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k-1023* (June 'aoj
* by Google
* by Google
BLASTING CAPS, SAFETY FUSE, CAP CRIMPERS,
ELECTRIC BLASTING CAPS, DELAY ELECTRIC
BLASTING CAPS, BLASTING MACHINES,
ELECTRIC SQUIBS, DELAY ELECTRIC
IGNITERS, CONNECTING WIRE, LEAD-
ING WIRE, GALVANOMETERS, RHEO-
STATS, CORDEAU, THAWING
KETTLES, BLASTING MATS,
TAMPING BAGS, ETC.
E. I. DU I
PONT DE NEMOURS & COMPANY
* by Google
id », Google
EXPLOSIVES themselves demand first considera-
tion when blasting is to be done, but the fact
must not be overlooked that they cannot be
properly exploded and will not develop their full
strength without certain materials and appliances
especially designed for the purpose. In addition to
those articles necessary to develop the energy of a
charge of explosives, there are other devices which,
although they may not be absolutely requisite, contrib-
ute to safety, certainty and economy in the use of
explosives. These are called "Blasting Accessories."
The importance of using Blasting Accessories that
are up to the highest standard in every respect cannot
be overestimated. The very best grade costs but a
trifle in comparison with the charge of explosives with
which they are used. It is poor economy to attempt to
detonate explosives with an inferior detonator, for this
always results in a considerable waste of the explosives.
The Du Pont Company has learned by more than a
hundred years of experience just what is required in
the shape of Blasting Accessories, and jealously main-
tains its standard of highest quality.
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Classes of Explosives
There are two general classes of explosives — deflagrating and
Deflagrating Explosives. — This class of explosives includes
all of those which are fired by sparks furnished by the spit (flying
DU PONT BLASTING POWDER GRAINS
sparks) from an electric squib, safety fuse or a miners' squib.
This class of explosives may also be fired by means of any of the
detonators intended for high explosives. The principal defla-
grating explosive is blasting powder.
Detonating Explosives. — This class of explosives includes all
the dynamites, nitroglycerin, ammonia, gelatin and Arctic and
Judson powders. They are not fired by sparks or flame, but
A CARTRIDGE OF DYNAMITE
require some powerful intermediate agent, such as an electric
blasting cap, blasting cap or cordeau. These agents are called
Deflagrating explosives, when loaded in large quantities, are
frequently fired or exploded by charges of high explosives.
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The Advantages of Strong Detonators
When high explosives are detonated, the stronger or sharper
the initial shock the more effective is the detonation of the charge.
It is a well-known fact that strong detonators will exert this effect
more powerfully than will weaker ones. To obtain the full value
of the explosive charge, it must be detonated completely. If the
detonation is incomplete, a greater quantity of explosive is
required to do the work, and large volumes of poisonous gases
may be evolved — a matter of serious consequence when the work
is underground. Instances are known where workmen have been
killed by gases given off from partially detonated or burning
Complete detonation results in a minimum of flame, a point
of first importance with those explosives intended for use in the
presence of inflammable gas or coal dust. Electric blasting caps
or other detonators too weak to detonate completely a charge of
high explosives may generate sufficient heat to ignite it.
The effect of a detonator on a charge of high explosives in
a bore hole is not infinitely powerful, but decreases with distance.
It is, therefore, easy to understand the necessity for using detona-
tors strong enough to ensure the effect of the detonator being
felt throughout the charge. It might be understood from this
that the detonator should be located m the center of the charge;
this would be considered correct had not numerous tests shown
that the greatest effect of the detonator is produced straight
away from its loaded end and in a line with its long axis. For this
reason it is advisable to have detonators pointed toward the
main part of the charge or to use not less than two electric
blasting caps in deep bore holes so that there is no danger of the
diminishing force of the detonators failing to detonate completely
the entire charge. This use of several detonators in a single
large charge acts also as a safeguard against the danger of an
occasional broken wire. The electric blasting caps should not be
farther apart, in deep holes, than from twenty to twenty-five
feet and for the lower strengths of insensitive explosives it is
better to have them even closer to each other.
A point to be remembered in buying detonators is that the
charge which they contain is weakened by moisture, and conse-
quently, unless storage conditions are of the best, a fair margin
of safety in strength should be allowed. Blasting caps, being
open at one end, are more quickly weakened by dampness than
are electric blasting caps.
Another strong argument for allowing a fair margin of safety
in strength when buying detonators is the very small cost of the
detonator in comparison with that of the charge of explosives
with which they are used. It is difficult to understand why any
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one, in order to save a few cents on the price of a hundred detona-
tors, would risk the misfire, partial detonation or imperfect
work of the charge of explosives in a bore hole, which would
result at best in the loss of several dollars and may cost thousands
if the charge burns in a gaseous coal mine or if unexploded
dynamite happens to cause a fatal accident.
The extended study and tests of explosives conducted during
the past few years by the United States Bureau of Mines have
clearly demonstrated the economy of using only strong detona-
tors, and cautions against the use of weak detonators are numerous.
The Du Pont No. 6 Blasting Cap and Du Pont No. 6 Electric
Blasting cap, recommended throughout this catalogue for
detonating high explosives, comply with the specifications for
strong detonators. The No. 8 Electric Blasting Cap and the No.
8 Blasting Cap have nearly double the strength of the No. 6.
Strong electric blasting caps and blasting caps should be used
with all high explosives for the following reasons:
They insure complete detonation.
They increase the execution of the explosive.
They tend to counterbalance careless and improper usage.
They offset, to some extent, deterioration of explosives and
detonators due to improper storage.
They reduce fumes from the explosives to a minimum.
They decrease the size and duration of flame.
They prevent the loss of the charge by burning.
Their effect carries further in long charges.
They reduce the chances of misfires.
Blasting by Electricity
Blasting by electricity is the most effective and economical
system, and surpasses all others in safety and certainty as well
as in results accomplished. Electric blasting makes it possible to
fire several charges simultaneously. Great economy of explosives
is effected by firing shots together, and it is often impossible to
obtain satisfactory results otherwise.
Many kinds of blasting can be accomplished only by electric
firing. Almost every kind of blasting that can be done by the
cap and fuse method can now be done more safely, quickly and
conveniently by electricity. With this method delayed explo-
sions, or "hang fires," are hardly possible, and, as the blaster
can always be a considerable distance away from the explosive
when it detonates, the possibility of accident is reduced to a
No method of blasting in gaseous or dusty coal mines, other
than the electrical one, deserves consideration because in all
others the ignition in the open of some burning substance is nec-
* by Google
essary, even though a device be used whereby the safety fuse or
squib can be ignited without exposing an open light or flame in a
It is believed by many authorities that disastrous explosions in
coal mines have been caused by a blown-out shot occurring shortly
after a number of other blasts have been fired. This cannot happen
if the firing is done by electricity, when as many shots as desired
are fired simultaneously. In submarine or other very wet work, no
other system is feasible. In underground work, where ventilation
is not good, burning safety fuse and miners' squibs increases the
smoke and fumes very materially. It is not uncommon for the
fire to break through the side of the fuse and ignite the charge of
explosives before detonating the blasting cap, resulting in poor
execution and increase in fumes. This cannot occur when the
blasting is done by electricity.
The equipment necessary for electric blasting is as follows:
Electric Blasting Caps* Connecting Wire
Leading Wire Blasting Machine
The Galvanometer and Rheostat will also prove of much
assistance and very often effect a saving of both time and money.
All of these accessories and their uses are fully described in
the following pages.
Electric Blasting Caps
An electric blasting cap, as the name implies, is a special form
of detonator fired or exploded by an electric current.
SECTIONAL VIEW OF ELECTRIC BLASTING CAP
The illustration above shows an electric blasting cap in section.
A is a copper shell, having a corrugation thrown out from the
inside, which holds the composition plug more firmly in place;
B is a chamber containing the explosive charge; C, insulated
copper wires entering the cap; D, the bare ends of the copper
wires, projecting through the plug into the charge; E, a fine wire
bridge soldered to and connecting the two ends of the copper
•For different clauses of work Che electric blasting caps are replaced by delay electric blasting
cap", waterproof electric blasting caps, submarine electric blasting caps, delay electric igniters
or electric saulbs.
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wires, which is heated by the electric current, thereby firing the
explosive charge; F, the composition plug holding the electric
blasting cap wires firmly in place; G, the filling material.
The strength of electric blasting caps is governed by the
amount of the explosive charge contained, and is expressed by
the numbers 6 and 8. The No. 8 Du Pont Electric Blasting
Caps contain nearly twice the charge of the No. 6 and are almost
twice as strong. Where large charges of explosives are used in one
bore hole the use of a No. 8 Electric Blasting Cap will more than
pay for itself in increased execution of the dynamite.
The following table describes fully the two sizes or strengths:
Grade No. 6 No. 8
Color of Label Red Green
Length of Shell 1 A' 2*
Calibre of Shell 273' .273*
There is also a No. 7 Electric Blasting Cap that is intermediate
between Nos. 6 and 8, but on account of one of these two strengths
being adapted to all general work, the No. 7 strength is not
recommended and is furnished only on special order.
The blasting cap wires, shown in the sectional view of the
electric blasting cap, vary in length to suit different depths of
bore holes and different classes of work. They must always be
long enough to reach a few inches out of the bore hole, and should
preferably be long enough to reach to the wires of the adjoining
Stock lengths of wires are:
4 ft. 10 ft. 16 ft.
6 ft. 12 ft. 18 ft.
8 ft. 14 ft. 20 ft.
Special lengths not shown above will be supplied on special
PONT ELECTRIC BLASTING CAP SHOWING WIRES
DU PONT No. 6 and No. 8 ELECTRIC BLASTING CAPS— EXACT SIZE
All electric blasting cap wires are well insulated. Copper
wires are ordinarily used^on account of the low electric resistance.
(See page 40 for tables of resistance.) Iron wires are also used
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to some extent, especially in coal mining, but on account of
the electric resistance of iron being about six times as great
as that of copper, a blasting machine cannot fire as many electric
detonators when iron wires are used as when copper wires are
used. (See page 40 for table of resistance of iron wires.) The
standard lengths of iron wires are 2, 4, 6 and 8 feet. Longer
lengths will be supplied on special order, but they are not recom-
mended. The iron wires are carefully insulated. For general work
copper wires are far superior.
Electric blasting caps are
packed in pasteboard cartons,
which are inclosed in heavy
wooden cases. The cartons
contain either 25 or SO elec-
tric blasting caps, depending
on the length of the wires.
Electric blasting caps with
wires from 4 feet to 16 feet
long are packed for domestic
trade 500 to the case, while
those with longer wires are
packed 250 to the case.
Th^e storage of electric blast-
ing caps should always be
given careful attention by the
consumer. If they are per-
mitted to remain for a long time in a very warm place, the water-
proofing material in the insulation dries out to such an extent that
the insulation may break when the wires are bent, and misfires
result if an attempt is made to use them in wet work.
The explosive charge in the electric blasting caps is very easily
affected by moisture, and if they are stored too long in a damp or
wet place they may deteriorate. This charge is also very sensi-
tive, and may be exploded by a moderately hard knock or jar.
Electric blasting caps should, therefore, be handled carefully.
Careful handling is also necessary on account of the delicate
bridge wire (see sectional view of electric blasting caps), which
may be broken by rough usage. When broken, the electric
blasting cap is absolutely useless. The wires must not be bent
sharply or forcibly separated at the point where they enter the
copper cap, as this may break or loosen the filling material and
permit water to enter and damage the explosive charge. These
precautions are necessary with all classes of electric detonators.
Care must be taken when tamping the bore hole not to break
either the electric blasting cap wires or the insulation on them, or
to pull the electric blasting cap out of the primer.
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Many misfires are due to
carelessness in loading and
tamping bore holes.
In each carton of electric
blasting caps there is a paper
tag called the "follow-up" tag.
In case any trouble is expe-
rienced with the electric blasting
caps, this tag should be pre-
served, as well as any unused
electric blasting caps, and, in
addition, the markings on the
wooden cases in which the car-
tons were packed should be
Du Pont Electric Blasting Caps are so constructed as to
be highly satisfactory for moist and wet work. They can be used
under several feet of water if the time between loading and firing
is not too great. They are not intended for use under great
heads of water, or for submarine work.
Waterproof Electric Blasting Caps
Although electric blasting cap wires and copper shells are welt
insulated against water, they are not intended for extremely wet
work, and if used in water, particularly under pressure, water
may leak into the cap so that the explosive charge is destroyed or
the electric current may "short circuit" through the water instead
of passing through the bridge wire, which is of high resistance.
For such work electric blasting caps with special insulation for
wet work are used. These specially insulated electric blasting
caps are called Du Pont Waterproof Electric Blasting Caps.
These are made in the same strengths, No. 6 and No. 8, with
the same lengths of insulated copper wires as the electric blast-
ing caps. Iron wires are not used. In order to give better
waterproofing the copper shell is longer than for electric blasting
caps so as to allow more space for filling material, shown at G
(see sectional view of electric blasting cap on previous page).
The copper wires have a special insulation which allows their use
in water not over 30 feet deep. Where the depth of water is over
30 feet and where the primers are to remain in the water for a
period longer than two days, the Submarine Electric Blasting
Caps are strongly recommended because of their special water-
Waterproof electric blasting caps must be placed within the
charge of explosives just the same as Electric Blasting caps, with
* by Google
the important difference that safeguards must be taken to pro-
tect the primers from water. The waterproofing of primers and
charges is discussed on page 61.
DU PONT WATERPROOF ELECTRIC BLASTING CAP
They must be handled in the same careful way as electric blast-
ing caps. They are packed in cartons, and then in cases of the
same size as are used for electric blasting caps. The weights of
packages are slightly greater than those of electric blasting caps.
Submarine Electric Blasting Caps
For under-water work, where the greatest safeguards against
water are necessary for safety and for developing the full strength
of explosives, a special Submarine Electric Blasting Cap is
used. It is made somewhat like the waterproof electric blasting
DU PONT WATERPROOF ELECTRIC BLASTING CAPSAND SUBMARINE ELECTRIC
BLASTING CAPS ARE MADE TO STAND THE SEVEREST UNDER-WATER
* by Google
■ LASTING ACCESSORIES
cap, with well -insulated wires and a long waterproof shell for
the detonating charge. It is further waterproofed by having a
heavy covering of gutta-percha over the shell and the lower or
cap ends of the wires.
Submarine Electric Blasting Caps are made in the same
strengths as Electric Blasting Caps Nos. 6 and 8.
To meet the requirements for under-water conditions. Sub-
marine electric blasting caps are furnished (on special factory
orders only) with gutta-percha insulated wires.
They are primed, connected and fired as are other electric
blasting caps, and the necessary precautions are taken to guard
against water entering the primed cartridge. (See page 61.)
Submarine electric blasting caps require the same careful
storing and handling as do other electric detonators. They are
packed in cartons as are electric blasting caps, but weigh slightly
Delay Electric Blasting Caps
In some kinds of blasting, particularly in tunnel and shaft
work, it is necessary to blast each round of bore holes in sections
or in rotation. It is generally a saving in time if this can be done
in such a way as to obviate the necessity of returning to the work-
ing face after each section has been blasted to arrange for the
next blast. When fuse and blasting caps are used to detonate the
explosive, the sections of fuse for the different bore holes are cut
in different lengths so that the charges will explode in the proper
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sequence if the fuses are lighted at about the same time. There
is practically no limit to the number of charges which can be
exploded in sequence with fuse and blasting caps in this way, but
electric firing is much more satisfactory for the many reasons of
safety and effectiveness pointed out in the chapter on Electric
Blasting. Under most conditions there is nothing to be gained by
dividing the round of holes into more than three sections. This
permits of cut, relief and rib shots.
