Put 1 lb. into a frying-pan, or iron ladle, with 3 ounces of marine glue; set it over the fire; and, as the glue melts, stir it about till thoroughly incorporated with the filings, or borings. When cold, bottle them, and cork. Marine glue may be obtained at Pattrick and Sons, 51, High Street, Whitechapel. It is 1_s._ per lb., which is the smallest quant.i.ty sold. Marine glue is made by putting pieces of india-rubber into mineral naphtha; the caoutchouc swells up; it is then to be triturated into a uniform ma.s.s, mixed with sh.e.l.lac, and melted. Wax solution, or stearine solution, rubbed up in a mortar, with steel filings, or cast-iron borings, also preserves them. The nitre of the gunpowder, however, attacks them, and ultimately rusts them; so that fireworks are never so brilliant as when recently charged.

_Sh.e.l.lS._

Sh.e.l.ls are hollow paper globes, fired vertically, from mortars, or iron tubes. They are made of various sizes, from 3 inches in diameter to 16 inches. To make a 3-inch sh.e.l.l. Turn a wooden ball, 3 inches diameter; and, round the middle, that is, the equatorial circ.u.mference, cut a V groove, or triangular channel, deep enough to receive a piece of raw or naked match. Remove it from the lathe, and cut it into two halves at right angles to the groove, that is, round a meridional circ.u.mference.

Construct a deal box, 4 inches square, 2 inches deep. Place one of the half globes, flat surface downwards, on the middle of the bottom of the box, and secure it with screws from underneath. Brush it, and the inside of the box, all over, with sweet oil, with a camel's-hair pencil.

Put some water into a basin; sprinkle into it as much plaster of paris as judged necessary; about 4 tablespoonfuls; pour off the water which floats above; stir up the plaster till h.o.m.ogeneous; pour it into the box; and, with a sash-tool held upright, beat the plaster in with the points of the bristles. Leave it to set.

Instead of having a wooden ball turned, a hemispherical concavity may be made by pressing, half way, into sand, one of the painted india-rubber b.a.l.l.s sold at the toyshops; and pouring plaster over it. Or, a basin, an inch diameter larger than the intended sh.e.l.l, can have the plaster mixed up in it, till about three-parts full; and then the bottom of an oil flask can be pressed into it. A narrow strip of blue paper should be previously pasted round the oil flask, at the proper height, as a guide to know the proper depth to which it may be pressed. The plaster, when partly dry, must be neatly trimmed; and may be left, permanently, in the basin. Or, a stiff paper cylinder, or a tin cylinder, may be made, an inch larger in diameter than the diameter of the intended sh.e.l.l: put the oil flask into this, neck downwards, and pour in dry sand, till only the hemispherical bottom of the flask is left exposed; level the sand; oil the flask; and pour in plaster, as before. Be careful that the mould is not less than half-an-inch thick in any part. Or, one or two, or more halves of the zinc, or copper globes, used for ball-taps, may be obtained of the plumber, and used for moulds, without further preparation.

TO MAKE THE Sh.e.l.lS.

Procure two kinds of paper; one imperial brown; the other sugar paper, printed paper, paper hangings, or any paper of a different colour from brown. The sh.e.l.l is supposed to be 3 inches; half as much again is 4-1/2; add to this 1-1/2 for a f.l.a.n.g.e, gives 6. Cut out a circular piece of the brown paper, 6 inches in diameter. Snip it all round with the scissors, in slits, reaching from the circ.u.mference, half way towards the centre; soak it in water, and lay it on a towel to drain. Have a piece of sponge, about the size of an orange; soak it also, and wring it. Place the piece of brown paper in the plaster concavity, and press it in neatly with the sponge, in all directions; it will fill up the mould, and overhang all round; press the overhanging part flat, so that it forms a f.l.a.n.g.e. Cut a piece of another coloured paper, into a strip, about 2 inches broad, and paste it well; then cut it across, backward and forward, like the letter W, which will reduce it to V-shaped triangles. Take these up, one by one; lay them in the brown paper, pasted side downwards, and press them neatly in with the sponge, making each slightly overlap the other. Let these also overhang to thicken the f.l.a.n.g.e. This being done, proceed with a layer of brown; and so on, alternately, till it gauges about 2-3/4 inches across. The sh.e.l.l will, then, be about 1/8 of an inch thick. Remove it, and proceed with others.

