REPORT ON ACCIDENTS IN MINES (ABSTRACT OF) BY HER MAJESTY'S COMMISSIONERS.

Appendix to the Journals of the House of Representatives, 1887 Session I, C-04

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1887. NEW ZEALAND.

REPORT ON ACCIDENTS IN MINES (ABSTRACT OF) BY HER MAJESTY'S COMMISSIONERS.

Presented to both Houses of the General Assembly by Command of His Excellency.

Abstract of Portions of the Final Report of Her Majesty's Commissioners appointed to inquire into Accidents in Mines, and the Possible Means of preventing their Occurrence or limiting their Disastrous Consequences; with Remarks by George J. Binns, F.G.S., Inspector of Mines, Dunedin. INTRODUCTION. The following abstract of the report presented by Her Majesty's Commissioners has been made with the view of diffusing information. The report itself—which is the result of upwards of seven years' labour of scientific and mining men whose names carry sufficient weight to give the highest authority to the conclusions at which they have arrived—is exceedingly bulky, comprising 120 pages of a Blue Book, with very copious additions in the form of appendices, &c, the whole filling 320 pages. The preliminary report was 520 pages in length. In the present abstract I have endeavoured to give the most important conclusions arrived at, and can only strongly recommend the perusal of the original report to those who may wish to go more minutely into this very interesting subject. 1. Methods op Ventilation and Working. In referring to these subjects the Commissioners point out that " the inefficient furnaces erected at the surface, of which many were to be seen thirty years ago, arc now practically abolished," and that in deep shafts well-designed furnaces, with from 50 to nearly 200 square feet of fire-grate area, and capable of circulating volumes of air ranging from 200,000 to 400,000 cubic feet per minute, are used; while many hundreds of mechanical ventilators are successfully adapted. It is to be regretted that in this colony surface-furnaces are not yet abolished. In speaking of anemometers, those made on the revolving-vane principle are commended. The report does not enter at any length into the relative advantages of the various systems of working, and devotes a considerable portion of the short space which is given to this subject to praise of the "long-wall" plan, wherever applicable. Though there may be mines in this colony whore this system could be introduced —and, indeed, it has been for many years applied on a small scale at Collingwood —I am afraid that the nature of the roofs usually overlying our coal-seams is not sufficiently elastic to allow of its being carried out with the maximum advantage. 2. Falls of Roof and Sides. As this is a matter mostly within the province of the miners themselves, it was not to be expected that the Commissioners would do much towards elucidating any means of prevention. The percentage of deaths from this cause is given at about 40 in Great Britain, while in New Zealand, from the commencement of inspection to the end of 1885, it was 62. The report calls attention to the following points : — (a.) The maintenance of ample supplies of timber in localities convenient to the workmen; (b.) The proper training of each miner to the best mode of timbering and otherwise protecting his working-place; (c.) The exercise of increased care on the part of the workmen in w 7atching the roof, sides, and face, and protecting themselves in time ; (d.) The introduction, as far as possible, of arrangements with the workmen which will make it their interest not to avoid the labour of putting up the necessary timber, cogwalls, buildings, or nogs for their proper protection ; (e.) The employment of special timber-men or deputies for the timbering of main ways, and also for the repairing as well as drawing of timber ; (/.) Preventing timber being left in the goaf of long-wall Workings, which would have tha effect of breaking the roof ; (a.) Driving the working-places as rapidly as possible by shifts of an ample number of workmen in each face, and so reducing the risk of falls and exposing the least number of meri to danger at any one time. "With regard to the interesting question of coal-cutting machines, the Commissioners state that they " cannot yet be accepted as a practical success." I—C. 4.

