Auriferous Drifts.

On this head I have only to record some observations that my time allowed me to make, whilst travelling between the different quartz-mining centres. Not having seen enough, therefore, to attempt any geological classification of the drifts, I will simply separate them into "newer" and "older," "upper" and "lower" drifts, as the case may be—main divisions, the existence of which everyone interested in the matter will easily recognise on visiting the Gold Fields.

Newer Drift.—Under this head belong all those extensive striking terrace formations of shingle and sand and a certain thickness, running from a few to perhaps over 100 feet of the flat stratum of similar material on which they rest, accumulated in those far-stretching, wide portions, of the present river-valleys, the original character of which as lake basins has long been recognised. The terrace formations of shingle, etc., resting on the rock of the ranges, fringing the valleys, the drift occurring in the smaller valleys or gullies between the ranges and the real river drift, are also here included. Besides the extensive sluicing operations which I saw executed in this drift along the banks of the Molyneux, Kawarau, and Shotover Rivers, the really grand scale on which hydraulic sluicing is carried on at Tinker’s (Blue Duck Claim, Manager, Mr. J. Spratt), and Dry Bread digging, excited most my admiration. To give an idea of the scale, I may mention that at Dry Bread, Greenbank and Company use 40 sluice heads of water with a mean vertical pressure of 130 feet, lessened about 25 feet through friction in the pipes, and have 4,500 feet of iron piping, besides an expensive stock of necessary appurtenances on the ground Although the stuff washed is very poor, still the enormous quantity sluiced through in a short time, work being carried on day and night, renders the operation highly profitable. Work like this is entirely unknown in Victoria; perhaps the only other place in the world where it is practised being California. The thickness of the drift which rests on the so-called "Maori bottom" surpassed, in some places, 30 feet, and considering this in connection with the promis- page 181cuous way in which, patches of it are worked along the foot of the Dunstan Range, though the generality are in front of, or near, the mouths of large permanent creek-valleys, one cannot help coming to the conclusion that the gold extends all along the foot of that range, the richer accumulations existing most probably in front of where the latter is most broken by rifts and gullies, whilst towards the centre of the wide valleys, it no doubt decreases in quantity, owing to causes to be explained further on. And the same chance I believe exists not only along the foot of the range on the opposite side of the wide valley, but also round the edges of all the other large old lake-basins. In fact, the resources of the Province of this kind of auriferous drift alone are practically inexhaustible, and their successful development only requires more of the enterprise and energy, as displayed by Greenbank and Company, in rendering the splendid water resources of the Province available for hydraulic sluicing. As some of the places which I consider very promising, and certainly deserving of the special attention of the drift miner, I may mention the part of the old Clutha lake-basin in the angle where the Bendigo Creek enters, and along the foot of the range on which the Bendigo Reefs occur. Also the extensive, so-called Miller’s Flat, between Arrow and Queenstown, which, to all appearances, represents an old channel of the Shotover River, and should, as such, be very rich, judging from the splendid yields obtained from the river workings higher up. Mr. Warden Beetham first drew my attention to this dormant field, the high prospective mining value of which is believed in by many miners in the district. Another very promising area I take also to be the extension of Macrae’s Flat towards the Taieri River.

