Chapter XLI: Explosions and Explosives

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_Introductory_

In the following pages I have made no attempt to scientifically discourse upon the composition and properties of explosive bodies, nor have I endeavoured, on the other hand, to write an elementary treatise on the subject; such matters have been fully attended to already by Berthelot, Guttmann, Eissler, and others, while much useful information is also obtainable in the _Dictionary of Explosives_ and the _Handbook of Service Explosives_. My object has rather been to offer to such of the educated public as already possess a general knowledge of the subject, a few remarks from a point of view from which it has never yet to my knowledge been approached except in Blue Books, while at the same time I have striven to avoid reiteration of information already published in our Annual and Special Reports.

Moreover, I have endeavoured to exclude, so far as may be, all matter not entirely germane to the question at issue, viz., the special risks connected with the trade in explosives in the United Kingdom.

Until the year 1845 “explosive” and “gunpowder” were to all intents and purposes synonymous terms, and even now as an explosive of universal application gunpowder stands unrivalled. In these days of specialism, however, it is being rapidly ousted from the field of battle, by cordite as a propellant, by lyddite as a burster for shells, and by gun-cotton as a destructive agent; from the field of sport, by the countless nitro-powders; from the quarry and railway tunnel, by the gelatine dynamites; and lastly, from the coal mine, by the so-called safety explosives. As a coal-getter pure and simple, irrespective of the question of danger from fire-damp and dust, it still, however, stands unequalled, and in view of the recent vast improvements in its manufacture--the result, no doubt, of legislative action--it would be exceedingly rash to state that its days are numbered.

The great epoch-marking events in the history of explosives may be briefly stated as follows:--

_First_, the discovery of the deflagrating properties of saltpetre in admixture with carbonaceous material, and its consequent utilisation in the form of Greek fire and such like destructive compounds, date unknown.

_Second_, the first use of gunpowder as a propellant, in or about 1320 A.D.

_Third_, the invention of gun-cotton, in 1845.

_Fourth_, the discovery by Alfred Nobel in 1875, that a variety of gun-cotton, or rather nitro-cotton, could be dissolved in nitro-glycerine to form the homogeneous jelly-like mass to which he gave the name of blasting-gelatine. To these may perhaps be added the discovery of the power of transmitting detonation possessed by fulminate of mercury.

Although there are doubtless many other important discoveries connected with the evolution of our multitudinous modern explosives, yet, without belittling the genius of their inventors, they may all be regarded as mere episodes, so to speak--the adaptation of existing principles. Thus, nitro-glycerine and dynamite followed naturally in the wake of nitro-cellulose, just as the gelatine dynamites and more recently ballistite and cordite were merely modifications of blasting gelatine. Perhaps the most important discovery in addition to those above mentioned was Sir Frederick Abel’s process of pulping and cleaning gun-cotton, or rather the principle underlying the process, viz., that only by thorough cleansing can stability be assured to a nitro-compound.

About lyddite there is little to say which has not already appeared in the daily papers, and of that little the greater part is confidential; but as regards its effect on the enemy, I have it on the authority of an artillery officer who was engaged in every action of the campaign which terminated in the relief of Ladysmith, that it was quite impossible to obtain reliable information. Even when a rout resulted from its use, it is doubtful whether this was not due as much to the steep angle of descent of the howitzer fire as to the explosive effect of the lyddite. The stories as to the wholesale havoc wrought at Omdurman, where entire ranks of horsemen are said to have been laid low by a single lyddite shell without a mark being found on them, must be accepted with caution. A shell filled with high explosive naturally bursts into very much smaller fragments than when filled with gunpowder, and the resulting wounds would in many cases no doubt be difficult to discern at a cursory examination.

Of all branches of the explosives industry fireworks are perhaps the most difficult to control. Not only is it a common custom at North of England weddings to improvise amateur displays by filling iron pipes with gunpowder and applying a light, but the actual manufacture of squibs and rockets is regarded in most quarters as a praiseworthy and legitimate occupation, provided there is no question of sale. That this is entirely erroneous cannot be too strongly emphasised--the fine on conviction being no less than £100 a day. Moreover, since the amateur pyrotechnist invariably includes both chlorate of potash and sulphur in his coloured fire composition, a mixture entailing grave risk from spontaneous combustion, and one which is on this account prohibited by Order in Council, a further offence is involved.

_Accidents in Manufacture and Use._

There is no industry possessing greater possibilities for sudden death to its operatives than that connected with the manufacture, storage, and conveyance of explosives; and there is no industry of an admittedly dangerous nature demanding fewer victims. The reasons for this happy result are not far to seek, and may be summarised in two words--legislation and self-interest. The destruction of property caused by an explosion in a factory is a mere fraction of the actual loss; for days or even weeks the employés may not only refuse to return to work, but may make use of the accident as a lever to obtain a permanent rise in wages. Moreover, in gunpowder factories particularly, where every trace is swept away, the cause of the explosion is often impossible to determine, and the vague feeling of unrest to which this uncertainty gives rise is by no means conducive to efficient work. Thus, even the apathetic manufacturer is constrained by motives of self-interest to enforce certain precautionary measures (which, however, he is quite prepared to relax under the strain of competition), while the conscientious trader who really has the safety of his workpeople at heart is only too easily persuaded by the additional incentive of personal profit to institute and maintain a very high standard of discipline throughout his factory. It is, however, extremely difficult for either of these individuals to differentiate between what may be called essentials and refinements, and the unscrupulous trader, in his anxiety to sail as near the wind as possible, may neglect some obvious precaution, whereas his less reckless rival may be seriously handicapped by a _too_ close attention to details. Here, then, is where legislation steps in, and by enforcing equal restrictions on all, prevents undue economy at the expense of safety--and, moreover, the public are properly protected. With the courteous assistance of the trade, I am able to give some figures in support of this. The total quantity of explosives manufactured per annum in the United Kingdom, exclusive of that which is produced in Government factories, is approximately as follows[143]:--