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3. Spontaneous Combustion. It is much to be regretted that on the above subject, fraught as it is with interest to so many coal-owners in the colony, the report should have but little to say, and that not of a nature to assist managers in overcoming this source of danger and expense ; though a very interesting and valuable paper on the causes of spontaneous heating of coal is contributed by Sir F. Abel, F.8.5., and Dr. Percy, F.B.S. 4. Miscellaneous Mine Accidents. In pointing out that the average of lives annually lost per thousand persons employed in the coal-mines of Great Britain has been reduced from 3'328, during the period 1861 to 1870, to 2-005 during the period 1880 to 1884, the Commissioners state that the decrease under the heading " Miscellaneous " has not been proportionate to that under other divisions. :|: In reference to the fatalities by falls of rock, and by accidents from tubs or trams, the report states that "it is important to point out that these form a class of disaster which in most respects lies outside the powers of inspectors to avert, and for the mitigation of which we have to look, after the first general arrangements laid down on the best plan, to the practical experience, the coolness in danger and the attention to discipline, of the workmen themselves." 5. Firedamp. The report naturally enters at considerable length into the subject of firedamp, the following being a brief extract of some of the most important conclusions arrived at : — The gas commonly known as "firedamp" is known to consist, when freshly given off by the coal, mainly of marsh gas, carbonic acid and nitrogen being present only in small proportions ; it is therefore natural to infer from the laws of the transpiration of gases through porous bodies that the gas which will escape first from the coal will contain a larger proportion of marsh gas, while that which comes off at a later period will be comparatively rich in carbonic acid and nitrogen. Thus the freshly-escaping gas may have a different composition from that met with in old workings. From laboratory experiments it was formerly considered that atmospheres containing less than 7 per cent, of firedamp were not actually explosive ; but the experiments of the Commission have proved that when little more than 4 per cent, of marsh gas is present, flame may be transmitted under circumstances which occur in a mine. If marsh gas, in a nearly pure state, enter the atmosphere of a mine, the proportion necessary to produce an explosive mixture will be so rapidly attained that the presence of the gas, as indicated by the formation of a cap or aureole on the flame of a safety-lamp, may escape notice. On the other hand, the gas in old workings is generally mixed with air, and the various stages between a mixture containing about 2'5 per cent, of marsh gas, with which a cap first appears upon the flame, and an explosive mixture, will be passed through so gradually that there is much more chance of a cap being observed. This difference in the facility of showing a cap may have given rise to the prevalent idea that there exists a specially dangerous kind of gas called a sharp gas (known in some parts of the country as silver gas), which does not give warning of its presence by a cap on the flame.f A mixture containing 9'38 per cent, of marsh gas is capable of explosion by special manipulation, but will not probably explode at the flame of a safety-lamp. The reason of this is that the explosive mixture during its passage from the external atmosphere to the flame comes in contact and becomes mixed with a certain amount of inflammable vapour which has escaped combustion, and a considerable amount of carbonic acid ; thus its character is changed. The report then points out that a mixture which may not be absolutely explosive may be capable of propagating combustion. A good many instances of sudden outbursts of gas are given ; and this is a danger which, unfortunately, will have to be guarded against in this colony. Already several minor outbursts have occurred, and, if the opemng-up of the coalfields has not the effect of entirely removing these causes of danger, the only course open will be to work entirely with safety-lamps in those collieries where they are likely to occur. On the subject of the influence of barometric pressure on the emission of gas and consequent explosions the Commissioners are somewhat guarded in their remarks. While recognizing that variations of atmospheric pressure exert an influence on the escape of gases which have accumulated in cavities, and, possibly, to a slight extent, on that of gases emitted directly from the coal, they discourage reliance on meteorological warnings, and state that the absence of a general connection between colliery disasters and barometric changes is practically established. In one case brought before the Commissioners it was suggested that lightning entering a pit had been the cause of an explosion, and the possibility of this is acknowledged. In this colony, on the west coast of the South Island, the electric current has on several occasions entered both coaland quartz-mines, and, without causing any great damage, made its presence most unmistakably felt. 6. Coal-dust. A very large amount of attention has been given to the subject of coal-dust in mines; and, although the generality of our collieries are not what may be called dusty, yet the remarks oil this point are of so much general interest as to be worthy of reproduction. The action and effects of coal-dust in connection with mine-explosions have been made the subject of careful study and com-

* It may be noted that the average per thousand in this colony for the years 1880 to 1885 was 1-67, and that including 1886, when no lives were lost, but for which.tho returns arc not yet in, the average annual deaths per thousand will probably be below I's. t The gas at the Greymouth Wallsond Colliery has frequently been referred to as of this nature ; which is readily explicable by the absence of old workings in the mine.

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prehensivo experiment by numerous workers since attention was first drawn, about forty-two years ago, by Faraday and Lyell to the functions exercised by coal-dust in "aggravating and extending the injurious effects of firedamp explosions." The results and conclusions which have been arrived at in this direction, and to which the labours of the Commissioners have contributed, are sufficiently complete and definite to warrant the following authoritative statements : The disastrous effects of firedamp explosions in coal-mines are almost always aggravated and extended by the existence of coal-dust in dry mine-workings and roadways. A gas-explosion in a dry mine, even if only of comparatively trifling nature, will raise and inflame coal-dust existing at the seat of the explosion or in the vicinity: the flame attending the explosion will be thereby increased and carried to more or less considerable distances, and may thus become communicated to any accumulations of explosive gas-mixture which may exist in goaves or other lurking-places at a distance from the seat of the original gas-explosion. The employment of an insufficient quantity of an explosive in a shothole of a strength which is in excess of the power applied, or neglect of sufficient tamping, will produce a blown-out shot —that is, an almost complete projection of the highly-heated products of explosion, and of a body of flame from the mouth of the hole as from a gun. And almost the same effect is produced if the charge of explosive is unnecessarily great. In a wet mine, or in the entire absence of coal-dust, the flame produced by a blown-out powder-shot is not projected to any considerable distance, but is considerably increased in volume if dry or slightly-damp small coal has been used as stemming for the shot. In a dry locality, where coal-dust exists, the flame is sure to be considerably increased and extended by the ignition of portions of the dust-cloud raised ; and this result is occasioned even in the entire absence of fheJamp. It is, however, well established that, even when the atmosphere is quite free from firedamp, an exceptionally inflammable and abundant coal-dust may, by its ignition, produce explosive effects similar to those caused by gas. If gas is present, even not above 2 per cent., under favourable circumstances the flame may be propagated to distant localities, where accumulations of explosive gas-mixture or deposits of very inflammable dust may exist, and extend the disastrous effects. Whenever a coal is w'orked which contains inflammable gas, the atmosphere will, at one time or another, and it may even be said generally, contain some small proportion of firedamp. Hitherto the absence of any indication in a lamp has been taken as conclusive evidence that a mine was free from gas, but that test fails when the atmosphere contains less than 2 to 2-5 per cent. Such a slight proportion not only enhances the danger due to dust, but is sufficient actually to give rise to an explosive mixture with the dust raised by a blown-out shot. By improved indicators such small proportions of gas can now be detected; but there is no means of preventing such contamination, which, though insufficient to cause danger alone, does so if dust co-exists in abundance in dry mine-workings when powder-shots are fired. It is thus seen that the firing of powder shots in a dry mine, where dust exists in abundance, must always be attended with disastrous results if even so small a proportion as 2 per cent, of firedamp is present. Eemoval of the dust, or laying it, by application of water alone, or in conjunction with deliquescent salts has not been found convenient or trustworthy ; therefore the only safe method when powder is used is by combining the removal as far as practicable with very copious' watering. 7. Explosive Agents. It will thus be seen that the safe use of powder entails much difficulty; but the extensive practical experiments of the Commission and others have demonstrated that efficient substitutes for powder are available, and that one or other of the following alternative moans may be employed both in coal and stone with equal efficiency, and at very little, if any, greater outlay. (a.) In some coal-seams the lime-cartridge will perform work quite equal to that accomplished with powder,* at no greater cost, and with absolute immunity from danger of explosion.+ (I>.) Mechanical appliances exist which will do efficient work, not only in some kinds of coal, but also in some stone or shale over or underlying coal. (o.) The so-called " high " or violent explosive agents, which are represented by dynamite or gelatine-dynamite and by gun-cotton or tonite, can now be applied, not only for working economically in stone or shale, but also for coal-getting, by using them in conjunction with water, according to one or other of the usual methods. The " high " explosives may be used, as indicated in (c) with security against the ignition of coal-dust thickly suspended in the air by a blown-out shot or by the effect of an overcharged hole, even when the air contains some small proportion of firedamp. To Dr. McNab belongs the credit of having first practically shown that the addition of water to the pow 7der-charge in a shot-hole would be of value in extinguising the flame caused by a powdershot ; but, though Dr. McNab's system proved useful in saving time in stone-drifting and similar works, owing to the absorption of some of the products of combustion by the finely-divided water, it was proved that no reliance can be placed upon it for producing a sufficiently extinguishing effect to prevent an explosion, in a gas-mixture or in a dust-laden atmosphere containing a small proportion of gas, by a blown-out powder-shot. A series of experiments made by the Commission by firing blown-out shots with dynamite, compressed gun-cotton, tonite, and gelatine-dynamite, and with the addition of water-tamping, all failed to ignite a favourable explosive mixture; while the same explosives minus the water-tamping, or powder plus the water-tamping, never failed to produce an explosion. The use of water-tamping, as applied by Dr. McNab, but in conjunction with the so-called " high " explosives, appears therefore to afford, protection against'coal-dust explosions when blown-out shots occur.