The different-coloured papers enable the eye to detect, in a moment, whether any part is left uncovered. When dry, cut off the f.l.a.n.g.e; make the edge straight: rub it on a sheet of gla.s.s paper, spread flat on a board. With a 9/16 inch punch, cut a hole in the middle of one hemisphere; to it, glue another hemisphere: and cover with two more layers of paper, or pieces of calico. The sh.e.l.l may, then, when dry, be filled with any kind of stars, or rains, that can be got through the hole. Along with the stars put 1/16 of their weight of meal powder for a bursting charge: that is, if the stars weigh 4 ounces, as they probably will, put 4 drams of mealpowder. Charge a roman candle case, 3/8 inch internal, (4-1/2)/8 external diameter, with sh.e.l.l fuse (see fig. 59); saw it into inch lengths. Cut a piece of calico, 2 inches broad, and long enough to go twice round the fuse: paste the calico all over, and roll the fuse in it, so that the envelope is flush at one end, and overhangs one inch at the other. Glue this in the hole of the sh.e.l.l, the flush end, a, fig. 93, of course, inward: the enveloped end, b, being to receive the match, 3/4 of the fuse may be pushed in, 1/4 of an inch left to project. With a printer's bodkin, or a stiletto, make a hole through both sides of the envelope, as at c and d; these holes are to be in a line with the groove; put through them a piece of raw match, in such a manner that it shall lie across the mouth of the fuse, and go, in the groove, round the sh.e.l.l underneath, and reach to e and f. Paste strips of paper over the match, the same as with tourbillions and saxons; or, the part of the match lying in the groove, may be in a leader pipe.

Weigh the sh.e.l.l, and take about 1/5 of its weight of coa.r.s.e grain powder, for a blowing charge. Make a cone of two or three thicknesses of paper; put the blowing charge into it; stick the cone on the bottom of the sh.e.l.l, and set by to dry. In the calico mouth of the fuse, tie a long piece of leadered match, and paste a strip of paper round, to make secure. If the mould has been made with the indentation of an oil flask, or with the globe of a ball-tap, it will, of course, not have a groove to receive the match; but this is of little consequence; the match can be drawn round outside, and covered, so as to appear as it does on tourbillions and saxons, like a vein on the back of the hand, when the fingers are held downwards.

Formerly mortars were made of sheet iron, riveted and bound round with cord, which latter would not prevent them cracking, if they were not thick enough: they are now made on an improved principle: the iron is rolled, by powerful machinery, of three thicknesses, exactly like a squib case; it is, then, made white-hot, and the three are welded together, with a steam hammer. Large mortars, also, have an iron bottom, or breech fixed in them, and are farther strengthened with a couple of rings, put on hot, and shrunk by cold, like tires on wheels; a third ring is put over the other two, as in the Armstrong guns. The mortar is placed in a hole, dug in the ground, a few inches left standing out; the earth is shovelled in, and driven down firm; a penthouse lid, to keep out rain, dirt, and insects, renders it complete. Amateurs require nothing of this kind. A small mortar may be a tube, open at both ends, and fitted with a wooden bottom, to which it is to be firmly screwed.

Fig. 94 represents such mortar: it may be 4 diameters high; and the foot should have a conical hole turned in it to receive the cone fastened to the sh.e.l.l. The match is lit at t; but this may have a long bit of touch-paper attached to it, if preferred.

