Page:Pyrotechnics the history and art of firework making (1922).djvu/278

 clips provided for the purpose, and is fired by percussion on the impact of the engine wheel. Bird scarers, consisting of a series of single crackers connected by a time fuse, and so arranged as to fire at regular intervals, have been much used for the protection of seed and crops.

The miner's squib and chieza stick or fuse lighter are to all intents port-fires for lighting the fuse in blasting operations in mines, their form and composition being adapted to the particular circumstances of their use.

The use of pyrotechnic compositions for photographic purposes is well known; those in use at the present generally contain magnesium, which has greater actinic value than any other firework composition.

Magnesium lights fitted up to fire with a trip line have been successfully used for obtaining photographs of big game in their native surroundings at night.

Smoke pyrotechnically produced has for several years been used for the testing of drains, and recently successful experiments have been carried out establishing the value of smoke as a protection for fruit blossom against frost.

It has also been used as an insecticide for use against various kinds of parasites; a poisonous smoke has been found of great use in the dislodging and exterminating of rats.

Another agricultural use of pyrotechnic, or in this case perhaps more correctly explosive composition, is the use of explosive cartridges for ploughing; that is, cartridges are exploded at a certain depth in the ground, the effect being to break up the subsoil. The explosive used is a mild and cheap form of dynamite.

The use of rockets and other explosive fireworks for producing rain has been much discussed recently. Many writers deny the possibility of success by such means. There cannot be the slightest doubt, however, that given clouds in the right