CHAPTER VIII.

Hoosac Tunnel—Drilling by Machine—Blasting with Powder—Nitro-Glycerin.

The Hoosac Mountain, whose summit is 2,700 feet above the sea level, is composed, according to the geologist, of mica slate, so compressed that near the West End the stratification is contorted, upheaved, and intermingled with quartz and pyrites; consequently the classification of the rock as “mica slate” conveys a very imperfect idea of its hard impracticable nature to the miner. To any one who will be at the pains of examining the masses lying near the powder magazine, built of massive stone, at the West Shaft, the hardness of this rock is at once apparent. Parts of this mountain have been found so hard and tough, and so difficult to drill, that thirty-four drills have been worn in drilling a blast hole thirty-six inches deep. This was an exceptional case, but similar hard layers are met from time to time. Had it not been for the Burleigh drill and Nitro-Glycerin, the sturdy indomitable perseverance of Massachusetts would have been severely strained, if not exhausted, in running this Tunnel.

The following extract from the Adams Transcript, for April 11, 1872, gives a summary of the progress made during the month of March, and the lengths remaining to be opened to complete the work:

HOOSAC TUNNEL PROGRESS FOR MARCH, 1872.

“East End, 120 feet; Central Shaft, eastward, 100 feet; West End, 140 feet, total, 360 feet. Total lengths opened to April 1, 1862: East End, 10,166 feet; Central Shaft, east, 617 feet, west, 325 feet, total, 942 feet; West End, 7,494 feet. Lengths remaining to be opened: between East End and Central Shaft, 2,054 feet—586 feet less than half a mile. Between West End and Central Shaft, 4,375 feet—855 feet more than two-thirds of a mile.”

A reference to the wood cut opposite page 80, shows the profile of the mountain and progress of the Tunnel to January 1, 1872.

The distance made during the month of March, in the East heading, was 120 feet of heading, 24 feet wide and 9 feet in height, exclusive of first enlargement or roof, and second enlargement of roof to full size or stopeing, which is usually carried on simultaneously to about 250 feet per month. This heading is being attacked by twelve of the Burleigh drilling machines, mounted on two carriages manned by eight miners and a foreman, who work for eight hours, with brief intermission whilst the charges are being fired. The drills are impelled by compressed air, making 300 strokes per minute, and calculated to strike with a force of 200 lbs. at each blow, perforating from one inch to five inches per minute, of a hole two inches in diameter when powder is used, and 1½ inch diameter for Nitro-Glycerin blasting. At the East heading, partly owing to the rock being softer than either at the West End or in the Central Shaft, partly to the miners being accustomed to powder, partly to the heavy battery of drills enabling twelve drilling machines to work at once, and thus make progress satisfactory to the contractors, who, wisely, let well enough alone, the holes when drilled to a depth of from two feet six inches to three feet, are each charged with from one to two and one-half pounds of blasting powder, then tamped; the carriages are drawn back, and the sixteen to twenty-six holes are fired simultaneously by means of a frictional electric machine. This takes place every four hours, exploding from 100 to 150 cartridges every twenty-four hours. The reader must not infer from this that every blast makes from two feet six inches to three feet of advance; because, first, the holes are never drilled for powder in a horizontal plane, but at an angle, sometimes upwards, sometimes downwards, to the right or left, the aim being, that a straight line drawn from the bottom of the hole to the face of the rock shall be shorter than the extreme length of the drilled hole, so that the charge or blast which exerts its force in the line of least resistance, may displace the rock between the bottom of the hole and the surface of the rock, and not collar the hole, that is, merely remove the rock surrounding the outlet of the drilled hole. It is usually found also, that the power exerted by powder is not sufficient, in working a heading, to blast out the rock from the bottom of the hole, but, most frequently, from the point where the cartridge begins, and the tamping terminates. Thus, if a hole be drilled at an acute angle from the face to a depth of thirty inches, with a line of least resistance of twenty-four inches from the bottom of the hole, and a fifteen inch cartridge of blasting powder be inserted, and tamping to the extent of fifteen inches be rammed in above the cartridge, the rock removed, will, under ordinary circumstances, be removed from about where the cartridge commences, that is about 12 inches, or it may be 14 inches, in a direct line from the face. And herein lies the very important distinction between powder and Nitro-Glycerin; the latter, bottoms, i. e., removes the rock from the bottom of (in roofing and quarry work beyond) the hole; with powder this is rarely the case. Moreover, as the depth of the holes is increased, so must the diameter be increased in proportion to the depth when powder is the blasting agent, but when the drilled hole is to be blasted out with Nitro-Glycerin, a diameter of 1¾ inches is sufficient for a hole having a depth of ten feet, and a line of least resistance of eight feet, a depth wholly inadmissible for powder, because the rock at that depth would act like the breech of a cannon, and the explosion would issue direct from the hole, only fracturing the edge, i. e., collaring the hole. With Nitro-Glycerin the holes need not be drilled at so acute an angle to the face of the rock, and need no tamping, that is, the drilled hole is left entirely open, and no time is occupied therefore in ramming materials over the explosive, and no risk is incurred in cutting the fuse or electric wire, as with powder, dualin or dynamite, all of which must be tamped. The explosion of Nitro-Glycerin differs from that of every other explosive in this, that the explosion is instantaneous, consequently the rock yields before any flash can reach the mouth of the drilled hole, and the work is done before the gases can travel six feet. Hence the necessity of deep holes; to charge holes only 30 inches deep (except they are from ⅝ to ⅞ inch diameter) is a waste of the material. The same charge will clear the rock to the bottom, with a hole drilled six feet deep, and in fact bottom the six foot hole, whilst a similar charge inserted in a 30 inch hole may leave three or six inches of the hole visible with its surrounding rock, after the blast. And here I cannot refrain from narrating what a narrow escape Nitro-Glycerin had at one time from being rejected at the Tunnel. In the dark days of this enterprise, when every cent expended was narrowly watched, and when it was favor enough for a miner to condescend to allow Nitro-Glycerin to be used in his shift, requests and entreaties for deep holes, and remonstrances that the holes were not drilled deep enough to give this explosive a fair chance, were found fruitless; until, finally, a consultation was held in the time-keeper’s office at the West End, the purport of which was, to notify the writer that no more Nitro-Glycerin was needed, as it did not answer expectations. The superintendent, at the West Shaft, was asked what reason I gave that greater progress was not made with the new explosive. His reply was: “Mowbray says the holes are not drilled deep enough, and, I think (he added) it is but fair his demand for deep holes should be complied with, before you throw up the use of Nitro-Glycerin. He has outlaid some $5,000 for the experiment, and you ought at least to see the effect of deep holes, before you decide.” Agreed; the superintendent then went to the foreman of the shift, and requested deeper holes, ordering six feet holes. “It’s no use,” was the reply; “it’s all nonsense; why, I tell ye, it won’t bottom a hole 30 inches deep; then how is it going to fare with a six foot hole; besides, we can’t drill six feet holes by hand in one shift.” “Then take two shifts to do it, and take three if it is necessary; this Nitro-Glycerin man says he must have deep holes, and he shall for this once, if I drill them myself, and it takes a week to do it.”