Classes I. to IV. (_i.e._ gunpowder, other nitrate mixtures,
nitro-compounds, and chlorate mixtures), 32,115 tons.

Class V. Fulminate of mercury being the only explosive of
this class made in any quantity, and the manufacture being
practically in the hands of two firms, one of which is domiciled
in the Channel Islands, I must not for obvious reasons disclose
the total output.

Class VI. (Ammunition). Here again it is impossible to specify
with any degree of accuracy the number of the various natures
of explosive coming under this head. Fifty million detonators,
electric detonators and fuses, and an equal number of yards of
safety fuse will not be very wide of the mark, while about 500
million cartridges for small arms are turned out by licensed
factories during the year.

Class VII. (Fireworks). About 1788 tons.

In the actual operations of manufacture 4828 persons are employed, the total number working within the licensed areas, and therefore more or less exposed to the effects of an explosion, being 11,098. During the year 1899, 54 accidents occurred in the manufacture of explosives, causing the death of 3 persons and injuries to 24, the average for the last ten years being 4.4 and 20.4 respectively. Of the 54 accidents no less than 32 were unattended with loss of life or personal injury--a fact that would be somewhat remarkable were it not that in many operations in which the application of force is required, or where the explosive is of an extra sensitive nature, accidents are unavoidable and provided for accordingly. “Prevention,” in fact, being impossible, a “cure” is applied. Among these specially dangerous processes may be instanced the “milling” or “incorporation” of gunpowder, the “pressing” of detonators, and the mixing of cap composition, during each of which the operator is either directly or indirectly specially protected.

In the following table I have endeavoured, by collecting the results of the last ten years, to show the relative risk attached to the manufacture of various classes of explosives. The classification is by no means in accordance with the Order in Council classifying explosives, but is better suited to the particular purpose in view.

_TABLE A._

Showing the Number of Accidents causing Personal Injury, and the
Number of Killed and Injured in the Manufacture of the Various
Natures of Explosive during the decade 1890–99, and the Number
of Persons now Employed.

+--------------------------+---------------------------+------------------------------------+ | | Accidents causing Loss of | Number of Persons Employed in the | | | Life or Personal Injury. | Manufacture of the various natures.| | +----------+-------+--------+----------+--------+----------------+ | Nature of Explosive in | No. of | | In the | In | Per 1000 | | course of Manufacture. |Accidents.| No. of Persons | Danger |Licensed| per annum. | | | +-------+--------+Buildings.| Area. +-------+--------+ | | |Killed.|Injured.| | |Killed.|Injured.| +--------------------------+----------+-------+--------+----------+--------+-------+--------+ |1. Gunpowder | 18 | 10 | 23 | 964 | 1,906 | .52 | 1.2 | |2. Nitro-glycerine and | | | | | | | | | Cellulose Explosives | 47 | 17 | 58 | 2034 | 4,021 | .42 | 1.4 | |3. Ammunition, exclusive | | | | | | | | | of Detonators | 39 | 5 | 43 } | | | | | |4. Fulminate Compositions,| | | } | 1155 | 4,267 | .23 | 2.2 | | in or out of | | | } | | | | | | Detonators and Caps | 48 | 5 | 54 } | | | | | |5. Fireworks | 23 | 7 | 26 | 675 | 904 | .77 | 2.9 | +--------------------------+----------+-------+--------+----------+--------+-------+--------+ | Totals | 175 | 44 | 204 | 4828 | 11,098 | .39 | 1.8 | +--------------------------+----------+-------+--------+----------+--------+-------+--------+

Under heading No. 2 are included the various smokeless powders for sporting purposes, but as a matter of fact no accident causing personal injury has occurred in their manufacture during the last ten years, and the same may be said of safety fuse, which comes under heading No. 3. The explosives of the ammonium-nitrate group also have a stainless record up to the present, and they no doubt possess a very high degree of safety in manufacture; but those of them which contain dinitrobenzol present another kind of risk quite independent of their explosive properties. This subject is, however, fully dealt with elsewhere by Dr Prosser White, and will not be enlarged on here. As regards their apparent safety in manufacture, too much stress must not be laid on their immunity from accident in the past. They can most of them be exploded by combined friction and percussion, and though as a rule only the part affected will explode, this applies also in the case of gun-cotton and many other admittedly sensitive compounds, and it would be rash to predict the result under circumstances specially favourable to the transmission of detonation.

