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:
[Illustration: Profile of the Hoosac Mountain, and Advance of Tunnel,
January 1, 1872.]
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.
[Illustration: “Stopeing out” Roof Enlargement (East End.)]
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.
[Illustration: Driving Bench Work and Dumping from Heading (West
End.)]
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.)