The deep (only six feet) holes were drilled, and charged; cartridges of same size as those inserted in 30 inch holes, were used, and fired, every hole bottomed, every miner was astonished, and from that day the use of Nitro-Glycerin was a necessity for the heading in the West End. But it was a narrow escape from what would have been deemed a failure. On another occasion, during a drought, the supply of water at the West End, where the Nitro-Glycerin was manufactured, gave out, and, being a necessity in the manufacture, we had to haul it by team. This was troublesome work, and cost money. There had been a change of engineers, and the gentleman now in charge, on the difficulty reaching him, determined first to ascertain whether Nitro-Glycerin was a necessity, before complying with the contract the Commissioners had made, and which involved a supply of compressed air and water, if they used Nitro-Glycerin. And to make no mistake, the holes of what is termed the “cut” in the heading, that is, two series of four holes each, in a parallel line from the roof, about nine feet high, were drilled about five feet apart at the face of the heading, and six feet deep, tending towards each other so that at the bottom of the holes they terminated about three feet apart. After charging and firing, the above gentleman and his assistant inspected the result. A mass of rock eight feet in height, five feet wide in front, and about five feet deep, with the rear end three feet wide, had been blown from its seat, some ten feet from the heading, and there stood, a monument (until block-holed) of the use of Nitro-Glycerin, when properly applied. “You shall have all the water you want, sir, if I bring it myself in pails,” was the energetic assurance of this gentleman, who felt satisfied that Nitro-Glycerin was a necessity for the Hoosac Tunnel.

