Dec. lo, 1885] 



NA TURE 



139 



illumination of a murky, dirty coal-pit, as in the transformation 

 of a plot of ground in South Kensington into fairyland." 



Attempts have been made in several of the mining districts 

 to apply electricity to underground illumination ; so far as 

 distribution of the light in main roads is concerned, no 

 great progress has been made, though there is now no reason 

 why glow-lamps, protected after the manner in use at our 

 Government Gunpowder Works (as shown in the recent Exhi- 

 bition), should not be distributed to considerable distances along 

 such portions of a mine. At Risca Colliery, in Monmouthshire, 

 at Harris's Navigation Colliery, near Pontypndd, and at Earnock 

 Colliery, at Hamilton, N.B., a commencement has .already been 

 made in this direction with satisfactory results. If, however, 

 the miner is to have an electric lamp for lighting up drifts and 

 working places, it must be .supplied to him in a self-contained 

 and really portable form, with absolute isolation of the glow- 

 lamp from the surrounding atmosphere, and with a store of 

 power sufficient to maintain an efficient light for ten or twelve 

 hours. 



The considerable improvements which have of late been 

 effected in accumulators, and the advance which has also been 

 made in the construction of constant primary batteries, have led 

 to ver)' important progress toward the attainment of these essen- 

 tials. Mr. J. Wilson Swan, universally celebrated for his 

 achievements in the matter of glow-lamps, has patiently pursued 

 the subjecL and has not long since succeeded in producing a 

 lamp which, with its small storage battery, weighs little more 

 than 8 lb., and which \\'\\\ furnish a light equal to from two to 

 four times that given by the better forms of safety lamp for a 

 duration of ten or twelve hours. Mr. Swan is sanguine that he 

 will ere long be able to effect an important reduction in the 

 weight and bulk of the lamp, and he is not less hopeful of elabo- 

 rating a primary battery similar in portability and light-giving 

 power, the substitution of which, if successful, for the accumu- 

 lator would have the advantage of dispensing with the necessity 

 for providing dynamo-electric machines and power for charging 

 the storage cells. Other workers besides Mr. Swan, such as 

 Mr. Coad and M. Trouve, have been applying small primary 

 batteries to the production of miners' lamps with some promise 

 of success, although as yet the results furnished do not bear com- 

 parison with those obtained by Mr. Swan with the storage 

 battery. Those wlio have spent any length of time under ground, 

 especially in the very low ivorkinss which abound in coal mines, 

 and at the high temperature which often prevails in the workings 

 of deep mines, will have experienced the fact that any incum- 

 brance may sometimes become very burdensome, and can well 

 understand, therefore, that the weight and size of even the 

 lightest form of battery with which an efficient light could be 

 maintained for a sufficient length of time, may prove grave 

 obstacles to its extensive employment. Moreover, as the 

 electric light can afford no indication of the condition of the 

 atmosphere in a mine-working, its employment may not allow of 

 the safety lamp or some other testing appliance being dispensed 

 with. But, even if used only as an auxiliary mean? of illumina- 

 tion in working places, such lights as those which S« an and 

 others will supply, will prove very valuable, and especially so for 

 exploring purposes, after accidents due to outbursts of gas, when 

 the best safety lamps may be of little use, even if they continue 

 to burn. Such electric lamps must indeed become formidable 

 competitors of the Fleuss lamp (included in the recent Exhibi- 

 tion), which has, in conjunction with the portable apparatus for 

 the supply of respirable air to explorers, already performed 

 important service in rendering access to mine-workings possible 

 where an ordinary lamp could not burn, and where the 

 atmosphere was too foul to support life for any time. 



The sudden escape into a mine-working of a very large 

 volume of fire-damp, the accumulating pressure of which has at 

 length overcome the resistance opposed to it, either by the coal 

 or by the stone which forms the floor or the roof of the mine, and 

 the outrxish of which is sometimes accompanied by the ejection 

 of very large quantities of disintegrated mineral, constitutes the 

 most formidable danger connected with this associate of coal, 

 because little or no warning is received of its occurrence, and 

 because the volume of gas suddenly liberated is often so con- 

 siderable that the most powerful ventilating currents are for a 

 time inoperative, while their very action may be to distribute 

 gas rapidly in the form of an explosive mixture with air, to 

 distant parts of the mine-workings. The volume of gas suddenly 

 set free varies very greatly : sometimes it is so considerable that, 

 even with very powerful ventilation, the workings have not been 



restored to a safe condition for work, in regard to comparative 

 freedom from fire-damp, until several days after the occurrence 

 of the outburst. 



