26. The “funnel and wire” operation is one to which the pyrotechnist has
recourse for many purposes, one of which I may as well mention here, as
it may fairly be said to come under the head of rocket manufacture—I
mean the preparation of _portfires_.
The portfires, used for firing rockets and fireworks, are generally made
in the following manner:—The former for this purpose should be of brass,
and not less than a quarter of an inch in diameter, and the wire for
filling them not less than one-eighth of an inch. Portfire cases are
usually made very thin, three rounds of such paper as that on which the
_Times_ is printed being quite sufficient. The cases are prepared in
precisely the same manner as that described for golden rains, and are
also primed in the same way. The following is the composition which I
use for
PORTFIRES.
Nitre 6 parts
Sulphur 2 „
Meal-powder 1 part.
Portfires may be made of almost any size, according to the purpose for
which they are intended. You will find three-eighths of an inch quite
large enough for the inner diameter of any that you are likely to
require. If they are to be used for firing exhibitions, you will find
that 8 to 12 inches will be a convenient length. The funnel and wire
apparatus is so cheaply made that you will be able to provide yourself
with two or three sets of these tools, of different sizes, so as to
answer any purpose.
We are thus brought to the conclusion of the subject of rockets and
their accessories. I trust that I have made my method of operation
sufficiently intelligible and plain. The main difficulty that meets any
one who attempts to describe a delicate and particular system of working
lies in the fact that when one is thoroughly conversant with his
subject, particularly in all its minutiæ, he is very liable to overlook,
or to treat as unimportant in his directions, some point because it
appears trifling to him, and is never likely to be forgotten in _his_
practice, the involuntary omission of which, however, may be a frequent
cause of failure in the hands of others. I have tried throughout to
evade any possibility of misunderstanding; and if I have been too
diffuse, it has been solely from the desire to avoid that which has
certainly been the fault of almost all the treatises on pyrotechny that
I have seen, viz., indistinctness arising from insufficiency of detail.