PYROPE. 578 PYROTECHNY. sium-aluminum ganiet, commonly called 'the precious garnet.' (See Gabxet.) It is usually deep red to black in color, and if it is also trans- parent, as it often is, it is valued as a gem. The principal localities where the gom varieties occur are different places in Bohemia, Saxony, and at Kimberlcy, South Africa; also at Elie, in Fjfe, Scotland, where they are popularly called 'Elie rubies.' Tliis gera is often called carbuncle and hyacintli by lapidaries. PYROPH'ORTJS (Xeo-Lat., from Gk. Trvpo- <p6pos, fire-bearing, from nOp, pyr, fire + -(p6pos, -j>lwros, bearing, from (pipuv, phcrcin, to bear). Any solid substance which is capable of taking fire on exposure to the air at ordinarj- or but slightly elevated temperatures. This property is possessed chiefly by finely divided solid bodies, such as metallic iron reduced from the oxide by ignition in hydrogen. The spontaneous inflam- mability in such cases is explained by the capacity of the powders for rapidly condensing air within their pores, thereby causing a considerable rise of temperature, while at the same time they pre- sent a large surface to the action of oxygen. The sulistances possessing this property include nu- merous salts, such as lead citrate or tartrate, which after ignition in a glass tube until gaseous matter is no longer evolved, and then being left to cool, take fire instantly im lieing thrown out into the air. 'Homberg's pyrophorus' is obtained by heating alum with lamjiblack or similar carbon- aceous matter. PYR'OPHOSPHOR'IC ACID. See Phos- phoric Ann. PYROPH'YLLITE (from Gk. ttCp, pi/r, fire -f €j>iov, pin/lloii. leaf). A hydrous aluminum silicate that is believed to crystallize in the mono- clinic system, although it is not usually found in distinct crystals. It has a pearly lustre, and in color ranges from white, through various shades of yellow, to green. It has a soapy or greasy feel- ing that suggests its similarity to various forms of talc, which it closelj' resembles. It occurs in some of the older rocks, and is found in the Urals, Sweden, Brazil, and in the United States in Xorth Carolina, Georgia, and Arkansas. It is used for the manufacture of slate pencils, the variety em- ployed for this purpose being known as 'pencil stone.' It is further used for making tailors' chalk ('French chalk'). The compact varieties, which are known as ariahnatolite, or pinite, have been extensively used by the Chinese and Japanese in the manufacture of small images and objects of art. PYRO'SIS (Xeo-Lat., from Gk. Trvpu<ns, a burning, from . Trupoi/i', pi/roun, to burn, from irCp, pyr, tire), or V.terbrash. A symptom of certain forms of indigestion in which there occurs at intei'vals a regurgitation of a considerable quantity of a watery acrid or acid fluid, generally accompanied by a burning sensation in the epigas- trium, frequently extending np behind the ster- num to the throat. In common parlance the re- gurgitation is called 'waterbrash.' and the sensa- tion 'heartburn.' See Indigestion ; Dyspepsia. PYR'OSO'MA. A compound, pelagic, lumi- nous tunicate. See Ascidian; Luminosity op Animals. PYROTECHNY, pir'6-tek'ni (from Gk. irOp, pyr, fire + t^xV. tcclinc. art). The art of mak- ing fireworks. The origin of pyrotechny is un- known, but the art was early practiced in the East and has attained to the highest degree of perfection among the Chinese and Japanese. Al- though inflammable compositions, known as Greek fire, were used in European warfare before gunpowder had become known among the Western nations, fireworks, as now de- nominated, became known to them about the middle of the fourteenth century, and we find record of their having been used as an accessory of public pageantry in 1588. The early development of fireworks in Europe was due to the Florentines, and the Italians long re- tained their supremacy in this field, since the popularity of pyrotechnic exlubitions was greatly increased during the eighteenth and the early part of the nineteenth centuiy through the in- genuity of the famous Italians Ruggieri, father and son, who charmed Rome and Paris by their displays. The prime materials employed in the manu- facture of fireworks are gunpowder, or its con- stituents, charcoal, sulphur, and saltpetre, or other oxidizing salts ; metals and metallic salts which on burning give rise to various shaped sparks, or a brilliant light, or which impart color to tile flame; touch-paper and fuze or quick- match, by which the charges are ignited and inflamed; paper and wood fi'om which to con- struct the cases and sticks; and resin, cam- phor, lycopodium, soaps, gum, lampblack, and similar bodies with which to modify the character of the reaction. In the use of gun- powder three effects are produced — heat, light, and sound. To produce reports, as with crackers, the gunpowder is used in the granulated condition and strongly confined in the rolled paper envelope which it is to rupture. Wlien, on the other liand, the gunpowder is first reduced to dust and then compacted by jiressure in a case, with an open end when burning, as in a rocket or a pinwheel, it may burn with the evolu- tion of light and heat and the production of gases which cause the rocket to rise or the pinwheel to revolve, but without a report. Roman Candles. In the Roman candle we have the stars or balls, made up of gunpowder ingredients mixed with color or light-giving ma- terials compacted into hard masses by the aid of gum or shellac, resting on loosely confined layers of granulated gunpowder, interspersed be- tween weil-compacted masses of slow-burning composition, all inclosed in a stout paper or card- board case. The stars are hollow and provided with a piece of quick-match by which they are ignited. The end of the case is primed with jiowder and capped with touch paper. Wlien the latter is ignited the priming powder is inflamed and this sets fire to the composition, or 'dark fire' as it is technically called, which slowly burns with the production of flame and sparks until the star is reached, when the grained gun- l)owdcr upon which it rests is ignited, bvu-ns rapidly, and expels the star with a loud report. Great care must be exercised in loading the cases of Roman candles, since a smaller charge of powder is necessary to propel a star to a given height the deeper the star is inserted in the case, and it is desired that the stars shall all be thrust out with equal force so as to describe the same path. Rockets consist of a cj'lindrical paper or