To the accidents in actual manufacture, those occurring during the storage and distribution of the finished product must also be added, since they may be said to have taken place under conditions to which the controlling provisions of the Act are intended to apply. Thus 69 accidents, causing 32 deaths and injuries to 81 persons, occurred under these headings during the decade 1890–1899, making a grand total of 76 killed and 285 injured in the period named, or an average of 7.6 killed and 28.5 injured per annum in that section of the industry which is presumably controlled by experts supplemented by Government inspection. Briefly, this result has been attained by (_a_) subdivision of risks, _i.e._, the number of persons allowed in any one “danger” building is strictly limited, and communication of explosion between buildings is prevented by the erection of mounds of earth or masonry, and by making the quantity of explosive in any building directly dependent on its distance from others; (_b_) scrupulous attention to cleanliness; (_c_) prevention of the introduction of matches and other dangerous articles, by providing suitable clothing without pockets, and by a thorough system of searching all those employed in danger buildings; and (_d_) the provision of an adequate number of escape doors opening outwards, and provided with safety latches so as to yield easily to a push from the inside. Many manufacturers of their own initiative go far further in these directions than is enjoined by statute, with the result that in discipline, efficiency, and immunity from accident, their factories compare most favourably with the Government establishments.

On turning to the question of risk in the _use_ of explosives, the prospect is not so pleasing; the contempt bred of familiarity is something appalling. It is not too much to say that 99 out of every 100 accidents would have been avoided by the exercise of reasonable care and common sense. Scraping out detonators with pins, thawing dynamite over the fire in tin dishes, driving gunpowder and dynamite with metal rods into roughly drilled holes, and boring out misfires, are only a few of the commonest examples of reckless folly. In mines alone there were no less than 29 persons killed and 195 injured by explosives during the year 1899, and this be it remembered in the handling and use of the finished article, each nature of which is thoroughly tested for purity and absence of extreme sensitiveness before being authorised by the Home Office, whereas in the course of manufacture many operations have to be undertaken which are known to be dangerous, even with the exercise of the greatest care. Quite recently a fatal accident was reported as follows:--“A. B. was charging a bore-hole in rock with pellet gunpowder. Finding a difficulty in inserting the charge, he was holding the tamping rod on the powder while his mate drove it home with a sledge-hammer, when, _for no reason whatever_, the charge exploded.” The italics are my own.

_TABLE B._

Showing the Number of Accidents in the handling and use of
the various Explosives during the decade 1890–99.

+----------------------------+----------+----------------+
| | | No. of Persons |
| Nature of Explosive. | No. of +-------+--------+
| |Accidents.|Killed.|Injured.|
+----------------------------+----------+-------+--------+
|1. Gunpowder[144] | 244 | 94 | 294 |
|2. Nitro-glycerine Compounds| 376 | 135 | 440 |
|3. Ammonium Nitrates | 44 | 12 | 41 |
|4. Detonators | 143 | 3 | 193 |
|5. Fireworks | 41 | 19 | 96 |
+----------------------------+----------+-------+--------+
| Total | 848 | 263 | 1064 |
+----------------------------+----------+-------+--------+
|Total in Manufacture during | | | |
| same period | 175[145]| 44 | 204 |
+----------------------------+----------+-------+--------+

In Table B, I have summarised the accidents which have occurred during the ten years 1890–99, in order to give some idea of the relative risk attached to the handling of the various explosives. It is, however, somewhat misleading in view of the impracticability of forming even a rough estimate of the quantity of each description used, and also of the fact that ordinary mining accidents with gunpowder are not required to be reported.

The accidents with ammunition other than detonators are so insignificant in number and effect that I have omitted them from the above table, but, on the other hand, the ammonium-nitrates now contribute their quota of casualties. Whatever margin of safety they may possess alone, it is nullified the moment the detonator is fitted, and without this deadly little adjunct they are useless. The ideal mining explosive is no doubt one which, while possessing the slow action and consequent “coal-getting” properties of gunpowder, together with its capacity for exploding without the use of a detonator, shall at the same time be as safe to manufacture, store, convey, and use in a “fiery” or dusty mine, as an ammonium-nitrate explosive. Moreover, it should have the plasticity of gelignite with similar immunity from injury by water, should require a bore-hole of but small diameter, and lastly, should produce on combustion nothing more harmful than CO_{2} and water. If to these advantages cheapness be added, and the inventor has sufficient capital to properly exploit its capabilities, such an explosive may possibly have a future before it--but the British miner is very conservative, and has a deep-rooted affection for gunpowder.

I have already referred to the system by which the quantity of explosive allowed in a licensed building is automatically regulated by the distance that can be maintained between the building and the nearest highway, dwelling-house, railway, etc., and from the social aspect the application of this principle is of more importance in the case of an isolated magazine or store (of which there are several thousand in the United Kingdom) than when only the various buildings of an individual factory are involved. Fortunately, owing to the care with which explosives of questionable stability are excluded from the authorised list, an explosion in a magazine or store is of the rarest occurrence in this country (and as regards foreign explosions figures are difficult to obtain), but in the following table I have been at some pains to set forth the results, from a destructive point of view, of a number of accidents with gunpowder and high explosives, even though they may not have occurred in magazines or stores, so as to enable the public to estimate for themselves the measure of risk offered by the unavoidable establishment in their midst of so great a quantity of “bottled energy.” I say unavoidable, since modern engineering feats would be practically impossible without high explosives, and admitting the necessity for their existence, it is assuredly safer to keep them stored in specially constructed and protected buildings, than to have them continually travelling about the country. In Table C “destructive effect” may be taken to mean structural damage to ordinary dwelling-houses due to the explosion itself, but not to projected débris. Nor does it include broken windows; to maintain a radius sufficient to prevent this would be practically impossible; at Erith, for instance, in 1864, windows were broken up to ten miles. In many cases much protection was no doubt afforded by mounds of earth and clumps of trees specially erected and planted for the purpose, interfering somewhat with the accuracy of the figures, but the margin of safety is in general so ample that no apprehension need be felt on this score.