That these sudden emissions of gas have been intimately 

 connected with some of the most appalling disasters which have 

 occurred in coal mines appears beyond question, and there is 

 equally little room for doubt that the firing of shots, or use of 

 gunpowder for blasting coal or stones in mines, has been, in 

 many cases, intimately connected with those disasters. 



The occurrence of a sudden outburst of gas is, however, 

 not essential to the production of disastrous results by 

 the firing of powder or other explosives in coal mines. 

 The flame developed by the firing of a powder-shot may, 

 without any favouring circumstances, be projected to a consider- 

 able distance beyond the face of the coal or stone in which it is 

 fired, if, as is frequently the case, the force is insufficient to 

 accomplish the fracture of the bore-hole in which the charge of 

 explosive is confined, and the highly heated products of the 

 explosion are entirely projected from the hole, as if the shot had 

 been fired from a gun. Experiments upon an extensive scale 

 made, on this head, by the Commission, have shown that the 

 flame from a so-called blown-out shot may .le projected to distances 

 of thirty or thirty-five feet, in galleries similar to mine-workings 

 or drifts, and if, as is frequently the case, the small debris of 

 coal, which lies ready to hand in the working places is used to 

 tamp the charge with, the volume of flame from a blown-out 

 piwder-shot is very greatly increased in length and volume, and 

 may therefore easily extend to goaves, old working places, or 

 cavities where a fire-damp- and air-mixture may be lurking. 

 This is, however, by no means the only, or even the most 

 prominent, danger which may attend the occurrence of a blown- 

 out shot in even the best ventilated coal mine, quite independently 

 of the possibility of a sudden release of a considerable volume of 

 fire-damp during, and consequent upon, blasting. But before 

 referring to what now appears to be well established as the 

 chief general source of danger attending the use of explosives in 

 coal mines, I must touch briefly upon the means available for 

 searching for fire-damp, and for inspecting the workings of a 

 mine, to asceitain that all is safe before men descend to work, 

 or before shots are fired. 



The first eftect of introducing a Davy or other safety lamp into 

 an atmosphere containing small proportions of fire-damp is to 

 cause the flame to elongate, the extremity becoming narrow and 

 more pointed as the proportion of fire-damp increases ; when the 

 latter approaches a porportion which produces with air an 

 inflammable, and ultimately an explosive, mixture, a pale blue 

 halo or cap is perceptilile over the flame, and this increases with 

 an increase in the proportion of gas, until the cage or gauze of 

 the lamp is filled with flame. A Davy lamp of small proportions 

 is generally preferred by the overmen or inspectors for gas-testing 

 purposes; the flame is always reduced to small dimensions, so 

 that slight alterations in size or form may be more readily 

 observed. An experienced operator may identify so large a 

 quantity as 2 per cent, of gas in the au- of a mine, but even 

 this is very doubtful, except in the case of exceedingly expert 

 obser\-ers, who may perhaps succeed in thus detecting the 

 presence of I '5 per cent, of fire-damp. 



It has, however, now been conclusively demonstrated to be of 

 the greatest importance that responsible persons in coal mines 

 should befurnished with reliable means forexpeditiously detecting, 

 without the exercise of any very special skill, smaller quantities of 

 fire-damp than it is possible to identify with certainty, even by 

 the exercise of great skill in the use of a safety lamp. Hence 

 much interest and moment attach to the efforts which have been 

 made from time to time by scientific men to devise sensitive and 

 reliable fire-damp indicators. The late Mr. Ansell applied in 

 several very ingenious ways some results of Prof Graham s 

 classical researches on the diflusion of gases to the construction 

 of sensitive fire-damp detectors, which, however, did not justify 

 the confidence at first placed in them. The same principles 

 have since been applied, but apparently with no greater success, 

 by several foreign inventors of so-called GrisoumHres. The 

 late Dr. Angus Smith and Prof. George Forbes have pro- 

 posed to detect and estimate the quantity of fire-damp in the 

 air of a mine by ingenious applications of other important 

 principles in physical science, and the acoustic indicator, lately 

 exhibited by Mr. Blaikley, is a very pretty application of 

 the principle utilised in a different way by Prof Forbes. 

 Various forms of eudiometrical apparatus have been con- 

 structed with the same object : the variations in the density of 



