e
fire from the cases. By means of these pipes the cases will
successively take fire, burning one upwards and the other downwards.
On the pintle fix a case of the same sort as those on the wheel; this
case must be fired by a leader from the mouth of the last case on the
wheel, which case must play downwards: instead of a common case in the
middle, you may put a case of Chinese fire, long enough to burn as
long as two or three of the cases on the wheel.

Horizontal wheels are often fired two at a time, and made to keep time
like vertical wheels, only they are made without any slow or dead
fire; 10 or 12 inches will be enough for the diameter of wheels with
six spokes.

_Spiral Wheels._--They are only double horizontal wheels, and made
thus: the nave must be about six inches long, and rather thicker than
the single sort; instead of the pintle at top, make a hole for the
case to be fixed in, and two sets of spokes, one set near the top of
the nave, and the other near the bottom. At the end of each spoke cut
a groove wherein you tie the cases, there being no fell: the spokes
should not be more than two inches and a half long from the naves, so
that the wheel may not be more than eight or nine inches diameter; the
cases are placed in such a manner, that those at top play down, and
those at bottom play up; but let the third or fourth case play
horizontally. The case in the middle may begin with any of the others;
six spokes will be enough for each set, so that the wheel may consist
of 12 cases, besides that on the top: the cases six inches each.

_Plural Wheels._--Plural wheels are made to turn horizontally, and to
consist of three sets of spokes, placed six at top, six at bottom, and
four in the middle; which last must be a little shorter than the rest:
let the diameter of the wheel be 10 inches: the cases must be tied on
the ends of the spokes in grooves cut on purpose, or on pieces of wood
nailed on the ends of the spokes, with grooves cut in them as usual:
in clothing these wheels, make the upper set of cases play obliquely
downwards, the bottom set obliquely upwards, and the middle set
horizontally. In placing the leaders, they must be managed so that the
cases may burn thus, viz., first up, then down, then horizontal, and
so on with the rest. But another change may be made, by driving in the
end of the eighth case two or three ladlesful of slow fire, to burn
till the wheel has stopped its course; then let the other c