Getting Gold: A Practical Treatise for Prospectors, Miners and Students Part 9

A good furnace should bring down the sulphur contents even of concentrates so as to be innocuous to mercuric amalgamation. The sulphur left in the ore should never be allowed to exceed two per cent.

A forty per cent pyritous or other sulphide ore should be roasted in a revolving furnace in thirty to forty minutes, and without any auxiliary fuel.

For ordinary purposes a 40-foot chimney is adequate for furnace work; such a chimney four feet square inside at the base, tapering to 2' 6" at the summit, will require 12,000 red bricks, and 1500 fire-bricks for an internal lining to a height of 12 feet from the base of the chimney shaft.

When second-hand Lancashire or Cornish boiler flues are available, they make admirable and inexpensive chimneys. The advantage of wrought-iron or steel chimneys lies in the convenience of removal and erection. They should be made in sections of 20 feet long, three steel wire guy-ropes attached to a ring, riveted to a ring two-thirds of the height of the chimney, and attached to holdfasts driven into the ground; tightening couplings should be provided for each wire.

Flue dust depositing chambers should be built in the line of the flues between the furnace and the chimney; they consist simply of carefully built brick chambers, with openings to enable workmen to enter and rapidly clear away the deposited matters. The chambers, three or four times the cross sectional area of the chimney flue, and ten to twenty feet long, can be built of brickwork, set in cement; the walls are provided with a cavity, filled with sand or Portland cement, so that there will be no danger of the incursion of air. In all furnace work the greatest possible precautions should be taken to prevent the least cracking of either joints or bricks. It is surprising how much the inadequate draft of a good chimney is due to cracks or orifices in the flues; and therefore a competent furnace-man should see to it that his flues are thoroughly sound, and free from openings through which the air can enter.[*]

[*] For full details of the most recent improvements in the cyanide process and in other methods of extraction, the reader is referred to Dr. T. K. Rose's "Metallurgy of Gold,"

third edition.

CHAPTER IX

MOTOR POWER AND ITS TRANSMISSION

It is unnecessary to describe methods by which power for mining purposes has been obtained--that is, up to within the last five years--beyond a general statement, that when water power has been available in the immediate locality of the mine, this cheap natural source of power has been called upon to do duty. Steam has been the alternative agent of power production applied in many different ways, but labouring under as many disadvantages, chief of which are lack of water, scarcity of fuel and cost of transit of machinery. Sometimes condensing steam-engines have been employed. For the generation of steam the semi-portable and semi-tubular have been the type of boiler that has most usually been brought into service. Needless to say, when highly mineralised mine water only is available the adoption of this cla.s.s of boiler is attended with anything but satisfactory results.

Recently, however, there is strong evidence that where steam is the power agent to be employed the water-tube type of boiler is likely to be employed, and to the exclusion of all other forms of apparatus for the generation of steam. The advantages of this type, particularly the tubulous form (or a small water tube), made as it is in sections, offers unrivalled facilities for transport service. The heaviest parts need not exceed 3 cwt. in weight, and require neither heavy nor yet expensive brickwork foundations.

WATERLESS POWER.

The difficulties in finding water to drive a steam plant are often of such a serious character as to involve the abandonment of many payable mines; therefore, a motive power that does not require the aqueous agent will be a welcome boon.

It will be a source of gratification to many a gold-claim holder to know that practical science has enabled motive power to be produced without the necessity of water, except a certain very small quant.i.ty, which once supplied will not require to be renewed, unless to compensate for the loss due to atmospheric evaporation.

Any carbonaceous fuel, such as, say, lignite, coal, or charcoal, can be employed. The latter can be easily produced by the method described in the Chapter on "Rules of Thumb," or by building a kiln by piling together a number of trunks of trees, or fairly large-sized branches, cut so that they can be built up in a compact form. The pile, after being covered with earth, is then lighted from the base, and if there are no inlets for the air except the limited proportion required for the smouldering fire at the base, the whole of the timber will be gradually carbonised to charcoal of good quality, which is available for the waterless power plant.

The waterless power plant consists of two divisions: First, a gas generating plant; secondly, an internal combustion or gas engine in which the gas is burnt, producing by thermo-dynamic action the motive power required. The system known as the Thwaite Power Gas System is not only practically independent of the use of water, but its efficiency in converting fuel heat into work is so high that no existing steam plant will be able to compete with it.