Older Drift.—This comprises all those enormous deposits of harder gravel and cement called "false bottom," "Maori bottom" from its brown colour,—upon which the newer drift rests in the extensive old lake-basins of the Manuherikia, Upper Taieri, Clutha, and other river valleys. Also, the cement and gravel worked on the tops of the ranges between Milton and Havelock, that remarkable cement deposit of the Bluespur, near Lawrence, and the false bottom of Weatherstone and Waitahuna Flats, which three latter it must be borne in mind, represent also nothing else than lacustrine deposits, though small in surface extent, yet of comparatively great depth. The character and relation of all these deposits to the newer drift would at once suggest, to anyone acquainted with the gold fields of Victoria, the existence of runs or leads in their deepest parts or gutters; for, from the fact that they are all composed of the same kind of rock-material as the newer drift, there is no reason why they should not be equally auriferous. But yet, on comparing the relative conditions under which deposition of water-worn material takes place in lakes and watercourses—river and creek channels—which latter the Victorian deep leads unmistakably page 182represent, we find great differences; namely, whilst in a continuous watercourse, with evenly falling bottom, the current is steady onward, deposition takes place all along, and—leaving exceptions, caused by turns and local obstructions unconsidered,—the heaviest material settles in the deepest part, it is not so in a lake. There the current of the water of a river, or any smaller watercourse, one entering at one end, or any part round the circumference of the lake, gets suddenly checked either on account of the surface expanse or the depth, or both combined, of the stagnant mass of water, and the consequence is that the heaviest of the waterworn material (including, with regard to both the newer and older drifts, most of the gold), settles along the side of the lake-basin, whilst towards the centre of the latter, there is gradually less and finer material deposited. And this process goes on tilt the basin is ultimately filled up, though towards the other end or outlet of the lake, the deposited material will then consist of an increasing thickness of poor and light stuff at the bottom, and a thinning stratum of heavy one at the top. Of course the more inlets or sources of supply the lake has, the more they vary in strength, the more irregularly they are distributed around the margin of the lake, and the nearer its outlet, the more irregularity will be observed in the arrangement of heavy and light material towards the latter part and the centre. For these reasons, therefore, the old deposits of the lake-basins mentioned do not, in my opinion, contain deep leads in the true meaning of the term, but what I think very likely, is, that a certain width around the circumference of each deposit is auriferous and payably, or, perhaps, richly so in front and near the mouths of old, or of those present main-watercourses, which seem also to have been the sources of supply in olden times. And thus, these sites would, respecting the Manuherikia basin, for instance, conform with those of the present upper drift workings (Tinker’s, Dry Bread, St. Bathan’s, &c.) Touching the payable character of the drift, the fact that the top part, as far as tried, contains no or but small traces of gold seems to indicate that, as is the case with the older drifts of Victoria, the gold is concentrated—has settled—in one, or perhaps several, thin layers of washdirt. If it were generally dispersed from top to bottom, the drift would, except in case of great richness, not pay to work on account of the difficulty and expense. Only in cases of circumscribed basins, there would be chance, especially if the inflowing currents were strong and much charged with material, of coarse stuff, and gold being distributed all over the basins, though the heaviest stuff and richest gold would likewise be deposited partly on the inlet sides, partly on those rises on which the currents impinged; and, if these were steep, it would partly also slide down to the deepest parts of the basins. Of this feature, the Bluespur furnishes, in my opinion, a striking example. In a long, but very narrow basin, the gold might also page 183be carried by the current far down the centre, and if supplies came in at places down the sides, such a trough might prove auriferous for its whole or the greater part of its length, just according to the number and position of these supply channels. In this respect the valley of the Waipori (false bottom), offers, I think, by no means a bad chance. If anything deserves the term "lead," it would be the old drift-filled channels leading into or connecting two or more lake-basins, lying in the same line of drainage, or the end channels leading towards the sea. Of such leads, some have been wholly or partly removed by denudation—they once existed over our heads, as Mr. Vincent Pyke aptly remarked to me for instance, that between the Bluespur and the false bottom of Weatherstone Flat, and part of the one that must have supplied the Bluespur from the north-west, both which, with the denudation of adjoining parts of the latter itself, respectively furnished the gold to Gabriel’s and Munroe’s Gullies. The cement deposit on top of the ranges between Milton and Havelock may also represent remnants of denudation of such a lead. However, I am convinced there are some channels of this kind yet existing, which it would be advisable to look for; for instance, two—one connecting the old drift-lakes of Weatherstones and Waitahuna Flats, and the other which fed the Bluespur from beyond Munroe’s Gully. In fact, I think, there is even a likelihood of the existence of similar deposits as the Bluespur in that direction. From what I learned about the Cardrona workings, they certainly seem to represent a true old lead, and so does also a deposit, Mr. H. J. Cope kndly informed me of, namely a succession of cemented gravel hills, commencing at the Eight-mile Diggings, Arrow River, at a height of at least 500 feet above Arrow, and dividing into two branches,—one terminating at Roaring Billy, the other at the Arrow River, about one mile from Arrowtown. This lead has in places been worked by adits, and found highly payable. In summing up my observations about the old drifts, I certainly think it not only very promising and advisable to prospect for the old channels between certain of the lake-basins mentioned, but also to test the false bottom of the lake-basins themselves at the places previously indicated. The cheapest and most convenient mode of effecting these trials would, no doubt, be by boring.