Dec. lo, 1885] 



NATURE 



141 



to express a decided view on the subject (such as Mr. Burt, Sir 

 G. Elliot, and the late Mr. Knowles), that blasting should be 

 prohibited, at any rate in fiery mines. It was admitted that 

 the cost of working coal would be much increased by the en- 

 forcement of the suggested prohibition, and the majority of 

 competent witnesses examined afterwards by the Royal Com- 

 mission maintained that the abolition of shot-firing in coal- 

 getting must be .attended by very formidable difficulties, and 

 must, in fact, cause the closing of many pits. 



I have shown that even the comparatively very small amount 

 of fire-damp which may, at any rate occasionally, pervade the 

 air in portions of mine-workings where thorough ventilation is 

 most effectually provided for, and may escape detection, suffices 

 to determine the production of a disastrous explosion, if, under 

 these circumstances, a blown-out shot occurs where an accumu- 

 lation of dust exists ; and that it is even possible, in the complete 

 absence of fire-damp, for a blown-out shot to give rise to an 

 explosion in a very dusty working or mine, where the coal is 

 of a specially inflammable and sensitive character. Such being 

 the ca-e, the fact cannot be ignored that last year's decision of 

 the late Home Secretary — which raised consternation in many 

 mining districts — to prohibit the firing of shots in any colliery 

 within a period of three months after the existence of gas had 

 been there reported (while the workmen were in any part of 

 the mine), is far from affording the contemplated protection 

 against disaster resulting from the use of explosives in the 

 ordinary maimer. 



This most grave aspect of the question has received the 

 .anxious attention of the Commissioners, who would not have 

 considered themselves justified in relinquishing their work until 

 they had practically investigated, as far as in their power, any 

 measure or suggestion appearing to afford promise of aid in 

 furnishing definite replies to the followmg important questions : — 



{(i) Whether sufficiently efficient substitutes for explosives exist 

 to warrant the assertion that their abolition need not interfere 

 very materially with the reasonably profitable working of 

 collieries ; 



(b) Whether, therefore, it is practicable to limit their use 

 strictly to localities where the absence of every possible risk of 

 explosion can be demonstrated ; or 



(c) Whether any modifications in the ordinary method of using 

 explosives in mines can be so confidently relied upon to guard 

 against, or overcome, certain dangers attendant upon bhasting 

 operations in collieries, that it may be practicable to clearly 

 define and lay down certain conditions which will insure the 



, safe use of explosives, either generally, or in all but special cases, 



1 which can be precisely defined. 



] As regards the first question : — The power and efficiency of 

 recently improved mechanical appliances for bringing down coal 

 or for driving headings or crossways, warrant the sanguine ex- 



I pectation that compressed air and even manual power may be, 



; at no distant day. brought to bear so advant.ageously in mines 



I where fire-damp occurs, as to render it no great hardship to dis- 



I pense with the use of explosives in some of the work where at 

 present they are considered indispensable. 



The considerable and very rapid increase in volume which 

 freshly-burned quicklime sustains when slaked, led, many years 

 ago, to attempts to apply it to the bringing down of coal ; but 

 the idea did not assume a really practical form until Messrs. 

 Sebastian Smith and Moore worked out a simple method of 

 applying the lime so as to insure the effective operation of the 

 disruptive force which it is capable of exerting, and to utilise the 



I considerable he.at, developed by the union of the lime with w.iter, 

 in the rapid generation and super-heating of steam in somewhat 



! considerable quantity, thus supplementing, in an important 

 manner, the force exerted by the expansion of the lime. The 

 public has been made familiar, in last year's and this year's 



I Exhibitions, with the general nature of Messrs. Smith and 

 Moore's lime cartridges. The Commissioners witnessed their 



I performances at Shipley Collieries soon after their successful 

 elaboration, and the results of subsequent inquiries and experi- 

 ments have convinced them that, for coal-getting, the lime 



I process can be, to a large extent, substituted for povvder, and 

 that its employment, while securing comparative immunity from 



, danger, is unattended by any important pr.actical difficulties. 



