FIRE 



3156 



FIRE-ARM 



Fire ( A.S. fyr). Word embracing 

 in its widest sense any manifesta- 

 tion of glowing heat. It commonly 

 denotes the visible effect of the 

 combustion of substances by means 

 of the chemical combination of 

 atmospheric oxygen with one or 

 more of their constituents, the in- 

 combustible residue being called 

 ash. Flame is formed when glow- 

 ing gas is produced, either as a 

 primary or as a secondary result 

 of the burning. There may also 

 be non -luminous vapours called 

 smoke or fume. 



The process of raising the tem- 

 perature of combustible or inflam- 

 mable substances to the point at 

 which self-sustaining combustion 

 proceeds is calledignition. This may 

 be brought about by solar radiation, 

 terrestrial heat, molecular action, 

 electrical discharge, friction, pres- 

 sure or percussion. Fire may be 

 extinguished before combustion is 

 completed by reducing the tem- 

 perature of the burning mass below 

 the ignition point, or by stopping 

 the access of air. In the domestic 

 and industrial arts heat and light 

 are commonly obtained from sub- 

 stances solid, liquid, or gaseous 

 which are called fuels, mostly de- 

 rived from carbonaceous materials 

 of vegetable origin. 



Primeval man first encountered 

 fire as a natural manifestation, 

 which he came to regard as an all- 

 devouring spirit to be feared and 

 shunned. Ages may have elapsed 

 before the recognition of fire as a 

 physical fact was followed by any 

 attempt to control it, and then to 

 turn it to account, at first perhaps 

 as a defence against wild beasts. 

 The next advance consisted in de- 

 vising means for its preservation, 

 an achievement which furnished a 

 potent incentive to a sedentary 

 habit of life. Out of this arose the 

 customs concerned with its per- 

 petuation, sanctity, and worship. 

 During this period of prehistory 

 were laid the foundations of the use 

 of fire for warming the person, 

 cooking food, hardening imple- 

 ments and utensils, and producing 

 artificial light. Fire-making, the 

 artificial production of fire at will, 

 which followed in due time, facili- 

 tated nomadism and migration, 

 and was destined to become man's 

 mightiest auxiliary in the conquest 

 of the globe. 



From the primitive notion of an 

 all-devouring spirit ancient philo- 

 sophy advanced to the conception 

 of fire as a thing stolen from 

 heaven, as in the Prometheus myth, 

 and then to the view, attributed to 

 Heraclitus (c. 500 B.C.), that the 

 universe was evolved from an om- 

 nipotent fire-god. Medieval al- 

 chemy pictured the world as com- 



posed of four elements : fire, water, 

 earth, and air. When modern 

 chemistry began, Boyle (1626-91), 

 while still holding fire to be a 

 material element, discovered that 

 air is essential to combustion. A 

 theory propounded by Stahl (1660- 

 1734), that combustible bodies con- 

 tain a substance called phlogiston, 

 which is released by their decom- 

 position, was not exploded until 

 Lavoisier (1743-94), after dis- 

 covering oxygen, explained burn- 

 ing as caused by this gas being ex- 

 tracted from air and joined to other 

 substances. 



Man is still confronted, as at the 

 beginning, by fire in its destructive 

 aspects. Sometimes they are re- 

 leased intentionally, as by the 

 wasteful agricultural methods prac- 

 tised by jungle-burning tribes in 

 India. Sometimes property is fired 

 maliciously, a felony punishable in 

 England as arson and in Scotland 

 as fire-raising. More evil, however, 

 is wrought by thoughtless or unin- 

 tentional incendiarism, or by the 

 operation of such causes as spon- 

 taneous combustion. Out of these 

 perils have arisen the organized 

 services concerned with fire pre- 

 caution, proofing, prevention, ex- 

 tinction, and insurance. The Great 

 Fire (q.v.) of London in 1666 was 

 one of the greatest conflagrations 

 on record. Since then still costlier 

 conflagrations have occurred in 

 Moscow, 1812; Paris, 1871; Chi- 

 cago, 1871 ; Boston, 1872 ; Balti- 

 more, 1904; San Francisco, 1906; 

 and Salonica, 1917. 



