570 



NA TURE 



[April 15, 1886 



Therefore, in dry mine-workings, where the removal of dust, 

 combined with copious watering cannot be carried out, and where 

 neither of the alternative methods {a) and {b) of working in coal 

 or stone can be advantageously substituted for blasting by means 

 of powder, in localities where fire-damp is liable to have access 

 to the mine-workings, shot-firing may be safely carried on, pro- 

 vided that any one of the "high" or violent explosives is 

 employed, in one or other of the modes described, in substitution 

 for powder. But the methods of operation which furnish effec- 

 tive safeguards when applied in conjunction with the high explo- 

 sives fail to furnish such safeguard when applied in the same way 

 together with powder. Unless, therefore, effective measures be 

 adopted for the removal of dust as completely as practicable in 

 the vicinity of the place where the shot is to be fired, such re- 

 moval being followed by copious watering, the employment of 

 powder, or of any explosive preparation of a similar nature to 

 powder, .should be prohibited in dry coal-mines where fire-damp 

 may pervade the air, and whereat the same time coal-dust accu- 

 mulations are unavoidable. 



^ With the view of promoting security from accidents under 

 circumstances where blasting may be practised in coal-mines we 

 would recommend that the following instructions be observed ; — 

 (i) Tliat all work involving blasting in mines should be in- 

 trusted 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 tlie first part of the tamping in small 

 portions. (5) That where safety-lamps are used and powder is 

 employed the 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 twenty yards of the shots to be fired that fire- 

 damp does not exist to a dangerous extent. 



The employment of the ordinary miner's fuse, which when 

 burning is liable to allow fire to escape from its extremity or 

 laterally into the atmosphere, should not be permitted in any 

 mine-workings where the exigencies of safety dictate the exclu- 

 sion of powder and the substitution for it of one or other of the 

 "high"^ explosives in conjunction with water. .Similarly, no 

 description of mining fuse, however safe in itself, should be 

 allowed to be ignited in such localities by means either of a 

 lamp-flame or of a wire which has been made red hot by 

 inserting it into the gauze of a safety-lamp, or by means of any 

 other source of fire, which, when applied to the' lighting of the 

 fuse, must come into contact with the atmosphere of the mine. 

 Electrical exploding appliances present very important advan- 

 tages from the point of view of safety over any kind of fuse 

 which has to be ignited by the application of flame to its 

 exposed extremity, as the firing of shots by their means is not 

 only accomplished out of contact with air, but is also under 

 most complete control up to the moment of firing. Their 

 simplicity and certainty of action have been much increased of 

 late years while their cost has been greatly reduced, and but 

 little instruction is now needed to insure their efficient employ- 

 ment by persons of average intelligence. For the foregoing 

 reasons the use of electrical arrangements for firing shots in 

 mines, where the employment of powder for blasting is inadmis- 

 sible, should be encouraged as much as possible. Where the 

 regular use of electrical exploding appliances is attended with 

 serious difficulties, as in wet mines, a special form of miner's 

 fuse, now procurable at a cost very slightly, if at all, greater 

 than that of the ordinary miner's fuse, and exempt from the 

 defect of a possible lateral escape of fire, should be employed, 

 but it should be used only in conjunction with a special self- 

 contained igniting arrangement. Such an appliance should be 

 constructed to fit over the entire exposed end of the fuse in a 

 shot-hole, and to ignite the fuse out of cont.act with the air, and 

 after the lapse of a definite interval {i.e. five minute^) from the 

 time when it has been set into action by the person in charge of 

 the shot-firing. Simple, cheap, and efficient forms of "igniter" 

 have been devised which fulfil these conditions. 



