Coal has been mined under the sea for many years in Cape Breton, and, in the future, the bulk of the Coal output of this island will have to come from submarine territory. In fact, the time is not far distant when the percentage of submarine coal will exceed that of the coal taken from the land areas, taking the Province as a whole.
The workings of No. 1 Colliery of the Nova Scotia Steel & Coal Company at Sydney Mines are the most extensive under-sea workings, occupying an area of 3 square miles under the entrance to Sydney harbour. The face of the deeps, in 1916, was about 1¾ mile distant from the shoreline, and the workings are being further extended through an area leased from the Dominion Coal Company, which will provide the Nova Scotia Company with an immediate extension of its submarine workings, and with access to its own areas lying farther out to sea; distant 3½ miles from the shore.
In the Lingan-Victoria basin, a limited area only of the coal seams is under the land, the bulk of the deposit being submarine. Five collieries are now working on submarine coal here, and others are projected.
In the Glace Bay basin the land area is practically worked out, that is, as far as the three upper seams--the Hub, Harbour, and Phalen--are concerned. There are, at present, six mines with workings in submarine territory.
In the Morien basin the bulk of the deposit is submarine; but it is not now being worked. In Inverness county, as elsewhere stated, the basins are mainly submarine, although there are some land areas that have not yet been developed.
The most notable submarine area is the seaward extension of the Sydney coal-field. So far as can be surmised from the geological indications on land, there is no reason to anticipate any abrupt termination of the coal seams, or any limit to their accessibility, except those imposed by the difficulties attending the extraction of coal at a point remote from the source of ventilation and mechanical power, among which problems not the least will be the expeditious transportation of the workmen to and from their work. The balance of probability is for the uninterrupted continuance of submarine coal seams beyond the physical limits of extraction, but, nevertheless, the exact conditions can only be established by exploration.
In calculations that have been made as to the available tonnage in these submarine areas, it has been usual to assume three miles from shore as the limit of extraction, but it seems reasonable to assume, from experience in other submarine coal-fields, notably the Cumberland coal-field on the west coast of England, that it will be found possible to mine coal up to a distance of between five and six miles from shore. How much farther seaward mining can be prosecuted, only time and actual experiment can demonstrate. An important factor will be the inclination of the coal seams, but so far as the Sydney submarine area is in question, the seams here dip so gently that the actual horizontal distance to be traversed will set limits to extraction before the depth of the cover, or burden of the superincumbent strata becomes too great. One limitation will be the cost of mining, and it may be the first limiting factor to make itself felt.
Many interesting problems suggest themselves as likely to arise as the extraction of the submarine areas proceeds, but the mining of the more remote areas will scarcely come within the lifetime of the present generation, whose obvious duty it will be to so prosecute the work of extraction as not to imperil the accessibility of the remaining submarine coal.
The provisions of the Coal Mines Regulation Act of Nova Scotia, relating to submarine mining, are tentative, and recognize the impossibility of making rigid rules where so much has yet to be learned from actual experience. The Act gives great discretionary powers to the Commissioner of Mines, and provides that before work is commenced in any submarine area the plans must be approved by the Inspector of Mines. Every new lift or level in a submarine mine is defined as being a new winning, requiring the sanction of the Inspector of Mines. No submarine coal is allowed to be wrought under a less cover than 180 feet of solid measures; but submarine passageways may be driven to win coal under not less than 100 feet of solid measures. When there is less than 500 feet of solid cover, submarine workings must be laid off in panels of not more than half one square mile in area; surrounded by barriers of coal not less than 90 feet thick, and pierced by not more than four passageways having a sectional area not greater than nine feet in width, and six feet in height.
The present law has not attempted to deal with the extraction of pillars in submarine territory, or to regulate the method of extraction where the solid cover exceeds 500 feet, except in making this conditional on the approval of the Inspector of Mines. The size of pillars to be left in submarine workings now proceeding or projected has in all cases been the subject of an agreement between the Inspector of Mines and the owners of the mines affected. There is reason to believe that future practice in submarine areas may permit the complete extraction of the coal without leaving any supporting pillars. It may also be found possible to use with advantage the method of "flushing" now largely adopted in European and in some United States collieries, by which the space left by the extraction of the coal is filled by sand or similar material "flushed" into the waste by admixture with water, and led into the workings by a specially constructed piping system from the surface.
The complete extraction of the coal permits of a more even settling down of the superincumbent measures, and lessens the danger of a break in the measures which might let in the sea-water.
If it is found necessary to leave permanent pillars in submarine workings, this will entail the complete loss of the coal contained in the pillars, and it will also bring into operation the limitation of extraction by the increased cost of mining at an earlier date than if it is found possible to dispense with permanent pillars, as the existence of a large area of permanently abandoned workings supported by pillars increases all mining costs, particularly that of ventilation, and adds an element of danger that is not present where the abandoned waste is completely filled, either by complete subsidence of the roof, or by some method of stowing.
If the system of mining in panels, now prescribed by the law, is followed, considerable care will have to be bestowed on the projections of the submarine workings, so as to avoid the exact superimposition or crossing of panel barriers in a higher seam upon the panel barriers in a lower seam; for presumably, if a solid block of coal surrounded by an extracted area in a lower
seam were exactly superimposed by a similar block also surrounded by an extracted area in a higher seam, or higher seams, the result would be a "hump" or inequality in the sea bottom, with a tendency to break the strata and let in the sea.
