Auxiliary fire-Oarrns are extensions of the ordinary novice to buildings, or 1•111•11 in :1 building, if desired. Small call-boxes are connected by wires Ns it Is the I I'• st street al:Inn-box, \S•ili•ll be in operatinn by breaking a glass in lbe small box and pulling It chain. A return signal shows whether or not, the street box lias :i•ied, 1 utomatic /irc-delcelors arc instrument's which will close au elect ric circuit when the sur rounding temperature readies a certain point, thereby setting in operation the ordinary lire alarm telegraph apparatus with which it is con nected. or riving a local alarm by ringing a gong, or both. Some form of thermostat is generally used t11 close till` of NVIIiI.11 as many nay be used as are desired; or what may be termed a thermostatie cable may be employed, traversing walls and ceilings as freely as nay be deemed advisable, or temporarily trailed m..er floors or over piles of goods. In such cables one of the wires forming the circuit is coated with expansive metal, wrapped with a yielding insulator, then further surrounded with a series of spirally ar ranged tine wires, forming the other half of the circuit. The calling on the inner wire is ex panded by heat and brought into contact with the outer. wires, so that the circuit is closed and a bell rung,. Miter deviees have employed the explosion of powder, the expansion of metallic rods, the breaking of wires, or burning of strings.
cnlfcII. Methods of transmitting news of outbreaks of fire are very old, but the perfection of the electric telegraph wits essential to the development of instantaneous and reliable apparatus, which was largely automatic. As
early as IS-15, Dr. NV. F. ('laiming, of Roston, published an article in the .1,.ircrl iscr of that city, outlining a fire-alarm telegraph system. In 1S51 the city of Roston appropriated $10,000 for testing the plan, it put in operation that year. 1)r. Claiming and 3.1oses 0. Farmer developed the system, which was constructed for Boston by Alt.. Farmer, and operated under his direction for several years. In 1857 these men patented the system. John N. 0ainewell boob IM'. interested in the matter in I5:55. and by 1869 had acquired the patent rights. Subsequently he dill much to improve and introduce the system, but the Civil 'War, eonser•atbon, and other obstacles were sufficient to prevent its introduction in more than some twenty cities by 1871. Ne\V York in stalled the fire-alarm telegraph system in 18,d9. 1 n 1875 the number of cities using the system was seventy-five, and since then its increase has been rapid, so that to-day most towns of 10,000 population or over. .11111 IllaIly smaller ones, have the tire-alarm telegraph. Althinigb carious sys tems are in use, that devised by Claiming and Farmer, and developed and improved by Game well and his associates and successors. is the one host generally einplit-ed in America. 01 the many automatic alarms depending upon either heat or the direct action of 11a me for operation, there may lie mentioned one patented in 1802 in England, by Joseph Smith. where reliance was placed upon the Miming of a string. For teleg raphy in general, and also a chapter on fire alarm telegraphy, consult slaver, .1 me•ican 7'cleg raphy (New York. I s99).