^ It has been shown that mines which have hitherto been con- 

 sidered free from fire-damp may have the air which passes 

 through them vitiated to an extent corresponding to about 2 per 

 cent, of its volume of marsh gas. The air in many such mines 



may probably never be entirely free from explosive gas, at all 

 events in the neighbourhood of freshly cut faces of coal and in 

 the return airways. It has been demonstrated in our experi- 

 ments that when the atmosphere contains 5 to 5 '5 per cent, of 

 marsh gas it becomes highly explosive. We have even obtained 

 explosions which, though less violent, might be nevertheless de- 

 structive of life if they occurred on the large scale possible in a 

 mine when the air contained only 4 per cent, of marsh gas. It 

 will thus be seen that air which would appear free from gas if 

 tested in the ordinary way may become by the addition of only 

 about 2 per cent, of marsh gas capable of propagating flame and 

 causing destruction, while the addition of about 3 per cent, con- 

 verts it into a highly explosive mixture. As we have already 

 pointed out, air which would appear quite free from gas if 

 examined by a lamp flame may become explosive when laden 

 with fine, dry coal-dust. It has been stated that appliances now 

 exist by which very small proportions of marsh gas in air may 

 be readily detected, and which can be used for examining the 

 atmosphere of a mine. With Liveing's indicator present, gas 

 in the air can be estimated with sufficient accuracy for all practical 

 purposes, even when the proportion is as low as o'25 per cent. 

 Maurice's indicator is also capable of giving accurate measures 

 of the proportion of gas, and is very portable, but the time re- 

 quired in taking an observation with the instrument in its 

 present form seems to preclude its practical application. 



The natural inference from the foregoing is that some mines 

 hitherto considered safe with naked lights may at times be in 

 peril. It may be that risks of e.tplosion, arising out of the 

 possibility of an unforeseen contamination of the air by fire- 

 damp to a dangerous extent in parts of the workings of some 

 coal-mines, can only be provided against by the invariable use 

 of safety-lamps. We have not, however, considered it advisable 

 to make a suggestion of this nature, because the great prepon- 

 derance of cisualties due to falls of stone and c:)al, over those 

 .arising from explosions, points to the importance of miners 

 having the advantage of superior illumination afforded by naked 

 lights in comparison \\ith even the best forms of safety-lamp, 

 when the circumstances of the mine, in regard to association of 

 fire-damp and coal-dust, do not necessitate the use of safety- 

 lamps. 



We have therefore arrived at the following conclusions ; — 

 (i) That it is most important that all mines should be care- 

 fully examined by means of indicators capable of detecting 

 as small a proportion as i per cent, of gas ; such examina- 

 tion to be made before the commencement of each day-shift, 

 and, in case of an interval, also before the succeeding shift. 

 (2) That in all dry mines where the air may be laden with 

 coal-dust, and where fire-damp is either known to be given 

 off from the strata, or may from experience be reasonably 

 suspected to exist, the Secretary of State may require safety- 

 lamps to be used, unless the owners and workmen of such 

 mines prove, to the satisfaction of a court of arbitration to be 

 appointed by the respective parties, that less liability to acci- 

 dents, generally, will be involved by the working of the mine 

 with open lights than by the use of safety-lamps. It should 

 be a special instruction to such court that the circumstances 

 of each mine be taken into consideration with reference 

 to the following points : (rt), the mode of working ; [b), the 

 nature of the coal-seams and of the roofs and floors of the seams 

 and of the adjacent strata ; (f), the proximity of the seams to 

 each other ; {d), the emission of gas from tlie seam, and the 

 liability to blowers or outbursts of gas from the coal, roof, or 

 floor ; (e), the order of working the seams of coal. For the 

 system which prevails in some places of working with mixed 

 lights — that is, with open lights and safety-lamps intermixed in 

 the same set of workings — there is no justification, and this prac- 

 tice should be strictly prohibited. We are of opinion that in 

 mines where safety-lamps are required, the position of lamp 

 stations, or places where open lights are allowed, in reference to 

 the possibility of access of vitiated air, should receive much more 

 attention than at present. It is desirable that, at convenient 

 places near the working faces, reserves of lighted and locked 

 lamps be kept available for exchange with those extinguished in 

 the workings. 



It has long been known that if the atmosphere become inflam- 

 mable the Davy and Clanny lamps, and in a less degree the 

 .Stephenson lamp, are unsafe in currents having velocities much 

 below those encountered in well ventilated mines. Our experi- 

 ments fully confirm this. The ordinary Davy lamp becomes un- 

 safe before a velocity of 400 ft. per minute is attained. The 