There is a marked difference between the conditions attending submarine mining on the western and eastern sides of Cape Breton island. On the western side, in the Inverness coal-field, the strata are much fractured, and the coal seams dip steeply. In the Sydney coal-field the seams are but slightly inclined, and the strata overlying and intervening between the coal seams consist of strong sandstones and impermeable marls and shales. Faults are rare, and the sea bottom is usually rock, without great thicknesses of sand or sand pockets. A great part of this submarine coal-field is territory that has been gradually encroached upon by the sea, not by subsidence of the measures, but by erosion of modern date geologically speaking. As the land area of the productive measures is remarkably free from faults or evidences of recent earth movements there seems no reason to anticipate the existence of faults in the area that has been encroached upon by the sea.
Two mines in Inverness county have been flooded by water from the sea. The Mabou mine was flooded in January, 1909, and the Port Hood mine in June, 1911.
At the point in the slope of the Mabou mine where the sea entered there was only 110 feet between the roof of the slope and the sea bottom.
In the Port Hood mine the water entered at a point where pillars were being drawn in the lowest level, supposed to be covered by 942 feet of solid measures. The inrush is estimated to have amounted to 3,000 gallons a minute in the initial stages, and the flow at the Mabou mine is thought to have been about 700 gallons per minute.
A Commission was appointed by the Nova Scotia Legislature to inquire into the causes leading to these inundations.
Concerning the Mahou incident, the Commissioners consider it was an error of judgment to have entered the seam under the comparatively thin cover, having in view the nature of the overlying strata.
Regarding Port Hood colliery, the Commissioners advise that in future "every reasonable means should be employed to ascertain the depth, nature and condition of the overlying strata before pillars are extracted in any submarine area."
The inundation of the Mabou mine was quite evidently the result of poor judgment, but the Port Hood inundation was of a sudden and unexpected nature, and while subsequent investigation showed peculiarities in the overlying strata that partly account for the inrush, it has never been shown that the break could have been guarded against.
While the actual physical conditions that led to this inundation are a matter of conjecture, and can probably never be exactly determined, it does not seem reasonable to suppose that the water from the sea entered through a vertical, or approximately vertical fracture in the roof of the seam
communicating directly with the ocean. The connexion with the sea is undoubted, because the water is certainly sea-water, and there was noticed a small daily rise and fall of the water corresponding in time to the tides, showing that the point of entrance of the water was near the shore, where the fluctuations of the tide would manifest their influence.
The pumping equipment of the mine had a maximum capacity of 110 gallons per minute, and was, of course, entirely inadequate to deal with an inrush of water of any magnitude. There was no reserve lodgment for water, and under these circumstances it cannot be said the inundation was an uncontrollable one. Much larger streams of water are being daily controlled in other Cape Breton collieries than seems to have entered at Port Hood.
The occurrence has served as a warning, and the necessity for emergency pumps and adequate lodgments in submarine areas was emphasized by this incident.
As there are no landmarks at sea, it will be necessary, when two or more seams are being worked in the same submarine area, to superimpose the plan of the workings of one seam upon those of the others, in order to gauge their relationship to each other, for where a number of seams are so shown, the result is very confusing. One method that could be used would be to paint a skeleton plan of the workings in each seam on plate glass, each seam being painted in a different colour, the plate glass sheets being placed one above another in natural order. This method has been successfully used to show intricate workings in faulted ground in the German coal-fields. The German engineers went a little further, however, and made their model to exact scale, both horizontally and vertically, showing the dip of the seams and the fault lines, so that the completed model represented in miniature a transparent cube of the earth's crust containing the mine workings.
The surveying and plotting in the submarine areas will have to be very accurately done, and subjected to most rigid checking, as there will be no opportunity for such useful checks as are made possible in land areas by shafts and boreholes.
As the method of extraction in submarine areas is subject to the approval of the Inspector of Mines, and as the Government is the lessor of the coal seams, the responsibility for the accuracy of the mine plans will necessarily be a joint one, and will not rest entirely on the coal operators.
Preparation, Washing, and Coking of Coal, and the Recovery of By-products.
The preparation of coal for the market at the Nova Scotia collieries has not yet reached the elaborate scale noticeable at European coal mines, because, hitherto,the coal has been mined from clean thick seams; but as the inferior and thinner seams come to be worked, more attention to the matter of preparation, and the rejection of impurities from the coal, will be required.
All the bankheads at the more recently developed collieries are equipped with shaking screens and picking belts. Coal is sold either as "run of mine," that is, without removal of the slack, or as "screened coal," the slack being taken out. The slack coal, made in the mining, amounts to between 25% and 30% of the runmine, and in some cases runs very much higher.
Slack coal for coke making has been washed for many years, and latterly, a little has been washed for the general market. The Dominion Steel Company has a washery on the Campbell "bumping table" principle, with a washing capacity of 100 tons per hour, which prepares coal for the coke ovens.