• See Report of Control and Inspection of Mines, New Zealand, 1883, letter referring to lime-cartridge blasting from Mr. Inspector Cox, P.G.S., to the Under-Secretary for Mines. 1 In the report of Mr. Evans, F.G.S., H.M.'s Inspector of Mines for the Midland District, five non-fatal accidents aro recorded as having occurred during 1885 from the ramming of lime-cartridges having blown out whilst watering the hole.

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The Commissioners conclude their remarks on this subject by the following recommendations :— (1.) That all work involving blasting in mines should be intrusted only to experienced workmen. (2.) That, in order to lessen the risk from blown-out shots, particular care should be taken that each shot should be assisted by under-cutting and nicking, or shearing whenever it is practicable. (3.) That the tamping, stemming, or ramming should consist of very damp or non-inflammable material. (4.) That, where strong tamping is needed, the compression of air at the bottom of the hole should be avoided by pushing in the first part of the tamping in small portions. (5.) That, where safety-lamps are used and powder is employed, tho shots should be fired only by specially-appointed shot-men, who, before firing the shots, shall satisfy themselves that the foregoing instructions are observed, and shall also satisfy themselves, by carefully examining all accessible contiguous places within a radius of 20yd. of the shots to be fired, that firedamp does not exist to a dangerous extent. 8. Safety-lamps . The next subject treated of in the report is safety-lamps; and into this branch the Commissioners have made very detailed and elaborate inquiries. Iu commencing, the report points out that the two causes, explosions of gas and falls of roof and sides, cause GO per cent, of the deaths in Great Britain, and that these two causes are intimately connected. In order to satisfy the requirements of safety, it is necessary not only that a lamp should be what is called a " safety-lamp"—namely, one which will not, under any probable circumstances, ignite an inflammable mixture of firedamp and air even when passing at a high velocity—but that it shall give a sufficiently brilliant light to enable workmen to guard against falls of coal and stone from the roof and sides. It is also necessary that the lamp should be so simple in construction as to be easily examined, and should not be liable to extinction when handled with ordinary care. Another matter deserving consideration is the relative facility afforded for observing the presence in the air of abnormal quantities of firedamp. It is hardly necessary here to do more than mention lamps which furnish an excellent light, while entirely independent of the surrounding medium. Of this character are the various electric lights which will be mentioned later, and the lamp invented by Mr. Fleuss, in which the source of light is a cylinder of lime maintained in an incandescent state by a spirit-flame fed by a stream of oxygen derived from a reservoir containing that gas under considerable pressure. Though exceedingly useful as a means of exploring after explosions, and in places where the atmosphere of a mine does not consist of air sufficiently pure to support combustion, lamps of this description are, fortunately, not at present required in this. colony. The class of lamps which merits consideration is that in which the light is fed by air from the mine. Sir Humphrey Davy discovered that under certain conditions wire-gauze is able to distribute by conduction the heat which it receives, and to subsequently emit it by radiation, so that it will remain, even when in contact with inflamed gas, at a temperature inferior to that required to bring about the combination of firedamp and oxygen in a mixture of the gases which is passing through tho gauze. Upon this discovery rest the many hundreds of so-called safety-lamps which have been brought forward; but even Davy acknowledged that this gauze, when constructed upon correct principles, could be trusted to prevent explosion only when the velocity of the air-current did not exceed a certain limit. Beyond this limit the flame may pass the gauze. At the time of Davy's invention air-currents in mines seldom exceeded a velocity of sft. per second, and under such circumstances the lamps of Davy, Clanny, and Stephenson were all safe. But at present in Great Britain velocities of even 30ft. to 35ft. per second are met with, and in this colony, though the velocities are usually low, 26ft. per second has been registered, and there are special circumstances in which a much higher velocity might occur; so that the employment of any but the approved kinds of lamps is inadvisable. It is thus seen that the more efficient becomes the ventilation of mines the greater becomes the danger from imperfect lamps, and the more care is necessary to prevent explosions of fire damp. The labours of the Commission have conclusively proved that tho Davy, Stephenson, and Clanny lamps are absolutely unsafe under certain conditions. There are two methods of behaviour for lamps when in explosive gas, either of which may bo. safe. The first, in which the light goes out, is obviously so ; the second, in which the gas burns inside the gauze, may or may not be dangerous. If the ignited gas be shielded from the mechanical action of the current, and if the lamp bo surrounded by glass, and the ignited gas be sufficiently distant from the glass to prevent the latter from becoming cracked by the heat, a considerable step towards safety is gained. In the Clanny and Mueseler lamps the light is surrounded by a glass cylinder, which may become cracked so as to allow the ignited gas inside to communicate with the external atmosphere. Injury to the glass may obviously arise from various causes, such as a blow, careless use by which the flame of the lamp is allowed to impinge on the glass, or by the impact of cold water on the heated glass. Another point requiring attention is the difficulty of maintaining at all temperatures sufficiently tight joints where the glass and metal parts meet. If too tightly connected the expansion of the glass by heat causes its fracture; if too loosely, an opening of a dangerous size may be left. " "Washers " of indiarubber and leather have Ibeen usually employed, but they are liable either to perish, or shift in position if strongly heated._ The report most strongly urges the use of asbestos millboard washers, and great care in examining the surface of the glass.