In drilling holes for blasting with Nitro-Glycerin, a depth of not less than five feet should be reached; six feet are better, but ten and twelve feet are the right depth for a heading, whilst fifteen feet for bench work, and eight feet apart, or, for quarry work ten feet apart, and ten feet from the face, provided the rock is hard enough (in clay, owing to the sudden shock Nitro-Glycerin is ineffective); exploded in holes of such a depth it will throw out everything before it—and make progress. How difficult to get miners to drill such holes, how many frivolous objections, how the wires and their connections will be tampered with to interfere with the intended blast, and how criminal, contrary, and pig-headed, they deem the contractor and Nitro-Glycerin man who insists on such depth of holes, I have often experienced, and it needs the firmness and vim of desperation to enter a quarry, descend a shaft, or go into a rock cutting, and oppose the life-long habits of men who believe honestly they know everything that concerns mining, and what they do not know is not worth knowing. But if once a blast is shewn, and they have to hoist out the rock, their obstinacy succumbs, and in three months, men, who knew it was poison, and so dangerous it was wicked to ask them to drill holes to receive it, have positively refused to descend a shaft if powder was attempted to be used merely in a comparative experiment, alleging, that the powder was unhealthy and not fit to be used at the bottom of a shaft, where the air was confined. And here let me truly add, I have never sent Nitro-Glycerin to be experimented with in any rock work, rock cutting, or rock tunnel, that was not followed by a large order, repeated until the end of the work, during my past experience of four years’ manufacture. Indeed, there have been only two cases where it was found inapplicable, and these were in hard clay, where it seems actually to mould for itself a chamber, compressing the walls of the drill hole, as if an enormous hydraulic ram had been inserted; but the tenacious mass is not displaced, it only suffers compression. When, therefore, holes can be made with a crow-bar, and not drilled, do not use Nitro-Glycerin, but if you have rock, be it as hard as emery, or as the magnetic iron ore of the Lake Superior or Ottawa Iron mines, the harder the better for the economy of drilling, which is very great, so few holes being required, the introduction of Nitro-Glycerin, with a good steam or air drill, causes the progress of the work to advance to that degree that it is only limited by the ability to remove the debris of blasted material. To return from this digression to my subject.

To effect this progress of 120 feet, probably about 3,000 holes have been drilled in an area not exceeding 24 feet by ten feet, requiring twelve drilling machines, and 60 horse steam power to compress the air requisite to drive the drills; add to this the powder, over a ton and a half, the electric exploders, the candles and oil for miners, and the fact that a mass of rock 120 feet long, ten feet high and twenty-four feet wide, has to be carried out and dumped two miles from where it was excavated, and some slight idea of the labor at this one point may be formed. Now take double this length of rock, viz.: 250 feet, increase its height to 15 feet, keeping its breadth of 24 feet—I say, take this mass which is torn from the roof, whilst the heading is being pushed, and bring it and dump it 1¾ miles from where it lay solid, and you have again another point on which you can begin to estimate the East End work. About 350 men, a locomotive, forty cars, 200 horse water power, machinists, blacksmiths a legion, for sharpening drills is hand work, so is picking up rock, loading cars, making track, and all this is done in the smoky, wet, grimy, confined tunnel, or round about its entrance, and you have a mixed, confused suspicion that this tunnel driving is a work needing high powers of organization; and, with the license of the miner, his pay day, his weddings and his wakes and funerals, which are all powerful reasons for quitting work, you have a still clearer idea of the anxiety such work involves.

CENTRAL SHAFT.

The Plate, opposite page 74, conveys an idea of the sinking of the Central Shaft at 891 feet depth; at the time of writing, May, 1872, however, this shaft had not only reached grade, but to a sump beneath grade at a depth of 1,040 feet; headings and enlargements have been also driven at grade, east and west, to meet the works from the East End, and from the Western Shaft. Owing to the stratification of the rock, which dips towards the west, great progress was anticipated in this direction; but man proposes and God disposes; on reaching about 300 feet westward, seams of water were struck, of so threatening a nature that a powerful Cornish pump was erected, at a cost reaching, in all its details, $80,000, and now, May, after enlarging the diameter of the former plunger pump, prudence suggests the temporary delay of any further disturbance of this water inlet (immediately under the divide of the mountain), until the present pumping force has sufficiently drained the sources of water supply to permit a further advance of this (the western) heading of the Central Shaft to be driven without involving a flooding out of the men working at the eastern heading. Meanwhile, from the sump, the excavations are enlarged to full tunnel size, the capacity of the Cornish and plunger pumps are being tested, and all energy summoned to meet any difficulties to be overcome when this western heading of the Central Shaft shall resume work. All the rock here has to be moved from the heading by hand power, and lifted (by steam power) 1,000 feet to the surface, yet, notwithstanding these adverse circumstances, during March, 100 feet was driven to the eastward alone. I append a memorandum furnished by Mr. E. A. Bond, of actual drilling and blasting, taken at this point during the dates given, being about the average performance.

On August 19th, 1871, on the north side of the east heading, machine No. 1, starting at 10 A. M., had at 2.08 P. M. drilled three holes, averaging about five feet four inches; the time actually occupied in drilling being 74 minutes, or an average of about 25 minutes to each hole. The remaining 2 hours and 54 minutes are accounted for by changes of drills, breaking of carriage, and an interval of 40 minutes for dinner. On the south side, machine No. 2, starting at 9.35 A. M., had at 2.09 P. M. drilled three holes, averaging about six feet four inches; the time actually occupied in drilling being 81 minutes, or an average of 27 minutes to each hole. The remaining 3 hours and 13 minutes are accounted for in a similar manner to the time of machine No. 1, except that there was no accident to the carriage. The average time of the two machines was about 26 minutes for the average depth of about five feet ten inches, being two inches and seven-tenths per minute. It will be seen by these facts that the actual drilling is but a comparatively small part of the work; bringing forward the machines, connecting to the air main, inserting the drills into the jaws of the machine piston, changing these drills as they wear down, oiling, releasing drill when stuck, removing back the machine carriage out of reach of the blasted rock, waiting for blaster to charge the holes, connect his wires, and apply the electric current to fire the exploders, removing the debris to clear the track for the approach of the drills—all these operations, so varied and yet so necessary, each consume a considerable quota of the eight hours allotted to each shift.