The Dominion Coal Company, in 1912, erected a "Baum" washer, having a capacity of 120 tons per hour; and three years later the Nova Scotia Steel & Coal Company installed a washer of the same type, but of smaller capacity. The "Baum" washer is of the "jig" type, the principal feature being, that the impulse to the washing-water in the jigs is given by compressed air. A feature of this washer is the recovery of all the fine coal, and economy in the use of washing water. The Inverness Coal & Railway Company has a small Jeffrey washer.
Several installations for briquetting slack coal have from time to time been put down. The Colonial Coal Company, one of the small companies operating in the Sydney field, successfully manufactured "ovoid" briquettes from slack coal, that found a ready sale, but the plant was destroyed by fire, and has not been rebuilt.
The analysis of the coals of Nova Scotia varies within comparatively narrow limits, and all the coals come within the bituminous class. As a rule, the purest coals are more fragile than those of lower grade. Some of the coals having a slightly higher percentage of volatile constitutents are well suited for gas-making purposes, while others with a higher percentage of fixed carbon, are preferred for steam-raising purposes, but there is a great similarity between the seams in the same district.
Comparing the different coal-fields, the Pictou seams are characterized by a high ash and low sulphur content. In the Cumberland area, some coals of remarkable purity are found in the Springhill seams, but the seams in the Joggins district have a comparatively inferior analysis. The Inverness coals are comparatively high in sulphur and ash content, and resemble the coals from the Joggins district. The best general analysis is shown by the seams in the Sydney coal-field. While, however, these comparative differences exist between the coals of the various coal-fields, a study of the table of analyses given on page 38, will show the general similarity of all Nova Scotian coals.
All the Sydney coals are suitable for coke making, and yield a good percentage of by-products. Some of the Pictou coals make an excellent coke, but not all the seams in this district yield a coking coal. Judging by the high percentage of nitrogen shown in the analysis of the Pictou coals, they should be valuable for use in any way that allows the recovery of the by-products. The Springhill coals do not yield a commercially strong coke,
"Baum" coal washing plant of the Nova Scotia Steel and Coal Company, at Sydney Mines: showing washery and concrete settling tank
"Baum" coal washing plant of the Dominion Coal Company, Sydney, N.S.: showing washery, and concrete storage pockets holding 8,000 tons of washed coal, also concrete settling tank
Blast furnaces and coke ovens of the Nova Scotia Steel and Coal Company, Sydney Mines
and the seams that are at present mined in the Joggins and Inverness districts are unsuitable for coke-making.
Coke is manufactured in by-product ovens at the works of the Dominion Iron & Steel Company and the Nova Scotia Steel & Coal Company. The by-products recovered are sulphate of ammonia, tar, and latterly, benzol. The waste gases are used in the open-hearth furnaces, in re-heating furnaces, and in the various processes of steel-making, and for steam-raising. The ovens of the Dominion Iron & Steel Company yield from eight to nine gallons of tar per ton of coal carbonized. The tar is taken by the Dominion Tar & Chemical Company, which has a plant immediately adjoining the coke ovens, and is there fractionally distilled for the manufacture of light oils, carbolic acid, creosote oil, disinfecting fluid, protective paints, pitch, and other tar products.
In 1915, the Dominion Iron & Steel Company commenced the recovery of benzol, and the distillation of toluol, at the request of the military authorities. The toluol is shipped to the Province of Quebec for nitration and the manufacture of the high explosive tri-nitro-toluol. Previous to 1915 the benzol had not been recovered.
It is also possible that the recovery of the carbolic acid for the manufacture of picric acid may be undertaken at Sydney; and in view of the large amount of explosives that are used in Cape Breton in mining coal, and in mining iron ore and limestone for the steel works, both in Cape Breton and in Newfoundland, there would seem to be an opening for the local manufacture of explosives.
It may be of interest to note that the Dominion Iron & Steel Company makes sulphuric acid, which is used in the manufacture of sulphate of ammonia, and in one or two processes connected with the manufacture of steel wire.
Surprisingly little use has been made of coal gas for illuminating and heating purposes in Nova Scotia. In the whole of the Sydney coal-field, for example, there is no gasworks, although the advantages of gas for heating and cooking, are undoubted; especially where economy of fuel and freedom from smoke is desired. With the exception of the by-product coke ovens used in the manufacture of coke for steel-making purposes, and two municipal gas works, the whole of the bituminous coal used in Nova Scotia is burned without any attempt at recovery of the by-products. The use of coke as a fuel is also unusual, and coke, made from bituminous slack coal, could in many instances be advantageously substituted for imported anthracite coal.
The manufacture of coke on a small scale nearer the larger centres of population would provide a clean fuel, and if combined with a modern plant for the recovery of the by-products, and the complete utilization of the gases, would not only provide a profitable market for slack coal, but would substitute a Canadian product for anthracite now imported from the United States.
There are very few soft coal regions where so little use has been made of coal gas and coke as is the case in Nova Scotia, notwithstanding that Nova Scotian coals are particularly suitable for gas manufacture, and are "fat" coals, yielding a larger percentage of by-products than any Canadian coals. The gas works of the Halifax Electric Tramway Company in Halifax, and the Yarmouth Fuel Gas Company, are the only gas works in the Province of Nova Scotia.
