It was the use of aluminium in pyrotechny which pointed the way to real incendiary composition, composition which exceeds the temperature of these primitive pitch and other elementary compositions by many times more than the flame of a candle exceeds the temperature of ice.
Bombs containing thermit, and later on thermalloy (a composition which set hard, and did away with the necessity of a case), were terrible weapons, giving a temperature which has hardly been exceeded by other means.
These compositions were almost identical with some of those containing aluminium used in pyrotechny for a considerable time before the war, but of course not for incendiary purposes. The intense heat is naturally accompanied by brilliant light, which was of great value to the pyrotechnists, the more so as aluminium compositions do not deteriorate on being kept as do those containing magnesium, and although the light is not quite so brilliant, and has less actinic value, the fact that it is considerably cheaper, combined with its keeping qualities, renders it a very satisfactory substitute for that rather expensive metal, in very many cases at least.
CHAPTER XI
THE CIVIL USE OF FIREWORKS
The utility of fireworks and the number of purposes to which they have been applied are far greater than most people imagine, both at sea, where possibly their usefulness is most fully exploited, on land, and since the war and its consequent developments of aeronautics, in the air.
Firework signals at sea are used in almost endless variety for the purpose of identifying vessels at night. Each shipping line has its own signal or signals, which are fired on such occasions as when passing Lloyd’s signal stations. These signals consist of hand lights, Roman candles, rockets, or Coston lights. The last-mentioned is a small hand light which is arranged to burn with either one colour or two or more colours in succession. This signal is used by the majority of foreign vessels. The signal used may be either lights burnt singly or together, or a light or lights burnt in combination with Roman candles or rockets. By making use of the various combinations a great number and variety of signals have been arrived at: a few typical examples will illustrate the kind of signals used.
The Zud-Amerika Lyn of Amsterdam burns a white light at stern, green at bridge and blue at bow. The White Star have a green light at bow and green at stern. W. Johnston and Co., a green light followed by a Roman candle, throwing three red and three blue stars, followed by a white light. The Aberdeen have a red light followed by a Roman candle, throwing red, white and blue stars three times successively, shown from aft. J. L. Burnham and Co., a blue light changing to white, then to red, followed by a red star.
The Cunard Line, off the coast of Ireland, fire a blue light followed by two golden star rockets. The Ulster Steamship Co. fire three vertical lights, yellow, blue and red, followed by two Roman candles fired together, each throwing two yellow, two blue and two red stars.
These examples will give some idea of the variety of signals used; they are often followed by another signal, or rather have a suffix which if fired has a particular meaning. For instance, a red light after the signal may mean “All’s well,” or a green may signify a wish to communicate. Some lines bring the whistle into the signal and combine long and short blasts with pyrotechnic signals.