The weight of raw timber, afterwards to be converted into charcoal, that will be required to produce an effective horse-power for one hour equals 7 lb.

If coal is the fuel 1 1/3 lb. per E.H.P. for one hour's run.

If lignite is the fuel 2 1/2 lb. per E.H.P. for one hour's run.

The plant is simple to work, and as no steam boiler is required the danger of explosions is removed. No expensive chimney is necessary for the waterless power plant.

Where petroleum oil can be cheaply obtained, say for twopence per gallon, one of the Otto Cycle Oil Engines, for powers up to 20 indicated horse-power, can be advantageously employed.

These engines have the advantage of being a self-contained power, requiring neither chimney nor steam boiler, and may be said to be a waterless power. The objection is the necessity to rely upon oil as fuel, and the dangers attending the storage of oil. A good oil engine should not require to use more than a pint of refined petroleum per indicated horse-power working for one hour.

Fortunately for the mining industry electricity, that magic and mysterious agency, has come to its a.s.sistance, in permitting motive power to be transmitted over distances of even as much as 100 miles with comparatively little loss of the original power energy.

Given, that on a coal or lignite field, or at a waterfall, 100 horse-power is developed by the combustion of fuel or by the fall of water driving a turbine, this power can be electrically transmitted to a mine or GROUP OF MINES, say 100 miles away, with only a loss of some 30 horse-power. For twenty miles the loss on transmission should not exceed 15 horse-power so that 70 and 85 horse-power respectively are available at the mines. No other system offers such remarkable efficiencies of power transmission. The new Multiphase Alternating Electric Generating and Power Transmission System is indeed so perfect as to leave practically no margin for improvement.

The multiphase electric motor can be directly applied to the stamp battery and ore-breaker driving-shaft and to the shaft of the amalgamating pans.

APPROXIMATE POWER REQUIRED TO DRIVE THE MACHINERY OF A MINE.

Rock breaker 10 effective horse-power Amalgamating pan 5 effective horse-power Grinding pan 6 effective horse-power Single stamp of 750 lb. dropping 90 times per minute 1.25 effective horse-power Settlers 4 effective horse-power Ordinary hoisting lift 20 effective horse-power

Allow 10 per cent in addition for overcoming friction.

Besides this electrical distribution power, which should not cost more than three farthings per effective horse-power per hour, the electrical energy can be employed for lighting the drives and the shafts of the mine. The modern electrical mine lamps leave little to be desired. Also it is antic.i.p.ated that once the few existing difficulties have been surmounted electric drilling will supplant all other methods.

Electric power can be employed for pumping, for shot firing, for hauling, and for innumerable purposes in a mine.

Electricity lends itself most advantageously to so many and varied processes, even in accelerating the influence of cyanide solutions on gold, and in effecting the magnetic influence on metallic particles in separating processes; while applied to haulage purposes, either on aerial lines or on tram or railroads, it is an immediate and striking success.

It is antic.i.p.ated that in the near future the mines on the Randt, South Africa, will be electrically driven from a coalfield generating station located on the coalfields some thirty miles from Johannesburg. Such a plant made up of small multiples of highly efficient machines will enable mine-owners to obtain a reliable power to any extent at immediate command and at a reasonable charge in proportion to the power used. This wholesale supply of power will be a G.o.dsend to a new field, enabling the opening up to be greatly expedited; and no climatic difficulties, such as dry seasons, or floods, need interfere with the regular running of the machinery. The same system of power-generation at a central station is to be applied to supply power to the mines of Western Australia.

CHAPTER X

COMPANY FORMATION AND OPERATIONS

All the world over, the operation of winning from the soil and rendering marketable the many valuable ores and mine products which abound is daily becoming more and more a scientific business which cannot be too carefully entered into or too skilfully conducted. The days of the dolly and windla.s.s, of the puddler, cradle, and tin dish, are rapidly receding; and mining, either in lode or alluvial working, is being more generally recognised as one of the exact sciences. In the past, mining has been carried on in a very haphazard fashion, to which much of its non-success may be attributed.

But the dawn of better days has arrived, and with the advent of schools of mines and technical colleges there will in future be less excuse for ignorance in this most important industry.

This chapter will be devoted to Company formation and working, in which mistakes leading to very serious consequences daily occur.