Very full details concerning the analysis of Nova Scotian coals, and of coking and washing tests, by-product recovery, boiler trials, etc., will be found in the Report on the "Coals of Canada," issued by the Mines Branch of the Department of Mines, Ottawa. (See Bibliography).
A summary of the averages of analyses of samples of coal taken from the several coal-fields of eastern Canada, extracted from the abovementioned publication, is given below.
It may be noted that the figures given in this table by no means represent the best analyses of Nova Scotian coals. They may be taken as a very moderately stated average, and as conservative figures.
Methods of Working.
The coal seams of Nova Scotia vary considerably in inclination and thickness, and naturally, the methods of mining vary accordingly.
Nos. 2 and 9 Collieries of the Dominion Coal Company: two coal seams are worked at this mine to contiguous shafts
"Princess" Colliery of the Nova Scotia Steel and Coal Company, Sydney Mines
Joggins mine: Maritime Coal, Railway, and Power Company, Cumberland county
In the Sydney coal-field the seams are surprisingly free from faults and interruptions, and maintain a uniform dip over large areas; a condition, which, combined with the regular cleavage of the coal, makes it possible to project mine workings ahead with considerable certainty that it will be possible to adhere to the plan laid down.
The majority of the collieries have been opened from the outcrop by slopes, in which both trip haulages and endless haulages are used. There are not any really deep shafts in the Sydney field. The deepest shaft is that of No. 2 Colliery of the Dominion Coal Company, which is 800 feet to the Phalen seam. The shafts are usually of the square or oblong timbered type, and it is usual to divide a shaft into compartments by wooden partitions. The Princess pit at Sydney Mines was sunk through strata that permitted heavy leakage of sea water, and it was necessary to use cast iron tubbing, but with this exception it cannot be said that any of the shafts in the Sydney field call for special mention. At most of the shaft collieries there is one shaft reserved for the raising and lowering of men and mine materials. With one or two exceptions access to the workings of shaft collieries is also possible through slopes on the same seam. The winning of the submarine areas will require shafts of greater diameter and more elaborate construction than those sunk up to the present time.
In Inverness county, and on the mainland of Nova Scotia, all the collieries in operation are slope mines, with the exception of the Allan shafts of the Acadia Coal Company, which, as mentioned elsewhere, are the deepest sinkings in eastern Canada.
The pillar and room method of extraction has been most generally adopted throughout the Province. In the earlier days of mining, no particular attention was paid to the size or strength of the pillars left to support the roof; and, as the seams were largely attacked along the outcrops, the mining operations of the present day have suffered from extensive crushes, and from the influx of surface water in large quantities, conditions which need not have occurred.
The longwall method of working has been adopted at various times and in various places, but it has never met with much favour at the hands of the local miners, who have been accustomed to pillar-and-stall work in dry and thick seams. As, however, the thinner seams come to be worked, the introduction of longwall methods is inevitable. The Dominion Coal Company has for several years worked the Emery seam on a longwall face. This seam averages 4 ft. 0 ins. to 4 ft. 6 ins. in thickness, and has a roof well adapted for longwall extraction. The coal is undercut by an ordinary disc-cutter driven by compressed air.
In other parts of Nova Scotia various modifications of the longwall method have been used successfully to meet special circumstances. At the Joggins colliery a modified longwall method is used, the coal being under-cut by a "Pickquick" rotary-bar cutter, electrically driven.
In Inverness county, and in some of the newer mines opened by the Dominion Coal Company in the Lingan-Victoria field, the inclination of
the seam varies from 15 to 35 per cent, and the ordinary arrangements of the pillar and room system are modified to meet these conditions. The coal is fed down to the main levels by a system of "balances," or, an adaptation of a gravity haulage, in which the weight of the loaded tub running downhill is utilized to pull the empty tub uphill. The equipment of these "balances" consists of a brake drum on which the rope is wound; a cage or tram to receive the pit tubs on a horizontal level; and a weighted tram to counter balance the loaded tub and pull up the empty tub. The cage, carrying the pit tub, is received at the foot of the balance into a pit in a siding off the haulage level, the floor of the cage being at the same elevation as the rails of the haulage level.
At the Springhill mines, where the inclination of the seams approaches and sometimes exceeds the vertical, the coal is lowered from the face down wooden chutes lined with sheet iron, and is dropped into cars in the levels below. No explosives are used, and sometimes the coal will come away so easily as to run for days without mining. Mining under these conditions of inclination is naturally much more difficult and more expensive than in seams of ordinary inclination. In those portions of the workings where the inclination will permit, the ordinary system of balances is, of course, used.
The coal in the development work and rooms is undercut by air-driven percussive pick machines, or so-called "punchers." Coal cutters of the radial post type are coming into general use. These machines consist essentially of a percussive cutter of rock-drill type mounted on a column, fitted with a worm-gearing which enables the machines to cut either vertically or horizontally, as desired. The radial machines do not impose as great a strain on the men operating them as do the "puncher" machines, moreover, they can be worked by comparatively unskilled men, whereas the successful operation of a puncher machine is a very specialized class of work. In some cases the coal is sheared on the side, or in the centre of the working face. A large amount of coal is still cut by hand, but the tendency is towards the elimination of the hand-pick miner. Pillar coal is mined by hand, except in the case of very large pillars, which are sometimes "split" by the use of machines.
