ALLUVIAL MINING IN OTAGO.

Otago Witness, Issue 1191, 26 September 1874, Page 4

ALLUVIAL MINING IN OTAGO.

The business of alluvial mining in Otago cannot be said to be in a very flourishing condition, so far as the employment of numbers is concerned. There may be considerable activity in some few districts, but, taking this branch of gold-mining as a whole, its value as a producing industry has become greatly lessened. The causes which have brought about, this state of things are various As we upon a former occasion said, the easily-wrought deposits of gold are gone ; nevertheless plenty of the precious metal is sill left behind — it is only more difficult of access. The question, therefore, naturally suggests itself: flow is this great industry to be maintained ? while we may, at the same time, consider how ib is that alluvial mining in general has lost so much of its activity and attractiveness. In this particular description of labour, everything depends upon the available water supply ; the sy>-t3in pursued now is almost universally that of ground sluicing, and the yieid of gold is entirely governed by the quantity of water at command. Water is nob only considered as a disentegrant for separating gold from earthly matter, but is essentially necessary as a mechanical agent to bring the earthy deposits within reach of the dissolving and separating process, and to accomplish this the <( hydraulic hose" has largely superseded manual labour together with the uss of ordinary mining tools and appliances. As a motive and propelling power, the use o£ water has only within the last few years come to be thoroughly understood by the miners, fox* whom, ■when they previously desired information upon this subject, the experiences oi California required to be hunted up ; while all that could be leai'nt was scarcely satisfactory, the circumstances of Otago and those of California being so widely different. Nothing valuable in the shape of information was to be obtained from Australia, as no vast operations by the mere application of water alone were conducted there : consequently Of ago gold-miners were compelled to plod along by themselves, and find out by personal experience what they could not possibly learn by any other means. This has been accomplished, and a state of perfection arrived at that where formerly six, eight, or even ten men were necessarily employed in a claim, two or three aro now sufficient, while the work itself is considerably less laborious. The benefits conferred are that ground can be worked with profit which, under the old system, could not be looked at ; while that which merely yielded a precarious existence La made to produce exceedingly handsome returns. But there is seldom any vety great advantage to be derived from a given line of action without some compensatory recoil, as in the case of all this economy aud elaborate use of water, difficulties have been created which, to a considerable extent, tend towards the defeat of the ©bject itself. The first is that the amount of manual labour formerly necessary in the work of extracting gold has been largely diminished. The second is, that the use of all our available water power is necessarily confined to fewer places, and mining operations are consequently not so wide spread. The last, and perhaps the most serious of all the evils, is that our over anxiety to obtain every available drop of water for mining purposes assists very materially to diminish the quantity, and we are met everywhere by complaints from miners that their supplies of late years have greatly fallen off. Many attribute this to a decrease in the rain fall, but such is not wholly the case, although one of the primary causes. The falling off is chiefly attributable to circumstances begotten of the necessities of the occasion, and over which we scarcely have any control. The cutting of so many water races, and the tapping in their course of every possible source of supply, ev^n to little insignificant swamps, leaves no room for any storage of water whatever — everything becomes dry and hard ; consequently, the rainfall finds its way immediately into the race*, and the ground, in an almost incredibly short space of time, becomes as destitute of moisture as if no rain had fallen. The heavy stocking of the runs with sheep is the second cause of a decreased water supply. The continuous cropping of these animals leaves no opportunity for moisture to accumulate under the shade of the natural herbage, 'and which used to shelter the grouml. and regulate the evaporation. T lie destruction of the bush and native scrub, without a doubt, has materially assisted to diminish the rainfall as well

as to leave the country dry and avid This, aided by causes already referred to, no doubt has tended to reduce the available water supply for mining purposes ; and there is no mistaking the fact that numerous little streams which formerly carried a sluice-head or so of water have been seriously reduced in volume, while the same process holds gond with larger supplies. Under the present improved system of mining the extent of auriferous ground that can be profitably worked is practically limitless. The areas alone comprised within the valleys of the Dunstan, the Manuherikia, the Marewhenua, and the slopes of the Hawkdun ranges, will afford employment for ages ; but not to any greatly increased numbers of people, unless we can add to our already available water supply. This, however, is a question of serious difficulty and expense, cnnveniently-ob-tained supplies being already occupied. What remains is therefore beyond the reach of private means and enterprise. Whether assistance from the Government can be successfully employed is a matter fox* grave doubt. What has hitherto been attempted under the Public Woi'ks scheme to assist miners tc bring in water has proved a miserable failure, and been productive of more harm than good. In the matter of the Mount Ida "head-race," the Government have it all their own way ; but the work has yet to be completed, and the promised forty sluice-heads of water delivered on the Mount Ida goldfield.