Instead of making a plaster mould, to form the sh.e.l.ls in, the sh.e.l.ls may be made by covering a wooden sphere, with paper, on the outside; when dry, they may be cut round in the lathe (a cross mark, with a pencil, having previously been made, as a guide to bring the same parts together again); the wooden mould removed; the cut edges glued; and the sh.e.l.l fitted up, in the usual way. Clean oil flasks may be covered with six or eight thicknesses of paper: paste an inch, or two, round the neck; when dry, cut through the cover, near the spherical part; file a notch all round, and snap it off. I have made excellent sh.e.l.ls this way; the chief objection against them is their limited size. Gla.s.s globes might be blown, of uniform size, in moulds, like bottles. Another ready way of making sh.e.l.ls, is to cover the india-rubber air-b.a.l.l.s, of the toyshops, almost as thin as soap-bubbles; when the cover is dry, a hole may be cut, for the fuse, with a penknife, and they are ready, at once, to receive the stars. Their shape is that of a prolate spheroid, fig. 106.

After eight thicknesses, or more, of paper have been pasted on, measure, with a tape, round the equatorial circ.u.mference, b e d, which suppose 17 inches; add 1 to this=18 inches. Measure from the pole, a, down the meridian by e to the opposite pole c, suppose 11 inches. Cut a piece of double-crown, 18 by 11; fold it down the middle, to a double thickness of 9 by 11; fold-again to 4-1/2 by 11; again to 2-1/4 by 11; there will, now, be eight thicknesses. Pencil the shape fig. 107 upon the top, and cut through the whole. Paste the eight gores on, as in fig. 106; for ornament, half may be pink; half, green. If these air-b.a.l.l.s could be blown in a spherical mould, of uniform size, they would obviate the gluing process, which is, at present, a tedious and necessary evil; they would, also, be much cheaper, as they could be supplied for about 4_d._ per dozen, and save the cost of a great deal of needless labour.

_CYLINDRICAL Sh.e.l.lS._

A sphere is, by no means, the best shape for a projectile; no one would think of making a roman candle star like a marble; the Minie bullets and the bolt-shot for our great guns are cylindrical, and far better fitted than globes for straight and rapid flight. Why not adopt the same shape for sh.e.l.ls? I find cylindrical sh.e.l.ls answer excellently. Have a former, for a small one, 2-1/2 inches diameter, and about 6 inches long, and with a handle like fig. 25. Roll a case upon it, 5 inches long, till the outside gauges 2-3/4 inches, or a trifle more. Turn a wooden bottom, 3/4 of an inch thick; half of it a tenon to fit the inside of the case, and half of it a f.l.a.n.g.e, equal to the external diameter, a, fig. 95.

Glue this firmly in, and farther secure it with 4 inch French nails; though, perhaps, this is not necessary. The top may be of the same shape; half-an-inch thickness will be sufficient. A hole, an inch in diameter, may be bored in it, with a centre-bit, to receive the fuse.

This fuse may be a cotton reel, with one of the f.l.a.n.g.es sawed off, and the end filed slightly tapering, as fig. 105; the enveloping piece of calico, or glazed lining, can then be pa.s.sed to the bottom, as indicated by the dotted lines; but a better way is to turn a piece of beech of the shape of fig. 96, with a collar, to prevent its being blown through, and a groove, by which the calico envelope can be tied. The length of the fuse may be about 1-1/4 inch; charge it by putting in very little at a time, and well mallet it. Pa.s.s a piece of naked match over the mouth of the fuse, and down the sides of the cylinder, as indicated by the dotted lines, fig. 95, having previously cut out a notch, at each corner, top and bottom, e, e, e, e, to guide it in a straight line. Take a piece of double-crown, about 20 inches long, and 7 broad; paste it all over, and roll the cylinder in it, in such a way that it shall be flush at top, and project at the bottom; press it round smooth with a cloth, or sponge, till the leaders form a vein on each side. When dry, invert it; put in the blowing powder; press the ends over, neatly, to form a bottom; and cover the whole with a circular piece of pasted paper. A sh.e.l.l of this size will hold forty gold rains, and a score or more blue stars, which have a very pretty effect. The head and the fuse may be in one solid piece, if preferred, as fig. 104; if the hole is longer than 1-1/4 inch, only 1-1/4 inch of it must be filled with fuse; a piece or two of match may fill up the rest. The mortar for this sh.e.l.l should be 18 or 20 inches high, and 3 inches internal diameter. The sh.e.l.l, when fitted up, will probably weigh about 14 or 15 ounces. The blowing powder may be 2 or 2-1/2 ounces of F grain, according to the fit in the mortar. The hole, in the wooden fuse, should be 3/8 of an inch diameter.