Up to within very recent years the blasting of coal was accomplished by loose black powder, fired by squibs, but this practice has very properly been abandoned. In the damp mines compressed powder, or "pellets" are used. The charge is fired by an ordinary squib, sometimes ignited by a wire heated by contact with the safety lamp flame, and inserted through a small hole specially bored in the lamp glass. The use of squibs is with good reason coming to be regarded with disfavour, and powder fuses fired by electric batteries are being introduced. In the dry and dusty mines, or in mines where gas occurs, so-called "safety" or "permitted" explosives are used, as "Excellite" or "Monobel." These explosives are, of course, fired by a fulminate of mercury detonator, and electric battery.
The quantity of explosive used varies with the nature of the seam, but from 4 to 7 tons of coal produced per pound of powder used, may be taken
The Springhill mines of the Dominion Coal Company
No. 12 Colliery: Dominion Coal Company
No. 4 (Caledonia) Colliery: Dominion Coal Company
No. 14 Colliery, Dominion Coal Company: showing electric hoisting engine house at rear of bankhead
No. 1 slope of the Minudie Coal Company, River Hebert, N.S.
No. 2 slope of the Minudie Coal Company, River Hebert, N.S.
Bankhead and colliery buildings, Inverness Railway and Coal Company, Inverness, Cape Breton, N.S. ( high resolution PDF, 0.3 Mb.)
as usual practice. Generally speaking, the tendency is to lessen the amount of powder used. Apart from the greater danger associated with a too free use of explosives, the coal is shattered, and an undue quantity of slack coal is created.
The yield of coal in proportion to the number of men employed is relatively high in Nova Scotia. The production per man employed, including all classes above and below ground, will average 2½ tons a day.
Horses are used underground in large numbers, but the tendency is now to avoid their use as much as possible, and to substitute mechanical haulage. The horses used average from 4 feet 8 inches to 5 feet 2 inches in height, and cost between $180 and $200 each. Mules are not used in Nova Scotia mines. The price of pit horses has doubled within ten years, and suitable animals are very difficult to obtain. For many reasons it may be expected that mechanical haulage will eventually supersede the use of horses underground.
In Nos. 2 and 9 collieries of the Dominion Coal Company, compressed air locomotives are used for haulage in and out along the main roads leading to the pit bottom. The main haulages are mostly operated by engines working on the surface, chiefly steam-driven, but in several recent installations, electrically operated. The auxiliary haulages underground are in one or two instances electrically operated, but are mostly driven by compressed air.
The hoisting equipment at the shaft collieries presents some unusual features. At several of the shaft mines in the Glace Bay district the loaded pit tubs are brought to bank on a "dumping cage." The pit tub rests on a pivoted platform, and as the cage approaches the bank, the platform is pressed by a spring against a curved termination to the shaft guides, thereby deflecting the platform, tilting the tub and dumping the contents through an end-door into an automatic weigh-tank, from which, after being weighed, the coal passes on to the screens. The pit tubs do not leave the shaft. At other mines the pit tubs are run out on to the flatsheets in the usual way.
At No. 2 Colliery of the Dominion Coal Company, the loaded tubs are weighed in the pit bottom, after which the coal is emptied by rotary tipplers into large inclined storage shoots excavated in the mine floor. From the shoots the coal is shot downwards into a hopper tank suspended from the hoisting rope, which in passing downwards automatically opens the door of the loaded storage shoot, and is filled with coal. When hoisted to the surface, the tank automatically discharges itself on to the screen. Normally, about 6 tons of coal is hoisted in the tank. The tank and frame-work together weigh 10 tons, so that the minimum loaded dead weight on the hoisting rope is between 16 and 18 tons. The entire operation is automatic, the best performance obtained reaching 57 hoists in an hour. So far as known this is a unique colliery hoisting arrangement.
Colliery Plant and Motive Powers.
The machinery at the Nova Scotian collieries is modern and powerful, and considering the comparative isolation of the coal-field, the mining
engineers of the Province have succeeded in following closely the most recent and approved developments in colliery equipment.
Water tube boilers of the Babcock type, are generally used, accompanied in most instances by arrangements for forced draft, and automatic stokers, designed to utilize slack coals and refuse. Chain grate stokers are also used considerably. The Dominion Coal Company has a battery of three Bettington boilers, fired by pulverized coal dust, and especially designed for using inferior fuels. Practically all the combustible matter in the fuel is consumed, and the residue is an irreducible vitreous slag. This battery of boilers was the first of the type to be erected in America. The Nova Scotia Steel Company, at its No. 1 Colliery, has a battery of Babcock & Wilcox boilers, three of the boilers being fired by waste coke-oven gases, and three others by a mixture of slack and coke breeze. These installations are mentioned, because they are typical of the tendency towards economy and the elimination of waste that has been a marked characteristic of recent mining practice in Nova Scotia. A number of exhaust steam turbines have been installed, and no doubt further economies will be effected in this direction. Several live-steam turbines are also in use for the generation of electric power, and a large turbo-compressor unit is shortly to be installed at Springhill mines for the generation of compressed air.
As in other mining districts, electricity is displacing steam as a motive power. At the newer collieries of the Dominion Coal Company and at several of the mines of the Acadia Coal Company and the Nova Scotia Steel Company, no steam is used, except for heating the buildings in the winter.
