of the cascable, in the mortices of which at each end are the screw pinions, through which the gun-screws pass in a perpendicular position on each side of the cincture. Through the back part of the bed, under the cascable, in fixed the perpendicular screw that drives the pinions, and, by means of a winch handle, gives the uniform vertical motion required for the elevation and depression of the gun's axis.

Having above described the form and construction of the invariable single fulcrum and train, that of the invariable double fulcrum may be now easily conceived by any engineer or mechanic, as the only real difference consists in the former acting with a single cylinder, and the latter with two parallel cylinders upon the chase plane of the carriage; the cylinder on the after-axle being divided into two parts, in order to give place to the train-rings (if necessary) and the chain-staple upon the same axle. The side standards of the double fulcrum may be indefinitely varied as to their form. That figure which presents the least surface with the greatest strength and curvature is the best in time of real action for rendering the shot of the enemy reflective and ineffectual. And I here observe, as one general maxim in construc tion, that all repellent or acute angles which may be cut by either round or grape shot are to be carefully avoided as much as possible in the configuration of the parts of this system. The side standards of the double fulcrum used in mounting the piece of heavy ordnance above-mentioned, are formed by describing the arch of a semi-circle upon the lower sill or frame, and an inverted arch of a small circle from the centre of the trunnion upon the periphery of the lower arch, the extreme diameter of which is eighteen inches, and that of the inverted arch, where the centres of the trunnions are placed parallel to the chase,

sixteen

sixteen inches. The height of the centre of each trunnion from the chase level is here equal to the diameter of the plat-band of the breech; and this height is called the radius of the fulcrum, which constitutes the sine of the angle of elevation to the gun's axis, and may be calculated to produce the angle of fifteen degrees. The side standards of this fulcrum being rounded off in every position, and united or combined by the strong segment of a large cylinder, twelve inches diameter, in place of a round transom. In the lower frame or sills are four setting screw-bolts, two on each side of the body, with their vertical cylinders, and with the base-plate below the суlinders, as described in the single fulcrum.

Having thus particularly explained the construction of the fixed or invariable fulcrums, both single and double, I shall now briefly describe the nature of that which produces the variable radius, and consequently any degree of elevation to the gun's axis from the plane of the horizon to the angle of forty-five degrees and upwards. This fulcrum, whether single or double, consists of two parts; first, the lower frame or sills, which contain the chase, cylinders, and axles, with the train and with the setting screws as above explained; secondly, the side standards united by a round transom, and forming two parallel triangles, the base of each resting or supported on the sides of the lower sills, which is in length equal to the base of the triangles, the perpendicular of each triangle or side standard being directly under the trunnions, and sufficient to admit in the first instance (by the train) of an elevation from ten degrees to fifteen degrees of the gun's axis, with the base resting upon the lower sills; the inclined plane of each triangle being towards the breech, and meeting the base on the after-part of the sills, where a strong joint is made as a centre upon which the fulcrum

is raised to produce the greatest angle of elevation; the front of each standard or triangle being the segment or arch of a circle, described by a radius from the above joint or centre, with the lower part of each segment passing through a mortice on each side of the carriage in the fore part of the sills. In this mortice, on each side behind the segments, are fixed two strong nuts or pinions on an axle parallel to the chase cylinders, which acting on the inside of the segments, from the axle being turned by two men with the centre handspikes, raises the gun and fulcrum, which at every five degrees of elevation is fixed by a strong iron lever or stopper passing into the segments from the sill on each side. The fifth part in construction being the bolster or head-bearing, combined by the tie or span iron with the legs; the bolster being a ring or circle of cast-iron placed on the plane of the fore staple with four friction balls; the diameter of this circle being nearly equal to the front of the carriage, which it bears, and turns with it round the centre pin. Below this is the fore staple, being an oblong plate of cast-iron, three feet in length, sixteen inches in breadth, and one inch thick, rounded at the end, having an open groove, two feet nine inches in length, and three inches wide, through which the centre pin passes from the deck or platform through the head of the carriage. In the lower part of the fore staple are the holes through which the staple-bolt passes that fixes the carriage by the centre pin at any given distance from the sill of the port or embrasure.

Sixthly; the bar of the fore staple being strongly secured by three iron bolts through the sill of the port, and its step at the other end fixed by a bolt to the deck or platform; by this means the gun and carriage are VOL. XII-SECOND SERIES. firmly

Z

firmly preserved in every position, and at all times correctly true to the centre of the port, or to the direct line of fire. From the bolster or head-bearing extends parallel to the base the tie or span iron, one inch in diameter, which, dividing into two parts, forms a triangle with the foot bar of the legs, about eighteen inches wide and the same in length, and to which it is fixed by two screw nuts on the outside of the bar; the legs of the carriage being two strong inverted segments of a circle, made of cast iron, standing inclined to each other, and perpendicular to the base of the carriage, with the circular or box foot of each leg about four feet apart; the upper end of each leg morticed into the butt of the carriage with a flaunch, so as to support the whole in a correct borizontal position. Under the foot of each leg I have at present fixed two metal cylinders upon a horizontal axle ; which construction I recommend as best adapted for naval service, where considerable friction is frequently necessary; but for fort service it is my intention to make use of cannon-shot, which will increase the velocity of the carriage in its horizontal range.

Seventhly, and lastly; for the purpose of producing the uniform horizontal motion or range of this system of artillery upon the deck of a line of battle ship or other ship of war, or on the platform of a battery, I here apply the easiest and most powerful means possible; which is, that of a swifter, being a piece of five-inch rope fastened to the centre of the bar and to each foot, and passing through a snatch-block, at a proper distance on each side of the carriage; and with a single block at each end of the swifter, I make use of a piece of three-inch rope, of sufficient length, the end of which is fixed to the trainpost, and the other immediately behind it to a staple in

the

the deck or platform. This train-post being fixed in a vertical position in the rear of the gun directly opposite the centre of the port or embrasure, one man brings the gun into position with the greatest facility.

Having here explained the construction and application of this system of artillery as employed in marine and fort service, it is hereby my intention, under the protection of the said letters patent, to construct, and bring into practice, such a set of wheels as shall receive the above carriage with its ordnance already mounted in manner above described, so that the same artillery may at any time, or on any occasion of necessity, be taken either from the deck of a ship of war or from the plat form of a battery, and brought to action in the service of the field.

In witness whereof, &c.

Specification of the Patent granted to JOHN HOULDITCH, of Long Acre, in the County of Middlesex, Coachmaker; for certain Improvements in the Construction of Fourwheeled Carriages of different Descriptions.

With a Plate.

Dated March 7, 1807.

To all to whom these presents shall come, &c. Now KNOW YE, that in compliance with the said proviso, I the said John Houlditch do hereby declare that the nature of my said invention, and the manner in which the same is to be performed, are particularly described and ascertained as follows; that is to say: in every description of crane-necked carriages, instead of fixing or