OUR INDUSTRIES. HOW TO MAKE GOLD-MINING PAY.

Otago Witness, Issue 1688, 29 March 1884, Page 8

OUR INDUSTRIES. HOW TO MAKE GOLD-MINING PAY.

(Written for the Qtatfo Witnem.) By JOHN A. MILLER. Chapter VII. — A Few Practical Observations. It is intended to treat in this chapter on a few items which are of value to practical men. rather than to the general mining speculator. , Cross-driving. — It is surprising to note the little resort which is had in New Zealand to cross-driving. There is scarcely a' mine in Victoria where cross-drives have not furnished a cry considerable quotum to the total yield of the mine. Nearly all reefs are accompanied by leaders or veins at greater or lesser distance from the main reef,, and which frequently are highly payable. Sometimes these veins' join the reef, when they are called feeders,, making the reef where they join it very rich. * Crossdriving should be much J more 1 Extensively undertaken in the exploration of mines than has hitherto been the case. If systematically followed there can be no doubt but it will lead to payable results, and cannot fail' in many cases to yield valuable information on the nature and character of New Zealand reefs, of which so little is as yet known and understood. . l - '; }'<•"' ' Fossicking. — With few exceptions, l the' system ot mining which obtains at present on most fields in the Colony is a kind of' from day to day style, aud mines are only being worked after a kind of " fossicking V manner., /While this "fossicking" is going on, nothing is. dona to open the mine, so as to follow up. the first crushing with another one, and as a rule a large amount of dead work haß to be done before more payable' stone can be taken out. This is the result of a want of system and of proper plans, for which the directory alone is answerable. The work of raising stone and of opening out the mine should always be going on at the same time, and the supply of -cake kept up constantly, until the mine is 'worked out. Under the present system of working, mines are being " mullocked " until the shareholders lose all faith in them, and they are abandoned as worthless and unpayable before they have been fairly opened out or'prospected. A quptation from a recent number of the Otago i Daily Times, may conclude 1 this observation: "Not until it is recognised bjr directors that the safety of the public, the safety of their own particular ventures, and even that of an important industry, depends primarily>upon the systematic - opening ' out and working of mines, and not on the artificial, price of its scrip, need any permanent and -lasting results be looked -for from mining enterprises, whereever carried on."- *It may ■be- added nothing>but the value of ' New Zealand* mines has prevented mining from dying ant unnatural death, and being strangled by a pernicious system, which, if applied- to any other, vocation wouldjphave long ago pressed the (life out of it. • Quicksilver. — A reference^ to. thei "proposal ■ to dispense with > quicksilver' in crushing machines may here' be. made, although the particulars have already been fully explained in' these articles. The- experiments tried in Obago to > do, away with quicksilver altogether have been pronounced entirely satisfactory in two instances/ in both of which the experiments have been on a sufficiently large scale to entitle them to be considered as coDclusive. But for the, reasons given it would, nevertheless, be preferable to use quicksilver in the stamper boxes, and have a number of quicksilver wells • soine, distance apart from each other. Beside? the experiments here referred to it may .be mentioned that the system of gold saving without copper plates has been extensively tried and universally employed by the Port Phillip, Company at Cluues, in Victoria, for, a long number of years. t ...-. v „•_,... Dynamite. — A few remarks on dynamite may also be considered as a practical item under, this heading. The difference between ordinary blasting powder and dynamite is that the former is granular and .the .latter is one c6mpact thas3." In the explosion,' of one grain sets fire^t'6 k and , expl6des Ol tne,. other, and the act of explosion extends therefore over a measurable length .of time; whereas in dynamite the explosion of the whole charge is almost instantaneous.' It follows therefore that 4 in open and loose-grained rock powder may be more effective, because its force if not so great as that of dynamite, is not so quickly spent. But by experiments which the writer himself has made, and which, so far as he knows," ate the first of the kind, the effectiveness of dynamite in open rock may be greatly 1 " inprestesd by " breaking " the charge ; that is by 1 inserting a portion of the charge with a ccatp t only, and no fuse, in the bottom of the hole, tamping up a portion and then inserting "the-'proper charge with cap and fuse attached. In this case the first charge explodes the second 'at,£he bottom of the hole, and very "good .results- have been obtained from this plan. At Macetown and Skippers the plan .of tamping dynamite ia pretty universally followed, and so far has not been attended by any serious accident, but the greatest care must be taken in tamping down the first few inches of the hole. It is still a prevailing notion amongst miners that dynamite acts- downwards. This, of course, ■iB altogether a mistake. Like every other explosive it acts in the direction of the least resistance, but in all blasting compounds in which nitro -glycerine forms the explosive medium, the shock of the explosion is bo sudden, that the atmosphere by its weight a<?ta witn sufficient resistance to cause very considerable effects. This ia proved by placing a charge of dynamite upon the surface of a stonej wjthout any bqrohole aj; all, only putting' over the charge a little wet clay; it does "not.matter how little, even if it were leas in weight than the charge itself, all that is required^ being the exclusion of the air, when this has been secured the desired result will be attained if enough' dynamite has been y}se(|. * l " '" 'n :