The Du Pont Delay Electric Blasting Caps have been devel-
oped for such conditions so that these three classes of shots may
be fired in rotation with a single set of wiring and with but one
application of the electric current, and in such a way that there is
no trouble from the first round of shots breaking the wires for
the second and third rounds, as is the case when two or three
sets of wires are used for a series of shots using only electric
There are two kinds of delay electric blasting caps — first
delay and second delay. These are so constructed that there
is a short lapse of time after the current is applied before" the
first delays explode, and 'a longerdelay before the second delays
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explode. It should not be understood that all first delays explode
simultaneously, but the variation in time is very little and all
first delays explode before any of the second delays. There is
also a little variation in the time of explosion of the second delays.
In practical work the delay electric blasting caps are used in
connection with Du Pont Electric Blasting Caps. As the electric
blasting caps explode immediately upon receiving the electric
current, they are used in the holes that are to go first, such as cut
holes, thereby relieving the burden on the second set of holes,
such as relief shots, which are primed with first delays. The
last set of holes, such as rib shots, are primed with second delays
and explode after all of the others are out of the way. A better
understanding of this loading may be obtained by a close study
of the illustration of a method of connecting delay electric
blasting caps as shown on opposite page.
Delay electric blasting caps are manufactured in Nos. 6 and
8 strengths, as are electric blasting caps. They are fitted with
copper wires only. The lengths of the wires are the same as for
electric blasting caps, and longer wires are furnished on special
order. The wires on the first delays are white, and those on
the second delays are blue, to distinguish them from one another
and from electric blasting caps before and after loading. A third
delay with red wires is furnished on special order.
Delay electric blasting cap wires are connected for blasting
just as are electric blasting caps. They may be connected in the
same series with any of the other Du Pont electric detonators or
with Du Pont Delay Electric Igniters. Delay electric blasting
caps are packed in cartons such .as are used for electric blasting
caps, but the packages weigh slightly more than packages of
electric blasting caps.
Weights and Dimensions of Packages of Domestic
Electric Blasting Cap Cases
22' x 9j*x9J'
22' x 9j*x9l'
22* x Mi's 91'
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Delay Electric Igniters
A delay electric igniter is made up of a cylindrical copper tube,
into one end of which the necessary wires, plug, etc., are inserted,
and into the other end is crimped a piece of fuse 2 inches, 4 inches,
6 inches, 8 inches, 10 inches or 12 inches in length. The igniters
are designated as first delay, second delay and so on to
sixth delay, respectively, the delay being determined by the
length of the fuse. They are made with insulated copper or
iron wires of the same length as the Du Pont Electric Blasting
Caps. Longer wires may be had on special factory orders, and
also longer lengths of fuse in order to secure more delays or
longer intervals of delay.
They are designed for firing charges of explosives in rotation,
one after another. By using Du Pont Electric Blasting Caps in
the cut holes or the first set of holes to be fired, first delays in
the second set, second delays in the third set, and then following
with the other delays in order.
When a delay electric igniter is used with dynamite it is neces-
sary to cut off a quarter inch from the end of the fuse, crimp a
No. 6 or No. 8 Blasting Cap to the fuse and insert it in a cartridge
of dynamite as a primer. When used with blasting powder,
it is not necessary to use a blasting cap, but the end of the fuse
only should be in contact with the powder.
DELAY ELECTRIC IGNITER
They can be used with success in tunnel driving, shaft sinking,
or any other work of this character when it is desirable to have
the shots fired in rotation. They can be used in dry or moist work.
The use of delay electric igniters is strongly recommended for
coal and other mining, especially where it is unsafe to fire more
than one shot at a time. By their use it is possible to load as many
as six shots, and with one set of connections and one application
of the current, to have each shot fired singly. This applies to the
use of both blasting powder and dynamite.
Where the copper shell is placed so that it is covered with
tamping there is a minimum of fuse smoke allowed to escape.
Delay electric igniters require the same careful storage as
other electric blasting accessories. They are packed in the same
kind of cartons as electric blasting caps. The number packed
in each carton depends on the length of the fuse.
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Blasting powder is best ignited in the center of the charge.
It is impossible to do this with certainty with miners' squibs
or safety fuse. It can easily be done with Du Pont Electric
When a charge of blasting powder in a long bore hole is ignited
at one end, it is always possible for some of the coal or rock to
move before the entire charge explodes, and thus relieve the con-
finement from the powder in the far end of the hole. This is most
likely to happen when large charges are ignited at the end nearest
the mouth of the bore hole. Then more or less of the powder at
the back of the bore hole, where the burden is usually the heaviest,
does very little execution, and a large flame and a great volume of
smoke are projected into the working place.
Attempts to ignite the charge at the center are sometimes made
by extending the fuse to that point; but this is seldom successful,
owing to the fact that most fuse will spit fire from the sides and
ignite the charge where the fuse enters it. Even the very best
tape and gutta-percha fuse will do this occasionally. The expense
attached to the use of the highest quality of fuse has caused this
method of igniting charges of blasting powder in bore holes to
be practically abandoned.
EXACT SIZE OF DU PONT ELECTRIC SQUIB
Miners' squibs, often used for igniting blasting powder charges
in bore holes, are sometimes uncertain in their rate of burning,
and may give but little time for the blaster to reach a place of
safety after lighting them. This makes it necessary, when a
number of shots are ready to be fired, for the blaster to return
to the face several times, causing the loss of valuable time.
The miners' squib also necessitates an opening in the tamping
which may result in the flames from the blast blowing back into
the open and igniting mine dust or gas. This opening makes gas-
All of these disadvantages are overcome by the use of Du Pont
Electric Squibs that give all the general advantages of electrical
firing. These Electric Squibs are similar in general appearance
to Du Pont Electric Blasting Caps, but have a heavy paper shell
or cap instead of a copper one. The end of the shell is closed with
a small cork, which should be taken out before using. The charge
in this cap does not detonate as does that in electric blasting caps,
but merely shoots out a small flame. When electric squibs are
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used, the charge of blasting powder can be ignited in the center,
thus giving a little quicker and stronger action, and insuring the
explosion of the entire charge before any of the surrounding
material can fall and cut off a portion of it. The bore hole can be
tamped solid, leaving no vent for a partial loss of the strength of
the powder. When the entire charge is exploded at once, less
smoke is given off by the blast. This, with the elimination of
smoke from burning safety fuse, or miners' squibs, results in
purer air, making it possible for both miners and draught animals
to do more work. Aside from better blasting and greater safety,
this one feature is of sufficient advantage to warrant the use of
Another advantage in •
using electric squibs is
that when it is 'possible
to fire more than one
shot at a time all of the
bore holes can be con-
nected in series and fired
at the same instant.
This results in a very
considerable saving of
time, as well as powder,
as shot firers can cover
much more ground than
when using fuse or min-
It is much safer to
blast with electric squibs
than with fuse or miners carton of electric squibs
squibs, because shots are
not fired until everyone, including the blaster, is a safe distance
away, and because danger of hang fires is entirely obviated.
Advantages resulting from the use of electric squibs are:
Control of moment of firing.
Simultaneous firing of a number of shots.
Greater efficiency of blasting powder.
Saving of time.
Elimination of fumes from safety fuse.
Decrease of smoke from blasting powder.
Electric squibs require the same good storage conditions as
electric blasting caps. Although they cannot be exploded by
shock or concussion as can electric blasting caps, they must be
handled just as carefully, for their construction is necessarily
delicate and they can be easily broken by rough handling.
* by Google
They are manufactured with 4, 6, 8, 10 and 12 foot copper
wires, and 4, S, 6 and 8 foot iron wires. Those with iron wires
are somewhat less expensive, but require a stronger electric cur-
rent to explode them, because of the inferior conductivity of iron
as compared with copper wire. They are also more easily affected
by moisture. We do not recommend electric squibs with iron
wires longer than 8 feet, nor do we carry them in stock.
ELECTRIC SQUIB WITH 6- FOOT WIRES
Electric squibs are packed 50 to the carton and 10 cartons to
the case. Gross and net weights of cases are as follows :
Kind of Wire
22* x 9}" x 9
22' x 91' x 9
36 lbs. •
22' x 11}' x 9
22" x 11}* x 9
22* x 11}* x 9
22' x 11}* x 9
22* x 151* * 9
Cases of }* material. For inside dimensions deduct o
: inch from each
The method of wiring electric squibs is exactly the same as
for other electric detonators. This is described on pages 45 to 51.
The use of electric squibs is highly successful for firing pho-
tographic flash powders. By their use any number of flashes
may be fired at the same time. The action is positive. For this
work the squibs may be fired by means of a blasting machine or
an electric lighting circuit. Photographic electric squibs are
made with 6-inch copper wires. They are connected up in
exactly the same manner as Du Pont Electric Squibs and Elec-
tric Blasting Caps.
- Connecting wire is insulated copper wire (No. 20 Brown &
Sharpe gauge). It is put up in 1-pound and 2-pound spools.
A 1-pound spool is 3 inches in diameter, 4 inches long and holds
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about 210 feet of wire. A 2-pound spool is
3 inches in diameter, 5j4 inches long and holds
about 420 feet of wire.
Connecting wire is used to join the wires of
the electric blasting caps together, when they
are not long enough to reach between the
adjoining bore holes. The ends of the connecting
wire must be scraped bright before connections .
are made. The joints should not be permitted to 'Twb.'siwoi) 1 ™
He in water or on wet ground. If this cannot
be prevented, the joint should be covered with insulating tape.
No. 21 (Brown & Sharpe gauge) Insulated Copper Wire is also
used for connecting wire, but is not recommended because it is
considered too small for best results.
A 1-pound spool of No. 21 Connecting Wire holds about 260
feet and a 2-pound spool about 520 feet.
The resistance of No. 20 gauge Insulated Copper Connecting
Wire is 10.14 ohms per thousand feet. The resistance of the No.
21 size is 12.78 ohms per thousand feet.
The wire commonly used for connecting electric blasting caps,
other electric detonators and electric squibs to the blasting
machine is known as leading wire. It is insulated copper wire
(No. 14 Brown & Sharpe gauge) and is furnished in coils of the
following lengths and weights:
200 ft about 4 lbs. 300 ft about 5.8 lbs.
250 ft about 5 lbs. 500 ft about 9.6 lbs.
The leading wire should always be long enough to keep the
blaster well out of the zone of danger.
Duplex leading wire is made by binding together two insu-
lated copper wires with an outside insulation, thus giving a return
circuit cable that may be handled the same as a single wire. It
weighs approximately twice as much as the same length of single
leading wire and can be had in coils of the same lengths.
Duplex wire is more satisfactory for use where the two end
holes in a blast are not far apart, as in stump blasting and similar
work. Single wire is generally
preferred to the Duplex where
the end holes are far apart, as in
quarry and electric ditch blast-
ing. Single leading wire is fre-
quently used for connecting wire
instead of the small gauge con-
necting wire, especially in large
ROLL OF LEADING WIRE
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SINGLE LEADING \
DUPLEX LEADING WIRE (ACTUAL SIZE)
Special Leading Wire for Miners
For the use of miners and a few other blasters who fire but
from one to three charges in a blast, and then under conditions
where it is not necessary to be far from the blast, a special 18-
gauge Duplex Leading Wire is furnished on special order in 100
and 150 foot lengths. This wire weighs 1.85 pounds per hundred
feet. This leading wire is intended only for the work specified
and is not intended for genera! blasting.
Leading Wire Reels
The leading wire reel is a valuable accessory in enabling the
blaster to coil up his leading wire with a minimum of kinking of
the wires. It keeps the two wires separate, avoiding the chance of
crank is built in
the form of a
handle for the
easy carrying of
the leading wire
reel. Aside from
its'use will save
its price many
times over in the
course of a few
LEADING WIRE REEL
Blasting machines are used to generate the~current for firing
blasts by electricity.
Du Pont Blasting Machines, with the exception of the Pocket
Blasting Machine, are small portable dynamos, in which the
armature is rotated by the downward thrust of the rack bar,
thereby converting muscular energy into electrical energy. They
are not magnetos, although they are often erroneously so called.
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A magneto has a permanent magnet for a field, whereas the dyna-
mos in the Du Pont Blasting Machines have electro-magnets.
They are wound somewhat differently from a dynamo built for
delivering a continuous current for power or lighting purposes,
in that the current in the Du Pont Blasting Machines is short cir-
cuited through the field magnets for the purpose of building up,
intensifying and storing the current until the end of the rack bar
stroke, when the whole accumulated current is sent out through
the firing line.
The construction of the push-down Du Pont
Blasting Machines is shown in the accompany-
ing illustration. 1, Rack bar, showing teeth
which engage the pinion on end of armature;
4, the contact spring, which, when struck by
the bottom of the descending rack bar, breaks
the contact between two small platinum
bearings, one on the upper face of the contact
spring and the other on the under side of the
bridge 5, and in this way throws the entire
current through the outside circuit; that is,
leading wire, electric blasting caps and
connecting wire; 8, 9, field magnets; 16,
revolving armature; 34, rack bar handle.
They are rated according to the number of
electric blasting caps that they can be
depended upon to fire when connected in
series. For convenience, the electric blasting
cap with 30-foot copper wires is taken as the
parts of du pont umt - There are six different sizes, all of
blasting machine which are two-post machines.
Du Pont Pocket Blasting M
The Pocket Blasting Machine is a light-
machine, having permanent field magnets, esj
made for coal mining, where it is not often n
to fire more than one charge at a time. It
serviceable for small jobs, such as stump t
boulder blasting. It has a capacity of
three electric blasting caps. It weighs 4J^
pounds. It is furnished with a removable
handle, which prevents its being operated
by any other person than the blaster.
Method of Operating
To operate the Du Pont Pocket Blasting Machine, first remove
the carrying handle from the socket and insert the firing handle,
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taking care to see that it is properly engaged in the teeth below.
Hold the machine firmly in one hand, with the other hand on the
handle. When ready to fire give the handle a quick, hard turn in
a clockwise direction. This generates the current and causes it to
flow through the leading wires
No. 2 Blasting Machine
The No. 2 size is generally used in stump and boulder blasting,
(or springing bore holes on large work, and for mining where it is
desired to fire more than five electric blasting caps at a time.
It is strongly made, weighs 15 pounds, and has a capacity of ten
electric blasting caps with copper wires, or seven electric blasting
caps with iron wires.
Its use, in connection with a large blasting
machine, will often save time and money,
being more portable and less expensive than
the size necessary for large blasts.
No. 3 Blasting
The standard size for
quarry and mine. Its ca-
pacity is thirty electric
blasting caps with copper
wires. Weight, 25 pounds.
Due to its small size this
blasting machine can be
easily carried and operated
with satisfactory results.
It is recommended for all
general blasting opera- N0.1 n 3 . 3
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dons, where a larger blasting machine is not necessary, and even
where a smaller one, except the pocket blasting machine, will do
It is small enough to be carried easily, and yet is strong enough
for any thing except the largest blasts.
This size has given satisfaction to users for many years and is
the most popular of all blasting machines.
No. 4 Blasting Machine
A large machine for quarry, mine and excavating work.
