Cc 2 The pressure of the contained water against the inner lap has a slight tendency to tighten the scam, but no great er internal lap is necessary than what is sufficient to pre vent the tearing out of the rivet. Mr. Perkins (see Trans actions of the Society of firts, vol. 33, p. 102) supposes he has made an essential improvement on Sellers & Pennock's plan, by suggesting a greater inner lap than that intro duced by them, which he thinks will be more efficient as a valve. Theoretically considered, there can be no gain from the extension of this lap, and, in practice, the redun dant leather, being unconfined, would warp in drying, and be most likely, when brought into use, to present a puck ered edge. and thus form channels leading to any existing defects in the seam.
It is convenient to have the hose in sections not exceed ing fifty feet in length ; the female part of the screw con necting these sections, should revolve on a swivel joint ; and it is important that the water way through the con necting screws should not be lessened. Mr. Perkins's plan to effect this is shown in No. 1, Fig. 6, where A is the female part of the swivel joint attached to the hose by the female screw, c c, and prevented from collapsing by the hoop ring, d, within it. On the outer side of the screw is a groove, b b, on which the swivel ring a a, revolves; this ring being fixed to the female connecting screw, B, by means of rivetting, on the end of it at f. The male screw, C, is at tached to another portion of the hose, in the manner al ready described.
The advantages proposed by Mr. Perkins are equally secured by making a small enlargement of the hose, at its junction with the screws, and employing swivel screws of the ordinary construction. Sellers and Pennock unite these to the hose, as shown in No II. Fig. 4, by making the tube m and the swivel tube f, which respectively join the male and female screws, F,'to the leather, a little tapering.
A fine screw, with a blunt edge, is cut on each tube. The ends of the hose being then surrounded by metal bands, B B, of proper diameter, the tubes are screwed into the hose by a lever, gradually compressing the leather between them and the bands, until they have fully entered, when the hose will be firmly held, attached to the connecting screws, M and F.
The present mode of rivetting hose has been in use upwards of thirteen years, as originally devised. The seam thus formed will last four or five times longer than that made with the best thread, and (excepting a few de fective rivets which may have been accidentally inserted and are readily replaced) will be of equal durability with the leather itself. The superior strength of this rivetted scam has rendered hose a much more important auxiliary in the extinguishment of fires than it ever formerly was; as it may be confidently relied on to conduct water, with safety, from engines to the summit of the highest buildings. Popular experiments have been made on this hose, show ing that water may be elevated in it, perpendicularly, two hundred feet, and the inventors compute the pressure with which they ordinarily test its strength to be equal to a co lumn of twice that height.
In all attempts to extinguish fires it is necessary that water should be thrown on the burning materials, and it is important that it should be thrown on in as compact a form as possible. Much of the water projected from an engine without hose to conduct it, is lost, as it never reaches the matter in combustion. In addition, should the water, by its rapid projection through the air, lose its adhesion, and fall in the form of spray into an intense flame, it will be chemically decomposed, and the gases produced will in crease rather than diminish the vigour of tue ..onflagra. tion.
This is not the only consideration recommending the present improved hose ; it is no longer of any consequence that the engine should be stationed contiguous to the building on fire, provided there is hose enough to extend from the engine to the spot where it is to be used. On the contraryit is advantageous to place the engine wherever it can be most conveniently supplied, and thence propel the water through the hose to the fire by tne power of the engine. A great additional gain is, that the use of the hose renders the formation of lanes unnecessary, by which many difficulties and delays are avoided.
In order to obtain in the most convenient and economi cal manner the conjoined advantages of the hose and fire engine, Messrs. Sellers and Pennock have devised a plan of fixing within the hose carriage, a double forcing pump equal in power to the common fire engine. This com bined machine is known by the name of HYDRAULION. The hose is carried on a reel, whose lower segment revolves within a box that forms a reservoir for water when the hose is wound off. At the bottom, near the hinder extremity of the box, so as not to interfere with the reel, the pump is securely fixed in a horizontal position, surrounded by a cylinder of about twice its diameter, which constitutes the air vessel. The ends of the pump and air vessel, being of equal length, are closed by plates drawn firmly against them by rods or bolts, the It orn plate having a stuffing box through which the piston rod works. The piston within divides the cylinder of the pump into two chambers, having two valves in each, through one of water is received from the reservoir, and through the other discharged into the air chamber. Over the valves in the air chamber thin metal plates are extended, called diaphragms, and their object is to receive the first impulse of the water, and thus prevent any exhaustion of the air. From the ful crum of the levers, and between the hose reel and sides of the box, arms project downwards, and are connected to a swivelled cross bar which passes under the reel ; to the middle of this cross bar, the piston rod is at tached by an intermediate joint, so that any motion given to the levers is imparted to the piston. When the water is thrown by this operation into the air chamber, it is carried thence by a pipe attached to an aperture in the bottom of that vessel, and this passing through the end of the box, is terminated by a screw to which the hose is at tached.