Deep Sinking and Deeply Seated Wealth

Progress, Volume IV, Issue 6, 1 April 1909, Page 199

Deep Sinking and Deeply Seated Wealth

11l the North the great question of the Thames goldfield is of getting the flood mine water out so that the lower deeps may repeat the fairy stories contributed by the upper levels to the history of quartz mining in the Dominion. Scheme after scheme of pumping, all based on Government subsidies, has been published and tried and for some reason has not prospered as it was expected to prosper. The fight goes on against nature, circumstances, and the speculator, who is often the greatest hindrance to true mining. In the midst of the controversy it is interesting to cast our eyes across to the Victorian goldfields, the Bendigo district of which is remarkable for the deepest mines in the world. We talk with breath almost bated of 1000 feet. There they reckon a mile as the limit possible, but not to be astonished at and likely to be one day left behind. The history of the sinking which has reached that astounding depth in the Victorian mining centre is full of enterprise and resource beyond the common, to say nothing of faith and courage beyond the power of belief. In the beginning the gold of Bendigo was alluvial, and men got rich by scratching the surface. Gradually the gold receded into the lower regions and was followed by increasing pertinacity and by increasing rewards. The famous ' ' Saddle reefs were discovered, and fortunes were made. These run continuously for long distances and for the whole of these distances not a duffer has ever been encountered. Three such lines stand out prominently as profitable, but there is no reason, the experts say, for believing that many more may not be discovered in the same formation, which is very extensive. The fear is that the policy of "Sink, sink, sink," which has done so much in the past, is approaching the end. In other words, after a history of golden yields improving directly as the depths, the time has arrived when it will not pay to take gold out of mines at these great depths. "Poor country," not "Worked out" is the cry beginning to be heard. It has driven private enterprise, which has held up its head so high in these regions, and done so much for the development of the quartz industry, to ask for Government help. The two best mines along the runs above described are, according to the director of the Bendigo School of Mines, the New Chum Railway, and the Victoria Quartz. Of these two the Victoria is the deeper — it is now being tested at a depth of 4,525 feet, a depth at which the illustration we publish in connection with the subject was taken — and the hopes of the deep sinkers are concentrated upon its fortunes. At 150 feet this mine paid £218,000 in dividends. At depths descending to 1,000 feet nothing was got worth speaking of. At 1100, 1700, 1800, 1900 feet the yields were enormous even for Bendigo. From the last to over 2600 the miners struck nothing. At 2700 the mine paid £90,000 in dividends before it gave out. In consequence of this alternation of success and failure, the former paying off the cost of the latter and

giving riches in addition beyond the dreams of avarice, the policy of "Sink, sink, sink" was persevered with. But now there is a change. The new reefs struck are large and imposing as ever, but they are not profitable. Depth after depth has been explored to the 4500 feet level mentioned above, without any good results. The rest of the story we will leave to be told by the expert afore mentioned (Mr. Donald Grant, M.M.E.), who has permitted us to extract from his sketch of Deep Sinking at the Bendigo Quartz Mines.

Mine Ventilaton. The management of the Victoria Quartzmine is under the guidance of Mr. Wilfred Rickard, who has been in charge for seventeen years. If the present reef carries

gold, Mr. Rickard can pay all expanses, and also do development work, on sdwt. per ton — truly a great performance from a reef nearly a mile deep. It is owing to his foresight that the mine can be wo eked now. Years ago Mr. Rickard made it imperative that adequate ventilation should be provided for at every stage, with the result that a fine stream of air is circulated by natural means even at the lowest levels. The shaft is a downcast; the air go°s to the bottom, and returns through the centrecountry winzes to the 3,384 ft. levei, and up the 180 Mine.

Rock-Temperature. The temperature of the water issuing from the rock at the bottom of the wime is 114° Fahr., but it cools rapidly — eveu in fa] i ing 3ft. after issuing from the icck the

temperature falls 6° Fahr. The temperature of the rock from a hole bored for 9ft. m the face of a dead end was ll"^ 0 Fahi. It might be imagined that it would be impossible to wrok with such surrounding temperature, but the incoming air. if not saturated, soon chills down the hot rock, and leaves a cold skin on the surface, through which the heat from the interior diffuses slowly; further, the issuing water i" soon cooled down. The water baled from below is only '86° to 88°, and the temperature of the air at the 425 ft. level varies from 72° to 75°, the higher temperature, as a rule, depending on the temperature of the air above. For instance, when it was 75°, the shade temperature on top was 95°, and when 72° the shade temperature was below 60°. I\l>. Rickard finds that the air is heated about 1° for every 100 ft. of

drives or crosscuts it passes through at the lower level; he also finds that he obtains better ventilation with north than with south winds — an opposite result from that obtained in shallow mines. The pressure of the air is equal to 34.75 in. of mem ry at the bottom, and water boils at 218.4°.

Gold at a depth of 5,000 feet. It is felt that the future of deep sinking in Bendigo will depend on the results obtained in this mine, or its deep rival, the New Chum Railway. Very few other fields have the same conditions. In many the reefs become poor, or pinch out altogether. Here it has been proved, contrary to the opinions once expressed, that quartz bodies, just as large, exist a mile below as at the surface. It has been proved that they have been just as good at 3,000 ft. as at shallow

levels. It lias been proved that low-grade stone would pay even at great depths ; but, unless some better encouragement is obtained in opening up the reefs now disclosed at the lowest levels in both these mines, it is certain that the shareholders, who have done so much, must reluctantly abandon them. If once abandoned, then there is only the remotest chance of work being again started, for it will mean shutting down mine after mine right along the line. No better opportunity for the Government exists than to aid the industry by continuing the work so long carried on without result by the shareholders of this company. The mine is well equipped, and with a few minor alterations the present plant could sink another 1,000 ft.. The cost of sinking and timbering complete at the lower levels amounts to £5 16s. per foot;

the water is comparatively light; and the centre country is camparatively close to the shaft. The conditions as to ventilation are such that another I,OOOft. will not make matters worse than at present. It may be said that, owing to the pitch of the country, other mines at a lesser level are in th i same formation as the Victoria Quartz ; but this aspect of the question, although interesting geologically, must not be measured against the commercial nature of the undertaking. If gold is got at a depth of over 5.000 ft., such as was obtained at 3,000 ft., then it means a new life for many mines which are now on the po ; nt of closing down.

Note above that ventilation is reported secure down to 6000 feet. If gold is plentiful refrigerating machinery will offer great possibilities. — Ed. P.