C—3.

may suggest themselves to designers of dredges, such as an independent set of buckets working on the overburden only, and stripping simultaneously with the ordinary work of the dredge, or of a small independent plant specially designed for the purpose. Viewed from the standpoint of gold-saving alone, the matter deserves far more attention than has yet been bestowed upon it; but there is another aspect of the question —viz., that of the permanent effects upon land in consequence of dredging operations —which warrants very serious consideration. It is now known that, in addition to the swampy lands where dredging is being successfully prosecuted in parts of Southland, payable auriferous gravels underlie really good agricultural land in that district, considerable areas of which have been put under offer to dredging companies at prices far above agricultural value. Taking into consideration the fact that, whereas the dredging of this land will only yield one crop of gold, it would be capable under ordinary conditions of yielding farm crops year after year indefinitely if left undredged, it forces the question, Can the gold be taken out of the ground without the agricultural value being greatly depreciated ? The answer to this may be in the affirmative, provided that the soil and clay are first stripped off the wash and deposited on the tailings. Going still further, I venture to affirm that ground now comparatively valueless from an agricultural standpoint on account of its swampy nature may be made to yield its crop of gold in the first instance, and be improved into land of a higher value for agricultural purposes by the very act of dredging if the overburden is stripped in advance, and deposited behind the dredge. The reason for this is not far to seek: Land is often swampy owing to the tight nature of the subsoil and strata below it. By dredging, the gravel-wash would be broken up and loosened, and, as ground which has been broken up from a tight, consolidated state requires a greater space than when in situ, it naturally follows that to put this ground back into the same superficial area its depth or thickness must be greater, hence the result is that the surface becomes somewhat raised. The looseness of the gravel deposited offers conditions of better filtration, thus drainage is more easily effected. The earthy and clayey matters are broken up by the action of stripping, and further disintegrated and intermixed by deposition on the dredge's tailings. Thus, with the concurrent action of atmospheric influences, the ground is raised, drained, sweetened, and generally improved. A dressing of lime following these operations would in many instances —in the Southland District, at least—result in the production of fairly good farm land. During the last two or three years there has been a decided move in the direction of very large dredges having a capacity for lifting an enormous amount of material. Where ground is deep a largs dredge is a necessity ; but I cannot entirely agree with the greatly increased lifting-capacity in many instances, for the simple reason that (in my opinion, at least) the area of tables for saving gold, and more particularly the arrangements for saving fine gold, have not received the additions and amount of attention which the treatment of an increased amount of material appears to demand. There is very little doubt but that this is a part of dredging operations which will bear considerable improvement. The question should not altogether be How much can the dredge lift ? but How much can the dredge successfully treat ? A dredge which is lifting 100 tons per hour, and only capable of efficiently treating 60 tons in the same time, cannot be said to be doing its work satisfactorily. Where a dredge is working on a flat which has been turned over two or three times, clay, soil, and wash are so mixed up that the loss of some fine gold is practically impossible, but there does not appear any legitimate reason why more than a very minute percentage should be lost where dredges are working on clean wash, free from clay, as in the Clutha (or, as it is often erroneously called, the " Molyneux ") Eiver and some of its tributaries. The necessity for dredges being designed to suit the class of. ground to be operated on becomes more apparent every year. In the Clutha Eiver the wash is, generally speaking, of a loose character, and readily falls to the buckets. This admits of the inclination of the bucketladder being much steeper than where the wash is compact, and has to be torn out. It has been urged that for conditions of the latter nature the buckets, when on the bottom, should be well ahead of the pontoons, and that in at least one instance an otherwise well-designed dredge failed to attain success from this very cause alone. It is probable that the explosion of a few well-placed charges of dynamite would (when this plan is feasible) afford considerable assistance to dredges working in tight ground. On banks and flats there would be no difficulty in this. At the time of writing all the working-dredges are, with the exception of one current-wheeler, driven by steam-power, the only electrically driven dredge, which was at work on the Upper Shotover, being under course of re-erection at Miller's Mat, near Eoxburgh. Dredges to be driven by electrical power ara in course of construction at Earnscleugh Flat, and at Fourteen-mile Beach, near Alexandra. Electricity will be generated by dynamos driven by water-pressure. A suggestion has been made to utilise the water of the Soaring Meg for generating electricity as a power for working the dredges now being built on the Kawarau Eiver. Where water-power is available, and coal expensive, electricity will no doubt play an important part in future dredging operations ; the wonder is that this question has not received far more attention in the past. The inconvenience and expense to which steam-driven dredges are subjected could in many instances be considerably minimised by the adoption of electrical power, and the space now taken up by boiler and coal would be available for the erection of more extensive arrangements for goldsaving. The question of comparative costs would, I think, result in favour of electrical power at places remote from a cheap coal-supply, even if the electric current had to be generated by steampower at or near a coal-mine. Cartage, wear-and-tear of bags (the latter averaging fully Is. 3d. per ton of coal used on dredges), and loss of time in getting coal on board are items of considerable expense. There is also another and most important point. Dredging has now become an industry which will last for a large number of years in various parts of the colony. It is also expanding. The question of a reliable coal-supply for power purposes in the future is one which dredging companies ought to take into serious consideration.

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