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 shell, and take about of its weight of coarse 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 shell, 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. the mould has been made with the indentation of an oil flask, or with the globe of a balltap, 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.

If

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 thick

nesses, 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 shell. 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 shells in, the shells 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 shell 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 shells this way; the chief objection against them is their limited size. Glass globes might be blown, of uniform size, in moulds, like bottles. Another ready way of making shells, is to cover the india-rubber air-balls, 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 circumference, 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 II 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 by 11; again to 2 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-balls 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 4d. per dozen, and save the cost of a great deal of needless labour.

CYLINDRICAL SHELLS,

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. not adopt the same shape for shells? cylindrical shells answer excellently.

Why I find

Have

a former, for a small one, 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 inches, or a trifle more. Turn a wooden bottom, of an inch thick; half of it a tenon to fit the inside of the case, and half of it a flange, 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 flanges sawed off, and the end filed slightly tapering, as fig. 105; the enveloping piece of calico, or glazed lining, can then be passed 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 inch; charge it by putting in very little at a time, and well mallet it.

Pass a