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Some attention is devoted to the subject of illuminants, the danger being noted of using the very volatile derivative of petroleum called " colzaline," the vapour of which forms with air an explosivo mixture. As, however, this illuminant is not employed in the colony, it is unnecessary to give the remarks in extenso. The Commissioners note that they have made experiments with over 250 lamps ; but, as only four are recommended for use, it will not be necessary to describe the rest. The " tin-can Davy " or common Davy lamp, surrounded by a case or can provided with a glass window, or constructed partially of glass, is highly commended in the report, which states that the addition " converts the Davy lamp, from one of the most dangerous, into one of the safest of the lamps in common use. The result of our earlier experiments," continues the report, " made it more generally known that the Davy and Clanny lamps, and, under special circumstances, the Mueseler lamp, are almost certain to cause an explosion when placed in a current of air sufficiently charged with firedamp, even if the velocity of the current is only from 6ft. to 10ft. per second," while no explosion is caused at a much higher velocity by a cased Davy. It may be useful, as giving an idea of how the testing of safety-lamps was carried out, to describe shortly the apparatus used by the Commission in conducting their very complete experiments. A wooden box, 20ft. long, and measuring 13'75in. by lOin. in section, was fixed with its sides horizontal and vertical. Near one end is an opening in the sides communicating with a small wooden chamber, on the top of which is placed an iron cylinder containing a nozzle (a Kortings blower), by which a jet of steam issues from a large boiler, and escapes by a trumpet-shaped opening into the air. This steam-blast, on the principle of an injector, causes a steady current of air to pass along the box from the open end towards the steam-jet, and by experiment any required velocity of current was found to be attainable. Thus, with an adjustable tap, an explosive current of any desired composition could be directed at any required velocity against the lamp under trial. Windows were also inserted into the box, so that the behaviour of the lamps under various conditions could be carefully noted. In some cases the conditions were varied so that the lamps weie inclined at a measured angle to the horizon; and in others screens were inserted in the box so that the explosive mixture impinged on the gauze at various angles; and in other cases the lamps were exposed to ascending or descending currents. "With this apparatus an enormou3 number of experiments were carried out and recorded. In view of the number of Davy lamps existing in this colony, the following decision of the Commission becomes very interesting : "It will be seen that in an explosive current with the very moderate velocity of 400ft. per minute the ordinary Davy lamp ceases to afford protection for more than a few seconds, unless the diameter of the gauze is very small The Davy lamp enclosed in a case of any form which completely shields the gauze from the direct action of the current may apparently be trusted in currents not exceeding in velocity 2,000ft. per minute, but for higher velocities the greatest care is necessary in designing the case and its relations to the enclosed lamp." The common Clanny lamp is found to offer very little more security than the Davy lamp, and is almost certain to ignite an explosive mixture in a velocity of 600ft. per minute ; it was found by experiment that if the percentage of marsh gas in the atmosphere bo reduced to 4-25 or thereabouts, Clanny lamps are extinguished, while Davy lamps are still liable to cause explosion. Like the Davy, the Clanny lamp is rendered much more safe when the gauze is protected from the direct action of the current by an external metal jacket or bonnet; and lamps thus protected did not appear dangerous in velocities of 1,500ft. per minute, or oven 1,900ft. per minute, but tin explosion was produced by a velocity of 2,857ft. per minute. The four lamps which are considered by the Commission to combine the quality of safety in a pre-eminent degree with simplicity of construction, and with illuminating power at least equal to that of any of the lamps at present in general use, are—(l) Gray's lamp, (2) Marsaut's lamp, (3) Evan Thomas's (No. 7) lamp, (4) the bonneted Mueseler lamp. In Gray's lamp (see C, Appendix I.) the air to feed the flame is brought down from near the top of the lamp by four tubes communicating with a small annular chamber surrounding a cylindrical strip of gauze under the glass. The exit-tube or chimney terminates at its upper end in a short cone, which is closed by a gauze diaphragm, having an area about double that of the section of the chimney. It is covered by a dome, through large perforations in which the products of combustion mainly escape. This lamp has a flat wick. The flame is not much affected by swinging the lamp through considerable angles, or by rapid motion up and down in a vertical direction. Three modifications of Gray's lamp have been tried: in the first, a horizontal gauze ring, extending from the neck of the oil-cup to the flange under the glass, has been added ; the second modification differs from the first only in the omission of the cylindrical strip of gauze which protects the inlet to the original Gray's lamp ; the third modification was merely experimental. In Marsaut's lamp (see B, Appendix I.), which is of the bonneted Clanny type, the inventor has taken an additional step in the direction of safety by the introduction of three gauzes in place of the single gauze cap of the ordinary Clanny. With these safeguards, the, lamp has not exploded in any current which could be produced. The illuminating-power also is good, being equal (with three gauzes) to about half a standard candle. Another bonneted Clanny lamp, the invention of Mr. Evan Thomas, is said to be, on the whole, the most satisfactory lamp tested by the Commissioners. (See A, Appendix I.) The following is a description : Inside the bonnet a brass tube lin. high fits the main gauze cylinder closely. To the upper end'of this tube is attached a horizontal brass flange extending nearly to the bonnet, so that an annular space only J & in. wide is left between the edge of the flange and the bonnet. The air, having entered the bomiet through horizontal slits near its lower end, passes through this annular space into the gauze cylinder and descends to the flame. The products of combustion escape through holes near the top of the bonnet, which are protected by a