Nova Scotia--particularly in Cape Breton--is subject to sleet storms in the spring, causing the phenomenon known as a "silver thaw." Ice to a considerable thickness is deposited on all overhead wires, sometimes breaking down both poles and wire; but despite this drawback, it has been found possible to transmit high-voltage currents for long distances with little or no interruption, provided the outside construction is properly designed to cope with the occasional severity of these local sleet storms. One of the Dominion Coal Company's generating stations has, for several years past, distributed electric current to collieries having a radius of twelve miles.
As an underground motive power, compressed air has been chiefly favoured in Nova Scotia, but recently, electricity has been largely introduced for driving underground pumps and haulages; and to a limited extent, electric coal cutters have been used at the coal face. No underground electric trolley-haulages are in use.
The development of electricity as applied to coal-mining in Nova Scotia is so recent that up to 1915 no regulations concerning the use of electricity were contained in the Coal Mines Regulation Act. In 1912, the Nova Scotia Government appointed a Commission to formulate suitable regulations, and these were made law in 1915. The regulations are very complete, following largely the recently adopted British electrical rules for coal mines. They cover not only the use and transmission of all electrical
Waterford Lake electric power plant, Dominion Coal Company: serving the Lingan-Victoria group of collieries
Interior of power house, No. 2 Colliery of the Dominion Coal Company, at Glace Bay, N.S.; showing air compressors and electric generators. (The unoccupied space in the centre of the floor is now occupied by the turbo-generator set shown on Plate XXV.)
Electric turbo-generator driven by exhaust-steam turbine. Dominion No. 2 Colliery, Glace Bay
power underground, but also the minor uses of electricity in the mines in connexion with shot-firing, telephones, signalling wires, and electric re-lighters for safety lamps. If properly enforced, the regulations prescribed by law should fully safeguard the future use of electricity in the coal mines of Nova Scotia.
The great submarine coal-field of Cape Breton offers a wide field for the use of electric power. The problem of the extraction of coal at great distances from the point of entrance of fresh air and power supply is largely that of the transmission of power, and electricity offers the only possible solution in the light of our present knowledge. There are very real dangers connected with the use of electricity at the coal face, but modern improvements in flame-proof motors lead to the hope that, under the spur of necessity, a satisfactory solution will be forthcoming. If, however, objections to the use of electricity at the face are sustained in future practice, it is quite possible to install air compressors, operated by electric power, safely enclosed, and suitably housed at some distance from the coal face, and to convey compressed air in the usual way for the operation of coal-cutters and small haulages at the actual working face.
When the workings of a submarine colliery reach under the sea for a long distance, say exceeding three miles, then the haulage problem will approximate to that of a railway system, with its feeder lines, marshalling sidings, and the main line. The main haulage entries will have to be constructed on a scale not hitherto attempted, with a view to rapid and continuous operations and the movement of large tonnages of coal. The subsidiary haulages will have to be separately operated, and the motive-power for their operation will have to be brought long distances. In the same way, the main ventilating currents will require to be carried onwards by auxiliary fans located "inbye." For many reasons the use of horses for underground haulage in remote submarine workings will be inadvisable, and mechanical appliances will require to be used in haulage, with as complete an exclusion of the labour of men and horses as may be found to be possible.
For all these various operations electricity promises the only possible motive power, except as modified by the local generation of compressed air, as already mentioned.
It may further be surmised that the illumination of the submarine workings will be exclusively by electric light. As is now common practice, the main roads will be lighted by the ordinary incandescent lighting circuit but it may be anticipated these circuits will be carried much farther "in-bye" than is now the case. The oil-safety-lamp may be expected to be entirely superseded by the portable electric miners' lamp, except as the oil flame light may be necessary for gas testing. Apart from the greater safety of the miners' electric lamp, the absence of the products of combustion, and the lessened drain on the oxygen in the air, will be greatly in favour of the electric lamp, when the submarine workings become so extended as to require auxiliary ventilation.
Mine Explosions and Fires.
The Cape Breton seams, while not by any means free from gas, do not give off an excessive quantity. The seams, hitherto, have been largely worked from the outcrops at shallow depths; the workings are characterized by comparatively low temperatures, and gob fires are unknown.
Between 1878 and the present time, there have been four minor explosions in Cape Breton collieries, but there has not occurred any mine accident in this field, involving, at one time, the death of more than twelve men.
On four occasions serious underground fires have occurred in Cape Breton. In two instances it was necessary to flood the workings by letting in the sea, necessitating a long period of idleness and heavy expenditure in pumping out the water after the fire was extinguished.
The Hub seam at its outcrop along the shore at Glace bay was set on fire in 1752, and was consumed along the crop of the seam for a distance of nearly one mile. The locality is still known as the "Burnt Mines," the shales adjoining the seam showing evident traces of fire.
The seams on the mainland of Nova Scotia show exactly opposite characteristics to the seams in Cape Breton island. Few coal-fields have been so troubled by mine fires, explosions, and the constant presence of gas as the Pictou field. One of the seams in this field is said by Indian tradition to have been on fire before the coming of the white man, and according to the late Dr. Gilpin, "Pictou" is the Indian word for explosion, and may be connected with the exudation of gas from the Main seam that has been so noticeable a phenomena of this locality.