On August 30, 1871, a blast was made in the east heading at 5.30 P. M., as follows: fourteen 7 foot holes were fired with 25 lbs. of Nitro-Glycerin, throwing out about 30 tons of loose rock; and one solid rock, diameter 9 × 4½ × 4 feet, and weighing about 24,000 lbs., a distance of 30 feet, a weighty testimonial to the explosive power of Nitro-Glycerin.

The expense incurred and difficulties met with, in working at the Central Shaft, will serve as a hint to contractors to make all due allowance in their estimates for striking a seam of water; work may go on smoothly for a long time; the general geological formation of hill or mountain may be well understood, and yet the contractor cannot tell but that he may strike a vein of quartz that may throw him back days and weeks in his drilling calculations, or a seam of water which will cost him thousands of dollars in machinery and labor to keep it under.

On December 7, 1870, the hoisting machinery broke at the Central Shaft, and then the following measurements of water were made. On December 3, the depth was 3 feet; December 13, 7 feet; December 15, 8½ feet; December 20, 21 1/6 feet; and December 24, 48½ feet. At midnight they commenced bailing with two buckets, one having a capacity of 341 gallons or 54.65 cubic feet, and the other 189½ gallons or 31.36 cubic feet. The large bucket was hoisted 1,075 times, bailing 58,745.3 cubic feet of water, and the small bucket 966 times, with 29,327.8 cubic feet of water, the whole amount being 549,179.0 gallons in 27 days, or 21,080.0 gallons per day.

The following anecdote is worth relating, as showing the wonderful escapes men sometimes have, when the chances are one hundred thousand to one against their lives:

In February, 1872, Thomas Hawkins felt tired and sleepy, and concluded to lie down in the east heading of the Central Shaft, about 30 feet distant from where the blaster was charging sixteen holes with Nitro-Glycerin, intending to retire when the holes were charged. But he failed, as we many of us do, to carry out his intention. When the blaster had charged his holes, he left the heading, connected his wires, and having halloed the usual warning “Fire,” and every thing being quiet, discharged his blast. Thomas Hawkins was awakened by the report of the blast, scattering 30 or 40 tons of rock, and annoyed to find his foot bruised, he limped out to meet the miners returning to their work, who now, when a blast is about to take place, unceasingly ask him where he proposes to take up his position, that they may choose an equally safe place.

An escape, as wonderful, at the West Shaft, is worthy of being recorded. On August 3, 1868, as Richard Dunn was advancing to the heading, with a can about a quarter filled with Nitro-Glycerin, his foot slipped, and, in trying to avoid falling, he swung the can over his head, striking the drilling machine frame, and fell prostrate, still holding the can; a rush of air was heard, and the can was found as shown in the photograph, page 66, the Nitro-Glycerin not having exploded. The man got up a great deal more unconcerned than those at work near him, and quietly went forward and filled his cartridges as if nothing had happened. As I told him afterwards, he will never be so near eternity again without actually reaching it. The can had been filled at a temperature of 45°F, and the temperature of the room where it had been stored for 36 hours, was about 65°, thus causing an expansion both of the Nitro-Glycerin and the air contained in the can.

The West End of the Tunnel comprises the brick arch and portal, well No. 4, the supplementary shaft, and what is known as the West Shaft. The brick arch has been driven through what is aptly termed, “demoralized rock,” for immediately after the spring thaw it becomes a quicksand, and spews into the tunnel from every direction. By driving small adits on each side, and a central adit some distance ahead of the main tunnel, Mr. B. H. Farren overcame this dangerous and difficult work, which at one time threatened his contract, and thus enabled the arch work to be carried on. Subsequently, the central adit was carried through to the West Shaft, and thus the costly and difficult task of lifting 420 gallons of water per minute, to a height of 320 feet, was avoided, and it now escapes by natural flow through the west portal. Drilling is practised here as described for the East End and Central Shaft; in the East End the heading is driven on grade, and the overhanging enlargement is “stoped” out by hand drilling worked from an arched stage, (see plate opposite page 85) thus avoiding the necessity of handling twice; mules draw the laden trucks, from the heading and beyond where this stopeing out of the roof is going on, to the locomotive, which hauls a train of cars laden with stone to the dump.

