Sketcher. Dynamite. (From the Cornhill Magazine.)

Waikato Times, Volume XXIV, Issue 1997, 25 April 1885, Page 6 (Supplement)

Sketcher. Dynamite. (From the Cornhill Magazine.)

(Co.VTiN'urn.) In 1803 Mr Nobel, who had for some time taken this chemical curiosity of nitro glycerine in hand, with a view of applying it to practical purposes, made public his first attempts of adding to the explosive power of gunpowder by impregnating the grains with nitro-glycerine, the earliest form of dynamite, which went far to prove the great power of the ' glonoin oil,' as it was then called. But its real era opened with 1861, when a charge of pure nitro-glycerine was first set off by a minute charge of gunpowder with certainty, and later in the year by the introduction of the detonator-cap containing fulminate of mercury, the mode now in universal use for developing the maximum force of all explosive agenta of the same class. This discovery raised the reputation of nitro-gly-cerine as a blasting agent to an extraordinary height, only to be checked again by a series of terrible accidents, due in some oases to spontaneous combustion of impurities, in others to ignorance and carelessness ; chief among which were those on board the ' European,' at Colon, in 1866 : at New-oast)e-on-Tyne in 1867, when, in burying frozen nitro-glyoerine, part was struck by a pick-axe and exploded, killing the mayor and six others; at Stockholm, in 1808, when Mr Nobel's factory was blown up ; and at Gvvm-y-Glo, in North Wales, 1869, in consequence of which the sale of the new agent was absolutely prohibited by tho Nitro-Glycerine Act 1869, nor, although that Act ib now repealed by the Explosives Act 187", is it now ever licensed for uso in a liquid condition Before this, however, Mr Nobel had resolved to discontinue its manufacture and to devote himself to tho discovery of an absorbent capable of holding enough for blasting purposes, and, in the form of a comparatively harmless solid, presenting a weakened solidification of liquid nitro-glycerine. By this admixture with a eolid substance, Mr Nobel felt confident that, apart from the question of safety, the explosive power of nitroglycerine, however it might bo weakenod, would at any rate bo greatly facilitated. The mobility of the particles and consequent tendency to yield mechanically to the force of a blow, or detonation which acts as a blow, would be considerably diminished by dilution and the addition of the solid substance. This was done, as we have already said, in June 1807, when the solidified preparation known here aa ' dynamite,' and in America as ' giant powder,' was first adapted for practical use. The discovery of dynamite was not due, as h&a been generally supposed, to accident, but to direct experiment. Tho first made consisted of charcoal and nitro glycerine, and, before the porous silica known as hieselguhr was finally adopted, numerous trials were made of various other absorbents, such as porous torra-cotta, sawdust, and ordinary and nitrated paper soaked in the liquid explosive and rolled into cartridges. During the siege of Paris, when the Kieselguhr ran short, the French engineers found tho best substitute to lie in the ashes of Boghead coal, and next to that in pounded sugar. And on one occasion, when a certain Welsh solioitor was much embarrassed by the possession of a large ' quantity of nitro-glyoerine, which he was ordered by Government neither to use nor to remove, he was driven in desperation to try on it the absorbent effects of brickdust ; with so much success that ho found himself summoned as an important witness to testify to the clearness of specification when, on Mr Nobel's application for a patent, it was called in question. Kiselguhr, the inert absorbent base of dynamite, is a sliceous earth of low specific gravity, composed of the remains of infusorial insects. Largo minos are worked in Europe, the largest and those yielding it of tho purest quality and lowest specifics gravity being situate near Naterlouas station, on tho railway from Hamburg to Hanover. There are also large beds in Aberdecnshiro, whence are drawn the supplies used by Mr Nobel's factory at Ardoer. Its high non-conductive power, which it owes entirely to its great porosity, is one of its most important properties ; a power so high that if a piece of only two inches long bo heated to white heat on the ona end, no inorease of heat will be noticed on the other. It is capable of absorbing from three to four times its own weight in nitro-glycerine, possessing the valuable advantage over other absorbents of resisting a greater degree of pressuro without parting with any of the liquid explosive it holds. In its licensed form, dynamite must not contain less than 2.) per cent, of this infusorial earth, though in Germany manufacturers have produced it in the proportion of 82 per cent, of nitro glycerine and 18 per cent, of kiesefwh*, without exudation. Thin, however, i« confined to Germany, and is never permitted to bo imported into Great Britain. The mixing of the hieielauhr with tho nitro-glyoerine is a delicate operation, and entirely performed by hand. The earth and the liquid are constantly kneaded and worked through the fingers until the whole is thoroughly fused, for any little knot or undigested lump, as is sometimes seen in bread, would present a detonation point which a blow would explode. With dynamite properly made, concussion is quite harmless. The experiment has been tried of fastening

