Page:Pyrotechnics the history and art of firework making (1922).djvu/182

 aquatic fireworks unless they have some essential difference from their parallel type for land display.

One unit, of the rocket class, which is so distinct is the "skimmer." This is in effect a stickless rocket with the cap (which is empty) fastened at an angle to the line of the main case. When fired the skimmer, as its name implies, skims over the surface of the water, with occasional dives under the suface in an erratic course. It requires for its safe display a considerable area of water. These are known by French pyrotechnists as "genouillères," from their shape.

Ruggieri and Frézier describe what they call "plongeons." These are gerbs charged in the ordinary way, except that before each scoop of composition a small quantity of mealed powder is added. This produces a jerky burning, the recoil of each puff of powder driving the gerb beneath the surface of the water; the jet of fire, of course, is sufficient to prevent water entering the case while so submerged. These, and other earlier writers, in their section devoted to aquatic fireworks, give directions for firing ordinary land fireworks on the water, which would almost appear to have been included with the idea of filling space. One item which is generally included consists of directions for firing rockets under water. Jones, under this heading, gives the following directions:

"TO FIRE SKY ROCKETS UNDER WATER.

"You must have stands made as usual, only the rails must be placed flat, instead of edgeways, and have holes in them for the rocket sticks to go through; for if they were hung upon hooks, the motion of the water would throw them off: the stands being made, if the pond is deep enough, sink them at the sides so deep that when the rockets are in their heads may just appear above the surface of the water;