176 



THE CIVIL ENGINEER A D ARCHITECT'S JOURNAL. 



[Junk, 



D E F is simply a cover of coppf-r, for the purpose of preventing the 

 entrance of obstructions, and is not an essential part of tlie instrument. 



Fig, 3. — Vertical section — full size. 



The valve opens a free communication with the external air as soon as 

 the water begins to fall out of the service, and by thus establishing an 

 equilibrium between the fluids around atid within, destroys any ten- 

 dency which the former might have to force an entrance. As soon, 

 however, as the service is again charged with water, the valve closes, 

 and prevents all improper escape." 



ON THE SUPPLY OF WATER FOR FIRES. 



" On the meanB of rendering large supplies of Water available in 



cases of Fire, and on the application of manual power lo the working of 



Fire Engines." By James Braidwood, Assoc. Inst. C.E. {Paper 



read at the Institution of Civil Engineers.) 



The plans at present in use, are so few and simple, that it is con- 

 ceived merely necessary to state the quantity of water required, and 

 to describe the most approved modes of supplying it, in cases of or- 

 dinary fires. If water can be obtained at an elevation, pipes with plugs 

 or fire-cocks on them, are preferable to any other mode at present in 

 use. The size of the pipes will depend on the distance and elevation 

 of the head, and also on the size of the buildings to be protected. It 

 may be assumed as a general rule, that the intensity of a fire depends 

 in a great measure on the cubic contents of such buildings; distinc- 

 tion being made as to the nature and contents of such buildings. If 

 no natural elevation of water can be made available, and the premises 

 are of much value, it may be found advisable to erect elevated tanks; 

 where this is done, the quantity of water to be kept ready and the 

 rate at which it is delivered, must depend on the means possessed of 

 making use of the water. 



The average size of fire engines may be taken at two cylinders of 

 7 inches diameter, with a length of stroke of 8 inches, making 40 

 strokes each per minute. This sized engine will throw 141 tons of 

 water in six hours, and allowing one-fourth for waste, 17G tons would 

 be a fair provision in the tanks for six hours' work ; this quantity mul- 

 tiplied by the number of engines within reach, will give an idea of 

 what is likely to be required at a large fire. If however there arc 

 steam engines, to keep up the supply through the mains, the quantity 

 of water kept in readiness may be reduced to two hours' consumption. 

 as it is likely that the steam engines would be at work before that 

 quantity was exhausted. This is what may be supposed to be re- 

 quired in case of serious fires in dockyards, in large stacks of ware- ^ 



houses, or in large manufactories. Where water can be had at nearly 

 the level of the premises, such as from rivers, canals, &c., if it is not 

 thought prudent to erect elevated tanks, the water may be conducted 

 under the surface by large cast iron pipes, with openings at such dis- 

 tances as may seem advisable for introducing the suction pipes, fig. 1. 

 This plan should not be adopted, where the level of the water is 

 more than 12 feet below the surface of the ground, as although a fire 

 will, if perfectly tight, draw from a much greater depth than 14 feet 

 (2 feet being allowed for the height of the engine), still a very trifling 

 leakage will render it useless for the time, at such a depth. 



Fig. 1. — Opening for SucUon pipe. 



The worst mode of supplying engines with water, is by covered 

 sunk tanks; they are generally too small, and unless very numerous, 

 confine the engines to one or two particular spots, obliging the fire- 

 men to increase the length of the hose, which materially diminishes 

 the effect (5f the fire engine. If the tank be supplied by mains, from a 

 reservoir, it would be much better to save the expense of the tank, 

 and to place plugs, or fire-cocks, on the water-pipe. Another evil in 

 sunk tanks, is, that the firemen can seldom guess what quantity of 

 water they may depend upon, and they may thus be induced to at- 

 tempt to stop a fire, at a point they would not have thought of, if they 

 had known correctly the quantity of water in store. Where sunk 

 tanks are already constructed, they may be rendered more available 

 by a partial use of the method shown in fig. 1. 



A great deal has lately been said as to extinguishing fires by jets 

 from water mains, without the use of fire engines. This, no doubt, 

 may be done under particular circumstances, where the pressure is 

 considerable, the pipes large, and if only one or two jets are required ; 

 but at large fires, where ten or twelve jets are necessary, the expense 

 would be too considerable, especially as where the largest fires may 

 be expected water is generally least wanted tor other purposes ; be- 

 sides, it appears wrong in principle to employ a power which de- 

 creases exactly in proportion to the extent to which it is used, inde- 

 pendent of the great loss by friction in the leather hose, which reduces 

 the delivery, and of course the height or force of the jet, 2i per cent, 

 for every 40 lineal feet of leather hose, through which the water 

 passes, aa was fully shown by the experiments. 



Fig. 2,— Common Fire-plug, 



