Imitative Fire-works
Take a paper that is blacked on both sides, or instead of black, the
paper may be coloured on each side with a deep blue, which will be
still better for such as are to be seen through transparent papers. It
must be of a proper size for the figure you intend to exhibit. In this
paper cut out with a penknife several spaces, and with a piercer make
a number of holes, rather long than round, and at no regular distance
from
each other.
To represent revolving pyramids and globes, the paper must be cut
through with a penknife, and the space cut out between each spiral
should be three or four times as wide as the spirals themselves. You
must observe to cut them so that the pyramid or globe may appear to
turn on its axis. The columns that are represented in pieces of
architecture, or in jets of fire, must be cut in the same manner, if
they are to be represented as turning on their axis.
In like manner may be exhibited a great variety of ornaments, ciphers,
and medallions, which, when properly coloured, cannot fail of
producing the most pleasing effect. There should not be a very great
diversity of colours, as they would not produce the most agreeable
appearance.
When these pieces are drawn on a large scale, the architecture or
ornaments may be shaded; and, to represent different shades, pieces of
coloured paper must be pasted over each other, which will produce an
effect that would not be expected from transparent paintings. Five or
six pieces of paper pasted over each other will be sufficient to
represent the strongest shades.
To give these pieces the different motions they require, you must
first consider the nature of each piece; if, for example, you have cut
out the figure of the sun, or of a star, you must construct a wire
wheel of the same diameter with these pieces; over this wheel you
paste a very thin paper, on which is drawn, with black ink, the spiral
figure. The wheel thus prepared, is to be placed behind the sun or
star, in such a manner that its axis may be exactly opposite the
centre of either of these figures. This wheel may be turned by any
method you think proper.
Now, the wheel being placed directly behind the sun, for example, and
very near to it, is to be turned regularly round, and strongly
illuminated by candles placed behind it. The lines that form the
spiral will then appear, through the spaces cut out from the sun, to
proceed from its centre to its circumference, and will resemble sparks
of fire that incessantly succeed each other. The same effect will be
produced by the star or by any other figure where the fire is not to
appear as proceeding from the circumference of the centre.
These two pieces, as well as those that follow, may be of any size,
provided you observe the proportion between the parts of the figure
and the spiral, which must be wider in larger figures than in small.
If the sun, for example, have from six to twelve inches diameter, the
width of the strokes that form the spiral need not be more than
one-twentieth part of an inch, and the spaces between them, that form
transparent parts, about two-tenths of an inch. If the sun be two feet
diameter, the strokes should be one-eighth of an inch, and the space
between, one quarter of an inch; and if the figure be six feet
diameter, the strokes should be one quarter of an inch and the spaces
five-twelfths of an inch. These pieces have a pleasing effect, when
represented of a small size, but the deception is more striking when
they are of large dimensions.
It will be proper to place those pieces, when of a small size, in a
box quite closed on every side, that none of the light may be diffused
in the chamber: for which purpose it will be convenient to have a tin
door behind the box, to which the candlesticks may be soldered, and
the candles more easily lighted.
The several figures cut out should be placed in frames, that they may
be put, alternately, in a groove in the forepart of the box; or there
may be two grooves, that the second piece may be put in before the
first is taken out.
The wheel must be carefully concealed from the eye of the spectator.
Where there is an opportunity of representing these artificial fires
by a hole in the partition, they will doubtless have a much more
striking effect, as the spectator cannot then conjecture by what means
they are produced.
It is easy to conceive that by extending this method, wheels may be
constructed with three or four spirals, to which may be given
different directions. It is manifest also that, on the same principle,
a great variety of transparent figures may be contrived, and which may
be all placed before the spiral lines.