Capacity, fifty electric blasting caps with copper wires. Weight,
This machine is a larger size of the same type as the popular
No. 3 Blasting Machine. It can be depended upon for successfully
firing as large blasts as are required on any except the very
No. 5 Blasting Machine
The No. 5 is a type of blasting machine embodying a number
of mechanical and electrical improvements. It is very easily
operated and built especially
rong to withsta"" 1
evere usage. It i
adapted for use
in quarry and
work, where it
is desirable to
fire a large
nators at one
time. It has a
capacity of 100
ing caps with
It weighs S3
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It is the best blasting machine
of its capacity ever produced.
No. 6 Blasting Machine
The No. 6 Blasting Machine,
while operated like the others, is of
a different type, embodying many
refinements of design, giving a
machine of great power and lighter
weight. It has a capacity of 150
copper wire electric blasting caps,
and is, by far, the most powerful
blasting machine made. !t weighs
only 37 pounds.
All Du Pont Blasting Machines
are securely boxed for shipment.
The shipping boxes make excellent
containers for storing and protect-
ing blasting machines when they
are not in use. " N " "
Table Showing Capacities and Uses of
Du Pont Blasting Machines
□f 30-foot Electric
B la* ting Caps.
1 to 10
1 to 30
1 to 100
1 to 150
Mining, stumping and boulder blasting.
Springing bore holes, all classes of small blasts.
General work and mining.
Large quarry and contracting work.
All classes of large blasts.
All classes of large blasts.
Operating a Du Pont Push-Down Blasting
To operate the push-down blasting machine (Nos. 2, 3, 4, 5, 6),
set it squarely on a solid, level place, connect up the wiring as
described on pages 45 and 48, lift up the rack bar by the handle
to its full extent, and with one quick, hard stroke push it down
to the bottom of the box with a solid thud using both hands. Try
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®2 -HJ Kf
PARTS OF DU PONT POCKET BLASTING MACHINE
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to knock the bottom out of the
machine. As the rack bar ap-
proaches the bottom, it becomes
more difficult to operate, because of
the "building up" of the current;
but the speed of the thrust should
not be diminished, because the
finish of the operation is more im-
portant than the start. Do not be
afraid of pushing the rack bar down
too hard. The machine is built to
stand it, and this is the only way to
use it successfully.
OPERATING A DU PONT
Blasting Machine Parts
The parts of these blasting machines are all standard, and
when worn out or broken can be replaced at a small cost. When
ordering, give the style and number of the blasting machine
in which they are used, as well as the number of the part as
shown in illustration on the following pages. Do not return
a blasting machine to us to be repaired without first securing
proper shipping directions from our nearest branch office.
List of Parts of Du Pont Pocket Blasting Machine*
P- 1. Winding Key.
P- 7. GuidePlateforWindmgKey.
(Should be ordered together
with P-34 Brass Case only.)
•P-10. Commutator Bear-
ing. (Should be ordered in
pairs with P-87 Gear Shield.)
•P— 11. Gear Bearing.
P-16. Armature, complete with
Heads and Commutator.
P-18. Armature Pinion.
P-21. Brass Screws (2) for Brushes.
P-22. Hexagon Nuts (2).
P-23. Brush Screw Insulators.
P-24. Brush Insulators.
P-26. Binding Post.
P-27. Thumb Nut for Binding Post.
P-29. Iron Screws (8) for Bearings
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P-34. Brass Case, complete with
P-7 Guide Plate for Wind-
P-35. Brass Chain, with Rubber
P-36. Wooden Handle.
taring, P-ll G
it [hey may t
Bearings, Pinion and Shaft.
Two Pole Pieces with Ends.
Half Gear Stop.
Brass Cap for Key-Hole.
Connecting Wire with Con-
P-83. Binding Post Insulators.
P-84. Leather Washer.
P-85. Fibre on Top Plate,
P-86. Hook for Chain.
•P-87. Gear Shield. (Should be
ordered together with P-10
Commutator Bearing and
rV 11 Gear Bearing.)
P-88. Release Spring on Half Gear.
P-89. Brass Collars with Set Screw.
P-90. Half Gear, Shaft, Contact
Spring and Copper Bur.
P-91. Screws (Oval Head) 2 for
P-92. Screws (Flat Head) 2 for
bottom of case.
P-93. Brass Screws (Oval Head)
for Guide Plate.
P-94. Magnets (3) Esterline.
P-95. Screws (1) for Pinion.
ar Bearing and P-87 Gear Shield should all
property drilled and fitted up-
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PARTS OF DU PONT No.. 1, 3 AMD i BLASTING MACHINES
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Parts of Blasting Machines Parts of Blasting Machine
Nos. 2, 3, 4 No. S
1. Rack Bar.
2. Guide Yoke.
3. Guide Rod.
4. Contact Spring.
6. Contact Screw.
7 Guide Plate.
8 and 9. Fields, a pair.
9 and 12. Field and Base Block.
10 and 11. Bearings, a pair.
12. Base Block.
13 and 14. Armature Heads and
Shaft, a pair.
18. Armature Pinion,
19. Pinion Spring.
21. Brush Screws.
22. Brass Nut.
23 and 24. Insulators.
26. Binding Post.
27. Wing Nut.
28. Armature Screws.
29. Bearing Screw.
30. Iron Screw for Base
31. Copper Rivet.
32. Iron Screw.
33. Iron Screw with Nut to
Bolt No. 12 to No. 45.
34. Mahogany Case.
35. Leather Strap,
36. Wood Handle.
81. Connecting Wire.
On No. 2 machine parts No, 9
(Field) and No. 13 (Base Block) are
cast together and cannot be sold
Rack Guide and Rear
Base Block. ,
Armature Rear Head and
Armature Front Head
Armature Complete with
i. Brush Screw.
i. Brush Insulators.
Resistance Coil Insulator.
i. Rear Bearing Bolts.
Iron Supporting Screw
Rack Bar Stop Screw.
Bolt with Nuts for
Brass Screw for Resist-
ance Unit Brackets.
Pawl and Spring.
Resistance Unit Bracket,
Pin for Intermediate Pin-
ion or Ratchet Gear.
Pin for Pinion.
Pin for Pawl Spring.
Screw for Contact Plate,
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•S I- 4
1 1 f
9l ffi 2' A
• f I 1
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PARTS OF DU PONT Nt* 6 BLASTING MACHINE
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Lilt of Part* of Du Pont No. 6 Blasting Machine
Rack Bar. 28. Screws for Rack Guide.
Rack Bar Guide. 33. Screws (or Generator.
Contact Spring. 35. Brass Handle.
Top Plate. 36. Handle for Rack Bar.
Rack Bar Guide Yoke. 37. Rack Bar Stop Screw,
nd 9. Fields. 38. Rack Bar Insulator.
Large Gear Bearings. 39. Screws for Shelf (brass).
Base Shelf. 40. Pinion.
Generator Front Bear- 40a Pinion Pin.
ings and Shield. 41. Ratchet Gear and Pin.
Generator Rear Bearings. 42. Large Gear, including
Brush. Pawl, Spring and Shaft.
Brush Holder. 55. Contact Plate.
Brush Spring. 56. Oil Cups.
Corners. 80. Armature, including
Screws for Large Gear Commutator.
Bearings. 81. Connecting Wire.
Binding Post (Regular 82. Motor, complete.
Standard). Mahogany Case.
Wing Nut (Regular
Care of Blasting Machines
Du Pont Blasting Machines are strongly made, and will stand
with little deterioration the treatment to which it is necessary to
subject them. Their mechanism, though designed as simply as
possible, is more or less complicated and delicate, and they must
be treated with at least some consideration. There can be no
possible excuse for throwing a blasting machine about, or permit-
ting it to remain exposed to wet weather or lying in the mud.
When a blasting machine is treated in this way its life will be
short and its usefulness limited.
Remember that good care will prolong the usefulness of the
blasting machine, will reduce the necessity for repairs and will
help to maintain its efficiency. The bearings and gearings should
be lightly oiled occasionally, but on the commutator, which is the
small copper-covered wheel on the end of the armature shaft,
never use oil. If the commutator becomes badly discolored or
dirty and needs cleaning, hold a piece of fine sandpaper, No. 00,
against it while rotating it slowly. Never use emery. See that the
two slots cut in the copper part of the commutator are clean, and
with no particle of metal or anything else in them which might
cause a short circuit. Keep the copper brushes (see 16, page 24)
clean, and see that they bear firmly on the commutator. Keep
the circuit*breaking contacts clean and bright.
When a blasting machine is not in use, store it in a dry and
comparatively cool place — not in a leaky tool box or on top of
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Every blasting machine is tested thoroughly before leaving the
works. If a new one does not give satisfactory results when
received, it may not have been operated properly or may have
been injured by rough handling during transportation.
Every blasting machine should be tested occasionally with a
Du Pont Rheostat.
The galvanometer is a small instrument used to determine
whether a blasting circuit is closed or open; that is, whether
the circuit is in the proper condition for the blast, or, because of
defective wires or poor connections, will fail to transmit the
electric current. The Du Pont Galvanometer can be used also
to measure the amount of resistance, thus indicating the existence
of leaks or short circuits. It is of value in testing not only blasting
circuits, but also individual electric detonators.
The instrument is a magnetic device in which an electric
current from a small chloride of silver dry cell moves a pointer
across a scale. There are two binding posts conveniently located
for connections. When a passageway (circuit) is offered, so
that the electric current can pass from one binding post to the
other, the current from the battery cell flows through this circuit,
traversing the galvanometer coil on the way, causing the pointer
to be deflected. The cell and needle are contained in a case made
of metal and hard rubber, which is in turn contained in a leather
carrying case. The galvanometer is small and flat and may be
carried comfortably in the pocket, or, when in use, slung from
the shoulder by the strap.
The battery cell is one selected after a long series of experi-
ments. While of long life and of great constancy, it is very weak.
The current which is sent through an electric detonator when
making a test with the assembled instrument is less than one-
tenth of the strength required to explode it. The length of time
a battery cell will last depends, of course, upon how frequently
it is used and how long the current is allowed to flow in making
each test. When properly used, one cell is sufficient for several
thousand tests. The simple form of connection enables the user
to easily replace the exhausted cell with a new one. The cell is
very small and light and can be sent by mail.
As the construction of the galvanometer and the methods for
using it are quite simple, the instrument is adapted to the require-
ments of the practical blaster as distinguished from the trained
electrician, whose finer instruments and methods would be at a
disadvantage under the conditions prevailing on the ordinary
electric blasting job. The galvanometer gives as accurate electri-
cal tests as are ordinarily needed in blasting work.
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DU PONT GALVANOMETER WITH CARRYING CASE AND
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We recommend the Du Pont Galvanometer to our customers
because it is a convenience and a time-saver and because the
exactness of operation which it makes possible secures better
execution from explosives, lessens the risk of blast failures, and
minimizes the danger of accidents.
Care of Galvanometer
Although the galvanometer is simple in design, and as sub-
stantially made as possible for such an instrument, some of the
parts are necessarily of delicate construction. It should, there-
fore, be handled carefully and kept perfectly dry.
The galvanometer should be tested before being used by placing
a short piece of copper wire momentarily across its two binding
posts. The wire having almost no resistance, the needle should
be deflected to its widest limit. If it does not move or go across
the scale, the battery cell is exhausted or weakened and must be
replaced by a fresh one.
To renew the battery cell, carefully take out the screws in
the face of the metal case, using a good screwdriver of the right
size. The exhausted cell is then easily lifted out, and the con-
necting wires transferred to the fresh cell. The only precaution
necessary is to be sure the + and — poles are connected to the
corresponding wires. The connectors at the ends of the cell
wires are marked + and — , and so no difficulty should be
Method of Operating
Testing a Circuit. — To test a circuit it is necessary only to
touch the ends of the two leading wires to its two binding posts,
after all connections are ready for the blast. If the circuit is
perfect the needle will move along the scale. If the needle does
not move there is a break in the circuit. If the needle does not
move as far as it should there is a place of high resistance, such
as a bad joint.
The galvanometer can be used for testing circuits only when
the electric blasting caps are connected in series. (See pages 45-
46.) In a parallel circuit, each electric blasting cap must be
tested separately. A parallel series circuit must be separated
into individual series and each series tested by itself.
Locating a Break.— To locate a break make sure that the
ends of the leading wires to be attached are separated and not
touching anything (see page 38). Secure a piece of connecting
wire, N, to one end connection, D, of the circuit. This wire
must be long enough to reach from the joint D to joint C. Now
touch the free end of the wire N to the contact post L of the
galvanometer, and either direct or through the second piece of
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leading wire M, touch the other contact post of the galvanometer
to the joint C. If the galvanometer now shows circuit while it
did not when the test was made from the other end of the leading
wires, the break is in the leading wires and they must be repaired.
If it does not show circuit, find the break in the electric blasting
cap or connecting wire by holding the end of wire N to contact
post L and touching the other contact post (or the short piece
of wire M touching the contact post on the galvanometer) to
each of the bare joints E, F, G, and H in succession. As long as
you are "inside" the break, these contacts will cause the needle
to be deflected. As soon as you get beyond the break or point
of high resistance, you get either a very slight deflection or none
at all. In this way the trouble can be quickly traced to the
break or bad joint. For instance, if a wire in bore hole No. 3
is broken, you get a deflection when M is touched to F, but none
on touching G; this shows that the break is between F and G.
The break can then be easily repaired if above the tamping.
If below the tamping and there are two electric detonators in
the hole, the broken one can be left out of the wiring and the
hole fired by the good one.
If there is but one electric blasting cap in the hole and its
wires are broken off below the tamping, the hole must be handled
as a misfired shot.
Testing Single Electric Blasting Caps.— Single electric
blasting caps can be tested, both before and after putting them
in the bore hole, simply by touching the ends of the electric
blasting cap wires to the two contact posts.
It is an excellent practice to test all electric blasting caps after
finishing the loading, but before tamping the hole, as well as
while tamping if the tamping is several feet deep.
The following table gives the resistance of Du Pont electrical
These include Electric Blasting Caps, Electric Squibs, Delay
Electric Blasting Caps and Delay Electric Igniters, with both
copper and iron wires, and Waterproof and Submarine Electric
Blasting Caps, with copper wires. Note that the Submarine
and Waterproof Electric Blasting Cap wires are No. 22 gauge
up to 18 ft. lengths, inclusive. In lengths of 20 ft. and over,
the wires are No. 20 gauge.
Copper wires, which are enameled, have the same resistance as
plain copper wires but have much better insulation.
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Table of Resistance in Ohms of Electrical Firing Devices
Table of Resistance of Copper Leading- and Connecting
Wire in Ohms per 1000 feet
No. 8 Brown &
(Usual size for power and light-
,' Standard gauge for leading
1 Sometimes used for short lead-
Each foot of electric blasting cap wire doubled (2 wires) has
a resistance of .032 ohms. The bridge of each electric blasting
cap has a resistance of 1.10 ohms. The bridge of the electric
squibs, delay electric blasting cap and delay electric igniter
has a resistance of .859 ohms. The resistance of the iron wire of
the size used for Du Pont Iron Wire Electric Firing Devices is
about 101.0 ohms per 1000 feet.
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Determining Resistance of Blasting Circuit
Connected in Series
To determine the resistance of any blasting circuit where the
electric firing devices are connected in series, multiply the resist-
ance of one firing device by the number in the circuit. Add to
this the resistance of the leading wire and the connecting wire,
and the result will be the total resistance of the circuit.