As showing how circumstances alter cases, a comparison of the results of the Regent’s Park explosion on 2nd October 1874, with that of Craig, near Montrose, on 5th March 1880, is somewhat striking. In the former case five tons of gunpowder exploded in the middle of London, without injuring a soul outside the barge on which the explosive was being conveyed; whereas at Craig, an ounce or two of nitro-glycerine--possibly less than an ounce--killed no less than five persons, and severely injured another.

To summarise, the explosives industry can scarcely be said to affect the health of the operatives, as this word is generally understood, although there is no doubt an ever-present risk of sudden mutilation or death. I have endeavoured to show, however, that with the precautions now universally adopted in this country, this risk is reduced to a minimum, and that in all other respects the high standard of cleanliness and smartness necessarily associated with the manufacture introduces a condition of affairs which cannot be otherwise than beneficial to those engaged.

Finally, the fact cannot be too strongly emphasised, that in dealing with explosives a policy of pin-pricks is strongly to be deprecated, unless the perpetrator is anxious to be translated to a higher sphere. In the words of the late Colonel Cundill, “the function of an explosive is to explode.”

_TABLE C._

Giving some particulars in connection with the Chief Explosions which have occurred in this country.

KEY TO COLUMN HEADINGS:
A: Date of Accident.
B: Place.
C: Nature of Explosive involved.
D: Quantity of Explosive involved.
E: No. of Killed.
F: No. of Injured.
G: Radius of destructive effect in yards.
H: Distance in yards from nearest inhabited house, now rendered
obligatory for this quantity.
I: Cause so far as ascertained, and Remarks.

