horns; press them down, and secure them with sealing-wax. Attach a cone, if desired.

Heads made like figs. 38 and 39 may be of three thicknesses of paper, pasted all over.

Fig. 39 shows the manner of tying on the sticks. No variation must be made in their lengths, and it is not advisable to alter their size. To adapt it to the wood, however, a slight alteration might be permitted. For instance, instead of square, it might be by, a slight increase one way, compensated by a slight diminution the other. It must, however, on no account, be so increased and diminished, as to approach the shape of a lath, as such stick would vibrate, and cause the rocket to quiver. When the heads are a paper bag of the shape of fig. 37, the stick must be tied on, as indicated by the dotted lines.

If the stick is suited to the rocket, it will, when suspended on the finger almost against the mouth, as at f, fig. 40, lie, not quite horizontal, but slightly sloping downward. The wood should be dry pine, free from knots. The sticks are generally cut with a carpenter's cutting-gauge. If the learner has a lathe he

will find a 6-inch circular saw convenient for cutting them.

For amateurs, a rocket is a good size; large enough, and small enough. If § and are made, two hollow drifts will be sufficient; for, one hollow drift. Very small rockets,

, are made for children; they are rammed solid, and a hole is pushed up them with a bradawl.

Rockets in former times, before the present days of competition, were charged in moulds. These were of gun-metal, bored truly cylindrical, furnished with hinges, to open and ad mit the case; they were then screwed up, and might be charged as hard as possible. Names were given them according to the bore of the mould, that is, the external diameter of the cases; a was termed an ounce rocket; a , a two ounce; a a quarter pound; a a half pound; a, a pound; a, a two pound.

These names were determined by theweight of a leaden ball of the same diameter as the bore. Now a sphere of lead, 7 inches diame90 lbs., or 1440 ounces; consequently one of 15 inches = 720 lbs., similar solids

ter =

being to each other as the cubes of their like dimensions: the latter sphere being twice the diameter from top to bottom; twice the diameter from left to right; and twice the diameter from front to back; 2 × 2 × 2 = 8.

The external diameter of the rocket being 7 inches, the internal would be 5 inches, and this would be a 90-pounder: hence, for an inch rocket, we have the proportion,

53 1440 :: 13 : 1152

so that a 12-ounce, or 3- quarter - pound rocket, ought to be a trifle above an inch. Required the weight of a rocket. 5

So that a is a trifle too large for a quarter-pound.

If, conversely, we require to know the size of a half-pound, or 8-ounce rocket,

So, properly, a half-pounder is a tride over The names in use enable the makers to understand each other, but they are not mathematically correct, and are of no utility to

an amateur.

The following table shows the true weight of leaden spheres, the dimensions being taken in inches.

Weight. Diameter. Weight. Diameter. Weight. Diameter.

And

*604 12

of the above numbers multiplied

by 8, give the correct names for rockets in eighths of an inch.

Required the true size of a half-pounder.

A trifle above, as before stated.

A cast-iron ball 6 inches in diameter weighs 30lb.

F

inches long. The

Wheel cases may be 5/9/ inches long. Cut the paper, without waste, into 4 strips, each 29 inches long. Fixed cases may be 7 inches long cut the paper the other way of the sheet, into 4 strips, each 22 extra length, for fixed cases, is to allow of their being reported; that is, filled at the end, with an inch, or more, of grain powder, to make a bang like a squib. The cases are to be gauged to the thickness of roman candle cases, but choked like rockets; internal, and external, are a good size. Two solid drifts will be required for wheel cases; one 5 inches long, besides the head; the other 3 inches : for the fixed cases it will be necessary to have one of 7 inches. They may be turned of box, beech, or ash; but gun-metal drifts are best, though by no means indispensable. If they are cast in gun-metal, they will simply require filing in the rough places. The cases