For example, if in a given blast 50 electric blasting caps with
copper lead wires 20 feet long are used, also 100 feet of No. 20
Connecting Wire and 500 feet of No. 14 Single Leading Wire (or
250 feet of Duplex Wire), the total resistance would be found in
the following manner.
One Electric Blasting Cap with 20 ft. copper wire has resistance
of 1.857 ohms. 50 of said caps have resistance of 92.85 Ohms
1000 (eet of No. 20 Connecting Wire has resistance of 10.14 ohms.
100 feet hasr« ' "" "
1000 feet of No. 14 Gauge Leading Wire has resistance of 2.521
ohms. 500 feet has resistance of 1.26
The total resistance of the entire circuit would be 95.12 Ohms
When exceptionally long lengths of leading or connecting
wire are used in blasting circuits, the resistance should be com-
puted and added to that of the electric detonators to guard against
overloading the blasting machine.
The question is often asked whether it is absolutely safe to
pass even the weak testing current of this galvanometer through
a single electric detonator. The only answer we can give is that
we have tested many millions with the Du Pont Galvanometer
without a single accident. There is nothing in the handling of
explosives, or electric blasting caps, that can be said to be entirely
Those who question the safety of testing with a galvanometer
in the manner outlined above can insure greater safety, when
testing a single electric blasting cap, by placing it in a short
piece of iron pipe, or similar receptacle, so that its accidental
detonation would do no harm. In locating breaks in a circuit
where the electric detonators are in the bore holes, the tests
can be made from a safe distance, through a pair of leading wires.
The latter procedure involves, of course, a trip to the loaded bore
hole every time the connections are changed for a new test.
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The I)u Pont Rheostat is a simple little instrument used for
testing the efficiency of blasting machines in an economical
and positive n
'i g £fs« k
One way to test, for exam-
ple, a No. 2 blasting machine,
which has a capacity of ten
electric blasting caps, is to
connect ten electric blasting
caps in series and then to the
blasting machine and operate
the machine. If all the electric
blasting caps fired, the ma-
chine would be working up to its rated capacity; if the electric
blasting caps did not fire, the machine would not be up to stand-
ard. The results obtained would be absolutely accurate.
The objection to this method is that it consumes so many electric
blasting caps, thus causing
needless expense. If a No. 5
or 6 blasting machine were
being tested, one hundred or
one hundred and fifty electric
blasting caps would be re-
quired for the test. Moreover,
the firing of so many electric blasting caps in the open would be
To obviate this expense, the Du Pont Rheostat is substituted
for all but one of the electric blasting caps, as is indicated in
the following diagram.
When such a series connection is made and the blasting ma-
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chine operated, the single electric blasting cap either fires or
does not fire, and indicates whether or not the blasting machine
is up to capacity.
The internal construction of the Rheostat is shown diagram-
maticallyon page 44. It is an arrangement of coils of high resist-
ance wire of a certain length, with the binding posts 1 and 6
attached to its ends, and the binding posts 2, 3, 4 and 5 attached
to it at intermediate points. The entire length of the resistance
wire in the Rheostat has a resistance sufficient to represent a test
of one hundred 30-foot electric blasting caps, with the leading
wire, connecting wire and all connections in the blasting circuit.
It will be noted that the binding posts, 1, 2, 3, 4, 5 and 6 are
not attached to the resistance wire at equal distances. The pur-
pose of this is to afford different resistances between different
binding posts, each representing a test of a certain number of
electric blasting caps. If wires X and Y are attached to binding
posts 1 and 2, the test represents a test of five electric blasting
caps; if to posts 2 and 3, of ten electric blasting caps; to posts 3 and
4, of twenty electric blasting caps; or to posts 4 and 5, of twenty-
five electric blasting caps. But the wires X and Y need not be
attached to adjoining posts. If, for instance, they are attached to
posts 1 and 4, the test represents the sum of the intervening
numbers, five, ten and twenty, or a total of thirty-five electric
As shown by the numbers stamped upon the hard rubber
between the binding posts, a large number of tests, representing
from five up to one hundred electric blasting caps, can be easily
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The resistances in the Rheostat are based upon 30-foot elec-
tric blasting caps and the required surplus resistance. If the
electric blasting caps in use are of shorter lengths, it will be
possible to fire a greater number than this test will indicate,
even, in some cases, up to twice the number. On the other hand,
there may be circumstances which will cut down the number
that can be fired below what the Rheostat test will indicate.
Chief among these is leakage of electric current in some part
of the blasting circuit, either from bare joints or wire touch-
ing damp ground, or other conductors, or from fluids of great
penetrating qualities coming in contact with the insulation of the
wires for too long a time before firing. Of these fluids, the worst
are the strong saline liquids, even though they be in small amounts,
and bore-hole washings in certain kinds of rock. If the electric
blasting caps differ greatly in sensitiveness to the firing current,
this will also cut down the number that can be depended upon
to fire simultaneously.
DIAGRAM OF CONSTRUCTION OF A RHEOSTAT
When testing blasting machines having capacities of more than
one hundred detonators, two Rheostats are used in series.
Should it be necessary to test a blasting machine for ninety
detonators, the resistance of ten, between posts 2 and 3, must be
blocked out. This is done by connecting these posts by means
of a piece of heavy copper wire or a coin. In this way the resistance
between any two posts can be subtracted from the total resistance
or the resistance between any two posts outside of the two that
are blocked out.
Be sure to use only one electric detonator or electric squib in
testing a blasting machine with a Rheostat.
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Table of Resistances of Rheostat in Ohms
The resistances furnished between the different posts of the
Rheostat are as follows:
Between 1 and 2. 16 ohms
Between 2 and 3 32 ohms
n 3 and 4 64 ohms
n 4 and 5 80 ohms
etween 5 and 6 128 ohms
1 and 3 48 ohms
Between 1 and 4 112 ohms
Between 1 and 5 192 ohms
Between 1 and 6 320 ohms
Between 2 and 4 96 ohms
Between 2 and 5 176 ohms
Between 2 and 6 304 ohms
Between 3 and 5 144 ohms
Between 3 and 6 272 ohms
Between 4 and 6 208 ohms
Wiring for Electric Blasts
When firing by electricity, whether using any of the electric
detonators, or electric squibs or delay electric igniters, the holes
may be connected in one of three ways,— in series, in parallel,
or in parallel series.
Series Connections.— When using a blasting machine all blast-
ing circuits must be in series. The series connection is made by
connecting one wire from each hole to one wire in the next hole
and so on to the end, when only the two end wires are left free.
These are connected to the ends of the leading wire. AH of this
is shown in the accompanying cut.
A. Blasting machine. B. The two strands of single leading »
C. Connections between leading wire and electric blasting cap wires.
D. Connections between electric blasting cap wires.
E. Connections between electric blasting cap wires and a short piece of con-
necting wire F, used to connect electric blasting cap wires that are
too short to reach from hole to hole. This may be left out when
long electric blasting cap wires are used, or it may be used between
all holes in some cases.
This method of wiring can also be used when a power or light-
ing circuit is used for firing the blast. A power current of 1J^
amperes is required for each series and a sufficient voltage to
overcome the resistance of the circuit, as is shown by the resist-
ance tables on page 40.
When duplex wire is used a piece of connecting wire, A, is
required to connect the extreme end to the leading wire as is
shown. This has a single objection in that it introduces an addi-
tional connection which, if improperly made, will increase the
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SHOWING USE OF DUPLEX LEADING WIRE
Some blasters prefer a slightly different method of making
connections which obviates the use of connecting wire in connec-
tion with duplex leading wire. It takes one less connection, but is
somewhat more expensive on account of requiring longer electric
blasting cap wires and demands the closest attention in order to
get a good circuit.
OF CONNECTING DUPLEX LEADING WIRE
An excellent method of making a series connection where
two lines of holes are used is shown in the following sketch. This
is of especial advantage when using two lines of holes with delay
electric blasting caps or delay electric igniters and in blasting
wide ditches. Either single or duplex leading wire may be used.
How three lines of holes for the use of delay electric blasting
caps or delay electric igniters or for very wide ditch blasts may
be connected in series is shown in the following diagram. Either
single or duplex leading wire may be used,
METHOD OF CONNECTING THREE LINES OF HOLES
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ANOTHER VIEW OF "SERIES-
CONNECTION, USING A
I— g g-\ be used with a power or !i
Parallel Connections. — When power or lighting circuits are used
for firing, the circuit may be connected in parallel. This type of
circuit differs materially from the series circuit, and is shown
graphically in the accompanying cut. For such a circuit, the
firing current must have \}4 amperes for each detonator or
squib, but the voltage of the current can be less than when the
connections of the same number of detonators are in series.
SHOWING PARALLEL METHOD OF CONNECTING UP WHEN POWER
OR LIGHTING CIRCUITS ARE USED
A. Power or lighting circw
C. Leading wires of suffii
B. Blasting switch for closing circuit,
length to keep the switch B a safe distance
from the blast and to reach past the last hole, to be fired.
D. Bore holes with electric detonators.
E. Connections between the detonator wires from holes D to the leading
Parallel Series Connections. — A circuit connected in parallel
series is a number of series circuits, two or more, connected in
parallel as is shown in the accompanying diagram. This type
of circuit can be used only with a power or lighting current.
Such a circuit requires i}4 amperes for each series, shown as E,
but the voltage required is less than the amount required to
overcome the resistance in the series having the greatest resist-
ance. The determination of this point is a slightly complicated
mathematical problem for the blaster, and it is best to allow a
large margin of safety in the way of too much voltage.
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METHOD OF MAKING PARAL-
LEL CONNECTIONS WHEN
POWER OR LIGHTING CUR-
RENT IS USED.
cannot be used with a
SHOWING PARALLEL SERIES CONNECTION HAVING TWO OR MORE CIRCUITS
A. Wires of power or lighting circuit. B. Blasting switch (or closing circuit.
C. Leading wires of sufficient length to keep the switch B at a safe distance
from the blast and to reach past the last hole.
D. Bore holes with electric detonators. E. Individual series of holes D.
NOTE: The parallel
series method of wiring
cannot be used with a
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Safety Firing Switch
The illustration shows a very
simple and effective way to
prevent the premature closing
of a circuit used to supply
current for electrical detona-
tion of explosives. With the
key in the hands of the shot-
firer he is the only one able to
close the circuit until he is pre-
pared to "set off" the shots.
Making and Protecting Wire Connections
The wiring or connecting of an electric blast must be well
and correctly done to insure success. The work of wiring may
be divided into three parts: connecting the detonator or squib
wires together either directly or by means of connecting wire;
connecting the proper detonator wires to the leading wire; and
connecting the leading wire to the blasting machine.
Connecting Detonator Wires. — Connections between detona-
tor wires or between detonator wires and connecting wires must
all be well made. First scrape the bare ends of the wires with
a knife blade, and then join them with a long twist (generally
known as "Western Union Twist") such as is shown in the
accompanying sketch. Such a twist should be tightly made to
SHOWING "WESTERN UNION" METHOD OF JOINING WIRES
CORRECTLY TWISTED WIRES COVERED WITH TAPING
keep the resistance in the joint down to a minimum. If there is
no bare end to the connecting wire, skin off about two inches of
the insulation. A later paragraph will give detailed information
about protecting these bare joints.
Never, under any circumstances, loop wires together as is
shown as the wrong way.
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Twenty-four holes with two electric blasting caps In eacn hole-
connected In series. The blast should be fired with a No. t
Machine, or with a power or lighting circuit of 110
LOOPED WIRES— THE WRONG WAY
Connecting Detonator Wire to Leading Wire. — In making
connections between detonator wires and leading wires the same
precautions must be observed with regard to cleaning the ends
of the wires. Wrap the detonator or connecting wires tightly
around the end of the leading wire about one inch from the end.
AN EXCELLENT K
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Then bend the end of leading wire back sharply and take a
turn or two of the detonator wire around the loop. This last
loop is simply to make a stronger connection to withstand any
accidental pull on the leading wire that might tear the connection
Connecting the Leading Wire to Blasting Machine. — The
connection of the leading wire to the blasting machine is made
by loosening the wing nuts on the two binding posts, inserting
the ends of leading wire into the small holes in the binding posts
and tightening the wing nuts down on the wires.
Protecting Bare Joints.- — The naked joints in the wires of a
blasting circuit must always be protected against short circuiting,
especially through water. This is done in several ways. When
connections He on moist ground they may be held up by support-
ing them on stones, blocks or sticks so that only the insulated
parts of the wires touch the ground and supports; or the joints
may be insulated with tape. While not generally needed where
the joints can be held off the ground, the taping of joints is
strongly recommended where the joints are covered by tamping,
where they cannot be held out of the water on props, and where
blasting must be done in a rainstorm. It is very desirable to
tape the joints of leading wire.
Blasting with Cap and Fuse
31 as ting Caps
Blasting caps are the detonators
used for firing high explosives when
electric blasting is not practiced.
They must always be used with safety
fuse, and are in no way interchange-
able with electric blasting caps. Using
blasting caps and fuse, it is not
possible to fire a number of blasts
simultaneously. Such blasting must
be don. with electric blasting caps B0X CONTA1Nmc , 100
or other electric firing agents. No. 6 du pont blasting
Blasting caps are small drawn cop- '""*
per cylinders, closed at one end and loaded with a small charge
of a very sensitive and violent explosive that is exploded by the
spit of sparks from safety fuse,
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Dimensions of Du Pont Blasting; Caps
Note. — The itaidt diameter of bath the No.
Ponl Blasting Cap is .2J0J'
Du Pont Blasting Caps are manufactured in the No. 6 and
No. 8 sizes and are exactly the same strength as the corresponding
designations of Electric Blasting Caps.
A No. 7 Blasting Cap is intermediate in strength between
Nos. 6 and 8, but as one of these two numbers is adaptable to
all general classes of blasting, the No. 7 strength is not recom-
mended and is furnished only on special factory order.
All blasting caps are packed in tin boxes, each containing 100.
Ten boxes are in turn packed in cartons and the cartons, with
sawdust, in wooden shipping cases.
No. 8 DU PONT BLASTING CAP
No. o DU PONT BLASTING
Packages of Du Pont Blasting Caps for
No. of Case Quantity per Case
In Oblong Boxes
No. 8 Blasting Cap*
500 11 pounds
1,000 151 "
1 1 pounds
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It will be seen that with
the exception of case No. the
number of the case indicates
the number of thousands of
blasting caps in the case. As
no cases contain 4,000 caps,
there is no No. 4 case.
All cases are well made of
sound lumber. Cases for ex-
port trade are tin lined to give
the blasting cap additional
protection. They weigh
slightly more than those for carton of blasting caps
Blasting caps should be stored in a dry place. When con-
yeying them to the work where they are to be used no moisture
whatever should be permitted to get into the charge which they
contain, as this charge is very quickly affected by dampness, and
will absorb moisture and deteriorate. Storage in damp places,
such as open sheds or tool boxes in mines, is likely to affect the
charge in blasting caps, and may weaken them to such an extent
that they will-not properly detonate high explosives.
The methods of attaching the blasting cap to the fuse, and of
priming high explosive cartridges with the blasting cap and fuse,
are described in other portions of this catalogue.
Du Pont Blasting Caps are
manufactured with the same
care and undergo the same
rigid inspections as do all other
Du Pont products. When prop-
erly used, they can be de-
pended on to do the work for
which they are intended.