; It has received extensive trial in many of our mining districts, 

 and also on the Continent, and has already taken firm root in 



I some parts of Staffordshire, Yorkshire, and Derbyshire. Its 



I elaborators do not contend that it afTords the means of dispens- 



I ing with the use of explosives, or of specially powerful 



mechanical appliances, in the removal of stone, or even in some 

 very hard coal ; but it is certain that in many collieries, 

 where the prevalence of fire-damp renders the use of the safety 

 lamp imperative, the replacement of shot-firing by lime-car- 

 tridges, while unattended by any increase in the cost of getting 

 the coal, would reduce the risk of explosions to those arising 

 from carelessness, or from what should now become the very 

 remote contingency of the use of unsafe or defective lamps. 



The idea has been entertained that, by surrounding or cover- 

 ing the charge of powder in a shot-hole with some material 

 which evolves vapour of water, or carbonic acid, when exposed 

 to sufficient heat, these would be liberated by the firing of the 

 shot in sufficient quantity and with sufficient rapidity to extin- 

 guish flame and sparks jirojected by it ; but the authors of such 

 suggestions have failed to realise the fact that the exposure of 

 these substances to heat on the firing of a shot would be almost 

 instantaneous, and would therefore leave, at any rate, the greater 

 proportion pnactically unaltered. 



It was suggested by me to the Commissioners that possibly 

 the sudden liberation of carbonic acid, confined in the liquefied 

 state, and placed either over or under the charge in a shot-hole, 

 might prove effective in extinguishing flame and sparks, and a 

 number of experiments have been made in this direction, with 

 considerable, though not complete, success. 



Dr. McNab was the first to put into practical execution the 

 idea of using water tamning, in the form of a long cylinder filled 

 with the liquid and placed over the powder charge ; with the 

 twofold object of extinguishing the projected flame and sparks, 

 and of diminishing, by dispersion of the water in the immediate 

 vicinity of the shot, the persistence of the powder smoke, which 

 is a source of much inconvenience and loss of time. While it has 

 been demonstrated that decided economy in time does result from 

 the more rapid clearing of the air from smoke when the water 

 tamping is used, many careful experiments conducted for the 

 Commission have shown that no reliance could be placed upon 

 the extinguishing power of water, applied in the way originally 

 suggested by Dr. McNab. 



In 1879 I suggested to the Commission a plan by which pos- 

 sibly the more violent explosives, of the dynamite class, might 

 be safely and efficiently applied to the getting of coal, based upon 

 the principle of distributing the force developed by the detona- 

 tion of small charges over a considerable area through the agency 

 of a column of water, within which the detonated charge was 

 confined. This principle, which has since received important 

 applications in connection with military service, appeared applic- 

 able to effect a modification of the shattering action, which 

 renders the violent explosives inapplicable to coal-getting, when 

 used in the ordinary manner, their effects being thus assimilated 

 to those of powder, while the sparks and highly-heated gases 

 projected by a blown-out shot might be effectuirly quenched by 

 the water which would envelope them at the instant of their 

 projection. 



Experiments carried out at Wigan in 1880, demonstrated that 

 the coal brought down by small charges of dynamite inclosed in 

 water compared very favourably with the best results furnished 

 by full powder charges, and these results have been fully con- 

 firmed by trials since carried out for the Commission in South 

 Wales. Absolute immunity from danger of the ignition of an 

 explosive gas-mixture by a blown-out shot of dynamite or similar 

 explosive agent was not found to be secured by this system of 

 blasting ; such was the case, however, then the blown-out shot 

 was projected into air containing fire-damp in proportions ap- 

 proaching that of an explosive mixtui'e, and in which a very 

 inflammable coal-dust was thickly suspended. It has a o been 

 found, in the Commissioners' experiments, that the supei position 

 of the water-tamping, according to Dr. McNab's original plan, 

 over a dynamite charge, appears to afford security aga nst the 

 ignition of a dust-laden mixture of air with a somewhat con- 

 siderable proportion of gas. 



Even while actively engaged in the completion of their Report, 

 the Commissioners are still pursuing this subject experimentally, 

 with the desire of furnishing, as far as in their power, decisive 

 and thoroughly reliable data regarding the amount of security 

 which appears to be afforded, by these methods of working, 

 against the most prominent and prevalent sources of danger in 

 connection with the use of explosives in coal mines ; and — while I 

 have been engaged upon this address — a still more simple method 

 of applying water to counteract the dangers arising from blown- 

 out shots has suggested itself to Mr. Galloway, — preliminary 

 experiments with which have furnished most important results. 



