682 PYROTECHNY 



this flame, -when viewed in the revolving mirror, appears to consist of a series of ser- 

 rations ; while, if viewed when the pipe is not sounding, it appears as a continuous 

 band. If now the resonator be brought close to the mouth of the pipe, the flame 

 attached to it is also agitated, and it is very easy to make the serrations of one flame 

 correspond with those of the other by slight changes in the adjustment. If the reso- 

 nator be removed gradually from before the month of the pipe, it will be seen that the 

 serrations no longer coincide, but, at a certain point, the elevations of one flame coin- 

 cide with the depressions of the other. On removing the resonator still farther, the 

 crests again combine, and on removing it still farther they again separate. On 

 measurement it is found that when the flames are in opposition, the distance of the 

 resonator from its first position near the organ-pipe is just half a wave-length ; and 

 when they again coincide, the distance is a whole wave-length. This same object may 

 be accomplished in another way, namely, by increasing the length of the tube con- 

 necting the resonator with its capsule. The resonators remaining stationary at the 

 mouth of the pipe, the increased length of tube which it is necessary to add to make a 

 trough correspond with a crest is equal to half a wave-length. He increases the 

 length of the tube by means of two glass tubes, one of which slides air-tight into the 

 other. If, instead of increasing the length of the tube, the air is rarefied by heating in 

 the tube, the same object is accomplished the same number of waves pass in a given 

 time through the tube ; but if the air is heated, each wave is increased in length, and 

 consequently part of the waves are driven, as it were, out of the tube. Therefore, if 

 the tube is made of iron, platinum, or other suitable material, and placed in a furnace, 

 we shall see, as the tube is gradually heated, the crest of the flame corresponding to the 

 resonator gradually passing away from the crest of the other flame, and finally corre- 

 sponding with the second crest, and then with the third, and so on. By counting the 

 number of waves thus driven out, and knowing the length of the tube, it is easy to 

 calculate the length of the waves remaining in the tube, and from these lengths the 

 increased temperature. 



PYROPE, or Bohemian Garnet. From the mountains on the south side of Bohemia, 

 imbedded in trap tufa. It occurs also at Zoblitz, in Saxony, in serpentine. 



PYROPHORUS. The generic name of any chemical preparation which inflames 

 spontaneously on exposure to the air. The sulphide of potassium is a good example 

 of this when it is prepared with lamp-black, in the place of charcoal. 



PYROTECHNY. (Feux cFartifice, Fr. ; Feuerwerke, Ger.) The composition of 

 luminous devices with explosive combustibles is a modern art resulting from the dis- 

 covery of gunpowder. The finest inventions of this kind are due to the celebrated 

 Euggieri, father and son, who executed in Eome and Paris, and the principal capitals 

 of Europe, the most beautiful and brilliant fire-works that were ever seen. The fol- 

 lowing description of some of their processes will probably prove interesting : 



The three prime materials of this art are, nitre, sulphur, and charcoal, with filings 

 of iron, steel, copper, and zinc, and resin, camphor, lycopodium, &c. Gunpowder is used 

 either in grain, half-crushed, or finely ground, for different purposes. The longer 

 the iron-filings, the brighter red and white sparks they give ; those being preferred 

 which are made with a very coarse file, and quite free from rust. Steel -filings and 

 cast-iron borings contain carbon, and afford a more brilliant fire, with wavy radiations. 

 Copper-filings give a greenish tint to flame ; those of zinc a fine blue colour ; the 

 sulphuret of antimony gives a less greenish blue than zinc, but with much smoke ; 

 amber affords a yellow fire, as well as colophony, and common salt ; but the last must 

 be very dry. Lamp-black produces a very red colour with gunpowder, and a pink 

 with nitre in excess. 



Golden showers are formed with lamp-black and nitre ; yellow micaceous sand is also 

 employed for the same purpose. All the copper salts tinge the flame green ; those 

 of strontia a red colour ; and baryta and its salts also impart a peculiar green. 

 Lycopodium burns with a rose colour and a magnificent flame ; but .it is principally 

 employed in theatres to represent lightning, or to charge the torch of a Fury. 



Fire- works are divided into three classes: 1, those to be set off upon the ground ; 

 2, those which are shot up into the air ; and 3, those which act upon or under water. 



Composition for jets of fire: gunpowder, 16 parts; charcoal, 3 parts. 



Brilliant revolving-wheel ; for a tube less than f of an inch : gunpowder, 16 ; steel- 

 filings, 3. When more than |: gunpowder, 16; filings, 4. 



Chinese or jasmine fire ; when less than of an inch: gunpowder, 16; nitro, 8; 

 charcoal (fine), 3 ; sulphur, 3 ; pounded cast-iron borings (small), 10. When wider 

 than 5 : gunpowder, 16 ; nitre, 12 ; charcoal, 3 ; sulphur, 3 ; coarse borings, 12. 



AJixed brilliant; less than j in diameter: gunpowder, 16 ; steel-filings, 4; or gun- 

 powder, 16, and finely-pounded borings, 6. 



Fixed suns are composed of a certain number of jets of fire distributed circularly, 

 like the spokes of a wheel. All the fnsees take tire at once through channels charged 