In each box of blasting caps
there is a small card known as
the "follow-up" card or inspec-
tor's ticket. In case trouble is
experienced with the blasting
caps this ticket, with any
unused blasting caps, should - -
be preserved in order to facilitate investigation.
Safety fuse is the medium of bringing sparks to fire blasting
caps or to ignite a charge of blasting powder. It is made up of a
thin train of powder tightly compressed in, and more or less
waterproofed by inner and outer wrappings or coverings.
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The different kinds of safety fuse made may be divided into
four classes, according to the kinds of blasting for which they
are intended. These classes are :
Dry work. Damp work. Wet work. Under water.
The classification of brands of fuse sold by the Du Pont
Company according to this standard is:
Hemp (black) f
Black Monarch J
nana. Wyoming. Colorado and New Mexico
. of Montana. Idaho. Utah and Arizona or t
3 of Wyoming. Colorado and New Mexico, o
: in the Eastern States,
.e Middle Western States.
Safety Fuse Packages
Safety fuse is manufactured in lengths of 50 feet, which lengths
are made into rolls. Two rolls are fitted, one inside the other, and
neatly wrapped in paper. The double rolls are packed in wooden
cases. Export orders are shipped in tin cans or tin-lined boxes.
The sizes of packages are given in the following tables:
Ensign-Bickford Company's Fute Package
Approximate Weights Outside Dimknsions
Hemp and Cotton
V x 7J*xl5*
r, Charter Oat, Clov
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For export shipments, fuse may be packed in water-tight cans,
containing 500 feet each, and snugly packed in iron-strapped
wooden cases, or in tin-lined wooden cases if preferred.
The packing and the weights of other fuse named in this book,
but not included in the tables, are approximately the same as for
similar classes of fuse on which detailed information is given.
It should be remembered that in all classes of blasting where
water is encountered the loading should be done and the
shots fired as soon as possible. While the brands listed for use
under water will burn through water when first loaded, they will
not withstand wetting for a long time, especially when under
pressure of several feet of water.
Hemp Fuse and Cotton Fuse are too small in diameter to prop-
erly fit the standard blasting cap, and should be used only for
exploding blasting powder charges where a blasting cap is unnec-
essary, unless a dynamite primer is used.
Burning Speed of Fuse
Safety fuse sold in the Eastern States burns, in the open, at the
rate of about thirty-two seconds per foot, except Charter Oak and
Clover brands, which have a burning speed, in the open, of about
40 seconds per foot ; that sold in the Middle Western and Western
States burns at the rate of between 36 and 39 seconds per foot.
This burning speed is subject to a variation of 10 per cent either
way. Fuse burns faster when tightly tamped. The length of fuse
used in a blast must always be long enough for the blaster to
retire to a safe distance.
Each fuse wrapper is stamped with a serial number, which,
with the markings on the packing case, should be preserved in
case trouble is experienced with the fuse, for identification and
to facilitate investigation.
Dimensions of Cases Containing Fuse for Export
Case No. (All Brands) 81' x 15' x 8'
" " 1 " " 8J* x 15* x 16 *
" " 2 " " 161* x 15' x 15 *
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Approximate Weights and Dimensions of Cases of
Fuse Made by Coast Manufacturing
and Supply Company
1,000 ft. case
2,000 (t. case
3,000 ft. case
6,000 ft. case
14J' x 15
26* x 15
37* x 15
37* x 15
* x 151"
American Eagle and Blue Label
1,000 ft. case
2,000 ft. case
3,000 ft. case
6,000 ft. case
141*x 151' x 81'
26' x 15J' x 81*
37* x 15J' x 81*
37' x 151' x 151*
1,000 ft. case
2,000 ft. case
3,000 ft. case
6,000 ft. case
141' * 151* * 81'
26* x 151' * 81'
37' x 151' x 81'
37" x 151* x 15}"
1,000 ft. case
2,000 ft. case
3,000 ft. case
6,000 ft. case
141* x 151* x 81'
26* x 151' x 81'
37' x 151' x 8}'
37' x 151* x 151*
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62 i lbs.
1,000 ft. case
2,000 ft. case
3,000 ft. case
42 i lbs.
6,000 ft. case
1,000 ft. case
2,000 ft. case
6,000 ft. case
10,000 ft. case 1 14 lbs. 23 lbs. 91 lbs. 14j" x 15J'
•Packed only in full caws of 1(
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Storage and Handling of Fuse
Safety fuse cannot be kept in good condition unless stored in
a cool, dry place. If stored in a hot place, the heat is likely to
melt the waterproofing material, causing it to penetrate to the
powder core or making the fuse too soft; or the heat may dry
out the fuse so that it will break when unrolled. If stored in a
damp place, the powder in the fuse soon absorbs moisture and
fails to burn properly.
When handling safety fuse, do not twist or "kink" it. Always
cut off at least two inches of
the end of the coil and insert the
fresh cut end of the fuse in the
blasting cap, because the powder in
the end becomes damp and ineffec-
tive very quickly. It is also likely
to spill out of the cut end after the
fuse has been handled a little. In
... ■ c ■ Ul DOUBLE ROLL OF SAFETY FUSE
either case a misfire might occur. with paper wrapping
Always cut the end of the safety removed
fuse which is to be inserted in the blasting cap squarely across
and not diagonally, as the point made by a diagonal cut may be
bent forward when the safety fuse is pushed into the blasting
cap, and in this way prevent the spark from shooting into the
blasting cap charge.
Always press the end of the safety fuse gently against the charge
in the blasting cap before crimping the blasting cap. AH safety
fuse, except Cotton and Hemp, is made to fit as snugly as possible
into the blasting cap in order to prevent water or moisture from
entering. If the safety fuse is found at any time to be a little too
large to enter the blasting cap, do not attempt to cut off any of
the tape or yarn, but squeeze or roll the end between the thumb
and finger until it is small enough.
It occasionally happens that when subjected to summer heat
the waterproofing of some kinds of fuse will absorb the white
material put on the outside, causing it to appear black or of a
dingy yellow color. This unfavorable appearance does not neces-
sarily indicate that the fuse is damaged. It is probably perfectly
good, but it should be tested, and this will readily determine its
If fuse is stored too long, it may be dry and hard, or the
powder may be impaired by age. Gutta-percha fuse is most
likely to deteriorate from age because the gutta-percha becomes
oxidized by contact with air.
In tape fuse, places may be found where the diameter is slightly
enlarged for about an inch in length. This is caused by the over-
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lapping of the ends of the tape where two pieces are sewed
together. It does not indicate any defect in the fuse.
When using blasting caps and safety fuse, it is essential that
the blasting caps be securely fastened or crimped to the fuse.
If the joining is not firm, there is danger that the fuse will be
pulled out when the primed cartridges are loaded and the bore
holes tamped. An imperfect joining makes the waterproofing
of the cap difficult. The most satisfactory crimp can be made
by using a cap crimper, — an instrument designed for the purpose.
The Du Pont Cap Crimpers
make a flat sleeve crimp which
holds the cap securely on the
fuse and makes waterproofing
possible with but a small
amount of waterproofing ma-
Du Pont Cap Crimpers are
made in two types, No. 1 and
No. 1 Cap Crimper is made
of blued steef. It is 5H inches
long and is made with the
sleeve type of crimping jaws,
having one handle pointed for
use as a punch in priming
No. 2 Cap Crimper is made
of steel, nickel plated. It is 7
inches long. In addition to
the crimper, it is provided with
a most effective fuse cutting
device, so designed as to pre-
vent accidental cutting of blast-
ing caps. One handle is pointed
for use as a punch and the other has a screwdriver point.
Both of these crimpers are so made that they cannot squeeze
the copper shell far enough into the fuse to interfere with the burn-
ing of the powder train and cause misfires. They are well made
of good material and, if used only for the purposes intended,
will give good service for a long time.
BLASTING CAP CRIMPED TO FUSE
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Du Pont Cap Sealing Compound
Du Pont Cap Sealing Compound is a material for sealing water-
tight the space between the shell of a blasting cap and the fuse
which is inserted into the blasting cap.
However well the cap may be fastened to the fuse by the
crimper, it is almost impossible to make a joint that will prevent
water from leaking in and spoiling the cap. The cap is especially
liable to damage from water when "countered" fuse is used,
because the uneven surface of such fuse formed by the spirally
wound cords leaves small air spaces between the fuse and the
shell through which water may leak down
into the cap. Therefore, whenever the cap
is to come in contact with water, it should
be made waterproof by sealing with Du
Pont Cap Sealing Compound.
After the blasting cap is crimped on the
fuse, the cap with two or three inches of
the fuse is dipped for a few seconds into
the cap sealing compound and hung up to
dry. It is not necessary to soak the cap
in the compound. By the time the com-
pound P° un d nas dried for about thirty minutes, a
water-tight joint is formed which will resist
almost any amount of water commonly encountered in blasting
with cap and fuse. The cap should be used soon after it is dry,
as the Cap Sealing Compound becomes brittle after a few days
and is liable to crack and admit water.
Du Pont Cap Sealing Compound is put up in half-pint, pint,
quart and gallon cans.
CAP SEALING COMPOUND APPLIED TO CRIMP
A high explosive cartridge containing an electric blasting cap
or other detonator is called a primer.
Primers must be properly made to insure the complete detona-
tion of the explosive; to keep the detonator from pulling out of
the explosive; to guard against moisture; to permit easy and
safe loading of bore holes; to keep the safety fuse, when blast-
ing caps and safety fuses are used, from pulling out of the
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Priming a Cartridge with Blasting Cap
and Safety Fuse
In making a primer with blasting cap and fuse, cut off a
sufficient length of fuse to reach from the charge of explosives
loaded in the bore hole to three or four inches above the collar or
top of the bore hole. In all classes of blasting, the length of the
fuse must be governed by the time required for the blaster to
reach a safe place after lighting the fuse.
After removing the cover of the blasting cap box, allow a single
blasting cap to slide gently into the hand. Never try to pick a
blasting cap out of the box with a wire, knife blade, stick, or
other hard substance. See that no foreign matter, such as dirt or
grit, is in the open end of the blasting cap; if there is any, shake it
out gently. If the end of the fuse is flattened, roll it between the
thumb and finger to round it out again and slip the blasting cap
gently over the end of the fuse so that the fuse reaches down to
the explosive charge in the blasting cap.
Do not twist the fuse into the blasting cap, and do not use
violence or force when handling the blasting caps or when making
When the blasting cap is placed on the fuse, fasten it securely
in place with a Du Pont Cap Crimper. The crimp must be made
close to the open end of the blasting cap as shown on page 62.
To make the crimp further down would in all probability cause
a premature explosion and seriously injure the blaster.
When the primer is to be used under water, the union between
the blasting cap and the fuse should be protected against moisture
by a coating of Du Pont Cap Sealing Compound or other suitable
Priming in the Side of Cartridges. — To prime a cartridge
in the side the blasting cap and fuse are handled as has just been
described. The hole is begun about an inch or an inch and a half
from one end of the cartridge, and should point in and toward
the other end, so that when the blasting cap is inserted it will
be as nearly parallel as possible to the sides of the cartridge.
// should never be punched straight through the cartridge, as such
a hole would not place the blasting cap in the proper position for
detonating the explosive. A blasting cap placed in such a hole
would be easily displaced or injured in loading. The correct
location and angle of such a hole are indicated page on 62. The
hole should be deep enough to receive the entire copper shell of
the blasting cap.
The blasting cap with fuse attached is slipped into the hole
and securely fastened by means of a cord tied around both the
fuse and cartridge, as is illustrated on page 62.
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MAKING UP A PRIMER WITH A BLASTING CAP AND SAFETY FUSE
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This method of priming in the side has the advantage of leaving
more space for placing the tamping stick on the primer, but it
cannot be used in such small holes as can the end primers on
account of the fuse lying alongside the cartridge and thereby
increasing the total diameter. This method does not place the
blasting cap in quite so good a position as priming in the end.
Such a primer is waterproofed by covering the joint between
the fuse and paper shell with a waterproofing material.
Priming in the Ends of Cartridges. — There are two good methods
of priming cartridges in the end.
PRIMING IN END OF CARTRIDGE
(a) With the handle of the cap crimper or a wooden awl, punch
a hole straight into the end of the cartridge to a sufficient depth
to receive all of the copper shell of the blasting cap and fasten
it there by means of a cord tied first around the cartridge and
then around the fuse, as is shown above. This is an easily made
and highly satisfactory primer.
To waterproof such a primer, close the hole where the fuse
enters the cartridge with suitable sealing materials.
(b) The other method is to unfold the paper from the end of
the cartridge and punch a hole directly into the center of the
exposed dynamite, close the loose part of the paper shell around
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the fuse, and tie it tightly. The process of waterproofing is the
same as stated in the preceding paragraph.
Priming in the end has the advantage of placing the blasting
cap or other detonator in the best possible position for deto-
nating the explosives used; but it sometimes has the disad-
vantage, especially when the bore holes are small, of bending the
fuse too sharply and causing it to be scraped or torn, and also
of not leaving sufficient room to place the tamping stick on the
primer to slip the latter into place in the bore hole.
There are a number of other methods of making primers, but
the three methods described are the only ones that have proved
to be safe and reliable.
Fuse should never be laced through cartridges of high explo-
sives, as the powder inside of the fuse may burn through the
covering or "side spit" and ignite the dynamite before the cap
explodes. This materially reduces the force of the blast.
Priming with Electric Blasting Caps
Primers can be made with electric blasting caps or other electric
detonators by any of the methods described for the use of blasting
cap and fuse. The waterproofing is done in exactly the same way.
Many blasters, however,
prefer to use a slightly
quicker method, which has
been found entirely satis-
factory. Punch a hole from
the center of the end of
the cartridge in a slanting
direction so that it will
come out at the side two or
three inches from the end,
insert the end of the dou-
bled over wires of the elec-
tric blasting cap, loop these
around the cartridge, and
punch another hole in the
top a little to one side of
the first and straight down.
Insert the capsule in this
last hole as far as possible
and take up the slack on
the wires. You then have
a primer in which the wires
do not cross each other at
rimers ° F any P° mt aiu * tne caps"! 6
electric is lying nearly along the
center line of the cartridge,
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a primer which hangs vertically, so that it is possible to load it
in the bore hole without its lodging against the sides.
The wires of electric blasting caps should never be fastened
around high explosive cartridges by half-hitching them, as a
strong pull might either break the wires or cut the insulation.
Priming with Other Du Pont Electric Detonators
Primers with other electric detonators, such as delay electric
blasting caps, submarine electric blasting caps and waterproof
electric blasting caps, are made exactly as are primers with
electric blasting caps, with the single difference that deeper holes
in the explosive cartridge are required to receive the detonators.
Priming with Du Pont Delay Electric Igniters
When delay electric igniters are used to detonate high explo-
sives a blasting cap is crimped on the end of the fuse, and the
priming then done as with blasting cap and safety fuse.
Operation of Detonators
The force of all explosives is exerted equally in all directions,
but blasting caps, electric blasting caps and all other Du Pont
detonators have copper shells so constructed that the shock from
the explosion is greater from the closed end than from the sides.
This is the end away from the fuse or wires. This closed end
is frequently referred to as the "business end". It should not
be understood that all of the shock from an exploding detonator
goes out from the end, for such is not the case. There is shock
in all directions, but the greatest shock is from the end. This is
indicated by the arrow in the following sketch.