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shield fixed in the bonnet. The main gauze cylinder is provided with a gauze cap. The bonnet is locked by a sliding bar, which cannot be withdrawn until the oil-vessel is removed. In a gasmixture the gas burns in the gauze cylinder only between the top of the brass tube and the lower edge of the gauze cap. The lamp seems very safe in all currents in which it was tested (up to 3,200ft. per minute for eight seconds), Lut its security would probably be lessened considerably if the bonnet and the flange on the shield ceased to be'eoncentric, and if any perforations were made in this flange. In air moving with any velocity up to 3,500ft. per minute the flame burns very steadily when the lamp is either erect or inclined. The flame is scarcely affected by violent oscillations of the lamp, or by rapid motion up and down in a vertical direction, and it is not extinguished by inclining the lamp until the latter is nearly horizontal. The Mueseler lamp (see D, Appendix I.) is, in Belgium, constituted the legal lamp for fiery mines, and exact forms and dimensions are prescribed, from which only the smallest divergence is allowed. As will be seen by the diagram, this lamp consists of a Clanny lamp, into which an interior chimney is introduced. The air which goes to feed the flame passes through the lower part of the gauze cap and then downwards through the horizontal gauze ring which supports the chimney. The products of combustion ascend under ordinary circumstances by the chimney; but when the lamp is so much inclined that the stream of heated air rising from the flame strikes upon the gauze diaphragm instead of going up the chimney, the action of the lamp is reversed, and it feeds down the chimney : the entering air, being highly charged with carbonic acid, at once extinguishes the flame; hence very great care is required in using this type of lamp. If, while the current is partially reversed, the lamp becomes surrounded by an explosive mixture, the gas-mixture outside the chimney becomes ignited, and if the current-velocity bo above 400ft. per minute the lamp behaves like a Davy, and an explosion will certainly follow. With the Belgian lamp, with a flame of normal size, and exposed in a vertical position to a horizontal current of any velocity, the Commissioners did not produce this result, but with a very small flame, such as is used for looking for gas, there is a danger of this accident. In Great Britain the Mueseler lamp has been altered by varying the dimensions, and particularly in removing the orifice of the chimney further from the flame. By this means tha danger of accidental extinction is reduced, but the safety of the lamp is much diminished; and even with the prescribed dimensions the Belgian lamp is not safe when it receives the current obliquely and is partially shielded from its action. A number of experiments with deflected currents proved this fact very clearly. By the addition of a bonnet to protect the gauze the Mueseler lamp is rendered very safe; but care must be taken to leave no gap between the bottom of the bonnet and the flange on which it ought to rest. Mr. A. H. Stokes, F.G.S., Her Majesty's Inspector of Mines, has added a shut-off apparatus, whereby the outlet of the lamp may be closed, and the flame extinguished. Morgan's lamp, which is of the bonneted Mueseler type, is also stated to be very safe, with the serious defect, however, of great weight and somewhat complicated construction. Since the report was published this lamp is said to have been very much improved. In the following table the main facts in reference to these lamps are collected: —

After giving these details of the various lamps, the Commissioners go on to make sundry suggestions for modification and improvements; and, after pointing out that the ultimate sources of danger with all these lamps is the breakage of the glass, they suggest that both the Marsaut and the bonneted Mueseler would be safer if there were no apertures in the bonnet for the admission of air except the holes in the horizontal flange which forms its base; also, that the holes in the top of the bonnet for the escape of the products of combustion should be completely above the top of the outer gauze. It is also suggested, with regard to the bonneted Mueseler, that the metal rim at the bottom of the gauze cap in lamps of Belgian manufacture, or the vertical ring on the lampframe which takes the place of this rim in most lamps of English construction, should be somewhat deeper than is usually the case. The object of this is to cause the intake air, after entering through the holes in the flange supporting the bonnet, to rise vertically as much as possible before passing through the gauze cap. An improvement might be made in the Mueseler lamp by introducing, above the glass, and below the horizontal gauze diaphragm, a ring of thin metal with a short vertical tube projecting

* The weight of those lamps is practically the same: different specimens of the same lamp vary by less than 2oz. | In an explosive current with this high velocity the gas sometimes continues to burn under the glass ring, but in general it is extinguished in a few seconds.