it between tho buffers of trucks, and running them together ; of throwing it from a great height on to the rocks of quarries ; of dropping on it heavy weights ; even of lighting a train of gunpowder laid on the top ; all without an explosion ensuing. To expode dynamite, as it is now manufactured, two conditions tnudt exist, and exist simultaneously — a violent concussion and a temperatuie of (100 dog. Fahr. These conditions wore found to be fulfilled by Mr. Nobel's do conator cap, charged with a few grains of fulminate of mercury. The commercial progress made by dynamite was at first slow. In 1807 there were only ten tons of it sold ; but seven years later the sale amounted to throe thousand ono 'lundred and tweuty. The reason was that not only did there exist a great prejudice against its ohief ingredient, nitio-glyccrine, but a great prejudice the other way in favour of gun-cotton, There were supposed to be many points of advantage in connection with ,»un cotton which dynamite, or at least the dynamite of that day, could not boast ; chief imong which were its superior chemical HtftbiUty, and its steady conduot under the influence of fire or concussion. At the date of tho S'owmarket explosion in Augu«t 1871, which for a time completely drove gun-cot-cotton out of the market, and from which it hai scarcely yet commercially recovered, there were sixty quarries in Great Britain employing 1(5,000 men who used it in to dynamite. So great was the confidence in it of the miner, that one of them is quoted as having deolared, ' When she cotton got wet, he put it in the sun ; but when there was no sun, he took it to bed with him and slept apon it, and by the morning it was nicely dry.' That loud Stowmarket tragedy shook down gun-ootton *nd sent up dynamite, and from that day its position as a blasting agent has never seriously been threatened. The early weakness of want of chemical stability was quickly cured, and for the last ten years no case of explosion has been registered due to spontaneous combustion. Decomposition, even if it occurred, as it might after the dynamite had been kept for years, could scarcely be anything else than harmless. But ' the old order changeth ' is an axiom in chemistry, and the hours of the supremacy of dynamite are numbered. The explosive of the future is undoubtedly blasting gelatine, f ,hc latest invention of Mr Nobel. Already on the Continont the manufacture of this new .igent has asaumed important dimensions, though, here, owing to the stringency of tho climatic test imposed by Government, its position is as yet scarcely established. Many of the later operations of the St. (xothard tunnel were oarried out with pure blasting gelatine ; and in Austria, the richest of all the European countries in mines except Great Britain, the factories where dynamite was for raerly mado are now given over to its manufacture. It is simply dynamite a base actif, containing ',) i per cent of nitro-glycerine, with a base of 7 per cent, of collodion wool, that is itself an explosive, in place of the inert kiesclguhv. Ai a blasting agent it is more homogeneous than dynamite, and, on account of its elasticity, is less sensible to outward impressions, while in handling or cutting the cartridges there is no loss of the material as sometimes occura with dynamite. Its further advantages are that the gases after explosion are lighter and thinner, and leave no dust, developing at the same time a more considerable power. Taking the power of dynamite fit 1,000, and nitro glycerine at 1,111, blasting gelatine, is represented by the figures I,">s">, in addition to which superiority it is capable, unhko dynamite, of retaining its nitro glyoerine when brought into contact with water. Sir Frederick Abel has kept it under water for a year without its undergoing the slightest chemical change. It is satisfactory to leflect that, so complicate and delicate is the process necessary for the production of this now explosive, it is npvor likely to be made by unskilled persona or concocthd in a back shop in Birmingham. The impetus of dynamite received from the ilownfall of gun cotton worked, as may be imagined, to tho commercial advantage of Mr Nobel, the sole patentee, and so went on working till the early part of 1811, when the patent und the monopoly expired together, and the importation, which has ever since gone on increasing, began. In 1882, there were twentyfour cargoe3 brought into this country, amounting in all to 1,008,0j0 lbs.; in 18^.1, forty-six cargoes amounting to 1,020,0.10 lbs. ; without taking into account the (>7,000 lbs. of the ' Echo ' that went to pieces and was lost on the Dutch coast, or the fifty tons of the derelict ' Cato,' towed into Hull and quickly towed out again with battened hatches by the prudent authorities. Theae cargoes, directly thoir arrival in the Thames is notified, are all sampled by the Home Ollioo before they are permitted to be landed or stored in the Hole Haven magazines, and until these samples are approved and passed nothing can be done with the cargo. In proof of the care that now characterises the foreign manufacturer, of the I'M) samples forwarded during tho last yeag to Dr Dupri, the Home ollice analyst, all were found to contain the required proportions of nitro-glycerine and Uchehfuhr, and to be of the necessary degree of purity. An fmpure or diproportioned sample would entail the return of the cargo to the homo of its manufacture. This importation has, of course, exercised an immense influence on the market price of dynamite, which, since the expiration of Mr Mobel's patent in March 1881, has dropped fifty per cent. From tho magazines that lie in secluded and licensed nooks all along the coast, tho explosive is carted inland and again stored at the great mining centres, to be dealt out by the hoensed agents. From the momont of landing all the carriage is done by cart, for, notwithstanding the clearly established fact that of all explosives dynamite is probably tho safest to carry (apart from the detonator it is abßoltely safe), the railway companies still obstinately iefu«e to have anything to do with it. They have no objection to petroleum, which iv JKd'J burnt a train and its living freight at Abergele. Over all tho foreign Hues dynamite may now be carried, the English companies hold out the last ; a shortsighted policy, as Colonel Majendio in his latest roports continues to reiterate, for it supplies the temptation to a surreptitious conveyance of prohibited explosives that is not always resisted. In Russia, before the prohibition was withdrawn, a Moscow firm was in tho habit of consigning dynamite under the descriptive heading of blacking, apiece of deception that ultimately caused the deportation of the partners to Siberia. And m this country, only a few weeka back, two fellow - passengers happening by nocident to exchange luggage, ono found himself in the possession of boots and the other of dynamite, a disaovery which tho one who should have had the boots soon mado public, and thereby entailed a heavy fino on tho other. It is calculated that if the railway were to supersede the cart there would bo a saving of '2.1 per cent, of time, to say nothing of the proper supervision and storage tho exploBivo would then obtain. There would then be no more instances of 2,000 lbs. of dynamite being carried through tho country in an open cart, or 1,000 lbs. left unguarded in a field by night, while the light-hearted waggoner goes and enjoys himself elsewhore. It now remains to consider what dynamite will, and what it will not, do. To begin with, like many persona who have great powers, it has at least two peculiarities — ono, that in small quantities it will harmlessly burn itself away, and the other that in a frozen state— and it freezes at the high tompevaturo of l(i degi. Fahr. — it is extremoly difficult to explode. For the first, it may bs safely said that out of every hundred dynamite cartiidges, ninetynine can be held in the hand and burnt. In the hundredth, there may possibly be one of those undigested knots or lumps we have spoken of, which, acting as a dotonation, would explode the rest. It is only in small quantities that dynamite can be so dealt with in safety, though Colonel Majondio tolls us he has been prcrent at the burning of so lmge a quantity as half a ton. But if dynamite may in almost all cases be burnt with-