+ ARROWS INDICATE THE DIRECTION OF GREAT-
EST SHOCK FROM A DETONATOR, THIS BEING
IN LINE WITH THE LARGE ARROW.
The purpose of detonators is to give off shock and heat to
charges of high explosives to cause detonation. The greater
the shock, the stronger the detonation and the better the work
that is done by the explosive. For this reason it is desirable to
have the detonators point directly toward the explosive charge. A
better understanding of this may be had by referring to the
accompanying figures. A shows a detonator pointing directly
away from a cartridge of high explosives. Using an insensitive
dynamite, the explosion of the blasting cap would not detonate
the explosive. B-shows a blasting cap the same distance from a
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cartridge of high explosives, but pointing parallel to the cartridge.
Using the same insensitive dynamite, if this cap caused any
detonation at all, it would be incomplete and weak.
\ e CARTRIDGE.
( BIA IT IMG
C shows the same insensitive dynamite and the blasting cap
the same distance away as before, but pointing directly toward
the dynamite. In this position the detonation of the dynamite
should be complete.
These positions of blasting cap and dynamite are purely
demonstration examples, and should never be attempted in actual
work. However, they illustrate just how a blasting cap or other
detonator should point.
A detonator should point, as nearly as possible, directly toward
the main portion of the charge of explosives.
Were the single blasting cap pointed diagonally across the
cartridge primer, as shown below, the shock to, and effect on, the
cartridges in the other end of the bore hole would be much less.
C, . . ' i
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Additional Blasting Accessories
Many high explosives containing nitroglycerin chill or freeze
and become insensitive in cold weather. When frozen, dynamite
is difficult to detonate or it may burn instead of explode. Burning
dynamite gives off fumes so poisonous that men have been killed
by them. Dynamite when chilled or frozen cannot develop its full
strength in a blast. Some provision, therefore, must be made for
thawing it and for keeping it thawed until it is. loaded into the bore
On work where these explosives are used
in large quantities, thawing houses are i
necessary; but even then the thawing
kettle should be employed to take the
explosives from the thawing house to the
place where they are to be used, to prevent
them from becoming chilled or frozen again.
If not more than two or three hundred
pounds of explosives are used at one time,
three or four large thawing kettles are all
that are necessary, as they will thoroughly
thaw that quantity of frozen dynamite in a
Du Pont Thawing Kettles are all made in one piece with a water-
tight compartment for the explosives, which is surrounded by the
receptacle for the hot water used to furnish the heat for thawing.
This hot water must not come in contact with the dynamite.
While Du Pont Thawing Kettles will retain their heat and keep
the explosive thawed for a considerable time, depending, of course,
on the nature of the weather, this effective period can be increased
to about five times as long if the warm kettle is kept in a barrel or
box with dry hay surrounding it. This hay can be held in place
by a cylinder of wire screen, so that the thawing kettle can easily
be removed and replaced. If the barrel be mounted on two wheels
with a tongue attachment, the dynamite can be readily drawn
from point to point about the outside work without being exposed
to the cold air until it is to be loaded in the bore hole. The
explosive may also be kept thawed by wrapping old blankets or
sacks around the warm kettle.
Under no circumstances must the water be heated in thaw-
ing kettles, even though the explosives be first removed, because
nitroglycerin exudes readily from warm dynamite, and enough
of it is likely to be found in the bottom of the explosives compart-
ment of a thawing kettle that has been in use for some time to
cause a serious accident if the thawing kettle should be placed
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Dynamite Thawing House Heated by Hot Water
Maruand Spaclficatioru (or This and OtW Thawing Houhi Fur nl>h«l on Application
I g J
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Dynamite Thawing House Heated by Hot Water
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over a fire. It is necessary to heat the water in something else
before filling the water jacket. The hot water must always be tested
before filling the dynamite compartment. If it is hot enough to burn the
hand, do not put the explosives into the thawing kettle. Never till the
water jacket unless the explosives compartment is empty. See that
the explosives compartment is perfectly dry before it is filled.
Thawing kettles should be kept clean at all times. Should any
of the explosive compounds leak out, the explosives compartment
should be thoroughly cleaned with a solution of sal soda.
The use of thawing kettles can, to a large extent, be done away
with by using low-freezing explosives such as Red Cross Extra
Dynamite and Red Cross Gelatin. Arctic Powder does not
freeze and never requires thawing.
Capacities and Dimensions of Thawing Kettles
Tamping bags made of heavy paper
are used in many places as containers
for sand, clay or loam used for tamp-
ing. They save time and trouble when
loading bore holes, particularly those
Tamping bags are a great conven-
ience to miners, and their use often
saves many times their cost in econo-
my of explosives.
They are also employed as con-
tainers for blasting powder when the
miner or blaster desires to make up the
charge in cartridge form, as is gener-
ally the custom when it is used in
mines, in open work that is damp, and
in holes pointing upward.
Tamping bags are made approxi-
mately two inches longer than shown
in the table below in order to provide
for folding at the end when filled.
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Tamping bags are put up in bundles of 500 each, and packed ten
bundles to the bale. They are manufactured in the following sizes :
No. In Bale
1* x 8*
lj" x 8"
1}" x 10"
37 j lbs
1 J* x 10'
1}' x 12*
14* x 16'
2" x 18'
Blasting mats are closely woven mats of hemp or wire rope.
They are used over blasts or between blasts and property to catch
or hold material flying from the blasts. Hemp rope is generally
used and is considered the best, although steel wire rope has been
tried with success. The mats are made of 1 inch, IK inch or
1 *4 inch rope, according to the demands of the customer. They
are not carried in stock, but are woven on order and are made in
any size required. If the blasting mats are to cover light charges
of explosives, they may be spread directly over the bore holes ; but
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if heavier charges are used, railroad ties or logs should be put
down first and the mats on top of them. Sometimes the mats are
propped on lightly supported uprights several feet above the blast,
so that when the blast is fired the flying rock is stopped by the
under side of the mat.
These arrangements are very effective in preventing the rock
from being thrown into the air and should always be adopted
when blasting is done near thoroughfares or buildings. Boards
and logs alone are not sufficient.
Cordeau, or detonating fuse, is a small lead tube, about the
same diameter as triple tape fuse, filled with a yellow explosive
compound which has a velocity of detonation of about 17,000
feet (more than 3 miles) per second. In other words, a piece of
cordeau 17,000 feet long, if detonated at one end, will explode
throughout its entire length in about one second. It is now used
principally in deep well-drill blast holes and similar large blasts.
In spite of the great velocity and strength of the detonation
of cordeau, it is very insensitive and cannot be exploded by ham-
mering, pinching or burning. It is, therefore, safe to handle and
load. It is exploded in actual use by means of blasting caps,
electric blasting caps or by detonating dynamite
The extreme violence of the explosion of cordeau is sufficient
to detonate high explosives lying alongside it in a bore hole.
Cordeau is furnished either with the plain lead covering or with
the lead covering surrounded with a second covering of cotton
SPOOLS Oh' CORDEAU
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cord, the first being called plain and the second countered. Coun-
tered cordeau is more resistant to abrasion of tamping materials.
Cordeau is shipped on spools containing from 100 feet to 500
feet each, not necessarily all of one length, the exact length of
each piece being specified on the spool head. The first number
shown represents the length m feet of the cordeau which would
be first removed from the spool, the next number the second
length, and the other number, if any, the third length.
Several accessories are needed when using cordeau. When it is ex-
ploded by means of a blasting cap and safety fuse, a "Union" is used
to hold the blasting cap firmly in place; when an electric blasting
cap is used a "Special Union" is used as shown in sketch below.
- 2 V-
UNION FOR ATTACHING A BLASTING CAP TO CORDEAU
SPECIAL UNION FOR ATTACHING ELECTRIC BLASTING CAP TO CORDEAU
For splicing two lengths of cordeau together a brass coupling
is used. A longer sleeve for making a stronger splice is shown
in the following sketch:
The Cordeau Ripper is a
special tool for ripping or split-
ting the cordeau covering at the
end when making connections to
a surface main line for a branch
or bore hole line as described in
the paragraph at the bottom of
the next page.
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Loading a Hole with Cordeau
The end of the cordeau is
tied to or laced through a
dynamite cartridge and it is
allowed to run off the spool
until the cartridge reaches bot-
tom and the cordeau extends
full length of the hole. The
rest of the charge is loaded in
the usual manner. If there is
water in the hole, the end of
the cordeau should be sealed
by hammering the lead to-
gether. When the hole is
tamped, the cordeau is cut
allowing six inches to extend
above the collar of the hole.
An electric blasting cap is
attached to the end of cor-
deau at each hole by means of
a brass union made for the
purpose. Then the electric
blasting caps are connected up
and fired in the usual manner,
The use of an electric blasting
cap at each hole is cheaper
and surer than using a surface
cordeau connection. The sur-
face line does no work other
than carry detonation.
Method of Making Surface Connection
The end of cordeau extending from the hole is split in half for
about 3 inches in length and separated. A special tool called a
ripper or slitter is used for this. A main or trunk line is laid
along the top of holes on the surface so that the main line lies in
the crotch formed by the split ends. These ends are twisted
tightly around the main line, one to the right, the other to the
left. A blasting cap or electric blasting cap is connected to the
end of the main line and fired, detonating the whole blast. As
many as 76 holes 86 feet deep have been fired with one blasting
cap. Great care should be used to see that connections are
tight and that the angle between the main line and branch line
is a right angle. The explosive in the tube will not stand water
and, in rainy weather, extreme care is necessary if surface connec-
tions are used.
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B L A S T I N G
_ EAU SPLIT
The load of dynamite in
well drill holes may be
broken as many times as
desired and still require
only one line of cordeau.
the cordeau is broken while loading the
explosives, no harm is done, but if it is
broken while tamping, some dynamite
should be loaded at that point and the tamp-
ing continued. The dynamite so loaded will
assure the continuation of the detonation
with no fear of a misfire.
JOINT CORRECTLY MADE^
METHOD OF WIRING FOR A BLAST FIRED WITH CORDEAU. USING AN
ELECTRIC BLASTING CAP OVER EACH KORIi [(OLE AND NO TRUNK
LINE !)!■■ CORDEAU
.-UNION ft ELECTRIC 3LA5T/NG CAP *~
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Elementary Electrical Principles Applicable to
Detonation of Explosives
1. In Fig. 1 is shown an ordinary dry cell battery, with its
two binding posts or connectors (A-B). These are called, respec-
tively, the positive and negative poles.
If the poles are connected with a piece of wire (C) an electric
current will flow through it, in the direction indicated by the
arrows, and will continue to flow until the chemicals are exhausted.
2. Such a wire affording a path for the current
from the positive to the negative pole of a battery
is called a circuit. The current flows only when the
circuit is complete, and a single break in the con-
tinuity of the wire stops the flow of current through- j
out the entire circuit.
The wire comprising the circuit can be much
longer than shown in Fig 1. — even many miles in
length — and still the current will follow it through-
out its entire length, as long as some shorter or
easier path between the two poles is not offered. If
the wire is covered with some insulating material
like silk, rubber or cotton, so as to prevent the cur-
rent from escaping from it and following some
shorter or easier course, then the wire may be
wound many times around other objects, or make
any number of bends and twists, and still the cur-
rent will follow it from one pole of the battery to
the other, with almost as much ease as it did the
short piece of wire in Fig. 1.
3. Now, how do we know that a current is flowing through
the wire in the manner described? We know it by its effects, and
a few of these effects, which are of great importance in under-
standing blasting by electricity, will answer for the present con-
a. First, if part of the ordinary thick copper wire used in Fig. 1
be replaced by a very fine piece of wire (G, Fig. 2), the fine wire
being preferably of iron, platinum or German silver, then the
difficulty which the current has in passing through this small
piece of wire, or, as electricians say, "overcoming its resistance",
will transform part of the current into heat. The fine wire will
become red hot, and even melt if the current is strong. This is
the principle made use of in tiring electric blasting caps. Another
familiar application is the incandescent electric light, where a
fine carbon or tungsten wire is forced to carry a large amount of
current, and becomes so intensely white hot (incandescent) that it
gives out light.
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b. Second, if wire insulated with cotton or
silk* be wound many times around a bar of ordi-
nary soft iron (Fig. 3), the ends of the wire
being connected with a battery so that the
current will flow through it, the iron bar will
become powerfully magnetic. As soon as the
circuit is interrupted! at any point, whether
by removing one or both wires from the battery,
or breaking or cutting the wire anywhere
throughout its length, nearly all the magnetismj
immediately departs from the iron. As soon as
the circuit is closed, the magnetism returns, even
though the opening and closing of the circuit is
performed many times a second and the point of
interruption is in a far distant part of the circuit.
If another piece of iron
for the magnet to at-
fig. i tract is balanced by a
spring over the magnet,
every time the circuit is closed it will be
drawn toward the magnet, and when the
circuit is opened the spring will draw it
away. Such a piece of iron provided f<
magnet to act upon is called an armature
telegraph sounder (Fig. 4) works on this
ciple, the armature in its up and down move
causing a lever to strike resonant metal
which give out the familiar clicks, by the
of which the operator reads the message.
other electrical instruments also work oi
c. Third, that an electric current is fl
through the wire (Fig. 1) can be show- _„
crossing part of the wire over a compass as F,G ' 3
■Non-conductors are those substances which do not c
difficulty. Strictly speaking, there are no perfect non-co
rry the electn
ors are those v
but the terms are in common use and are convenient and
rubber, sulphur, silk, cotton, paraffin, tar, resinous mater;
of poor conductors, but its conductivity 1b greatly Increa
likely to be derived from rocks in drilling, are dissolved
silver heads th
ng the best no
da, oils. etc. W
sed when vari
d,tS"'T5;5.biSS'!'ilK'S SSSK s?
ed to by electn
as "closing" t
JSoft iron readily loses nearly all its magnetism as soon
iron the more readily it becomes demagnetized, although
depends a permanent magnet. The magnetism left in a
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in Fig. 5. Ordinarily, of
course, the needle of the com-
pass will point north and
south, and the wire above it
should run in the same direc-
tion. But as soon as the con-
nection with the battery is es-
1C ' 4 tablished the needle will be
deflected, so that it will stand at right angles to the wire, or, in
other words, point east and west. If the end of the wire that is
connected with the positive pole of the battery be transferred
to the negative pole, and vice versa (that is, if the "poles be
changed") the needle will reverse its direction, so that the end
which pointed east before will now point west.
4. The needle will also reverse its direction if the wire C,
Fig. 5, be moved from its po : *" : —
above the needle to one below
shown by the dotted line. In
words, the direction of the
electric current affects the
direction in which the mag-
netic needle is deflected, /
deflecting it one way when I
passing above the needle V
and in the opposite way
when passing below it. Tl
very greatly intensify the acti
the magnetic needle, by putt
wire about the compass, as s
such an arrangement, all the
the needle are carrying the ci
and all those below in the opposite direction. They fig. i
all, therefore, tend to deflect the needle in the same
manner, and the effect is very greatly magnified ; so much so, that
an instrument constructed on this principle indicates the pass-
age of currents that are too feeble to be detected by any
other means. Such an instrument is called a galvanometer.
5. Practical Magnets.— The electromagnet is much more
powderful when, instead of the wires being wound on a straight
bar;as in Fig. 3, the bar is bent U shape, as shown in A and B, Fig.