+--------+----------------+----------+------+----+-------+---------+----+-------------+ | A | B | C | D | E | F | G | H | I | +--------+----------------+----------+------+----+-------+---------+----+-------------+ |1/10/64 |Erith |Gunpowder | 51 | A large | 3080 |3500|Unknown. | | | | | tons | number | | | | |11/8/71 |Stowmarket, |Gun-cotton| 12½ | 24 | over | 466 |1030|Malicious | | | Suffolk | | tons | | 50 | | | introduction| | | | | | | | | | of acid | | | | | | | | | | into pure | | | | | | | | | | gun-cotton. | |2/10/74 |Barge on Canal |Gunpowder |5 tons| 3 | 1 | 400 | 525|Ignition by | | | in Regent’s | | | | | | | the cabin | | | Park, London | | | | | | | fire of | | | | | | | | | | benzoline | | | | | | | | | | vapour, | | | | | | | | | | which | | | | | | | | | | communicated| | | | | | | | | | to the | | | | | | | | | | gunpowder. | |21/4/76 |Cymmer, |Dynamite | 160 | 13 | 2 | 37 | 50|Probably due | | | Glamorgan (in a| | lbs. | | | | | to candle | | | tunnel) | | | | | | | falling on | | | | | | | | | | to the | | | | | | | | | | explosive. | |12/5/76 |Herodsfoot, |Gunpowder | 4½ | 3 | | 150 | 470|Workman | | | Liskeard | | tons | | | | | struck a | | | | | | | | | | spark with | | | | | | | | | | wooden | | | | | | | | | | mallet while| | | | | | | | | | “breaking” | | | | | | | | | | press cake. | |30/6/77 |Floating |Detonators| 3300 | 3 | |No houses| 250|Probably due | | | magazine | | lbs. | | | near | | to the fall | | | off Gravesend | | | | | | | of a case | | | | | | | | | | containing | | | | | | | | | | detonators. | | 6/8/78 |Victoria |Gunpowder |1 ton | | 2 | do. | 150|Lightning. | | | Colliery, | | | | | | | The nearest | | | Bruntscliffe, | | | | | | | house at | | | Yorkshire | | | | | | | 220 yards | | | | | | | | | | was quite | | | | | | | | | | uninjured. | |29/11/78|Elterwater, |Gunpowder | 500 | 3 | 1 | 20 | 65|Unknown. | | | Westmoreland | | lbs. | | | | | | |21/2/79 |Hall’s |Gunpowder | 3½ | 1 | 8 | 300 | 360|Probably due | | | Factory, | | tons | | | | | to | | | Faversham | | | | | | | accidental | | | | | | | | | | breaking of | | | | | | | | | | shaft in | | | | | | | | | | “glazing” | | | | | | | | | | house. | | 5/3/80 |Craig, |Nitro- |about | 5 | 1 | | |In a kettle | | | Montrose | glycerine|1 oz. | | | | | placed on | | | | | | | | | | the fire. | |19/3/81 |Blackbeck, |Gunpowder | 1800 | 3 | 3 | 45 | 148|Breaking down| | | Haverthwaite | | lbs. | | | | | “mill cake.”| |21/7/81 |Gatebeck, near |Gunpowder | 1100 | 2 | |Under 50 | 100|Unknown, but | | | Kendal | | lbs. | | | | | while | | | | | | | | | | “pressing.” | |29/9/83 |Furness, |Gunpowder | 2½ | 1 | 3 | 240 | 255|Probably | | | Inveraray | | tons | | | | | spark from | | | | | | | | | | adjacent | | | | | | | | | | chimney. | |17/11/83|Pembrey, near |Dynamite | 300 | 7 | 1 | Only a | 65|Blow on | | | Llanelly | | lbs. | | |few yards| | frozen | | | | | | | | | | dynamite. | |26/7/84 |Blackbeck, |Gunpowder | 1400 | 4 | | 50 | 125|Lightning. | | | Haverthwaite | | lbs. | | | | | | | 3/5/87 |Hounslow |Gunpowder | 7600 | 1 | | 60 | 390|Probably | | | | | lbs. | | | | | fracture of | | | | | (but | | | | | machinery in| | | | | not | | | | | glazing | | | | |all at| | | | | house, or | | | | | once)| | | | | malicious. | |22/6/87 |Cornbrook, |Picric | (?) | 1 |Several| 180 | (?)|Formation of | | | Manchester | acid | | | | | | picrate of | | | | | | | | | | lead during | | | | | | | | | | a fire. | |7/11/87 |Kennall Vale, |Gunpowder | 1050 | 2 | | 30 | 100|Spark in | | | near Redruth | | lbs. | | | | | “pressing.” | |22/1/90 |Roslin, near |Gunpowder |2 tons| 6 | 1 | 120 | 200|Probably | | | Edinburgh | | | | | | | matches in | | | | | | | | | | mixing | | | | | | | | | | house. | |22/10/90|Roslin, near |Gunpowder | 2500 | 2 | | 150 | 160|Repairing | | | Edinburgh | | lbs. | | | | | glazing | | | | | | | | | | reel. | |11/1/92 |Floating |Fireworks | 10 | | |No houses| 525|Friction | | | magazine, | | tons | | | near | | light. | | | Gravesend | | | | | | | | | 3/9/92 |Barque |Gunpowder | 20 | | | Nearest |1525|Fire on | | | “Auchmountain,”| | tons | | |house at | | board, not | | | off Greenock | | | | | 1¼ | | known how | | | | | | | | miles | | originated. | | | | | | | |uninjured| | | |24/2/97 |Ardeer, |Nitro- |about | 6 | 8 | 200 | 200|Unknown. | | | Stevenston, | glycerine|1 ton | | | | | Damage was | | | N.B. | | | | | | | to _wooden_ | | | | | | | | | | buildings | | | | | | | | | | only. | |19/1/98 |Blackbeck, |Gunpowder | 1¾ |None| None | 60 | 187|Fall of roof.| | | Haverthwaite | | tons | | | | | Damage small| | | | | | | | | | on account | | | | | | | | | | of good | | | | | | | | | | position. | |26/5/00 |Blackbeck, |Gunpowder | 1800 | 2 | |Building | 148|Probably | | | Haverthwaite | | lbs. | | | at | | failure of | | | | | | | |100 yards| | one of the | | | | | | | |uninjured| | columns of | | | | | | | | | | press. | |30/5/00 |Huddersfield |Picric | (?) |None| None | 140 | 400|Probably due | | | | acid | 6800 | | | | | to formation| | | | | | | | | | of picrate | | | | | | | | | | of lime | | | | | | | | | | during a | | | | | | | | | | fire. | +--------+----------------+----------+------+----+-------+---------+----+-------------+

II.

_Products of Combustion: Fumes._

All explosives in practical use contain carbon. If there be also present a sufficiency or an excess of oxygen this carbon is generally burnt on explosion to carbonic anhydride, CO_{2}. This is a poisonous gas. If, on the other hand, there is a deficiency of oxygen the carbon is only partially burnt and carbon monoxide (CO) is formed. This is a vastly more poisonous gas. But in any event the products of combustion are distinctly harmful, and it is misleading and mischievous to assert of any explosive that it gives off “no noxious fumes.” Some are, however, as already stated, worse than others in this respect. Gunpowder, gun-cotton, and lyddite (picric acid) are all deficient in oxygen. The two latter, being chemical compounds, are of constant composition, viz.:--

