68. We will now proceed to speak of cracker mines, another very
effective item in exhibition pyrotechny. With regard to the crackers
that are employed for this purpose, I cannot think that you will
economise at all by trying to make them yourselves. In order to make
them all of one uniform size and shape—and these points must be attended
to particularly in the manufacture of crackers for mines, otherwise you
will be unable to pack them properly in the bags or mortars—a
considerable amount of apparatus of rather an expensive kind is
required, and is in fact indispensable. The money laid out in the
purchase of this apparatus would furnish you with many grosses of mine
crackers. If you will be advised by me, you will purchase them of Mr.
Darby, whose crackers for this purpose are, in my opinion, exceedingly
good. The only difference between mine crackers and those usually sold
at the shops for the 5th of November is in their _priming_. Instead of
having touch-paper, at which they are lighted, a piece of bare
quick-match is left projecting from the mouth, which, of course, takes
fire very readily.
[Illustration: [Fleuron]]
The mortars used for throwing crackers differ from those employed for
throwing serpents in being square instead of round. I shall speak only
of one size of cracker mortar, because you can at your pleasure fire
from it any number of crackers from one dozen to four dozen by adopting
my plan of packing them. If you are about to use a pasteboard mortar,
you must have a square former made, two inches and three-quarters square
and six inches long. Upon this former make a very strong mortar with
well-pasted cardboard and thick paper, and let it be thoroughly dry
before you use it. Glue into one end of it a piece of wood an inch thick
for a bottom.
You will now require just the same kind of packet of gunpowder as was
spoken of under the head of serpent mines. This packet may contain an
ounce and a-half of common powder. Put it into the bottom of the mortar,
flat side upwards; then put a piece of thin paper, smeared over with
meal-powder paste, meal-powder side upwards, and then proceed to put in
your crackers in the following way:—You will find two dozen a very good
number for cracker mortars of this size. I frequently use _three_ dozen,
but this is not necessary. I will suppose that you have determined to
use two dozen. Take _six_ of these; pack them side by side, so that
their primed mouths are arranged in a line; tie them in this position
with a piece of cotton; make four of these packets containing six
crackers; now put them into the mortar in such a way _that the
projecting pieces of quick-match are all turned inwards_, as shown in
the drawing at the page of illustrations. The crackers will, of course,
all be lying on their sides. Now down the centre of this arrangement lay
three or four pieces of bare quick-match, which shall be in immediate
juxtaposition to all the primed mouths of the crackers, and which shall
reach down to the meal-powder pad. Thus you will infallibly insure the
lighting of all the crackers before the charge of powder takes fire at
the bottom.
Over this mine, and as an introduction to it, you can, if you please,
place a fountain-case, as with the serpent mines, gluing it into the
centre of the lid of the mortar, and connecting its tail end with the
crackers below.
But the most useful plan for exhibition purposes is to have an _iron_
mortar for these mines, made about two inches and three-quarters square
(interior measurement), and six inches in depth. Iron mortars should
have a very substantial foot of wood. If an iron mortar is employed for
cracker mines you must have a wooden former made, about two and a-half
inches square and six inches long, on which to form the paper bags that
are to contain your powder, crackers, &c. The arrangement of the
contents of these bags is precisely the same as that recommended for the
filling of the _pasteboard_ cracker mortars, except that of course a
piece of quick-match must be left projecting from the top of the bag by
which the whole is fired. Take especial notice that after placing the
parcels of crackers in the bags, as directed above, the cotton which
binds each parcel must be cut so as to liberate the crackers, otherwise
you will have four parcels of crackers instead of twenty-four crackers
making their appearance at the explosion of your mine.
In the page of illustrations, fig. 108 represents a section of a
pasteboard serpent mine; _aa_, the fountain-case; _bb_, the serpents;
_c_, the meal-pad; _d_, the packet of powder; _ee_, the match passing
from the fountain-case through the bundle of serpents; _f_, the wooden
block at the bottom of the mortar; _gg_, the lid. 109 represents an iron
serpent mortar. 110 represents a mine bag for firing from an iron
mortar. 111 represents the arrangement of crackers in a cracker mine.
The drawing will be found about the right size, and crackers packed in
this manner cannot fail to light.