The following remarks on the Pictou coal-field made by Mr. R. Smith, before a Select Committee of the House of Commons, in 1835, are of interest:--
Three explosions involving serious loss of life have taken place in the Pictou field, and at Springhill mines. In 1891, an explosion occurred causing the death of 125 men.
Safety lamps are now used in every important coal mine in Nova Scotia, although it is only within the last decade that the use of safety-lamps has become so extended. The N. S. Coal Mines Regulation Act requires the use of a locked safety lamp wherever the presence of inflammable gas is reported. At many of the collieries a type of lamp is in use that is locked magnetically, and cannot be opened except by the use of an unlocking device kept on the surface. These lamps can be lit after locking by an electric
ignition device, and electric re-lighters are provided underground at convenient places to re-light lamps that may have gone out underground.
The occurrence of mine explosions was not surprising under the conditions that attended early mining in Nova Scotia--conditions that were not peculiar to Nova Scotia alone, but were to be found in Great Britain also, at that time. One notable explosion, that caused the death of 55 men, arose out of a combination of naked lights, furnace ventilation, black powder, and the presence of gas. It is probable that defective ventilation, and a diminished percentage of oxygen in the mine air may have acted as a deterrent of mine explosions under these conditions.
The mainland collieries are subject to gob fires, arising from spontaneous combustion in the wastes. Some of the causes predisposing to this tendency are probably the steep inclination of the seams and their extra-ordinary thickness: preventing complete extraction of the coal, and rendering it difficult to avoid sliding movements of the strata, and crushing of the coal. The constant presence of gas, and the generally inflammable and bituminous nature of the adjoining shales, combined with the unusually large quantity of timber supports needed in the thick seams, and the other conditions mentioned, have given rise to a series of mine fires that have been a most serious drawback to the profitable operation of the Pictou and Cumberland fields.
The late Dr. Gilpin, when Deputy Commissioner of Mines for Nova Scotia, in 1894, contributed to the Institution of Mining Engineers a comprehensive account of explosions in Nova Scotian coal mines. A chronological summary, condensed from this paper, and supplemented by the addition of particulars of later date, will be found as an appendix to these present notes. (See page 61).
A study of the causes of the mine explosions and fires listed in the appendix will disclose that significantly many of them originated from the use of explosive, either from "blown-out" shots or the ignition of gas feeders by the explosive used. Open lights were responsible for other explosions and fires.
One violent explosion was brought about by the drawing of pillars in a lower seam which let down burning material from an upper seam that had been on fire for many years.
A curious and well authenticated case was an explosion in an abandoned colliery, caused by the ignition of accumulated gas in the mine workings by a lightning flash which travelled down the mine shaft.
Adequate ventilation, the prohibition of open lights in the presence of gas, the substitution of "permissible" explosives and electric detonators for loose or compressed gunpowder, are conditions now to be found in the majority of Nova Scotian collieries. The future will in all probability see the introduction of still more conservative methods in the use of explosives, and it may be found possible in some instances to avoid altogether the use of explosives in the extraction of the coal, or, at least, to considerably lessen the quantity employed. It may also be anticipated that the use
of naked lights in coal mines will in time be entirely prohibited, whether gas has been reported or not.
As the mine workings descend into deeper and warmer strata, the coal dust problem will become more serious than it has been in the shallow, cool, and usually damp workings of the areas in which the first mine winnings were situated.
Dr. Gilpin's conclusion with regard to the influence of coal-dust was, that:--
This opinion was expressed in 1894, when the explosive properties of coal-dust were not so freely admitted as is the case to-day. The large currents of fresh air that modern mine ventilation affords, passing rapidly through the workings, have emphasized the coal-dust problem, and in districts where the winter temperature of the outer air descends to zero or below, these ample ventilating currents extract great quantities of moisture in their passage through the workings, and thereby increase the dust danger.
Owing to the wide difference between the winter and summer temperatures, there is a wide range in the percentage of moisture in the mine air; the divergence being probably more marked at the mainland collieries, where, because of their more inland position, and in the case of Springhill mines, the greater elevation, the winter temperatures are lower, and the moisture in the outer air is less than is usually the case in Cape Breton island.
Since about 1907, many of the coal companies have provided oxygen breathing apparatus to assist in the fighting of mine fires, and in recovery operations after mine explosions.
The Dominion Coal Company, the Nova Scotia Steel and Coal Company, and the Acadia Coal Company, have well-equipped stations where these apparatus are stored, and where men receive instruction in their use.
In a number of instances the use of these devices by trained men has given valuable assistance in extinguishing or sealing off mine fires, and in recovering such areas afterwards.
Probably the severest test to which breathing apparatus has been subjected in Nova Scotia was the fighting of a mine fire at the Albion mines in June, 1913. This fire was fought by hose and water at close quarters, a helmeted man playing with hose on the fire itself, and other men behind relieving him at short intervals. On several occasions the flames came back on the men, and at one time it was necessary to carry out a fall of burning material in buckets. The fire was eventually extinguished--actually put out--and not smothered by walling off as has generally been necessary. A sentence from the Deputy Inspector's Report is worth quoting:--
Collieries, general office, and Rescue Corps, of the Acadia Coal Company, Stellarton, N.S.
