The valves are brass plates, ground to fit the circular brass seat on which they rest; being accurately ground, no leather is required to make them tight. The whole valve is put together, and then slipped into grooves, cast in the side and bottom of the sole for its reception. If any of these valves should fail, it is only necessary to unscrew and remove the covering plate, when they can be got at without disturbing the other parts of the engine. In Newsham's engine, if one of the suction valves became deranged, the engine had to be taken completely asunder, before the defect could be remedied, p is one of the working barrels, six inches in diameter, with a seven-inch stroke, made of cast brass, carefully bored and screwed down upon the iron sole k, with copper screws, an intervening leather making the joint perfect. The piston q is of two circular brass plates, placed in strong leather caps, and bolted together. The top of the barrels is a little above the level of the cistern, so that when the latter is filled with water it may not run into the barrels, and wash away the oil with which the pistons are kept constantly covered.

Projecting arms on each side of the main shaft e, work the pistons by means of slings within the piston rod, which is forked to the height necessary for that purpose, but ends in a cylindrical rod, working in a guide plate above r, which preserves the parallelism of the piston throughout its stroke The main shaft works in brass journals at s s s. The sole k is made so as to form an inclined plane from h to i, which causes all the water to run out of the engine after it has ceased working. The principle of action in this engine is similar to that already explained while treating of Newsham's, and therefore requires no further mention here.

In the year 1793 Mr. Joseph Bramah took out a patent for a new fire engine, with sundry improvements and additions. This engine was essentially different in its construction from those already described. It consisted of a large horizontal metal cylinder, having a flanch at each end, to which two end caps or covers were screwed. These caps enclose all the working parts of the engine, and have brass bearings with stuffing-boxes in their centres, for carrying in an air-tight manner the working axis of the engine. Within the cylinder is placed a strong metal partition or radius, the lower edge being joined to the cylinder, and the uppermost edge, which is grooved, made so as exactly to fit the circle of the latter. The axis is armed with two wings or fans, on each of which is placed a valve opening upwards, to allow the water to pass through them. These fans are made to move water-tight against the sides and end caps of the cylinder, by means of leather on their edges. When the axis carrying the fans is fixed in its place, the groove in the metal partition described above, is filled with hemp, or some other soft material, so as to press on the under surface of the axis, and cause it to move in a water-tight manner.

The fans being a diameter of the cylinder, divide it into two parts, the lower of which is again divided by the radius partition into two compartments, in each of which an aperture is cut through the cylinder opening into the suction passages; these apertures, like those in the fan, are closed by valves opening upwards. A vibratory motion being given to the fans by means of levers on the axis, the capacity of the two lower compartments of the cylinder becomes alternately enlarged and diminished; the consequence of this is, that water becomes drawn up into the cylinder, gets above the fans on either side, and is then forced out through the exit pipe, the stream being rendered equable by means of a spherical air vessel placed on the top of the cylinder. This was a novel and ingenious contrivance, and produced a very compact engine; a great drawback, however, upon its advantages, was the difficulty of packing and making it water-tight in the first instance, and the still greater difficulty of keeping it so for any length of time, if much used.

Subsequently Mr. Rowntree introduced an engine, in which he attempted to embody all the advantages of Bramah's engine, and to avoid its defects. Mr. Rowntree's principal improvement consisted in the employment of one fan, a radius of the cylinder, instead of two; the vibration of the fan took place in the lower half of the cylinder, the partition being placed above. Mr. Rowntree, however, succeeded but imperfectly with his engine, which has been greatly surpassed by a more recent invention by Mr. John Barton, which is decidedly the best engine hitherto constructed on the vibratory principle.

The accompanying drawing and description will convey an accurate idea of Mr. Barton's engine, and show the principle of action in this, as well as in the two former contrivances. The figure affords an end view of Barton's engine, mounted on a suitable cistern upon wheels, a is the cylinder, or working barrel, of brass or iron: b is the fan or piston, which, like Rowntree's, is a radius, but his was placed below the centre, while Barton's is situated above. The fan is composed entirely of metal, on the expanding principle, with springs and segments, as in Barton's metallic pistons, c c c c are four valves, all opening upwards; d is the air vessel, with the exit orifice at its lower part; e is the cistern, which may be kept full of water for immediate use on the breaking out of a fire. This engine, like all the former, is capable of working from a pond, etc. by means of a suction hose, as well as from water poured into the cistern, the supply, as in Newsham's engine, being regulated by a three-way cock placed within the cistern.

The engine is worked by the elevation and depression of the handles h h, connected with the axis of the fan b, which vibrates backward and forward in the upper part of the cylinder, and delivers at each stroke nearly one-half of its contents, and may be regulated so as to give more or less, as required. The working of the fan or piston b, being perfectly air tight, tends to produce a vacuum below, on that side of the cylinder a where the handle is elevated, and the pressure of the atmosphere causes water to rush up into this space. During this stroke the air that occupied the other side of the cylinder has been partly expelled, and this space, on the second stroke being made, is filled with water, while that already on the other side of the piston is forced up into the air vessel, and thence through the exit pipes in a continuous jet.