33

H.—3

generally rendered quite useless. It maintains, of course, a certain value, if shaft sinking from it, and erection of hoisting and pumping machinery in a chamber constructed inside, have to be adopted for deeper working. But in such cases it is generally questionable, considering the discomfort and greater expense of this method, whether the working by shaft right from the surface might not in reality have been the cheapest at the start. 3. Whilst every lower adit will generally be much longer, and consequently more costly than the preceding higher, useless one, and take a longer time in construction, a good shaft remains permanently useful for direct deeper working, and in the generality of cases a new block of a reef will thereby be opened far sooner and cheaper than by a long adit coming in at the same depth. Where adits are considered the most advantageous, and the prospects of a reef under-foot of an upper adit warrant it, an intended lower one should by rights always be commenced at tho same time as the exploitation of the reef above the upper adit, in order to .render the interval between the productive periods of working as short as possible. 4. In case of the abandonment of a mine, the machinery attached to a shaft has always a certain value. These several conditions on the question of " shaft v. adit " are only intended, however, to bear upon the real opening and working of single mines. Shafts- are out of the question in tho case of large main adits, intended for working several adjoining mines or of draining them of water, or of such to be driven for prospecting purposes at considerable depth across the country. For both these kinds of adits, the Carrick, Bendigo, and Skipper's Creek districts offer special inducements and facilities; and whilst at Bendigo a Deep Tunnelling Company is already in operation, another is contemplated to be formed at the Carrick Range. Particulars about these are given in the respective appendices. Exploitation of the Reefs. —The matter of exploitation, or of working the reefs, practised in the progressive mines of the different reefing districts, is, one single case excepted, " over-hand stoping," and I must say that, unless the broken nature of the ground prevented it (Nugget and Cornish, Skipper's Creek), wherever tho mines were far enough advanced (most of the mines on the Carrick reefs), I find this mode of working carried out systematically, and with due regard to rendering levels and winzes safe, by timbering and filling worked-out places with mullock. The exceptional case alluded to is Logan's Reef Mine, which, considering the small width of the reef, is, contrary to general mining rule, worked by " underhand stoping," and very economically, I must admit; yet, in a certain measure, at the expense of safety to the workmen, by not properly filling the worked-out spaces with waste. Speaking generally, this method, which is only practised in very wide lodes (two to three fathoms) —for instance, in Cornwall —has, no doubt, many advantages over stoping over-hand; but also very serious disadvantages. As the principal advantages may bo mentioned, that working, by being carried on downwards, is easier, allows the use of heavier tools, and the men stand secure and convenient; whilst in over-hand stoping it is more inconvenient and tiring, though the weight of the rock, in acting downwards, facilitates it; it is also more dangerous, especially in jointed, fissured, and loose ground, as the men have to work underneath. Tho disadvantages of underhand stoping consist chiefly in the great expense entailed by the necessar3 r timbering and mode of disposing of the waste in the filling up of the worked-out places, it (the waste) having to be piled on platforms in front of the stopes. Next comes, that more manual labour is required in raising the ore from stope to stope, that the miner has to contend with water, and is often troubled with bad air. These drawbacks are so serious that, according to mining report, the method comes more and more out of use, and is likely to be entirely superseded by over-hand stoping. As working is at present being carried on in the progressive mines I examined, hardly anything is done in prospecting the country in the hanging and foot walls of the reefs ; but as this is of great importance and often very profitable, touching the discovery of rich, small companion reefs, branches and leaders, the driving of occasional small crosscuts ought not to bo neglected. Before leaving this subject I have to draw special attention to one great defect I found in the management of most of the mines, namely, the non-provision of correct and detailed plans of the workings. I need not enter upon detailing the advantages such plans have in the systematic management of a mine, and the understanding and tracing of occurrences of unforeseen mining features (faults, turns, breaks of the reefs, &c). Every experienced mining manager knows these well enough. But I must say that, before entering upon the driving of adits, preliminary mining surveys of the ground and tho preparation of working plans are quite indispensable, in order to avoid false conclusions as to distances, errors in direction, &c. (See Lucknow Reef, in appendix 6.) The reason of these deficiencies hitherto consists, I was informed, in the want of qualified mining surveyors, and, considering tho importance of the subject, I would therefore take the liberty to recommend the Government to appoint several surveyors of this class for the principal mining centres. Touching the duties of these gentlemen, they might, as is the case in Victoria, consist in the surveying of leases and claims, and in the execution of over and under-ground mine surveys, all which, as private work, to be paid for by the parties requiring it; whilst, during intervals between such work, the preparation for the Government of detailed topographical plans of the mining districts, to aid geological examination, might be carried on at certain fixed rates. Chances of Peospectino foe New Aueifeeous Reeps. As regards the chances of the occurrence of other auriferous reefs in the districts under notice, I consider them to be very good. In the neighbourhood of Saddle Hill Reef, several (four) good-looking, strong reefs crop out, which, as superficial prospecting has already proved them to be slightly auriferous, might likely yield payable stone on being tried at other points in their lines of strike. But, besides this, there is, in my opinion, a very good chance of the existence of an auriferous reef about the head of a highly auriferous gully, worked abreast of the Saddle Hill Reef, on the right hand side of the main road leading from Dunedin to the Taieri. In the neighbourhood of the Canada Reef, Tokomairiro, the finding of rich quartz specimens outside the lines of the reefs opened, coupled with that of rich, nuggetty gold in the north branch of the Tokomairiro River, is pretty good evidence of the occurrence of other auriferous reefs in that district. That the Gabriel's Gully reef should be the only auriferous one in the Tuapeka district is also very unlikely. And, touching the country round 5—H. 3.