite a rush for shares in claims in the same locality. A success of this sort, coupled with the fact that very good returns have been obtained from other dredges, has been taken advantage of by many who simply take up shares for the sake of trafficking in them, and shares have changed hands at large premiums where the dredge is not yet built, nor likely to be for several months to come. This may be smart business, but it cannot be considered as legitimate mining investment, as such premiums cannot be said to be honestly warranted until a dredge has got to work and proved the capabilities of the claim. Claims have been pegged out in some few instances —presumably for the sole benefit of promoters—where dredging is practically out of the question. It does not necessarily follow that, because dredging has developed a method of alluvial mining which has been successful in places where other methods would be commercial failures, this process is applicable everywhere. There are conditions where hydraulic mining, or even tunnelling, would be more suitable than dredging. This has been demonstrated near Naseby, Otago, where hydraulic elevating had to be reverted to. One or two properties have been put on the market and floated as dredging concerns where, if I am not mistaken, the conditions are far more favourable for hydraulic sluicing and elevating. But dredging has taken such a hold on the public in some parts of the colony that no other form of mining will be considered as an investment. This condition is no doubt responsible for the large number of "dredging" claims, good, bad, and indifferent, which have been put before the public during the past few months. Beferences have been made in the reports of the last two or three years to the successful working of dredging plants on flats to which a sufficiency of water can be brought for floating the machine and treating the material lifted. Very large areas of this class of ground are now being worked, and will be worked in the future. There need be very little fear of results in most cases if the precaution is taken of having the ground properly tested by a series of small shafts sunk at various points, and the material treated by a cradle or sluice-box prior to placing a dredge on the claim. By this necessary preliminary much valuable information may be obtained as to the nature of the ground to be worked, and the average yield which may reasonably be looked for. From the information so gained a suitable dredge may be designed. This is a very important feature, and one to which insufficient attention has been paid until within the last year or two. Where flats and river-banks carrying a clayey overburden above the wash are worked by dredges it is found that lumps of clay, and water carrying clayey matter in suspension, are responsible for the loss of gold to a very appreciable extent, although some few dredge-masters are very loth to admit what is clearly the case. Others have admitted that they believe their worked ground would pay to dredge again for the gold lost in the first working, provided that thoroughly up-to-date plants, designed for the efficient saving of gold, were adopted. That there is some reason to think this is so is evidenced by the fact that in a few instances dredges are now working at a profit on ground which had previously been worked three times over by hand-labour —the last time by Chinese diggers. I only know of one case where a dredge-master has actually taken the trouble to systematically ascertain his loss from the cause referred to. In this case it was found as the result of treating measured quantities of tailings that gold amounting to 2 gr. per cubic yard of tailings treated was lost. This may be taken as a fair index of what is going on where the auriferous wash is overlaid by a heavy subsoil and clay. The dredge at which this test was made is a small one with a capacity of about 1 cubic yard per minute. Allowing the dredge to actually raise one-half its theoretical capacity, or 30 yards per hour for twenty working-hours daily, a loss of 2 gr. per yard amounts to 15 oz. per week. Even if the loss is only 1 gr. per yard, it is enough to cover the working-expenses of the dredge in question, the gross yield of which is about 20 oz. weekly on a working-cost of 7 oz. Taking the average profit of this dredge at, say, 10 oz. per week, at £3 15s. per ounce—£37 10s.—by forty-four weeks per year (thus allowing ample time for holidays, repairs, &c), we get an annual profit of £1,650 on a capital expenditure of some £2,500. This, after allowing for depreciation, gives a return of fully 50 per cent, on the capital invested, and, as has been shown, could be very materially increased if some satisfactory method were adopted for preventing the loss of gold. The most natural way to overcome the difficulty appears to be the adoption of a system of first stripping the overburden from off the wash. This would allow the latter to be more efficiently treated in the screen, sluice-boxes, or tables. It is purely a question of doing it in the least expensive method so far as the prevention of gold loss is concerned, and in many instances might be effected by dredges taking a preliminary cut level with the bottom of the clay. No doubt some alterations in the ladder and bucket-chain would in certain instances be necessary, but as it is. possible to make the former telescopic, and the lengthening of the latter is a comparatively small matter, there need be no great difficulty (with future dredges especially) in stripping a reasonable distance ahead of the face of wash, with a consequent reduction in the amount of gold lost. It may be urged that the adjustments which this plan would necessitate would take up time. This is true, but the results would in the great majority of cases fully justify the means. Other methods 6—C. 3.

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