At practically every mine there is an organized surface fire brigade, with equipment. Considerable use is made of portable chemical fire extinguishers, which are provided at suitable points, both above and below ground. At many collieries the compressed air pipe lines in the mine are so arranged that they can be quickly connected to a pump, and used as water lines in case of an underground fire.
Oil-Shales and Inferior Coals.
Bituminous shales, or oil-shales, occur in considerable quantities in New Brunswick and Nova Scotia. A brief reference to these deposits will not be out of place, as the oil-shales are associated with the coal seams, and have many characteristics in common.
The matter of the profitable commercial utilization of the oil-shales of the Maritime Provinces was thoroughly investigated about 1908, and a very full and detailed report of the occurrences of these oil-shales was published by the Department of Mines, Ottawa, in 1910; together with a description of the successful oil-shale industry of Scotland. Full information on this interesting subject will be found in the various writings of Dr. R. W. Ells, to which the reader is referred. (See Bibliography).
Dr. Ells' report is of greater interest since the war commenced than it was when published, because of the increased importance that now attaches to all sources of hydrocarbon compounds, within thc Empire, and because improved processes of distillation, and more complete recovery of the by-products, have enlarged the commercial possibilities of the oil-shales, cannels, and inferior coals.
A series of samples of New Brunswick shales, aggregating 41 tons, was passed through the experimental retort of the Pumpherston Oil Company in Scotland, and yielded an average of 40.09 gallons of crude oil, and 76.94 pounds of ammonium sulphate per ton of shale retorted.
Tests made of the Pictou oil-shales have shown a yield of crude oil of from 20 to 40 gallons per ton; while the oil-coal, or "Stellarite" from the Pictou district is said to have yielded from 53 to 77 gallons per ton, and picked samples, over 120 gallons per ton.
The oil-shales of Albert, Kings, and Westmorland counties, in New Brunswick, exist in enormous thicknesses. The shales yielding the largest quantities of oil and ammonium sulphate are the so-called "paper shales," a finely laminated deposit having numerous remains of fossil fishes between the leaf-like layers of the shales; and a close-grained chocolate-coloured shale, having a conchoidal fracture, and sometimes, a "curly" texture resembling felt.
In Pictou county, and in Antigonish county, Nova Scotia, large deposits of oil-shales exist, of which tile most striking and well known example is the "Stellaritc" oil-shale found near the town of Stellarton.
Previous to the discovery of the petroleum wells in the United States, about 1860, the Pictou oil-shales were mined for exportation to the United States, where they were used for the enrichment of illuminating gas, and a
commencement was made in the retorting of the New Brunswick shales for the extraction of oil. The finding of petroleum in huge quantities stopped the further development of oil-shale mining.
Should the demand for mineral oil at any time become such that its extraction from the oil-shales of the Maritime Provinces is made commercially profitable, these immense deposits will doubtless be utilized.
The commercial possibilities of the extraction of oil from shales will depend very largely on the successful recovery of the by-products, as has been exemplified in the case of the Scotch oil-shale industry.
The coal companies are more interested in the distillation of oil-shales than is perhaps realized, because not only do some of the oil-shale deposits occur within the mining areas of coal companies now operating in Nova Scotia, but these companies have also access to large quantities of inferior coals, coaly shales, and screenings, which, at some future date may, very conceivably, be found to yield a sufficient percentage of hydro-carbons to justify the extraction of these.
No use has, up to the present time, been made of the shales accompanying the coal seams in Nova Scotia, great bodies of which are admirably adapted for brickmaking; with the single exception of the fireclay bed underlying the third seam at the Drummond colliery of the Intercolonial Coal Mining Company, at Westville, Pictou county. At this colliery a seam of fireclay 5 feet 6 inches thick, is mined along with the coal seam. A buff-coloured firebrick, suitable for lining ladles used in handling molten metal, and for the lining of slag cars, is made from this day, and is extensively used for these purposes by the local steel companies.
Suitable shales are obtainable from the roof and wastes of the underground workings of the collieries, or can be quarried where the shale cliffs are exposed along the sea-coast. Trial samples have demonstrated that an excellent brick can be made from the shales associated with the coal seams in Cape Breton, and there is no reason to doubt that the shales in the other coal-fields of the Province would give equally good results.
The Nova Scotia Steel Company, will, by the autumn of 1916, have completed a small brick plant for the utilization of colliery shales. The shales will be ground dry, the water being afterwards added, so as to obtain a uniform day. If a suitable fireclay is available, this Company may find it possible to supply its own needs in bricks for ladle linings. If the enterprise of this Company proves successful it will probably be the means of creating greater interest in the possible utilization of the colliery shales.
There is, unfortunately, a decided scarcity of true fireclay in the Province, and no ganister beds, such as are associated with some of the Millstone Grit coal seams in England, have as yet been discovered in Nova Scotia.
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Last Modified: 2004-11-08
Originally Produced by: Canada Department of Mines, Government Printing Bureau
The information contained on this site is not provided for the purpose of factual
representation. Instead, it is provided in an historical context. Every effort has
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Bulletin No. 14, The Coal-Fields and Coal Industry of Eastern Canada.
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