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Lamp. Weight without Oil. Illuminating Power in Standard Candles. Current Velocity of Explosive Mixture during Trial. Duration of Trial in Explosive Mixture. vlarsaut, 3 gauzes 2 „ 2 „ 2 „ vlueseler, with bonnet Lb. *2-75 // 0-4 to 0-5 0-6 to 0-7 3,100 2,000 800 2,650 2,850 2,650 3,100 2,857 3,200 Mill. sec. 2 0 1 0 15 0 5 0 if II n 0-3 to 0-4 t Iray it I! li II 1 0 1 0 1 40 7 40 a • • • • • • 3van Thomas, No. 7 ... 3-25 0-4 to 0-5

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downwards at its inner edge, somewhat (say Jin.) less in diameter than the internal diameter of the glass. This would prevent the gas when ignited under the gauze diaphragm, from being in immediate contact with the glass, and so would retard, if it did not prevent, the formation of cracks in the glass. A great objection to the use of a bonnet on a safety-lamp is that it prevents a workman, after he has received his locked lamp, from satisfying himself that all the gauze caps are in the lamp, or, in the event of gas firing in the top of the lamp, from seeing the state of the gauze. This objection might be removed without risk by providing the bonnet with two vertical slits at opposite sides, each about -|in. wide and lin. long, closed by plates of mica firmly secured to the bonnet by metal frames. As the bonnet is not liable to any considerable rise of temperature, the objection to the use of mica does not apply here. The principal danger to Gray's lamp appears to be the liability to fracture of the glass from the heat produced by the gas burning at the cylindrical strip of gauze immediately under it. In currents of low velocity this ignited gas heats the lower edge of the glass strongly, and in currents of high velocity a stream of ignited gas passes completely across the lamp from the windward side, and plays directly on to the glass at about the middle point of its height on the lee side. This, of course, speedily cracks the glass. The substitution of a horizontal gauze ring for the cylindrical gauze strip partially removes this defect; and this, with the introduction of a thin cylinder of refractory glass, placed loosely in the lamp, so as to leave an annular space between it and the outer glass, while diminishing the risk to the latter from burning gas, reduces the light by only about 10 per cent. The top of Gray's lamp requires some modification, as in its present form the lamp may easily be tampered with. As the supply of air in this lamp is drawn nearly from the top, it would seem to be particularly suited for searching for firedamp. Automatically-closing lamps, which, by the action of a spring and a filament which becomes burned by the ignited gas, close either the inlet or outlet or both, have been invented, but they seem somewhat complicated, and not of so permanent and simple a nature as would enable them to withstand the dust-laden atmosphere and rough usage likely to be met with in a mine. The locking of safety-lamps is a question which must obviously be of the greatest importance; and, although magnetic and pneumatic locks have been examined, the report gives the palm to the " lead-plug " lock, which consists of an ordinary lead rivet connecting the oil-vessel with the lampcase, and stamped with a letter or mark which may be varied from day to day. The following extract from the report is worthy of attention, as it deals a blow at a timehonoured custom among firemen and others whose duties have led them to search for gas : "Mr. J. B. Marsaut has drawn attention, in his valuable work entitled ' Etude sur la Lampe de Surete des Mineurs,' to a source of danger attending the use of certain safety-lamps in a still atmosphere which had not previously been investigated. When a lamp is raised into a cavity containing pure gas, or air mixed with a large proportion of gas, the flame is speedily extinguished if the lamp is allowed to remain in the highly-vitiated atmosphere ; but if the lamp is quickly lowered again into comparatively pure air the extinction of the flame may be prevented. In thus raising a lamp into gas, especially if the lamp is constructed to draw the air for the maintenance of the flame into the part of the lamp above the flame, the upper part of the lamp will become filled with a mixture of gas and air, containing too much gas to be explosive or even inflammable. When the lamp is lowered into pure or nearly pure air, this gas-mixture will become rapidly diluted with air, and so become inflammable. It is therefore possible that the greater part of a lamp may, by this process of raising and lowering, become nearly filled with a highly-explosive mixture without the flame being extinguished : an explosion inside the lamp must then follow. The intensely-heated gases (or vapours) resulting from this internal explosion necessarily undergo considerable expansion, and a portion must pass out of the lamp through the gauze with a velocity which increases, for a given volume exploded, as the area of the gauze decreases. If, then, its area in a lamp of given volume is sufficiently restricted, the heated gas will pass out so rapidly that the gauze will be unable to cool it below the temperature at which an explosive mixture will ignite. Supposing this event to happen when the gauze is surrounded by the inflammable mixture of gas and air which must exist near the mouth of the cavity, this mixture will become ignited and an explosion will be produced outside the lamp which may be attended with serious results. If the flame be very small, greater facility is afforded for the formation of an explosive mixture in a large part of the lamp, and an internal explosion is more likely to occur than when the flame is of its ordinary size." Experiments carried out by the Commission verified the conclusions arrived at by Mr. Marsaut. The proper testing of safety-lamps before being taken into a mine is obviously of the greatest importance, and the report points out that the simple examination of a safety-lamp is a very imperfect test of its safety, and that even plunging it into an explosive mixture is not sufficient. The Commissioners therefore suggested that a vertical metal cylinder about Bft. high and Bin. to lOin. in diameter should be provided, near the bottom of which are a number of concentric burners with spaces between them, through which air can be drawn by the ascending gas. By proper regulating means a fairly uniform and highly explosive mixture may be maintained in the cylinder. When a lighted lamp is lowered into the cylinder not too rapidly, if perfect it will be extinguished ; if imperfect it will almost certainly ignite the surrounding gas-mixture. As previously stated, the Commissioners devote considerable attention to the subject of illuminants for safety-lamps, and give the following information : "The conclusions to which we have been led are that a seal-oil of good average quality is decidedly superior in point of general burning qualities (i.e. duration of uniformity in the height of flame produced) to refined rape (or colza) oil; and that by the admixture with either, but especially with seal-oil, of petroleum or paraffine-oil of a flashing-point not lower than 80° Fahr., in the proportion of not more than one