C_{12}H_{14}O_{4}(O,}NO_{2})_{6} and C_{6}H_{2}(NO_{2})_{3}OH

respectively, and their lack of oxygen can be seen by inspection of their formulæ; but the ingredients of gunpowder, being merely mechanically mixed, may be varied at will so as to produce on combustion the minimum of CO compatible with other requirements. In blasting, for instance, where there is no outlet for the gases formed except by disruption of the rock or coal, the production of a large volume of gas at high temperature is in theory all that is necessary--the time taken to attain maximum pressure is of comparatively little importance. When there is a deficiency of oxygen a proportion of the carbon is converted into CO, giving for equal weights of oxygen double as much gas as is produced in the formation of CO_{2}, and thus, although the heat evolved in conversion to CO_{2} is more than half as much again as in conversion to CO, yet the maximum pressure is theoretically about the same. Calculations of maximum pressures are, however, somewhat unreliable, owing not only to the fact that at the high temperature of explosion the complex potassium salts found in the cooled residue undoubtedly undergo dissociation, but also to the uncertainty which exists as to whether gases, especially compound gases, obey, at very high temperature and pressure, the usual law as to the relation of pressure to volume. Practical experience would certainly seem to contradict the theory of equality in blasting efficiency between high and low grade powder, since far better results are undoubtedly obtained with the former. For use in fiery or dusty coal mines or in confined spaces there is, of course, no comparison between them. According to Noble and Abel the percentages of CO evolved by Curtis’s and Harvey’s best sporting powder, containing 75 per cent. of saltpetre, and by ordinary blasting powder, containing but 62 per cent. of this ingredient, are as 2.47 to 15.22; the hydrogen sulphide, another poisonous gas, being also increased from .83 per cent. in the case of the former to 3.89 per cent. in the latter. On the occasion of the peculiar accident at Crarae Quarry, Lochfyne, in September 1886, when no less than 40 persons were rendered insensible (7 of whom succumbed) by the fumes from a monster blast, the powder used contained 74 per cent. of saltpetre, and only yielded 3.6 per cent. of CO on combustion. Since 150 persons were present, it is more than probable that, had gunpowder of inferior quality been used, the mortality would have been very much greater. Gun-cotton is an even worse offender in this respect, yielding on detonation, according to different authorities and according to the pressure under which it is exploded, from 28 to 45 per cent. of CO. For mining purposes this percentage has been much reduced by the admixture of a due proportion of barium nitrate to supply the necessary oxygen for theoretically complete conversion of the carbon to CO_{2}, and although this happy consummation has not been fully attained, yet this explosive, under the name of tonite or cotton powder, has been used in mines with good results, the products of combustion, according to Sir F. Abel, furnishing little or no carbonic oxide. Prior to the introduction of this modification, several fatal accidents had already occurred in the use of gun-cotton by itself. For instance, no less than 12 persons were injured, one fatally, in April 1878, by the fumes from a gun-cotton blast during the construction of a mine tunnel at Halkyn, Flintshire.

Lyddite, on the other hand, of whose fumes we have been hearing a good deal of late, yields not only a large proportion of CO, but also a notable percentage of free carbon, as is evidenced by the black smoke arising on detonation. In small quantities, however, complete detonation is somewhat difficult to achieve, a yellow deposit being the result. This deposit, mingling with the black smoke tinged with the blue-grey of the pulverised rock, may possibly have given rise to the “green fumes” which were, according to eye-witnesses, a marked feature at Paardeberg and elsewhere. The proportion of CO formed is doubtless greatly in excess of that evolved by gunpowder--especially of the good quality alone used by the War Department--but it is difficult to believe that even in the most favourable circumstances the atmosphere could be rendered unfit to breathe by the bursting of lyddite shells. If this possibility existed half Huddersfield must have been asphyxiated by the recent explosion of picric acid at the works of Messrs Read, Holliday, & Sons. Owing to its exceedingly bitter taste, the sifting of the dry acid gives rise in some cases to sore throat and distressing cough, necessitating the use of a respirator by those employed in this operation, but that these symptoms are mere inconveniences not affecting in any way the general health of the operator is shown by the fact that the workers complain that they cannot keep themselves on account of the tonic and appetising effect of the acid! It is also, in solution, an excellent cure for burns.

Into the question of the physiological effect of CO poisoning I do not propose to enter, but would refer the reader to the reports and papers on the subject by Dr Haldane, whose classical investigations in this connection are unrivalled; but it is of importance to note that all explosives, except nitro-glycerine (_i.e._ Kieselguhr dynamite), and certain of the ammonium nitrates, produce on explosion a proportion of this deadly gas. Nitro-glycerine, or glyceryl tri-nitrate, as it might more properly be called, contains, as shown by its formula, C_{3}H_{5}(O,NO_{2})_{3}, more oxygen than is required for complete combustion. The manner in which it decomposes on detonation may be expressed according to the majority of authorities by the equation:--

2C_{3}H_{5}(O,NO_{2})_{3} = 6CO_{2} + 5H_{2}O + 6N + O

giving the following percentages--

Carbonic acid 58.15
Steam 19.82
Nitrogen 18.50
Oxygen 3.52
-----
99.99
=====

the products thus contain nothing more deleterious than carbonic acid gas. Even if, as is possible, the excess of oxygen combines with nitrogen to form nitrous oxide, the proportion of NO formed can only amount to 6.60 per cent., a quantity which, under no conceivable circumstances, could produce fatal effects.