7, for in this position both
ends can be made to act at
once upon the same piece of
iron, and they can attract it
with double, or more than
double, force. It is also found
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that the wire in the middle of the electromagnet doas not have as
much of an effect as that near the ends, and for this reason the
wire is not generally wound on the middle part, but only on the
ends, as shown in B, Fig. 7. Again, it is ordinarily advantageous,
from the manufacturing standpoint, to make the iron core of a
magnet in sections, afterwards fastening them together, as shown
in C, Fig. 7. The sections H-I can then be wound with the
wire, just as thread is wound on a spool, securing great efficiency
as well as ease in manufacture (D, Fig. 7).
Such electromagnets, when of large size and actuated by
powerful currents, are of tremendous power, and will lift masses
of iron weighing tons.
6. If a piece of soft iron, i. e., an armature (paragraph 3-b,
page 77), be placed between the poles of a conveniently shaped
magnet, as shown in Fig. 8, the piece of soft iron is also caused to
become magnetic. North polarity is induced in the end near,
or in contact with, the south pole, and vice versa.. If the position
of the armature is reversed, so that the end A is nearest the
south, and B nearest the north pole of the magnet, then the
armature reverses its polarity, so as always
to present its south end to the north
end of the controlling ("field") magnet.
This it does, even though the reversal of
ends is very rapid, such as would result
from fixing a shaft into the armature at
J, and rotating it rapidly in the direction
shown by the arrows.
We have seen (paragraph 3-b, page 77)
that passing an electric current through
wire wound upon a soft iron bar is capable
of causing it to become magnetic. The reverse of this proposition,
namely, the induction of an electric current in the wire about an
iron bar by causing the bar to become magnetic, is also true with
certain limitations. Take such a bar wound with wire (A, Fig.
9) and connect the ends of the wire with a galvanometer (the
construction of which is explained in paragraph 4, page 78),
bo that we will know whenever a current passes. Now cause
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the end of the bar to approach the live electromagnet B, Fig. 9.
All the time it is approaching B, the galvanometer shows that
an electric current is passing. When the movement is stopped,
the current stops.
If the movement be reversed, that is, if the wire-wound bar
be moved away from the magnet, the galvanometer will again
show that a current is passing, but in the opposite direction.
The reason the current is set up (induced) in the wire around
thejiron bar is that the iron bar is caused to become magnetic
as it approaches the live magnet (paragraph 6, page 79), and
loses this induced magnetism as it is withdrawn ; and there is a
natural law that any change in the magnetic condition of an iron
core will induce an electric current in wire around it.
It may be argued that the result is not an electric current,
but a series of electric pulsations. That is perfectly true ; but if
the pulsations are sufficiently frequent, through rapid rotation of
the armature shaft, they produce similar enough effects to the
steady flow of a battery current to be available for most purposes.
But the currents induced in the armature do more than pul-
sate. If the ends of the armature wire are connected with a gal-
vanometer, and the armature slowly revolved so that the move-
ments of the needle can be watched, the needle will be found to
swing first to the east, then to the west, then east, then west again,
changing direction with each half revolution of the armature. If
the end of the galvanometer needle should be equipped with a
pen, so that it could make a mark on a paper tape moved steadily
beneath it by clockwork, the tracing that would be obtained by
this experiment would look like Fig. 10.
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In this illustration, Fig. 10, the straight line A B is the mark
the pen would make if the paper were moved forward with the
needle at rest and pointing to zero, or north. The wavy line
C D is the mark made by the needle when such a current, con-
tinually reversing its direction, is sent through the apparatus.
Such a current is called an alternating current.
But it is evident from what has already been said (paragraph
4, page 78) that such an alternating current would not do to
energize the field magnet. In order to maintain the constant
polarity of the field magnet, the current supplying it with energy
must be in one direction, like the battery current. This is called
a direct current. The alternating current induced in the armature
is, therefore, rectified or changed into a direct current by means
of the commutator (Fig. 11).
The commutator in the blasting machine consists of a cylinder
of hard fiber or rubber, covered with copper, and mounted on
the same shaft which drives the armature. The copper is cut
lengthwise into two sections (A and B, Fig. 11). These are
firmly attached to the surface of the hard fiber very close together,
but not touching; that is, they are insulated from each other by
the fiber which carries them. One end of the armature wire is
connected with section A, the other with section B.
The current is taken off of the commutator for use by copper
brushes, C and D (Fig. 11). Now, as the commutator revolves
with the shaft, while the brushes remain stationary, the section
A is in contact with brush C for half a revolution, then with
brush D for the other half. The same thing happens to
section B. Therefore, the effect of the commutator is to
change the alternating armature current into a direct current,
and the tracing which the recording galvanometer will make on
the tape, when it receives the current from the dynamo equipped
with the commutator, is shown in Fig. 12.
The alternating current would fire electric blasting caps as well
as the direct current; but if it were not converted into a direct
current as it is, we would either have to energize the field magnet
with a battery or use a permanent magnet. With the present
arrangement, we simply lead the rectified current from the arma-
ture through the wire on the field magnet, which is thus energized
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by the current from its own armature. At the start, the very
slight residual magnetism which is retained by the field magnet
(see noteft. paragraph 3-b, page 77) is sufficient to set up a feeble
current in the armature. This in turn makes the field magnet
stronger, and the stronger field magnet develops a stronger cur-
rent in the armature. Thus the machine "builds up," as it is
called, until after a few revolutions it is working at its full power.
You can notice this when you push down the rack bar of a blast-
ing machine. The first part of the stroke is easy, but after the
armature has made a few revolutions it pushes quite hard, be-
cause the magnet has become strong and putts back on the
armature, tending to resist our efforts to turn it,
The dynamo just described, which is used in most American
blasting machines, is one of the simplest and earliest forms of
dynamo. Those used for generating powerful currents for elec-
tric lighting and power are more complicated, and more efficient
electrically than those made on this simple design; that is, if the
blasting machine dynamo were constructed on modern principles
it would take less power for the same output of current or give
greater output with the same amount of power, whichever way
one chooses to look at it. But, for the purposes to which a blast-
ing machine is put, considerations of simplicity outweigh this kind
of efficiency. Blasters would rather exert a little more muscle in
operating the blasting machine than pay for the increased cost
of repairs to a more modern dynamo, not to mention the increased
initial cost. Indeed, it is doubtful if a more satisfactory blasting
machine could be reasonably asked for than the ordinary push-
down blasting machine just as it is now made. Certainly no
other piece of electrical machinery would stand the misuse to
which many of these blasting machines are subjected in practice,
and still continue to do good work, day after day and year after
year, as many of them do in spite of it all.
Let us now dissect an ordinary blasting machine, as a review,
and see how these electrical principles apply. Fig. 13 shows a
two-post blasting machine. Note the field magnets 8 and 9
with their winding of coarse wire. In the figure the armature 16
can be seen with its winding of finer wire.
Note the brushes 20, bearing on the commutator just as
already described, and see where the ends of the armature wire
are soldered, each to its respective commutator section. On the
other side is the rack and pinion ratchet movement, by which the
downward thrust of the rack bar I imparts rotary movement to
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the armature. This is so simple that anyone can see at a glance
how it works, and it need not be dealt with here.
There is one part of the blasting machine, simple, but of great
importance, which has not yet been taken up, and that is the
"shunt," sometimes called the "circuit breaker." This is the brass
contrivance 4 placed in the bottom of the box. It is really
nothing but a brass spring which makes contact with the bridge
5, when in its normal position, the parts which come in contact
being covered with platinum, so that they will remain bright and
make a good electrical connection.
The function of this shunt is as follows: The spring 4, called
the contact spring, is connected by means of a piece of heavy
copper wire to one of the binding posts, 26, representing one
pole of the dynamo; the bridge is con-
nected with the other binding post,
representing the other pole of the
dynamo. When the contact spring
is up in contact with the bridge a
short, easy circuit, called a shunt
circuit, of practically no resistance, is
offered for the electric current to pass
from one pole to the other — in the
language of the electrician, the dyn-
amo is "short circuited". While the
rack bar is being pushed down, the
blasting machine is building up the
current generated passing across the
shunt, so that by the time the rack bar
is near the bottom of the stroke the
dynamo is working at its maximum.
When the rack bar strikes the contact
spring, however, separating it from the bridge, the short circuit is
broken, and the current of the dynamo has now no other way to
pass from one pole to the other except by flowing out through the
electric blasting cap circuit, and it does this just at the instant
when it is at its maximum strength. The fine bridge wire in each
blasting cap heats up instantly, causing all the caps to explode
at the same time.
Were it not for the shunt, operating as just described, current
from the dynamo would begin to flow through the electric blasting
caps as soon as one started to push down the rack bar. It would
be a very weak current at first, gradually increasing with the
building up of the blasting machine. Such a current is not well
adapted to fire a number of electric blasting caps simultaneously,
because it is impossible to make all of exactly the same degree of
sensitiveness, and with the gradually increasing current, the more
sensitive electric blasting caps would fire first, breaking the circuit
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and causing the less sensitive ones to miss. By employing the
shunt, on the other hand, no current is sent out from the blasting
machine until there is ample power to fire even the least sensitive.
Effective Use of Electric Blasting Apparatus
Almost anyone can use electric blasting accessories and obtain
good results, merely by following general instructions. However,
the knowledge of the principles underlying their action, which will
have been gained by reading the previous chapter, will be a great
aid in obtaining their highest possible efficiency. Again, when
the man who understands the principles encounters difficulties, he
knows how to overcome them, while the man who does not under-
stand has to be helped out of his troubles.
Care of Blasting Machine
One who knows the internal construction of the blasting
machine, and has learned from examination and study what a
nice piece of mechanism it really is, will generally take good care
of it. Keeping it, when not in use, in a clean, dry place is the
first thing you can do to help the blasting machine help you.
Down in a wet tunnel or mine is not a good place to store such
an instrument, and if it must be used in such places, as is often
the case, and it cannot be taken to the surface between times
(which is sometimes the case), a water-tight closet or box should
be built for it, in as good a location as can be found. Remember
that the case is only wood, and, if saturated with water, may
swell and put the internal parts out of adjustment. Occasionally
rubbing a little oil — preferably thick cylinder oil — into the grain
of the wood will help it to resist the water. The best way to
apply the oil is by rubbing the box with a greasy rag.
When you use the blasting machine, try to find a clean, level
place to stand it on, such as a dry plank, so that the bottom will
not be all wet when you put it away after using.
, After the principles of its operation are thoroughly understood,
the efficiency of the blasting machine may be kept up to the maxi-
mum by occasional inspection and care of the internal parts,
although they are so constructed as to seldom require much care.
The first thing to be considered in caring for the dynamo and
working parts is occasional oiling. Much judgment should be
used here, for too much oil is worse than none at all. The only
parts that need oil are the bearings of the armature shaft and of
the armature pinion'. The other iron parts that can be reached,
particularly the faces of the armature (not the wire), should
be wiped off with a greasy rag to prevent them from rusting. No
oil should be used on, or allowed to come in contact with, the brushes
and commutator, nor with the contact spring and its contact points.
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For this reason, the amount of oil used in any part of the blasting
machine should be small; if too much is used, the oil will after-
wards flow over into places where it is not wanted. This is
especially the case when the rack bar is oiled. Too much oil
here will inevitably flow down upon the contact spring and
its contact points, and cause a poor electrical connection with
the bridge. In fact, a poor electrical connection at this point is one
of the most common causes of the poor work and erratic behavior
of the blasting machine. Wiping off the rack bar and guide rod
with a greasy rag will give them all the lubrication they require.
The friction incident to ordinary usage will generally be suffi-
cient to keep the surfaces bright where the brushes bear upon the
commutator, unless some misguided person has oiled them. In
that case, the oil should be removed as well as possible by thor-
ough cleaning with a rag saturated with gasoline. If the brushes
seem to be too rapidly wearing into the commutator, so that they
absolutely demand some kind of lubricant, use a little graphite
taken from a soft lead pencil. After removing the oil by the use of
gasoline, be sure that all the gasoline and its vapor are out of the
box before closing it up; if confined, the vapor may afterwards
ignite and blow the box apart.
All contact points on the contact spring, bridge, and else-
where may be cleaned occasionally with fine sandpaper. How-
ever, sandpaper should be used in or about a blasting machine
only with the greatest care. Dust or fine particles from the
sandpaper must not be allowed to get into the working parts of
the machine, as they will cause these parts to wear out rapidly.
Care must also be taken, especially when cleaning the platinum
contact points, not to rub too vigorously. A gentle rubbing is
sufficient to remove any dirt or oxide and brighten the parts,
whereas a few vigorous rubbings will grind off the platinum
points themselves. If the platinum is ground away so that only
brass remains, the working of the machine will be impaired, for
the brass quickly becomes oxidized by the hot flash given off when
the circuit is broken, and thereafter fails to make a good contact,
The joints connecting the various electric blasting caps, lead-
ing wires and connecting wires that are to comprise the circuit
often do not receive as much attention as they should. It is true
that mere contact between perfectly clean wires is sufficient to
permit the passage of the current, but it is almost impossible to
get them perfectly clean, and the joint should, therefore, be made
in such a manner as to press together a considerable amount of
the wire, after it has been cleaned as thoroughly as possible.
This preliminary cleaning or scraping should never be neglected.
There is sure to be tar or grease present from the waterproofing
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materia] used, as well as oxides, dirt and some kind of foreign
material that has adhered to the wire.
There are many methods of making joints, some of them good
and some bad. The one generally recommended is made as
shown in the following illustration :
Another good way, if one has pliers to finish up the joint, is
that shown in the lower cut. This is made in the same way as
the joint in the previous figure, except that the ends, which are
left long for that purpose, are twisted together.
It is much easier to connect together wires of the same size
than wires of different sizes, such as leading and electric blasting
cap wires. For this purpose, a joint like that shown on page 50
is good— the spring of the thick wire keeping up a tension on the
small wire, and causing it to make a good contact. It is difficult
to make a nice joint under such circumstances, but it can be
made good electrically if the wires are first thoroughly cleaned.
Joints in the leading wire, when they must be made, should be
made with special care. Those in the connecting and electric
blasting cap wires, as a rule, have to do service only for a few
minutes or hours; but those in the leading wire will be there while
the leading wire lasts, and if poorly made will give trouble long
after their location is forgotten. The above illustrations show
how such joints should be made. The method is just the same
as that recommended for the electric blasting cap wires, except
that these joints should be about 2 or 3 inches in length. It pays
to have joints in the leading wire soldered. Some of the most
peculiar and erratic troubles are due to defective joints in the
leading wire, which worked satisfactorily for a number of shots,
but afterwards became bad through corrosion having formed
between the contact surfaces. The electrical condition of such
a joint is liable to change on the slightest movement of the wire,
to be good one minute and bad the next, and for that reason to
cause a trouble difficult to locate.
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Of course, wherever a joint has been made, the wire will be
bare of insulation, and the question is often asked whether, in
such cases, it is always necessary to use insulating tape for
covering the bare places. Where these joints are in the leading
wire, and especially where they are in electric blasting cap or
connecting wire which is to be inside of the bore hole and covered
with tamping, they should be taped. If the joints are not to
go underground, it is not absolutely necessary to tape them;
it will be sufficient if they are elevated and kept off the ground,
or from touching anything, by placing blocks of wood under
the wire near the joint. Joints in the leading wire can be treated
in this way also, thus avoiding the necessity of taping them;
but it is a nuisance to have to go all over the line blocking up
bare places before a blast, when the whole trouble could be
avoided by a few turns of insulating tape. In fact, a well made,
soldered and taped joint puts the leading wire in almost as good
condition as when new, while a few questionable joints are sure
at some time to be a source of annoyance, delay and danger.