At the West End, however, the roof of the heading is driven in line with the roof of the tunnel, which is hereby left complete as the heading progresses; this involves trucking by hand, and dumping the rock from the heading over the bench to the lower level, see plate opposite page 90, and is not found so economical as the East End method. These differing methods of working, however, were not started simply as experiments, but for good engineering reasons; at the East End, the dump was ample below the grade of the outlet, whereas, at the West End there was no opportunity to get out at the portal, on the line of the intended railroad; all the rock here had to be lifted (until the portal and arched work were completed) up and out of the West Shaft, and dumped on to the mountain side, and, to avoid being impeded by water, the heading was driven on a level higher than the grade of the Tunnel, thus ensuring good drainage for the most important part of the work, as it was then deemed, viz.: monthly linear advance. For the Commissioners were servants of the public, and the advance, rather than the enlargement of the Tunnel, was the measure of their success so far as public opinion was concerned.

Only by a personal visit to this enormous work can a correct idea be obtained of the expense, ingenuity, engineering skill, and indomitable energy of the several foremen and superintendents at the four divisions, viz.: East End, under Mr. Blue; at the Central Shaft, under Mr. Roskrow; at the West Shaft, Mr. Williams, with underground superintendent, Mr. White; and at the West Portal or arch work, the sub-contractors, Messrs. Hocking and Holbrook; all of whom are daily devising more expeditious methods of detail, in compassing the great end sought by each brigade, the completion of the Hoosac Tunnel contract at the time specified.

And whilst this energy, this organization, and all this development of the highest grade of modern engineering, are being devoted to carrying out the expressed wish of the majority of the people of Massachusetts, the malcontent minority is sleepless in offering every possible obstruction to the work; in Governor’s council, in consulting engineering supervision, in committee of assembly, in the newspaper press, covert expression of the opposition has found vent, and been doubtless useful in its way. But is it not time this opposition should cease? Must our citizens be for ever confined to one route from their Capitol to the West? Surely there will be traffic enough and ample, to remunerate both lines, when the Hoosac Tunnel route is open. If so, the time is approaching for a generous welcome from the opponents of the Hoosac Tunnel, and the conditions “at owner’s risk and at corporation’s convenience” may cease to appear on our freight notes.

Instructions for Handling and Using _MOWBRAY’S_ TRI-NITRO-GLYCERIN.

1. Handle carefully, avoiding a sudden jar or concussion, and be very careful, if any is spilt outside the can, to avoid striking it against any hard substance.

2. When solid, thaw out by placing the cans in a tub of warm water, not hotter than the wrist can bear, first pouring warm water into the can, and always remove the can before adding more hot water to the tub.

3. To fill Cartridges, &c.—Hold the Cartridges to be filled over a tray, say 2 feet by 3 feet, the bottom of which should be covered with Plaster of Paris (which will not readily explode when saturated with Nitro-Glycerin.) The soiled Plaster of Paris should be frequently renewed.

4. If the Nitro-Glycerin in a liquid state is kept in store or magazine for some time, the cork should be loosely inserted, and a pint of cold water poured in each can, to be frequently poured off and replaced with fresh cold water in warm weather, taking care to retain the bladder under the cork. It is preferable, when ice can be procured, to congeal the Nitro-Glycerin.

5. Use Funnels (gutta-percha if they can be had) for filling water holes. Under no circumstances whatever attempt to tamp the drill holes; it is unnecessary, and may kill the man who attempts it.

6. Hot irons to warm the water, or soldering the cans, will be sure to cause explosions.

7. Never sledge or attempt drilling in a hole or seam where Nitro-Glycerin has been spilled; fire an exploder, which will effectually clear it up.

8. Never pour Nitro-Glycerin into a hole unless perfectly sure that it is a sound hole, or will hold water; if seamy always use cartridges.

9. To obtain the best results with Nitro-Glycerin, drill deep holes, 6 feet or more. Use powerful exploders and well insulated wires. It is cheaper to fire by electric battery with simultaneous explosion, than to fire several holes with tape fuse.

10. Look out after a blast for any unexploded cartridges lying around.

11. Never allow any but the most careful persons to handle or have charge of the Nitro-Glycerin, and insist upon the use of every precaution to prevent an accident or explosion.

12. Never allow empty Glycerin cans to be used for any other purpose, but destroy them by a fuse and exploder, or building a fire under them, first, however, removing them to a safe distance.

13. Examine your cans from time to time, and notice if, at the level of the Nitro-Glycerin, any pin-holes have eaten through; in such case procure a new can, or stone jar, and empty the contents out, not trusting your hold to the upper part of the can, lest it may give way.

14. When solid, or congealed, it is absolutely safe; if possible, therefore, any surplus should be stored surrounded with ice, since no explosion can take place when it is solid.

GEORGE M. MOWBRAY. North Adams, Mass., June, 1872.

APPENDIX.

A.

MEMORANDA FOR CONTRACTORS.

1. There are very different qualities of Nitro-Glycerin, varying from 50 per cent. in blasting force, and the same manufacturer, unless able to control absolutely every detail of his work, cannot insure a precisely similar product, even from similar ingredients.

2. The best Nitro-Glycerin may be simply fired, or only exploded, or its full blasting effects achieved, precisely according to the initial velocity or force used to start the explosion; two cents in an exploder therefore may save ten dollars in a blast.