If; however, nitro-glycerine be decomposed by simple combustion, not detonation, the nitrogen and oxygen in the NO_{2} molecules do not appear to be dissevered, the result being that not only are highly poisonous nitrous fumes given off, but the proportion of available oxygen is also so much diminished that a considerable quantity of CO is formed. Many instances are recorded of fatalities due to the inhalation of these nitrous fumes, and there is also at least one case (in September 1892) when the symptoms pointed to CO, or rather to a combination of CO and CO_{2} as the cause of death, the two victims being rendered unconscious on the spot, and dying before help could arrive. In cases where death has resulted from breathing nitrous fumes only, the end has generally been deferred for some considerable time, amounting in one instance to no less than 40 hours after the inhalation. The symptoms are identical with those observed in cases of poisoning from nitric acid vapour, viz., very little inconvenience is felt at the time,--in fact the person affected has generally partaken of food, and in one recorded case, enjoyed a smoke, before noticing anything wrong,--subsequently difficulty in breathing, accompanied by violent coughing, is then experienced, which increases until death. An accident from these fumes, which occurred in September 1879, during the construction of the Severn Tunnel, by which two men lost their lives, has been very fully reported on by Col. Ford, late Chief Inspector of Explosives, in Special Report No. XXVI., dated 30th October 1879, and he there quotes several other interesting cases brought to his notice by Dr Dupré. Moreover, since the issue of that report, several instances have occurred where dynamite has been accidentally ignited in a mine gallery, and has caused fatal injuries, not by explosion, but by the fumes given off.

The notorious “nitro-glycerine headache” must not be forgotten. This is due to dilation of the capillary blood-vessels, or rather of the arteries, by which means the circulation is largely and suddenly increased. This effect is achieved either by inhalation of nitro-glycerine vapour, or by absorption through the skin, so that it results from handling the manufactured compound, as well as from being present in a building in which the hot explosive is deposited. No one can enter a cordite drying room or “stove” without experiencing a peculiar sensation at the heart and at the back of the head, which, in the absence of fresh air, soon develops into a headache which reduces to insignificance all the other ills of life. Some suffer more than others, but in no case, so far as I can gather, has any permanent harm resulted from this cause, and on most people the fumes appear to lose their effect after a few days. With certain individuals, on the other hand, it is a matter of weeks before they become inured, and during that period they are never free from sickness and headache; moreover, a very few days’ absence from contact with the explosive causes a return of the original susceptibility. The best remedies are strong coffee, and a linseed poultice applied to the back of the neck. Like most poisons, nitro-glycerine is used in medicine, and has undoubtedly been the means of prolonging many lives in cases of angina pectoris. Its freezing point is high, viz., about 40° F., and once frozen it cannot be thawed below 50° F. Thus, nitro-glycerine compounds are frequently found frozen hard in June; in fact, for a great part of the year they have to be thawed before use, and this process, unless carefully carried out in proper warming-pans, constitutes a very considerable danger. The lesson is gradually being learnt that dynamite will explode at temperatures below that required to ignite it, owing to the heat produced by the chemical action set up by the decomposition, which commences long before the point of ignition is reached. Three accidents in thawing occurred during the year 1899, and between the years 1872 and 1898 no less than sixty-eight accidents due to this cause took place, involving the death of 68 persons and injuries of a more or less serious nature to 97 others.

Inasmuch as nitro-cotton contains too little oxygen for complete combustion, and nitro-glycerine contains more than is necessary, it may well be imagined that a very powerful explosive would result from an admixture of the two in proper proportions. This was first effected by Alfred Nobel in 1875, and the invention of blasting gelatine, as the resulting compound was named by him, may be said to mark an epoch in the history of explosives. Provided the nitro-cotton be in the form of the penta-nitrate only, 100 parts of nitro-glycerine would theoretically be required to satisfy 10 parts of nitro-cellulose, but in actual practice it is impossible to ensure the absence of lower nitrates, and as the degree of nitration of the cellulose decreases the necessary proportion of nitro-glycerine increases. If, however, the percentage of nitro-cotton is reduced too low, it is impossible to comply with the Home Office conditions as to exudation. Thus, in this country, where the usual proportion is 9 of nitro-cotton to 91 of nitro-glycerine, a certain quantity of CO is invariably produced by the explosion of even the best blasting gelatine; and cordite, which contains 37 per cent. of cellulose hexa-nitrate to 58 per cent. of nitro-glycerine, the balance consisting of vaseline, produces no less than 32 per cent. of CO. The gelatine dynamites, a most popular class of blasting explosive, and the majority of smokeless powders, may be said to be based on blasting gelatine.

As regards those ammonium-nitrate explosives, of which dinitrobenzol forms the combustible ingredient, several fatalities have occurred in their manufacture, generally from neglecting to make use of the respirators and gloves supplied to prevent introduction of the poison into the system. In one recorded case, however, viz., on 6th June 1889, at the Roburite Company’s Works, a workman was engaged in cleaning out an air flue through which the fumes from three mixing pans were discharged, and owing to the admittedly ultra-dangerous nature of the work, wore a handkerchief over his respirator, and was entirely clothed in indiarubber, but in spite of these precautions was fatally injured by the fumes. According to the manufacturers, the injury to the health of the workpeople in the ordinary process of manufacture is more apparent than real, but the wish may possibly be father to the thought, and the industry has not been in existence long enough to provide reliable statistics.

III.

