The intention of this Machine, as represented in [Plate 46], [fig. 2], was to retard the fall of any body, or person, suspended to it, so as to prevent any concussion on reaching the ground. The means are brought to view in the perspective sketch given of the Machine. It is a kind of jack, inclosed in a case, and supposed to be laid carefully aside in the house represented in [fig. 1] of this [Plate]. The Machine has a barrel, much like that of the jacks used for roasting; round which a rope is coiled, of sufficient length to reach the ground: and a wheel, connected with this barrel, works in an endless screw, which turns a shaft also like that of a common jack, but somewhat stronger; and finally, to this shaft is fixed a small cross piece, carrying, on pins, two weights y z, inclosed in the fixed barrel x; by the centrifugal force of which enough friction is created, to prevent the acceleration of the falling body—whether a person or weight of any kind.
There is, moreover, a jib a, [fig. 1], fixed between some, or all, the windows of the house whose inhabitants it is wished to guard from the danger of fire; this jib having the property, from the form of it’s foot, of taking by the suspension of any weight to it, a position perpendicular to the wall: Insomuch, that by the act of suspending the Machine to the jib—engaging the wrist in the noose n, and perhaps the foot in another loop of the same cord; a person may safely flee those dangers from fire, of which so many persons become the unhappy victims.
Since the [46th. Plate] was engraved, it has occurred to me, that a method should have been shewn for raising the cord n, ([fig. 2]) after each descent. This operation might be performed by a handle put on the axis of the Machine, accompanied by a ratchet on the wheel, just like the similar parts of a jack for roasting. But, lest the inmates of a house on fire, should not have presence of mind enough to perform this operation, it might be better to have a spiral spring in the Machine, to be wound up by the descending body, and of force sufficient to raise again the cord after such descent.
OF
A SECOND FIRE-ESCAPE,
By breaking the Fall.
This Machine is also shewn in [Plate 46], at [fig. 1]. It consists of a large truck, A, to be drawn rapidly to any house on fire, by one or more horses. The carriage or frame part B B, is an open square frame subtended by a first sheet of sack cloth, similar to the sacking of a bed: and on this are laid five, or more, air mattrasses made of sack cloth, and varnished on the inside so as to be nearly air-tight; I say nearly so, for it is not intended they should form a spring capable of returning any object thrown on them. On the contrary, each of the mattrasses has, at one or both ends, a valve 1, 2, &c. opening outwards, but kept closed by proper springs, so as to determine the pressure at which the air shall escape; that pressure being carefully graduated, so that the upper mattrass shall give way with ease, the second with greater effort, and the successive ones with progressive difficulty, until the under one remains totally closed, and stops the falling body altogether. By these means, if enough mattrasses are used, and they are duly regulated, a person may jump from a house of three or four stories without incurring any danger. As to the length and breadth of this fire-escape, it should be ample enough to give the sufferers confidence to take the leap, and as small as an easy passage in the principal streets would require.
One thing must be described in words—as the mechanism to which it relates is fixed under the truck; and could not be seen in this perspective figure. These mattrasses are filled with air by an horizontal air pump, worked by a crank, which the axle itself of the hind wheels of the truck forms: whence, by pinning this axle to either of the hind wheels, the very motion of the carriage, as drawn by the horses, would distend the mattrasses—which would thus be ready for use the moment they arrived on the spot; and moreover, when there, this air could be replenished, after using, by turning this axle, through the wheels, by hand cranks slipped on it’s ends at the place of the linch-pins. Or, in fine, this operation might be performed by an air pump prepared for it alone, and placed in any convenient part of the Machine.