See that the match is everywhere carefully covered. A sh.e.l.l of this size will be amply sufficient for amateur purposes. Perhaps it will be advisable to try a fuse an inch long the first time; it will be better that the sh.e.l.l should burst, while still ascending, than that it should pitch. One or two trials are, in all cases, necessary; but as these sh.e.l.ls go a great height, they will bear a little longer fuse.

A cylinder holds half as much again as a sh.e.l.l of equal diameter; consequently, when the depth is twice the diameter, which is the best proportion, it holds three times as much as the spherical sh.e.l.l. If the latter be 3 inches diameter, it may be represented by the numbers 3 3 3 = 27. If the cylinder be 3 inches diameter, and 6 inches deep, it will be as 3 3 6 1-1/2 = 81. Practically, it will hold more, especially of rains, or serpents, as they pack better in a cylinder.

The spheroidal sh.e.l.l, like the spherical, is, also, 2/3 of its circ.u.mscribing cylinder.

Putting D, the diameter of a spherical; and d, that of a cylindrical sh.e.l.l, the length being always double the diameter; then D = 3 d.

Required the diameter of a cylindrical sh.e.l.l, that shall be of equal capacity with a spherical sh.e.l.l, of 12 inches diameter.

12 = 1728; 1728 3 = 576 = d, and

?576 = 83 = d.

so the cylindrical sh.e.l.l will be 8-3/10 inches diameter, and 16-3/5 inches long.

The same computation is more readily effected by multiplying the diameter by ?(1/3);

?(1/3) = ?(9/27) = 1/3 ?9 = 693.

Then 693 12 = 83, as before.

Sh.e.l.ls, for war purposes, are both spherical and cylindrical; the latter are, sometimes, built up in pieces, which dovetail into each other; they are, then, set in a cylinder, and melted lead is poured round to bind the pieces together. For lighting up the country, to discover the movements of the enemy on a dark night, sh.e.l.ls are fired, containing strong calico parachutes, carrying blue lights. Magnesium lights are, of course, more effective.

The bottoms and tops of the cylindrical sh.e.l.ls, previously described, may be turned out of a plank of wood: elm, ash, common mahogany, or good yellow deal; and, as many amateurs who possess a lathe, know of no contrivance for holding flat pieces of board without making a hole through them, the following plan may be adopted. On the screw-chuck, fig. 102, screw a piece of deal board, previously sawn nearly circular, and as large as the lathe will take: let it be of a thickness to entirely hide the point of the screw; turn it to a circle; and over the face of it, with a blacklead pencil, while it is revolving, make a number of concentric circles, as in fig. 103. Also, cross it with two straight lines, pa.s.sing through the centre, at right angles to each other. Cut the wood, intended for the bottom of the sh.e.l.l, into a square; make a hole at each corner, and with 4 screws, or 4 French nails, screw or nail it on the face: the concentric circles, and the two diametrical lines crossing them, will act as guides to centre it. I have thus been able to cut into a circle, in the lathe, so thin a substance as a piece of writing paper. It may be held on with 4 tin-tacks, or a touch of gum.

A nest of 6 or 9 little sh.e.l.ls, each containing a separate colour, rains, serpents, crackers, &c., may be enclosed in a large sh.e.l.l: the fuse of these may be a very short piece of a squib-case, with the string wound 7 or 8 times round the choke, to form a f.l.a.n.g.e, to prevent its blowing through.