It is not necessary to go deeply into the question why, in the mining industry more than any other, it should be deemed desirable as a general rule to carry on operations by means of public Companies, but, as a matter of fact, few names can be mentioned of men who mine extensively single handed. Yet, risky as it is, mining can hardly be said to be more subject to unpreventable vicissitudes than, say, pastoral pursuits, in which private individuals risk, and often lose or make, enormous sums of money.

However, it is with Mining Companies we are now dealing, and with the errors made in the formation and after conduct of these a.s.sociations.

The initial mistake most often made is that sufficient working capital is not called up or provided in the floating of the Company. Promoters trust to get sufficient from the ground forthwith to ensure further development; the consequence being that, as nearly 99 per cent of mining properties require a very considerable expenditure of capital before permanent profits can be relied on, the inexperienced shareholders who started with inflated hopes of enormous returns and immediate dividends become disheartened and forfeit their shares by refusing to pay calls, and thus many good properties are sacrificed. In England, the companies are often floated fully paid-up, but the same initial error of providing too little money for the equipment and effective working of the mine is usually fallen into.

Again, far too many Companies are floated on the report of some self-styled mining expert, often a man, who, like the schoolmaster of the last century, has qualified for the position by failing in every other business he has attempted. These men acquire a few geological and mining phrases, and by more or less skilfully interlarding these with statements of large lodes and big returns they supply reports seductive enough to float the most worthless properties and cause the waste of thousands of pounds. But the trouble does not end here.

When the Company is to be formed, some lawyer, competent or otherwise, is instructed to prepare articles of a.s.sociation, rules, etc.; which, three times out of four, is accomplished by a liberal employment of scissors and paste. Such rules may, or may not, be suited to the requirements of the organisation. Generally no one troubles much about the matter, though on these rules depends the future efficient working of the Company, and sometimes its very existence.

Then Directors have to be appointed, and these are seldom selected because of any special knowledge of mining they may possess, but as a rule simply because they are large shareholders or prominent men whose names look well in a prospectus. These gentlemen forthwith engage a Secretary, usually on the grounds that he is the person who has tendered lowest, to provide office accommodation and keep the accounts; and not from any particular knowledge he has of the true requirements of the position.

The way in which some Directors contrive to spend their shareholders'

money is humorously commented on by a Westralian paper which describes a great machinery consignment lately landed in the neighbourhood of the Boulder Kalgoorlie.

"It would seem as if the purchaser had been let loose blindfold in a prehistoric material-founder's old iron yard, and having bought up the whole stock, had shipped it off. The feature of the entire antediluvian show is the liberal allowance of material devoted to destruction.

Ma.s.sive kibbles, such as were used in coal mines half a century ago, are arranged alongside a winding engine, built in the middle of the century, and evidently designed for hauling the kibbles from a depth of 1000 feet. Nothing less than horse-power will stir the trucks for underground use, and their design is distinctly of the antique type. The engine is built to correspond--of a kind that might have served to raise into position the pillars of Baalbec, and the ma.s.s of metal in it fairly raises a blush to the iron cheek of frailer modern constructions. The one grand use to which this monster could be put would be to employ it as a kedge for the Australian continent in the event of it dragging its present anchors and drifting down south, but as modern mining machinery the whole consignment is worth no more than its value as sc.r.a.p-iron, which in its present position is a fraction or two less than nothing."

Next, a man to manage the mine has to be obtained, and some one is placed in charge, of whose capabilities the Directors have no direct knowledge. Being profoundly ignorant of practical mining they are incompetent to examine him as to his qualifications, or to check his mode of working, so as to ascertain whether he is acting rightly or not. All they have to rely on are some certificates often too carelessly given and too easily obtained. Finally, quite a large proportion of the allottees of shares have merely applied for them with the intention of selling out on the first opportunity at a premium, hence they have no special interest in the actual working of the mine.

Now let us look at the prospects of the a.s.sociation thus formed. The legal Manager or Secretary, often a young and inexperienced man, knows little more than how to keep an ordinary set of books, and not always that. He is quite ignorant of the actual requirements of the mine, or what is a fair price to pay for labour, appliances, or material. He cannot check the expenditure of the Mining Manager, who may be a rogue or a fool or both, for we have had samples of all sorts to our sorrow.