Page:Pyrotechnics the history and art of firework making (1922).djvu/189

 a Dutch military engineer of that name. The next size is the royal 5-1/2-inch, and above that 8-inch and 10-inch.

Ruggieri (1821) is the first writer on the subject to have the shell and lifting charge in a unit as is the practice to-day, which indicates constructionally a great advance over his predecessors, although the fillings show little progress.

The modern shell is arranged with a "lighter" of quickmatch, long enough to reach from the top of the shell when in position in the mortar to a sufficient distance outside the mouth to enable it to be ignited without danger. The lighter fires the time-fuse in the top of the shell, and at the same time two pieces of quickmatch which run round the shell in grooves worked in the paper shell case, and ignites the lifting charge, which is contained in a flannel bag, or in the case of small shell, a paper cone.

The lifting charge projects the shell into the air and the time fuse, which is arranged to burn through at the top of the shell's flight, ignites the bursting charge which opens the shell and fires the contents.

The modern varieties of shell are almost infinite. Colours have been brought to a wonderful pitch of depth and brilliance, besides various kinds of fire for stars, producing stars with tails of the same and contrasting colours.

Another class of shell, which might be called the compound, consists of shell filled with fireworks of other kinds—Roman candles, tourbillions, wheel-turning cases, small shell, and what gives undoubtedly the most dramatic aerial effect yet devised, with rockets. The "thunderbolt," a shell 16 inches in diameter, containing a hundred 4-ounce rockets, has always been a popular feature of the Crystal Palace displays.

Another variation of the shell is the comet, which is in effect a small shell (generally about three inches) with an