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part by measure to two parts of the vegetable or animal oil, a considerably superior ilhiminant is obtained. It should be added that the experiments afforded no indications that the mixed petroleum and oil were consumed in unequal proportion at different periods during the burning of the lamp." The cost of colza-oil in Dunedin being about 3s. 9d. per gallon (I am not aware that properlyrefined seal-oil is to be obtained), and that of good kerosene being Is. 9d. per gallon, this improvement of the illuminant is in this colony attended with decided economy. A few remarks are devoted to the attention necessary to wicks, and the following is an epitome : — (1.) The wick should not fit too tightly into the burner. (2.) If the wick is plaited it should consist of loosely-spun threads very loosely plaited. (3.) The wick should be thoroughly dried. (4.) A new piece of wick should be employed every time the lamp is prepared for use. The electric light is naturally the means of illumination to which all mining men look for eventual freedom from accidents, both on account of the safety connected with an enclosed lamp and the excellent light, which would tend to the prevention of accidents by falls. The Commissioners, however, were convinced that, while the electric light could be used for the illumination of the pit-bottom and the adjacent main roadways without much difficulty, the possibility of safely extending a system of conductors and lamps to any considerable distance into the interior of mineworkings was open to serious question. To be, therefore, of any use a miner's electric lamp must be self-contained and portable. A lamp of this description has been invented by Mr. J. Wilson Swan, whose lamps, as used for ordinary purposes, are so well known. As described by the Commissioners, it consisted of a secondary battery of seven cells enclosed in an ebonite battery-case of cylindrical form, and measuring 7'sin. in height and 4-25in. in diameter, and weighing 91b. to 91b. Boz. A small, wellprotected glow-light is fixed to the side of the case, and, when properly charged and fitted, it gives a light which is maintained for several hours at between two- and three-candle power, and which, even after being continuously in action for eleven hours, furnishes a light of about one-and-a-half-candle power; while at the expiration of twelve hours it still gives more than double the light of a Davy lamp when in good burning condition. Mr. Swan, the report states, was then engaged in reducing the weight of the lamp.* The principal objection to the electric light was that it gave no indication of the presence of gas ; but this has been got over by an adaptation of Liveing's firedamp-indicator to Swan's electric lamp. At a meeting of the North of England Institute of Mining and Mechanical Engineers, held on the 9th October, 1886, Mr. J. W. Swran read a paper describing the latest improvements in his electric safety-lamp. A considerable reduction had been made in size and weight, the latter being only sflb., and the cells are made liquid-tight, so that the lamp may be inclined, or even inverted, without danger. The principal alteration is in the firedamp detector, which is on the same principle as those of Monnier, Coquillion, and Maurice. By an ingenious arrangement of springs and a cam air can bo admitted to or excluded from a vessel in which is a small platinum wire. This wire is switched into communication with the battery, and becomes red-hot: when it is allowed to cool some coloured liquid is raised in a tube by the condensation of the watery vapour of the burnt gases, and gives an indication of the percentage of marsh gas, it is claimed, down to J per cent. The current is produced by a secondary battery, which is charged at a dynamo requiring, for a thousand lamps, five-horsepower. The cost of renewals is stated to be, in England, 2d. or less per lamp per week. The cost of the lamp itself is said to be at present £2, without the gas-indicator. 9. FIEEDAMP-INDICATOES. The ordinary method of testing for firedamp is, of course, by the flame of a safety-lamp, and it was at one time thought that the length of the cap on a flame would give some measure of the proportion of firedamp in the atmosphere. This idea, however, has been abandoned. The experiments of Messrs. Kreischner and Winkler show that, if the air contain 1 per cent, of gas, the reduced flame exhibits only the faintest traces of a cap when the illuminant is benzine or a mixture of rape-oil and petroleum, while with rape-oil even these traces disappear. When 2 per cent, of gas is present in the air, the cap may be distinctly seen on the flame of a benzine lamp, almost as distinctly on the flame produced by mixed rape-oil and petroleum, but less distinctly on the flame of rape-oil. Their experiments also indicate that, for small proportions of gas, the cap is most distinct in lamps to which the air is admitted below the flame, whichever illuminant may be employed. The lamps used by these experimenters were either of the Clanny type or of the Boty type, but with the inlet-holes protected by gauze; and they state that these lamps are more sensitive to the presence of gas than those of Davy and Stephenson. "If this be so," says the report, "the smallest proportion of marsh gas which can be distinctly detected by the Davy lamp, the lamp generally used in this country (and, it may be added, in New Zealand) for the examination of the air of a mine, is from 2'5 per cent, to 3 per cent." The experiments of Mr. Galloway, Sir P. Abel, and others have proved that about 2 per cent, of firedamp in the air of a mine may, when a very inflammable coal-dust is thickly suspended in it, produce under certain conditions a violent explosion. It is plain, therefore, that an ordinary safetylamp does not afford the means of ascertaining whether the workings of a mine are sufficiently free from gas to insure safety.

* Professor Lupton, F.G.S., speaking at Leeds on" the 11th October, 1880, stated that the Swan lamp weighed sJlb., and that a primary-battery electric lamp lent by Mr. L. F. Walker weighed only 2|lb., but gave an inferior light.