3. Ten per cent. of water diffused through Nitro-Glycerin, giving it a milky appearance (Nitro-Glycerin emulsion), will diminish its effective blasting results 30 per cent.

4. Thirty per cent. more blasting power is evolved, when the Nitro-Glycerin reaches the bare rock of the drill hole, than when, by insertion in cartridge, the metal of the cartridge and a layer of air or water are interposed between the blasting gases and the rock.

5. Pure Nitro-Glycerin may be safely stored, and does not readily change; impure Nitro-Glycerin needs only time and temperature to explode spontaneously.

6. In hard pan, or indurated clay, Nitro-Glycerin is not so economical as powder; in granite, gneiss, hornblende, quartz and other hard rocks, the harder the better, especially in large erratic boulders, the larger the better, Nitro-Glycerin will enable the tunneling, cut or block-holing, to be performed at half the cost as compared with gunpowder.

B.

“OVER-SENSITIVE” EXPLODERS.

The term, “over-sensitive,” has been used in the foregoing pages, and applied to exploders. Mr. Joseph Dowse, of Lockport, Illinois, applied “fulminate of copper” (a discovery of Dr. John Davy) as a priming for exploders, and patented the application, observing in his patent that parties unaccustomed to the preparation of fulminates had better leave this preparation alone. The sequel shows Mr. Dowse’s caution was not superfluous. Two manufacturers, provoked by the commercial inconvenience of the constant return of exploders owing to their inefficiency, have resorted to this “over-sensitive” priming, and received the following warnings:

In 1869, Mr. Stowell was standing in the office, on Sudbury street, Boston, whilst Mr. H. Julius Smith was packing 200 exploders in a rubber bag, in which an ebonite electric machine had been placed. Mr. Stowell remarked, “Is it safe to crowd them into a bag like that?” “Oh yes, perfectly safe,” was the reply, when instantly 170 out of the 200 exploded, severely burning and injuring both Smith and Stowell, the latter being confined to his bed for five weeks in consequence.

A similar explosion occurred to Mr. Smith on another occasion, the copper caps penetrating the fleshy part of the thigh, in almost the same parts as Mr. Stowell had been wounded, and burning the eyelashes, eyebrows and face severely; by this accident Mr. Smith was confined to his room for a considerable time.

Mr. Smith’s partner, in touching some of this priming, whilst moist, in a wooden bowl, was also severely burnt by its detonation, the face, eyebrows and eyelashes being injured, and himself confined to his room for four days.

On Thanksgiving day, 1869, Charles A. Brown was handling some of this priming, incautiously touching it on a piece of glass with a steel knife; it exploded, and the consequence has been deprivation of sight.

One Hogan, in the Fall of 1871, working in Charles A. Brown’s exploder factory, lost the sight of one eye, the other being severely injured, by imprudently omitting his helmet (usually worn whilst handling this material), and proceeding to move some of the primers whilst drying the same.

The superintendent, foreman of machine shop, foreman carpenter and blaster, engaged in connecting the wires, at the enlargement of the East End, were killed April 21, 1871, by a premature explosion, caused by the lightning striking the iron rails, whence the induced and ambient electricity, radiating to the leading wire, fired the over-sensitive exploders which were inserted in the charges of Nitro-Glycerin.

At the Burleigh Mine, Georgetown, two men were killed from similar causes producing similar effects.

An exploder, from one of the above manufacturers, placed in a cartridge that was being lowered with forty pounds of Nitro-Glycerin from the Government scow, at Dimon’s reef, to the diver below, exploded by reason of the friction of the insulating wire as it passed through the hands of Superintendent Pierce; now, as there were 300 pounds of Nitro-Glycerin on the scow, had it exploded, it must have destroyed the scow and every soul (about 40) on board. Fortunately, the fulminating charge was as imperfect as the priming was over-sensitive, confirming remarks on page 42.

These casualties, the comments of the press, together with the constant explosions in the factories of those who prepare “over-sensitive” exploders, are beginning to influence both principals and employees, and it is hoped exploder makers will eventually succeed in either resorting to the Abel priming, or discover, in the records of the Patent office, some formula that they can imitate, not so sensitive as that of Mr. Jacob Dowse, and whose proprietor is equally indifferent, or not “over-sensitive” to infringement. It is too much to expect they will surprise their friends, as Sheridan is reported to have astonished his, when, after repeated failures to guess how he became possessed of a new pair of boots, he coolly announced, “he had actually bought and paid for them.”

Meanwhile, the manufacturer of Nitro-Glycerin, if he would avoid the additional risk of exploder accidents, which are invariably laid to Nitro-Glycerin, must make his own exploders, and try to construct the necessary electric apparatus to fire them, until further developments have stimulated those who have entered into these trades to perfect their wares.

C.

PROFESSOR ABEL ON EFFECTS OF INITIAL EXPLOSION ON EXPLOSIVES.