Cylindrical sh.e.l.ls should, of course, be filled before the head is glued in; this can have the fuse previously fixed in, and ready.

_ASTEROID ROCKETS._

These differ from other rockets only in the head, which contains a parachute for floating a coloured case, attached to the strings. The parachute is best formed of silk, or alpaca; it may also be made of black glazed lining, or of tissue paper, carefully rubbed, till the stiffness is removed. The colour should be dark, that it may be invisible. If of silk, or alpaca, the parachute may be 20 inches square, with 4 strings attached to the corners; or it may be made of 6 triangular pieces, sewed together, like an umbrella. If of tissue paper, the paper may be 6/8 of a circle, or 6/8 of an octagon, as fig. 97. The tissue paper must be strengthened with a piece of crochet cotton, running round the edge, as shown by the dotted lines, fig. 101. It is simply laid on, and the paper snipped at each corner, with the scissors, pasted, and turned back. The radius of the circle may be 15 inches.

For the lance, or colour, roll the case of 3 thicknesses of writing paper, on a 5/8 former: it may be 2-1/2 or 3 inches long, and pasted all over. Turn a little wooden pulley, a, fig. 98, of a diameter to nearly fit the cylindrical head of the rocket; a hole in the centre of this pulley receives the colour; round the pulley, in the groove, lay a piece of chenille, fig. 100; twist the wires of the chenille 2 or 3 times together, and cut off flush. To charge the lance, set it on a flat surface, and drive in a film of meal powder, or sh.e.l.l fuse; then 1/3 of an inch of crimson star composition; 1/3 of an inch of green, &c., till nearly full; stop the end with plaster of paris, pressed in flat, with a knife. Paste a strip of paper round the mouth, so as to overhang not more than 1/8 of an inch; lay in two short pieces of match, one across the other, and tuck in, or press down, the pasted overhanging edges; this will keep the match from dropping out. Glue the pulley on, about midway of the case; envelope the end b with a bit of glazed lining. Take a piece of string, fig. 99; bring the ends together, and tie in a knot.

Insert the knot in the envelope, and tie round above it, as at fig. 100, leaving the loop out, to which to attach the strings of the parachute.

Let the strings be 2 feet long: fasten them to the loop; gather them together; wind them round the colour, above the pulley; fold the parachute neatly, and bring the edges down over the strings, nearly to reach the pulley: this will keep the parachute a little open, and help it to expand. Both the tissue paper and the glazed lining should be well rubbed, to get the stiffness out of them. To ascertain how a parachute will act, the learner can take the colour case, and stop one end with plaster, fill up with sand, and stop the other end with plaster. Fire it in the day time. Silk, alpaca, and glazed lining parachutes I can vouch for; tissue paper I have never tried, but am told it answers if it has not remained folded so long as to get set.

Between the top of the rocket and the mouth of the colour is to be a little pad of grain powder. Make a little square or circular paper bag with double-crown, and having put in the grain, and made the joining secure, smear both sides in the usual way, and sift dry meal over. If the rocket is to be fired at home, the parachute may be put into a long cylindrical paper bag, and left quite open at the top; but if intended to be carried to a distance, a thin bung may be put in at top, or a piece of turned wood: or a thin piece of paper may be pasted on it. In this case, be careful that it does not get stuck to the parachute.

Instead of the cylindrical head and the chenilled pulley, the head, fig.

39, may be used; and the protecting power from the fire to the strings supplied by putting a quant.i.ty of bran or sawdust. The cone must be held on, with not more than two thicknesses of double-crown.