Fire Alarm. Mechanism for 

 making known the fact that a fire 

 has broken out. An electric fire 

 alarm is a device which automati- 

 cally closes an electric bell circuit 

 when the air in its neighbourhood 

 attains a high temperature such as 

 would be due to an outbreak of fire. 

 The expansion of matter by heat is 

 the principle used in fire alarms of 

 all kinds. The mercurial type con- 

 sists of a thermometer with plati- 

 num wires entering the bulb and the 

 top of the tube through fused 

 joints. When the mercury rises to 

 a certain height it completes the 

 circuit of which the wires form part, 

 and a bell rings. An adjustable 

 form has the top of the tube open 

 and a sliding upper wire. 



Pneumatic alarms are operated 

 by the expansion of air in a closed 

 tube or vessel, and the pressing out 

 ot a diaphragm which brings a 

 moving contact against a fixed 

 contact. One variety has a bowl- 

 shaped container with a concen- 

 trically corrugated top. The 

 chamber is partly exhausted and 

 then sealed. An alarm is given if 

 the air inside be expanded by heat, 

 or the chamber leaks and the 



vacuum is broken, as in either case 

 the diaphragm bulges outwards. 

 In another variety air at atmo- 

 spheric pressure is contained in a 

 small chamber and in very fine 

 tubes running from it round the 

 walls of the apartments it protects. 

 The air in the- tubes is heated 

 quickly by a fire and communicates 

 its pressure to the main chamber. 



Metallic fire-alarm contacts em- 

 ploy two metals of unequal ex- 

 pansibility. A common form con- 

 sists of a bar, compounded of a 

 strip of steel and a strip of copper 

 welded together, or otherwise 

 rigidly joined, fixed at one end and 

 free to move at the other. When 

 the bar is heated the copper ex- 

 pands more than the steel, and the 

 bar curves towards the steel side, 

 bringing the free end against a 

 contact. 



The May-Otway alarm has a 

 horizontal steel bar several feet- 

 long, to the ends of which the 

 extremities of a piece of copper 

 wire are fastened. A contact-piece 

 hangs from the centre of the wire. 

 The bar and the wire form together 

 a very obtuse-angled triangle. If 

 the temperature rises slowly on a 

 hot day, for example the steel 

 bar takes in heat as fast as the 

 copper wire and their relative 

 lengths are changed but slightly, 

 whereas a sudden influx of heat 

 affects the wire much more quickly 

 than the bar, and the wire droops 

 sufficiently to let its contact-piece 

 touch a contact below. This 

 quality of discrimination is im- 

 parted in various ways to several 

 other kinds of automatic alarms. 



Fire-arm. Generic designa- 

 tion of weapons which throw a 

 missile by virtue of the propellant 

 power generated by a charge of 

 suitable explosive. While popu- 

 lar use is inclined to restrict the 

 term to such weapons as can con- 

 veniently be used by hand, such as 

 rifles, sporting guns, and pistols, 

 these are more correctly termed 

 small-arms (q.v.), and fire-arms in- 

 cludes even the largest artillery. 



The history of fire-arms is, natur- 

 ally, closely associated Avith that of 

 explosives, but there is no doubt 

 that in early times progress was 

 far more dependent on the smith 

 than the powder -maker, as the 

 latter was always in a position to 

 supply a more powerful explosive j 

 than the contemporary guns j 

 could employ with safety. The 

 invention of fire-arms is usually 

 ascribed to a German monk, Ber- 

 thold Schwarz, but the date is not 

 definitely known. From illustra- 

 tions and accounts in contemporary 

 manuscripts, it is evident that guns 

 were in use by 1320, and the Eng- 

 lish used them at Crecy, 1346. 