out explosion, it is extremely dangerous to heat. Set fire to it "on an iron plate, and it is almost a certainty that il will burn away ; heat it from underneath, and it is almost an equal certainty that it will violently explode. Should any reader of this paper ever find himself in the possession of dynamite which ho is not anxiona to keep, it will be safest for him to strew it in small quantities, with considerable breaches of continuity, and then set it alight. And let him be caieful to withdraw some little distance from the soene, for though with dynamite properly exploded there are no evil odours, the nitrous fumes of it when burnt are extremely disagreeable, and even dangerous. As for the second peculiarity, the difficulties attending explosion in a frozen state, Mr. Mowbray, the American engineer, has proved in his work at the Iloosac tunnel that the difllculty increases in proportion to the solidity with which the dynamite is frozen, and that, if the mass be broken up and pulverised, the ordinary detonator will be found sufficient, though the explosion will be one of somewhat diminished violence ; and further, that whatever the degree of temperature may be, twenty-five grains of fulminate will be found enough to set it off. This freezing dilViculty has been the causo of the majority of the acoidents that of late yeara have attended the use o' dynamite, for, notwithstanding the special directions issued by Mr. Nobel with each packet that leaves his factory, miners are constantly found (as they are found to light their pipes at the open Davy lamp, and to drive in the head of a powdercask with a red-hot poker) to thaw the cartridges at the fire instead of in the proper method, by the application of warm water in double tin caßes. Frozen dynamite will almost always explode by ignition, instead of burning away as in the normal condition, and the increased number of accidents during the past year are almost without exception due to the carelessness of the men in dealing with it in this state. In foreign factories it was at one time not uncommon to let them thaw the cartridges in their pockets by the heat of the body, but, as this led to the theft of an article that was at that time very expensive, it has been discontinued. (To be Continued.)