It is best not to have any more joints in the circuit than are
absolutely necessary. Joints are especially objectionable when
they have to be lowered into the bore hole because the electric
blasting cap wires are too short. These wires should be long
enough to prevent the necessity of making this kind of joints. It
is even better to have them long enough to connect directly with
the wire of the electric blasting cap in the adjoining bore hole,
thus avoiding the use of connecting wire as well as saving time.
When connecting wire ts required, old electric blasting cap wire that
is full of joints and bruises from having already been through a
blast should not be used. Use new connecting wire. The use of
old, damaged electric blasting cap or connecting wire is the worst
kind of false economy. No experienced contractor needs to be
told how expensive it is to have a long period of delay after the
men have been ordered away from the work, while the blaster
pokes around, looking for the "reason why the shot did notjjo,"
all men, horses and machinery idle meanwhile.
Preparing the primer is really one of the most important steps
in all blasting operations. And yet, how frequently we find this
work entrusted to one of the least skilled among the workmen.
It ought to be done in the safest suitable place that can be found,
and it should also be done in the manner which is calculated to
secure the best results. Yet both of these considerations are fre-
quently violated, and the priming is done in the thawing house or
magazine where an accidental explosion would be certain to cause
widespread disaster, and is also done in a manner just the oppo-
site to that recommended by the manufacturers of explosives and
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blasting accessories. These methods have been given in detail
in other parts of this book.
In spite of the recommendations of the manufacturers, how-
ever, it is very seldom one finds a blaster making primers in the
right way, the reason generally given being that "it is too much
trouble to hunt up strings and tie them". Of all operations where
results justify a little extra trouble, none can exceed in impor-
tance the making of the primer, for upon this depends the success
of the entire blast. Of course, it takes a little longer to make
primers in the proper way than it does by the half-hitch method,
but the extra time is well spent, and it should be borne in mind
that it is the time of one man, while the time spent in "hunting
trouble" is the combined time of all the men, horses and machinery.
There never yet was a cheap misfire.
The primer especially must be well thawed, and in the best possible
condition. If the bore holes are wet, it is well to seal up the place
where the detonator has been inserted in the cartridge by means
of soap, tar or some other waterproofing material, since, if the
explosive immediately surrounding the detonator is impaired in
any way, it is likely to cause a failure or inferior work of the entire
blast. Firing Shots Promptly
Once the loading has commenced, a blast should be loaded and
fired as quickly as possible. Many things may happen to detract
from the efficiency of a charge after it is loaded, and the chances
increase with every minute that elapses between loading and
firing. The dynamite may freeze if the rock or ground is cold
enough. Water may work its way into the explosive charge or into
the electric blasting caps. The insulation on the wires may be
affected by moisture, so that the leakage of current will cause one
or more charges to miss.
Operating the Blasting Machine
The blasting machine should always be operated with as much
force as the operator can exert. Try especially to finish the last
part of the stroke with your full power, for when the rack bar
nears the end of the stroke it will push quite hard, tending to
check the movement, and yet the end of the stroke is the most
important of all. It takes a man with considerable strength and
with some skill to get the full force out of a large blasting machine.
It is, of course, obvious that no more current is required to
fire strong electric blasting caps than weak ones. Those with
very long wires, however, do require more current, for the small
copper wire which is used has some resistance. An electric blast-
ing cap with 26-foot wires would take about twice as strong a
current to fire it as it would if the current could be delivered close
to the electric blasting cap instead of having to go through the
2 6- foot wires.
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Testing Blasting Machines and Electric
Blasting Caps to Avoid Misfire
Many careful blasters have long wished for some means to
guard against misfires by which the blasting machine and the
individual electric blasting caps could be tested, before attempt-
ing to use them. If they could always be used just as they come
from the factory, without being subjected to the unfavorable con-
ditions they so often meet with in transportation and storage, it
is probable that there would be little need for testing because
every manufacturer carefully tests his goods before sending them
out. The Du Pont Company tests its detonators twice. Electric
blasting caps are liable to damage during transportation and
storage, and particularly so if they are stored in a damp place.
The Du Pont Rheostat should be used in testing blasting
machines. For testing electric blasting caps and the blasting
circuit, the Du Pont Galvanometer is recommended.
A test with almost any kind of testing instrument would be
sufficient to reveal the most common defect, the presence of a
broken bridge in an electric blasting cap. All instruments,
however, will not indicate those electric blasting caps which are
defective through a short circuit, such as those in which the
electric blasting cap wires are not insulated from each other
within the electric blasting cap, or have accidentally come into
contact after having been manufactured. In such cases, the
electric blasting caps would fail to fire, of course, because the
current would follow the short circuit and not go through the
bridge. To identify electric blasting caps defective from this
cause, it is necessary to have some form of instrument which
will show fairly accurately the electrical resistance.
When testing electric blasting caps, they should always be
placed in such a position that if one of them should happen to
explode accidentally no one will be injured. Placing them around
the corner of a stone wall or behind a stump or stone is an easy
and safe way, or, if there are but a few of them, they can be buried
under a foot of dry sand. If there are many, so that the total
amount of fulminate is considerable, the particles of sand them-
selves would become projectiles capable of injuring anyone near by.
Of course, there are occasions, as for instance, when there has
been a misfire and it is necessary to locate the trouble, when some
risk must be taken, even to making use of the galvanometer in
testing electric blasting caps that are loaded in bore holes with
explosives, and often in locations where the firing of the charge
during the test would be disastrous to the tester. But under
such conditions, the very remote danger of the test replaces
the much greater danger which always exists whenever a blast
misfires and the blaster is hunting about for the reason,
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Under such circumstances, there is no doubt that a great saving
in the total amount of risk results from locating the trouble
with accuracy and celerity, even though there be a remote risk in
the test itself. The current from a Du Pont Galvanometer has
never been known to explode an electric blasting cap. The chances
of firing an electric blasting cap while testing are thousands of
times greater when an ordinary series magneto telephone bell or
other unsuitable instrument is used. Several persons have been
badly injured in this way because they not only made use of an
improper testing instrument, but also neglected to place the
electric blasting cap in a safe location. It is remarkable what
extensive damage the flying particles of copper from one of these
electric blasting caps are capable of doing.
The current from a magneto bell is too weak to fire an electric
blasting cap by heating its bridge, but it is of sufficient intensity
to jump across small gaps, such as would result if an electric
blasting cap had a broken bridge, and the broken ends were very
close to each other. When the current jumps across such a gap,
a spark is produced which is often sufficient to ignite the explosive
mixture. Another way in which an electric blasting cap might
become sensitive to the current from a magneto bell is by the for-
mation of corrosion between the ends of a break, such as where,
through the entrance of moisture, the copper wire had corroded
off the bridge at one of the soldered joints. Should the electric
blasting cap subsequently dry out, it may show a resistance
several hundred times greater than normal, and would be very
likely to fire from the current from a magneto bell, while there
would be very little likelihood of its firing from the weak cur-
rent from a suitable testing battery like that in the Du Pont
What lulls the suspicion of a blaster who tests with a magneto
(and the matter is mentioned here because there are many who
do) is the fact that he is often able to test a great many electric
blasting caps with it before one of them explodes in the testing
process. But some day one that is defective in the manner above
described is encountered — and then, too frequently, it means a
maimed hand, blindness or worse. For this reason, the use of
any kind of testing current, except that from a weak battery
used in connection with a galvanometer, or Wheatstone bridge,
is most earnestly condemned, and further, the electric blasting
caps should be placed in some location where they will do no
harm if one should explode. When the test of a loaded bore hole
must be made, and it is impracticable to attach the leading wires
and test from a safe distance, the test should be undertaken with
the full recognition that it is a risk, even though a remote one
when a suitable instrument is used, and no one but the tester him-
self should be exposed to the risk.
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General Precautions to be Observed with
Regard to Explosives
DON'T forget the nature of explosives, but remember that with
proper care they can be handled with comparative safety.
DON'T smoke while you are handling explosives, and DON'T
handle explosives near an open light.
DON'T shoot into explosives with a rifle or pistol, either in or out
of a magazine.
DON'T leave explosives in a field or any place where animals can
get at them. Cattle like the taste of soda and saltpeter
in explosives, but the other ingredients would probably
make them sick or kill them.
DON'T handle or store explosives in or near a residence.
DON'T leave explosives in a wet or damp place. They should
be kept in a suitable, dry place, under lock and key, and
where children or irresponsible persons cannot get at
DON'T explode a charge to chamber a bore hole and then imme-
diately reload it, as the bore hole will be hot, and the
second charge may explode prematurely.
DON'T do tamping with iron or steel bars or tools. Use only a
wooden tamping stick with no metal parts.
DON'T force a primer into a bore hole.
DON'T explode a charge before everyone is well beyond the
danger zone and protected from flying debris. Protect
your supply of explosives also from danger from this
DON'T hurry in seeking an explanation for the failure of a
charge to explode.
DON'T drill, bore or pick out a charge which has failed to
explode. Drill and charge another bore hole at least two
feet from the missed one.
DON'T use two kinds of explosives in the same bore hole, except
where one is used as a primer to detonate the other, as
where dynamite is used to detonate Du Pont Low Pow-
der. The quicker explosive may open cracks in the rock
and allow the slower to blow out through these cracks,
doing little or no work.
DON'T use blasting powder, permissible explosives or high
explosives in the same bore hole in coal mines.
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DON'T use frozen or chilled explosives. Dynamite, other than
Red Cross, often freezes at a temperature between
45° F. and 50° F.
DON'T use any arrangement for thawing dynamite other than
one of those recommended by the Du Pont Company.
DON'T thaw dynamite on heated stoves, rocks, bricks or metal,
or in an oven, and don't thaw dynamite in front of, near
or over a steam boiler or fire of any kind.
DON'T take dynamite into or near a blacksmith shop or near a
forge on open work.
DON'T put dynamite on shelves or anything else directly over
steam or hot-water pipes or other heated metal surface.
DON'T cut or break a dynamite cartridge while it is frozen, and
don't rub a cartridge of dynamite in the hands to com-
DON'T heat a thawing house with pipes containing steam under
DON'T place a hot-water thawer over a fire, and never put
dynamite into hot water or allow it to come in contact
DON'T aliow thawed dynamite to remain exposed to low tem-
perature, but use as soon as possible.
DON'T allow priming (the placing of a blasting cap, or electric
blasting cap in dynamite) to be done in a thawing house.
DON'T prime a dynamite cartridge or charge or connect bore
holes for electric firing during the immediate approach
or progress of a thunderstorm.
DON'T carry blasting caps or electric blasting caps in your
DON'T tap or otherwise investigate a blasting cap or electric
DON'T attempt to take blasting caps from the box by inserting
a wire, nail or other sharp instrument.
DON'T try to withdraw the wires from an electric blasting cap.
DON'T fasten a blasting cap to the safety fuse with the teeth or
by flattening it with a knife; use a cap crimper.
DON'T keep electric blasting caps, blasting machines or blasting
caps in a damp place.
DON'T attempt to use electric blasting caps with the regular
insulation in very wet work. For this purpose secure
Du Pont Waterproof or Gutta-percha Covered Electric
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DON'T worry along with old, broken leading wire or connecting
wire. A new supply won't cost much and will pay for
itself many times over.
DON'T handle safety fuse carelessly in cold weather, for when
cold it is stiff and breaks easily.
DON'T store or transport blasting caps or electric blasting caps
with high explosives.
DON'T store safety fuse in a hot place, as this may dry it out
so that uncoiling will break it.
DON'T lace safety fuse through dynamite cartridges. This
practice is frequently responsible for the burning of the
DON'T operate blasting machines half-heartedly. They are built
to be operated with full force. They must be kept clean
DON'T cut the safety fuse short to save time. It is a dangerous
DON'T expect a cheap article to give as good results as a high-
DON'T expect explosives to do good work if you try to explode
them with a detonator weaker than a No. 6 (red label).
DON'T leave detonators exposed to the direct rays of the sun.
DON'T leave detonators where the rays of the sun will strike
them after passing through glass.
DON'T have matches about you while handling explosives.
DON'T store explosives so that the cartridges stand on end.
DON'T open cases of explosives in a magazine.
DON'T open cases of explosives with a nail puller, pick or chisel.
DON'T prime both ends of a cartridge of explosive when making
primers of half cartridges, with a blasting cap or electric
blasting cap, before cutting it in two. Cut the cartridge
in half and prime each piece separately.
DON'T use a needle of iron or steel when firing by means of
miners' squibs. Use one of copper or brass.
DON'T keep blasting caps or electric blasting caps in the same
box or container with other explosives in the field. Keep
DON'T use electric blasting caps of different manufacture in the
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Advantages of Strong Detonators 8
Bags, Tamping 70
Blasting by Cap and Fuse .".... 51
Blasting by Electricity 9
Blasting Caps 2,51, 52
Blasting Caps — Electric 10
Blasting Machines 23, 27
Blasting Machine Parts 29, 31, 34
Blasting Mats 71
Burning Speed of Fuse 55
Cap Crimpers 59
Cap Sealing Compound 60
Capacities of Blasting Machines 27
Care of Blasting Machines 34, 84
Cordeau Accessories 73
Connecting Wire 21
Delay Electric Blasting Caps 15
Delay Electric Igniters . . 18
Electric Blasting Caps 10
Electric Squibs 19, 20
Effective Use of Blasting Apparatus 84
Elementary Principles of Electric Blasting 76, 84
Equipment Required for Electrical Blasting 10
Fuse 53, 54
Fuse — Storage and Handling 58
Galvanometer 35, 36
Igniters— Delay Electric 18
Leading Wire 22
Leading Wire Reels 23
Locating a Break 37
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1 N D EX — Con tinued
Making Wire Connections 49, 50, 51, 85
Method of Operating Galvanometer 37, 39
Operating the Blasting Machine 24, 25, 27, 88
Operating Galvanometer 37
Packages of Electric Blasting Caps 17
Packages of Blasting Caps 52
Packages of Fuse 54, 56, 57
Parallel Circuits 45
Parallel Series Circuit 47
Parts of Blasting Machines 29, 31, 34
Photographic Squibs 21
Pocket Blasting Machines 24
Precautions 91 , 92, 93
Priming Cartridges 61, 63, 64, 65, 66, 87
Reels, Leading Wire 23
Resistance Tables 39, 40
Resistance of Blasting Circuit 41
Rheostat Resistance Table 44
Safety Fuse 51,52
Safety Firing Switch 49
Special Leading Wire for Miners. 23
Squibs— Electric 19, 20
Squibs— Photographic 21
Submarine Electric Blasting Caps 14
Storage & Handling of Fuse 58
Tamping Bags 70
Testing Blasting Machines 89, 90
Thawing Kettles 67
Thawing Houses, Plans for 68-69
Waterproof Electric Blasting Caps 13
Wiring for Electric Blasts 45,46,47,48
Wire Connections 49, 50, 51
Wire — Connecting 21
Wire — Leading 22
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'SAFETY FIRST" RULES
For Handling, Storing, De-
livering and Shipping
THE Du Pont Company will furnish,
upon request, a set of rules printed
on cloth for posting in magazines.
Provision is made for the signature of the
official in charge of the mine or other
work requiring explosives.
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