_Explosives in Coal Mines._

Reference has already been made to the dangers attending the use of certain explosives in fiery and dusty coal-pits. In view of the vast quantity used in coal-getting, and of the somewhat complex nature of the problem presented, also having regard to the wholesale destruction of life, and consequent widespread misery entailed by a pit explosion, originating perhaps in quite an insignificant ignition of fire-damp or even of coal-dust, the question as to what does or does not constitute a “safety” explosive has been discussed in all its bearings in every civilised country. The results obtained are, however, hardly satisfactory--no two experts, or rather groups of experts, appear to agree. The systems by which increased safety is sought to be obtained may be dubbed for general purposes the French, German, and British. It would be quite impossible in the space at my disposal to trace the gradual development in each country of the researches, theoretical and experimental, which have in each case culminated in legislative action. Other countries have, so far as I can gather, adopted one or other of the above systems, or modifications of them, but, so far as general principles are concerned, the above classification may be accepted as correct. Thus, in France, the criterion of safety is the _calculated_ temperature of explosion, which must in no case exceed 1500° C.; in Germany, increasing quantities of the explosive under examination are fired unstemmed in a regulated mixture of pit-gas, coal-dust, and air, and no charge may be fired in practice exceeding the maximum weight shown to be safe under the above conditions; lastly, in this country, an arbitrary but semi-practical test has been established, and in the prescribed mines no explosive may be used, until it has satisfied this test. Having been connected with the Woolwich Testing Station since its inception, any comparison by me of the merits or demerits of the three systems would be worthless, but I venture to hope that it will be conceded that the _principle_ underlying our own method is sound, however defective the details may be considered by rival investigators. The truth of the matter is, that the whole question is most involved, safety depending not on one condition but on many. The temperature, the time, and the products, gaseous and solid, of the explosion, the weight of the charge, the depth and diameter of the bore-hole, the quantity and quality of the stemming, the position of the bore-hole with reference to surfaces or obstacles on which the hot gases may impinge, the composition of the atmosphere of the mine, the meteorological conditions, the structure of the rock or coal in which the shot is fired, and last but not least, the means of firing--all have their say in the matter; and it is ridiculous to attribute to the inherent qualities of an explosive a calamity really due to the negligent or reckless misuse of it. An analysis of the official reports on mine explosions caused, or rather probably caused, by shot firing during the last twenty years, is somewhat instructive in this connection, and may be deemed worthy of perusal, with this preface, however, that the information has been obtained from the published reports only, and with no facilities for reading between the lines (see pp. 617–618).

The natural inference to be drawn is, that if a “permitted” explosive alone is used, and the charge properly stemmed with suitable material, and if, moreover, a very moderate quantum of judgment and common sense is used in selecting the position of the bore-hole and the weight of explosive necessary to do the work, the risk of an accident under this head is practically eliminated.[146]

_TABLE D._

A List of Explosions of Gas and Dust in Coal Mines caused
by Shot-firing, on which Reports have been published, with
Explanatory Extracts from these Reports.

In the year 1899, during which period an increased amount of attention was paid to the above points, out of no less than 147 ignitions of fire-damp or coal-dust only 6 were caused by the flame from explosives used in shot-firing.

I will conclude with a very concise description of a few of the best known explosives in common use, other than gunpowder.

(_a_) MILITARY.

_Cordite._--Nitro-glycerine, gun-cotton, and vaseline, reduced by means of acetone to a gelatinous paste, which is then “squirted” into cords through dies of varying diameter by hydraulic or screw pressure. The rate of combustion depends on the diameter of the cords.

_Gun-cotton._--Cellulose hexa-nitrate--pure cotton or cellulose steeped in a mixture of the strongest nitric and sulphuric acids, and thoroughly washed.

_Lyddite._--Trinitrophenol or picric acid, a mixture of carbolic acid (phenol), and concentrated sulphuric acid treated with strong nitric acid, picric acid crystallising out.

(_b_) SPORTING.

The name of these is legion. The best known are _Amberite_, _Ballistite_, _Cannonite_, _E.C._, _Schultze_, _S.S._, and _Walsrode_, and the vast majority are based on nitro-cellulose. This is mixed with other comparatively unimportant ingredients, and granulated, gelatinised, and hardened in a suitable manner, the method of manufacture varying according to the explosive.

(_c_) BLASTING.

_Ammonite_, _Amvis_, _Bellite_, _Electronite_, _Roburite_, and _Westphalite_, form with a few others seldom met with in this country a group of explosives derived from the admixture of ammonium-nitrate with various carbonaceous substances, such as dinitronaphthalene, dinitrobenzol, starch, and resin. They are comparatively safe to handle and convey, but suffer in keeping from the hygroscopic nature of the ammonium-nitrate, which necessitates their enclosure in absolutely waterproof cases.

_Blasting Gelatine._--Nitro-cotton dissolved in nitro-glycerine to form a jelly. This is probably the most powerful explosive in general use.

_Carbonite._--About 27 per cent. of nitro-glycerine absorbed in a “dope” of woodmeal and saltpetre or nitrate of barium.

_Dynamite._--75 per cent. of nitro-glycerine absorbed in 25 per cent. of an infusorial silicious earth called “Kieselguhr.”

_Gelatine Dynamite._--Nitro-glycerine thickened by the addition of nitro-cotton, and combined with woodmeal, charcoal, or certain other non-explosive ingredients.

_Gelignite_, the most commonly used of all the high explosives, is practically gelatine-dynamite with the addition of saltpetre.

_Tonite_ or _Cotton Powder_ is a mixture of equal parts of gun-cotton and nitrate of barium.

_Fulminate of Mercury_, used for detonating nearly all high explosives, is a grey precipitate obtained by treating with alcohol a solution of mercury in nitric acid. It is extremely sensitive to percussion or friction.

A. COOPER KEY.

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Dangerous tradesChapter XLI: Explosions and Explosives

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