nches and a half in diameter, and as much high; round
the base of it drive a line; on this line fix four spokes, each two
inches long, so as to stand one opposite the other; then fill four
nine-inch one-pound cases with any strong composition, within two
inches of the top: these cases are made like tourbillons, and must be
rammed with the greatest exactness.

The rockets being filled, fix their open ends on the short spokes;
then in the side of each case bore a hole near the clay; all these
holes, or vents, must be so made that the fire of each case may act
the same way; from these vents carry leaders to the top of the cone,
and tie them together. When the rockets are to be fired, set them on a
smooth table, and light the leaders in the middle, and all the cases
will fire together and spin on the point of the cone.

These rockets may be made to rise like tourbillons, by making the
cases shorter, and boring four holes in the under side of each at
equal distances; this being done they are called _double tourbillons_.

_Note._--All the vents in the under side of the cases must be lighted
at once, and the sharp point of the cone cut off; at which place make
it spherical.

WHEELS.

Wheel-cases are made to any length; which must always depend on the
size of the wheel, but must not exceed the length of each angle.

Charge for wheel-cases, from 2 oz. to 4 lb.

lb. oz.
Meal-powder 4 0
Saltpetre 1 0
Brimstone 0 8
Charcoal 0 4

The filings in this composition may be varied by using a portion of
sea-coal, glass-dust, saw-dust, &c., or a combination of the whole.

SLOW FIRE FOR WHEELS.

lb. oz.
Saltpetre 0 4
Brimstone 0 2
Meal-powder 0 1-1/2

or, 1 oz. of brimstone may be used with 1 oz. of antimony.

DEAD FIRE FOR WHEELS.

oz. dr.
Saltpetre 4-1/4 0
Brimstone 0-1/4 0
Lapis-caliminaris 0 2
Antimony 0 2

_Single Vertical Wheels._--There are different sorts of vertical
wheels; some having their fells of a circular form, others of an
hexagonal, octagonal, or decagonal form, or of any number of sides,
according to the length of the cases you design for the wheel; the
spokes being fixed in the nave, nail slips of tin, with their edges
turned up so as to form grooves f