Mr. Abel, of the Woolwich Arsenal, Great Britain, in an abstract of the Proc. Royal Society xvi. 395, observes:

The degree of rapidity with which an explosive substance undergoes metamorphosis, as also the nature and results of such change, are in the greater number of instances susceptible of several modifications, by variation of the circumstances under which the conditions essential to chemical change are fulfilled. Excellent illustrations of the modes by which such modifications may be brought about are furnished by gun-cotton, which may be made to burn very slowly and almost without flame, to inflame with great rapidity, but without development of great explosive force, or to exercise a violent destructive action; according as the mode of applying heat, the circumstances attending its application, and the mechanical conditions of the explosive agent are modified. Nitro-Glycerin or Glonoin, which bears some resemblance to chloride of nitrogen in the suddenness of its explosion, requires the fulfillment of special conditions for the full development of its explosive force. Its explosion by the simple action of heat can be accomplished only when the source of heat is applied for a considerable time in such a way that chemical decomposition is established in some portion of the mass, and is favored by the continued application of heat to that part; under these circumstances the chemical change proceeds with very rapidly accelerating violence, and eventually brings about a sudden transformation of the heated portion into gaseous products, which transformation is instantly communicated throughout the mass of Nitro-Glycerin, so that confinement of the substance is not necessary to develop its full explosive force. This result can be obtained more expeditiously, and with greater certainty, by exposing the substance to the concussive action of a detonation produced by the ignition of a small quantity of fulminating powder placed in contact with or near to the Nitro-Glycerin.

The development of the violent explosive action of Nitro-Glycerin, freely exposed to air, through the agency of a detonation, was regarded until recently as a peculiarity of that substance; but Abel’s experiments have shown that gun-cotton and other explosive compounds and mixtures do not necessarily require confinement for the full development of their explosive force; this result being obtained (and very readily in some instances, especially in that of gun-cotton) by means similar to those applied in the case of Nitro-Glycerin, viz.: by the percussive action of a detonation.

The action of a detonation in determining the violent explosion of gun-cotton, Nitro-Glycerin, etc., cannot be ascribed to the direct operation of the heat developed by the chemical changes of the charge of detonating compound used as the exploding agent. An experimental comparison of the mechanical force exerted by different explosive compounds, and by the same compound employed in different ways, has shown that the remarkable power exhibited by the explosion of small quantities of certain bodies (the mercuric and argentic fulminates) to accomplish the detonation of gun-cotton, while comparatively large quantities of other highly explosive agents are incapable of producing this result, is generally accounted for in a satisfactory manner by the difference in the amount of force suddenly brought to bear in the different instances upon some portion of the mass operated upon. Most generally, therefore, the degree of facility with which the detonation of a substance will develop similar changes in a neighboring explosive substance may be regarded as proportionate to the amount of force developed within the shortest space of time by that detonation, the latter being, in fact, analogous in its operation to that of a blow from a hammer, or of the impact of a projectile. Several remarkable results of an exceptional character have, however, been obtained, which indicate that the development of explosive force under the circumstances referred to, is not always simply ascribable to the sudden operation of mechanical force. Thus silver fulminate, which explodes much more suddenly, and with much more powerful local force than mercuric fulminate, nevertheless, when applied under the same conditions, does not induce the explosion of gun-cotton so readily as mercuric fulminate. Five grains of mercuric fulminate enclosed in a case of stout sheet metal, and exploded in close contact with compressed gun-cotton, caused the detonation of the latter, but five grains of silver fulminate enclosed in tin-foil, though it appeared to produce quite as sharp a detonation as the same quantity of the mercury salt enclosed in the stout case, did not explode the gun-cotton with which it was surrounded, but merely scattered the mass; when enclosed in the stout sheet metal case, however, the five grains of silver fulminate accomplished the detonation of the gun-cotton. Iodide and chloride of nitrogen are much more susceptible of sudden explosion even than silver fulminate; nevertheless, the iodide does not appear to be capable of causing the explosion of compressed gun-cotton; and the chloride of nitrogen shows but little capability of producing the same effect, fifty grains being the smallest quantity that will answer the purpose.

Lastly, it is found that Nitro-Glycerin when exploded by a charge of mercuric fulminate, will not bring about the explosion of compressed gun-cotton placed in contact with it, though under precisely similar circumstances the explosion of gun-cotton or of Nitro-Glycerin will induce the explosion of a larger mass of its own kind.

These results point to the conclusion, that the effect of the detonation of one substance in causing the explosion of another depends not only on the force, but also on the nature of the vibrations developed in the former; the most probable explanation of the observed results being that the vibrations attendant upon a particular explosion, if synchronous with those which would result from the explosion of a neighbouring substance in a state of high chemical tension, will, by their tendency to develop those vibrations, either determine the explosion, or, at least, greatly aid the disturbing effect of mechanical force suddenly applied, while, in the instance of another explosion, which develops vibratory impulses of a different character, the mechanical force applied through its agency, has to operate with little or no aid, so that greater force or a more powerful detonation is required in the latter case to accomplish the same result.