_COMPOUND FIREWORKS._

Fig. 108. A triangular: 3 wheel cases and a case colour, at a. These cases are tied either to a hexagonal piece of deal board, or to three spokes, radiating from a nave. The colour is sometimes tied to a nail, driven in to receive it; or, it may be fixed on to a little peg. The peg is shown, by the side, at b. It is turned with a tenon, c; this tenon is glued in a hole, bored in the spoke; the part b may be half an inch in length; through it bore a small hole; charge the case colour on a foot, that enters the case half-an-inch; this void fits on to the peg b; pierce the case, through the hole in the peg, with a bradawl; push a bit of binding wire through, and twist. This is a far better way than tying it to a nail, as it cannot drop off. If the colour gets blown off, as it often does when tied, the piece is half spoilt. The colour may either stand at right angles, so as to face the spectator; or it may be fixed so as to lie in a plane with the wheel cases, very slightly sloping upwards; the mouth of the colour should point the same way as the mouth of the cases; if it were placed in the opposite direction, it would meet the current of air, be blown back upon itself, and burn the case rapidly. With respect to the wheel cases, it is obvious that the mouths must all point in the same direction; the slightest consideration would suggest this; it is necessary, therefore, to have some certain rule of proceeding, so as to avoid mistakes. Now supposing, for the mere sake of ill.u.s.tration, if you had a case in your hand, it were to take fire, you would naturally wish the fire to be directed _from_ you. Let this, then, be the guide. You are about to tie the cases on a wheel. Sit, to do so; take the wheel between your knees: place a case upon it, with the choke end _from_ you; tie, near the choke, also near the end; turn the wheel, place another case upon it, choke end _from_ you; and so forth. Without this certain way of proceeding, you would be very embarra.s.sed with the 12 cases on fig. 112; but, by attending to it, not the slightest difficulty will be experienced. Some of the cases will point obliquely upwards; some downwards; but they will all point _from_ you. In the end of the last case, as at x, fig. 108, put a little dry clay, to prevent a stray spark igniting it, and tie the envelope; or, tuck in the envelope, like as with an ounce of tobacco. Avoid every source of failure. Even the knots of the strings, with which the cases are tied on, are apt to come undone; they should either be touched with a dab of glue, or have a piece of paper pasted over them.

Fig. 109. A double triangular: 3 cases tied to the spokes; 3 to the previous 3. Double triangular frames are also made, with 6 spokes, on a long nave, 3 behind 3.

Fig. 110. A vertical wheel, illuminated. This is a wheel, with spokes, and a rim, or felly. The wooden hoops of the toyshops will furnish the latter. The illumination, as it is called, is made by lances, nailed with 1/2 inch Flemish tacks to the nave. The lances should be of different colours, but they ought, as nearly as possible, to keep time with each other. To effect this, it is necessary previously to adjust them; thus. Charge a number of cases, exactly two inches long, with different colours; use the same scoop to all, and give each the same number of blows, that they may be rammed as uniformly as possible.

Fasten a string to the end of a leaden bullet, and tie a loop at the other end of the string. Let the length from the top of the bullet to the top of the loop be 39 inches. Suspend this from something, and set it swinging. Light the lances, one after another, and count the number of oscillations each endures. Keep a list of these, and write against them 10, 12, &c., or 5 per inch, 6 per inch. The bullet will indicate seconds, with the length of string recommended; and it matters not whether you give it a start of 6 inches, or 12 inches; for, if it goes twice as far, it goes twice as fast, so that the swings isochronise; the inestimable discovery of Galileo, which led to the invention of the pendulum. In order that the lances may be nailed on, they should be charged upside down, and left with 1/2 an inch vacancy; they can then be pinched flat, to receive the tack. Sc.r.a.pe out a little from the other end, and prime with very slightly damped meal.

Fig. 111. A rainbow wheel. This is a vertical wheel, generally with 3 colours, as drawn; the tail of the second, or mouth of the third, lights a; the mouth of the fourth, b and c; but any arrangement may be made.

Place the colours, red, green, blue, at different distances from the centre, so as to form rings, equidistant, when burning. Suppose the spoke 12 inches long; place the colours at 3, 6, and 9 inches from the centre. It receives its name from its resemblance to the rainbow.

Fig. 112. A caprice, or furilona, according to the number of the cases.