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One of the simplest firedamp-indicators is that of Mr. Pieler, which consists of a large safetylamp constructed to burn alcohol with an argand wick : there are various chimneys and air-tubes, but, as the lamp is unsafe in a very moderate current, it is not in its present state admissible in mines. The indicators of Monnier, Coquillion, and Maurice are dependent upon the combustion by a heated platinum wire of the marsh gas contained in a closed vessel filled with the air of the mine, and the consequent contraction in the volume of the enclosed gas-mixture. Other indicators are dependent upon the alteration of pressure produced by the combustion of the inflammable constituents of firedamp ; by the rise of temperature consequent upon sudden compression of the air ; by the difference in diffusive power between pure air and air mixed with marsh gas; by the difference in specific gravity ; by observing the length of a tube, containing the air to be tested, which gives the maximum resonance when a tuning-fork of given pitch is set in vibration near its open end; and by many other means more or less suitable for use below ground ; but the one most adapted for use appears to be that of Mr. Liveing, who utilizes the increased brilliancy given off by a heated platinum wire under the following circumstances: When a heated platinum wire or platinum in a finely divided or porous condition is in contact with a mixture of marsh gas and oxygen or air, the marsh gas is wholly or partially consumed, and the heat generated by the combustion is to a certain extent communicated to the platinum, which consequently attains a higher temperature than it would do if surrounded by air, all other circumstances being the same. Mr. Liveing's indicator is constructed as follows : In a narrow box, about Bin. long, are fixed two spirals of a fine platinum wire about 4in. apart: these are arranged to have equal electrical resistances, so that when the same electric current passes through both spirals they are raised to the same temperature. One of these spirals is enclosed in a tube with a glass cover at the end facing the second spiral; this tube is air-tight, and is filled with pure air. The second spiral is surrounded by a cylinder of wire gauxe, also having a glass cover at the end facing the first spiral. Directly between the glass covers is a small wedge-shaped screen, placed so that one of the inclined surfaces is illuminated only by light from the first spiral, while the other is exposed only to light from the second spiral. This screen can be observed through a narrow glass window in the top of the box, and it can be moved until the two inclined faces are seen to be equally illuminated. The junction line of the two inclined screens traverses a graduated scale, and its position relative to the spirals can be thus determined. By turning a handle outside the box an electric current is passed through both the spirals of sufficient intensity to raise them in air to a moderate red heat. The following table, giving the results of observations made by Mr. Liveing, shows that, ay the percentage of marsh gas rises, the ratio of the illuminating-powers of the two spirals increases very rapidly. Column 1 shows the percentage of marsh gas present in the air. Column 2 shows the ratio of the illuminating-power of the exposed spiral to that of the spiral in pure air. Col. 1. Col. 2. Col. 1. 001. 2. 0 ... ... 1 2-50 ... ... 6-0 0-25 ... ... 1-23 3 ... ... 8-55 0-50 ... ... 1-52 3-50 ... ... 12-7 1 2-24 4 19-3 1-50 ... ... 3-10 4-50 ... ... 31-0 2 ... ... 4-28 5 ... ... 51-4 With regard to firedamp-indicators, the Commissioners have arrived at the conclusion that " it is most important that all mines should be carefully examined by means of indicators capable of detecting as small a proportion as 1 per cent, of gas ; such examination to be made before the commencement of each day-shift, and, in cases of interval, also before the succeeding shift." 10. Shaft-accidents. In Great Britain, as also in this colony, shaft-accidents are of rare occurrence. The report states that at the Navigation and Deep Duffryn Collieries, in South Wales, nearly six millions of persons had gone down and been brought up a shaft 1,290ft. deep without a single accident. At Eosebridge Colliery Mr. Bryham has raised, with a flat steel rope, from 2,400ft. deep, in fifty-five seconds, for ten years, and from l,Boot. for eleven years before, and never had a fatal accident. The first safety-cage prominently brought before the public was that of Mr. E. N. Fourdrinier, which depended on wedges drawn in between the guides and the framework of the cage by a spiral spring released on the breakage of the rope. " The plan proposed by Kope," says the report, " in connection with the system of two cages with a baiance-ropo passing from the bottom of one to the bottom of the other, is also one intended to act by arresting the descent of the cage gradually. In this arrangement a pair of side-ropes connect the top of the two cages, and pass over special pulleys resting on spring pedestals, which are sot on the pit-head frame : these pedestals, when the weight comes .upon them, act as a brake. Although circumstances may sometimes favour the action of safety-clutches, it is evident that serious danger will still remain from the possible rupture of the guides, in consequence of the strain put upon them by the sudden checking of heavy weights (which may amount to 10 tons) when moving with velocities of 30ft. to 60ft. per second. In the earlier days of these inventions much confidence was placed in their certainty of action ; but we have ourselves observed that several varieties, after being tried for a few years, have been discarded, whilst, with regard to others which survive, opinions are much divided as to whether they do not introduce fresh sources of danger. There are, in fact, many cases on record of clutches coining into operation when not required. On the other hand, experience has unfortunately shown that many examples of safety appliances have, at the critical moment, failed to act, some even when provided with a brake-lever under control of a practised man, in addition to an automatic arrangement. Such appliances will, of course, have the best chance of acting successfully with the ascending rope ; and, in cases where the speed is moderate, and the conductors are solidly made of wood, or of iron or steel rails, we hope that some 2—C. 4.

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of them may yet be found available. We have, however, examined several varieties of the safetycages in use, as well as those exhibited at successive international exhibitions, and we have considered a large number recently described and figured in an elaborate paper by Herr Sulbach, and we are unable to come to the conclusion that any one of them is a trustworthy safeguard against accidents." " Safety-hooks," for detaching the rope and suspending the cage, are spoken of more favourably, the Commissioners expressing a belief that no definite objection can be brought against their use, and a further opinion that the best appliance for preventing fatalities from over-winding is an automatic steam-brake attached to the winding-gear. With regard to testing ropes, the report states: "It is important to remember that the strength of a rope, if tested for its whole length, may be seriously affected by too great a strain being put upon it in the process of testing, and hence that any step in this direction must be taken with great caution." The Commissioners attach great importance to the systematic inspection of each mine by the workmen, as provided for in General Eule 30 of "The Coal-mines Eegnlation Act, 1872," and recommend that this provision be generally and regularly acted upon. The same power is possessed by the miners of this colony under General Rule 47 of " The Coal-mines Act, 1886," and it is to be hoped that they will avail themselves of it. [ Approximate Cost oj Paper. —Preparation, nil; printing (1,350 copies), ,±'G IGs.j.

By Authority: Geougs Didsbuby, Government Printer, Wellington.—lBB7.

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