D.

NITRO-GLYCERIN CAR OFF THE TRACK.

The perfect safety with which Nitro-Glycerin can be transported, when congealed, is demonstrated in the following fact, which should effectually banish from the minds of freight agents and express companies the objections which they have heretofore successfully urged against carrying Nitro-Glycerin by rail; so far, at least, as concerns that manufactured by the writer.

On May 3, 1872, a special car loaded with seventy-nine cans containing 4,800 pounds of congealed Nitro-Glycerin, was being transported over the Chesapeake and Ohio Railroad, from Huntington to Charlestown; C. J. Cheshire, Assisting-Superintendent at the Maysville, Ky., Works, was on the car running at the rate of 18 miles an hour; suddenly the car jumped the track, and was dragged over the ties, some of which were two feet ten inches measured distance apart (the new roadway not then ballasted), for a distance of 684 feet, before the train could be brought to a stand still, to the no small consternation of Mr. Cheshire, the engine-driver and stoker. The rough jolting had no effect whatever on the Nitro-Glycerin, except tumbling some of the cans off the car, and in a few hours, the car being replaced, transportation was resumed, and one more experience of the properties of our Nitro-Glycerin added to the list.

E.

ACCIDENTS AT THE HOOSAC TUNNEL.

Until within the last two years there has been no complete record kept in the State Engineer’s office of the casualties among the miners at work on this great undertaking; but a careful examination of the existing records, and of the superintendents at different portions of the work, has enabled us to present the following analysis of the accidents, causing death or injuries to miners, which have occurred within the past three years, and to this we append the accidents by gun-cotton, Erhardt’s powder and fire, which, although of an earlier date, from their peculiar nature have had special memoranda made in regard to them.

ANALYSIS.

Killed. Injured. Killed and injured by falling rocks, tumbling down Shaft, and the usual casualties of miners other than those mentioned below, 14 12 Fire—Burning Central Shaft, 13 Over-sensitive Exploders, 7 a number. Dualin (about 600 lbs. actually used), 1 3 Erhardt’s Powder (less than 500 lbs. used), 3 10 Gun-Cotton (about 250 lbs. used), 1 4 Nitro-Glycerin (about 150,000 lbs. used), 5 5 Gun-Powder (most of the accidents from powder, occurred at an earlier date than our record, which in this respect is necessarily incomplete), 2 3 ——— ——— 46 37 8 ——— 45

This analysis shows 46 killed, and 45 (allowing 8 as the “number” vaguely mentioned in the records) injured by the various sources of accidents referred to, and as the relation of Nitro-Glycerin to other explosives is what especially interests our readers, the following comparative analysis of the deaths in proportion to the number of pounds of each explosive used at the Hoosac Tunnel, will enable them to form some idea as to the comparative safety of those mentioned.

ANALYSIS.

Killed. Amount used. Proportion lbs. of deaths per 100 lbs. Erhardt’s Powder, 3 500 .6 Gun-Cotton, 1 250 .4 Dualin, 1 600 .16 Nitro-Glycerin, 5 150,000 .0003

As Nitro-Glycerin has 13 times the explosive power of gunpowder, our readers, who are accustomed to use the latter for blasting, can easily ascertain the percentage of accidents in proportion to the amount used, and so judge for themselves as to the comparative safety of these explosives.

Really, whilst using, only two lives have been lost; one man rashly advancing to the charge, although advised to desist, whilst his fuse was burning; the other, on change of shift, after a blast, a cartridge having failed to explode, and the blaster neglecting to examine whether his cartridge had exploded, allowed the new shift to proceed drilling in the same rock, and within one inch of the same spot previously drilled, and where a charged cartridge was contained, when after a few inches of drilling progress, they came on to the concealed cartridge—explosion followed. In the magazine where three were killed, in order to hurry up, after a previous night’s spree, it had become the practice, notwithstanding peremptory warnings, to remove the cover of the stove, and expose the naked can of Nitro-Glycerin to the naked fire, of course, explosion must, as it did, follow this reprehensible folly, and disobedience to orders, resulting in killing three men.

I have established Tri-Nitro-Glycerin Factories

At North Adams, Massachusetts, ALFRED WALLACE, Foreman;

At Maysville, Kentucky, JOHN WALLACE, Superintendent;

At Kingston, Province Ontario, Upper Canada, H. H. PRATT, Superintendent;

In order to facilitate supply, and make deliveries at least possible cost for freight.

GEO. M. MOWBRAY, NORTH ADAMS, MASS.

Where orders for Exploders, both electric and tape fuse, gutta-percha insulated leading and connecting wire, of quality very superior to any hitherto made in the United States, should be addressed.

Agent in New York City: W. B. TOWNSEND, No. 40 Broadway (Room 39.)