838

Stea?n Fire-Engines.

[Book III.

vere that few can continue it above a minute or two at a time, when ifrelays of men are not ready, buildings on fire are left to fate. The jarsor concussions produced by the violent contact of the levers with thesides of the carriage at every stroke, is a source of Waste of firemen’senergy, and want of uniformity in their movements when at Work, isanother. In the 29th vol. of the London Mechanics’ Magazine, a contri-vance is described for diminishing the shocks consequent on the contactof the levers with the carriage. It consists of three spiral springs enclosedin cylindrical cases secured on each side of the carriage ; pads rest on thesprings and project above each case, and upon them the levers strike whenpulled down. Blocks of eaontchouc were previously tried, bnt the vio-lence of the blows soon rendered that material useless. The velocitywith whieh engines are sometimes worked also occasions a useless expen-diture of their strength ; we have seen some drawing water through Ion»suction pipes, and the pumps worked so quickly that the water certainlyhad not time to pass through the hose and fill the cylinders, ere the pis-tons began to descend.

If some mode of making the carriage immovable, and the pumps wereworked by long cranks on each side, the firemen could not only performfifty per Cent more labor, but they could do it with less exertion, andconsequently endure it longer. A modification of the plan adopted inthe Ypres engine, page 325, would be still more effective; in additionto which ropes might be attached to the bars, and any number of specta-tors could then assist.

If we review the progress of fire-engines in modern times, from thesimple syringe to the splendid machines of the present day, we shall findthat every important improvement in the apparatus for raising the water,was a nearer approach to the engine described by Heron . Previous tothe 16th Century, syringes or squirts only were in use, and not tili theSpiritalia had been translated and printed do we meet with the applica-tion of pumps. At first a single working cylinder was employed, and thepiston moved by a single lever as in No. 144; then two cylinders, eachworked by a separate lever, were United to one discharging pipe—nextthe double lever, as figured by Heron , by which an alternating movementof the pistons, and a more efficient application of the force employed wassecured ; then the goose-neck, also mentioned by Heron —and lastly, theair vessel made its appearance. If the beautiful and philosophical deviceHst mentioned, be, as some persons have supposed, a modern invention,why is it that no one has ever rose up to claim it 1 Js not this a tacit ad-mission that it was derived directly from the Spiritalia, or from Vitruvius ’sdescription of the machine of Ctesibius '! To the ancients, then, we areindebted for the most valuable features in our fire-engines, and it is notunreasonable to conclude that those used in ancient Egypt and old Rome were as effective as ours. If they were not, it is very stränge that Heron should have hit upon that construction of them and that arrangement oftheir parts, which we have only acquired after a Century spent in ex-periments.

Of late years “ steam fire-engines” have been introduced with successin some parts of Europe : a small horizontal steam-engine with its boiler,being arranged. on the carriage of the fire-engine. One large pump cylin-der only is used, and its piston and that of the steam cylinder are attachedto the same rod. Mr. Braithwaite, a London engineer, was, we believe,the first who made one of these machines. The steam cylinder was sevenand a halfinches diameter, and the pump six and a half; the water wasforced through an ajutage of seven-eighths of an inch, to an elevation of