and having a perforation through it called the fid-hole, with an iron plate, e, called the fid-plate.

The mast is held up in its erect position by two wedge pieces f,f, bearing against the fid plate e, and upon a bar g, which may be called the fid, passed through the fidhole, and resting upon the tressel-trees. Behind the wedge pieces, f, there are pieces, h, h, introduced, in order to keep the wedge pieces from sliding back, when the mast has been thus fidded.

On preparing to unfid the mast, two men only are necessary to perform the operation, which is done by first withdrawing the two small looking pieces, h, h, and then if the weight of the mast is not sufficient to push the wedge pieces f, down the inclined planes, g, the screws, i, i, are to be turned, the points of which bearing against the ends of the fid plate, cause the wedge pieces f,f, to recede upon the inclined planes of the bar g, and thereby allow the mast, d, to descend, so as to hang in the bearing tackle, which has been previously attached to the mast, and passed through a sheave at bottom, when the fid bar being released, may be readily withdrawn, and the mast lowered by ropes as usual. The fid, g, is proposed to be made of iron, but if of sufficient substance may be of wood; in which case its upper surface must be shod with plate iron..

Fig. 2, is another contrivance for fidding and unfidding masts, which consists principally in the employment of two sliding bolts, for supporting the upper mast; a, a, is the lower mast; b, b, the tressel-trees; c, c, the crosstrees; d, d, is the upper mast, shewn in section. Upon each of the tressel-trees an iron box, e, is affixed, for the purpose of receiving the sliding bolts, f, and their screws, g. The mast being raised by the top tackling, in the usual way, into its situation, the bolts, f, are both forced

up into the fid-hole, by turning the screw g, as at A, and by the points of the bolts, f, bearing against the fid plate, the mast is supported and confined in its elevated situation, or, as it is technically called, fidded.

When it is intended to unfid the mast, the bolts, f, are withdrawn from the fid holes, as at B, by turning the screws, g, the contrary way; and the support, that is, the fid being thus removed, the mast then hangs in the bearing tackle, or top ropes, and is lowered as usual.

Fig. 3, represents another mode of adapting the sliding bolt fid; d, is the upper mast; b, the tressel-trees; e, e, iron boxes affixed to the tressel-trees, for the purpose of securing the sliding bolts, f. The point of the bolt is seen at A, passed into the fid hole, and supporting the mast by the fid plate resting upon it. The heel of the bolt is intended to stop against a rebate in the under part of the box, and the bolt is confined in that situation by a screw, g, pressing upon its tail.

When it is required to unfid the mast, the screw, g, must be turned, so as to allow the tail of the bolt to rise sufficiently for the heel to pass over the rebate, by which means the point of the bolt will have assumed an oblique angle to the fid plate, and the mast bearing upon it, in that situation, will then exert sufficient force to slide the bolt back in its carriage, and liberate the mast.

Fig. 4, exbibits the sliding bolt fid, last described, with a tail screw and a sliding guide adapted in a different way to the foregoing contrivance.

In this fig. a, a, is the lower mast, d, d, the upper mast, supported on one side, as at A, by the end of the sliding bolt being passed into the fid hole; b, b, are the tressel-trees, on which are affixed the iron carriages, e, for the bolts, f, to slide in; k, is a staple made fast by screws, or otherwise, to the hinder part of the carriage, for the

purpose of confining the action of the sliding guide 7. When the mast is fidded, the heel of the bolt stops against the rebate of the carriage, and the thick part of the guide l, intervening between the bolt and the staple, the tail is prevented from rising, and, consequently, the bolt cannot be slidden back, the mast is thereby securely fidded.

.

In order to unfid the mast, the screw g, which passes through the back part of the guide, 7, must be turned, the point of which bearing against the end of the bolt, causes the guide to be drawn back, and the tail of the bolt being thereby allowed to rise, the heel passes over the rebate, and the weight of the mast bearing against the point of the bolt, forces it back, as at B, by which means the mast is liberated.

Having described the improved fids as applied to standing masts, for the purpose of fidding and unfidding the upper masts of ships and other vessels, the patentees observe, that they do not mean to confine themselves to that particular situation only, as a similarly constructed apparatus is also applicable to bowsprits, and various other masts and spars, to which they claim their exclusive adaptation. Neither do they confine themselves to the particular metals or materials mentioned in describing the construction of the said apparatus.

And, lastly, they claim as their invention, the adaptation and employment of sliding bolts or wedges in the manner made, or having the properties of the sliding bolts or wedges, such as have been above described, for the purpose of fidding and unfidding the upper masts, and other masts and spars as aforesaid, of ships and other vessels.

To JOHN VALLANCE, of Brighton, in the County of Sussex, Esq. for his Invention of an Improved Method or Methods of abstracting or carrying off the Caloric of fluidity from any Congealing Water, (or it may be other liquors ;) also, an Improved Method or Methods of producing intense cold; also, an Improved Method or Methods of applying this Invention, so as to make it available to purposes, with reference to which temperature above or below the freezing point may be rendered productive of advantageous effects, whether Medical, Chemical, or Mechanical.

[Sealed 28th August, 1824.]

THE principal intention of this invention, (like that for which Mr. Vallance obtained a patent in Jan. 1824, (see our 8th Vol. page 251,) is to produce ice with rapidity; and in the usual elaborate style of that gentleman's literary productions, the present specification commences with a philosophical dissertation upon the principles by which water is congealed into ice, and which principles are embraced under two heads, (viz.) the abstraction of caloric by the contact of colder bodies, and the escape of it by radiation and evaporation. In this latter case, the air acts as an absorbant of moisture, and carries off the heat from water by evaporation, which process is greatly assisted by a strong current of air passing over the surface of the water; hence, a brisk wind greatly promotes freezing.

The present invention is, therefore, to be considered as an improvement upon the mode formerly proposed as above mentioned and which consists in the construction and employment of an apparatus very imperfectly represented

in Plate XV. at fig. 7, a, a, a, a, is a double cylinder, divided near the middle by a partition, b, b, in the centre of which is an aperture communicating between the upper and lower cylinders; d, is a piston, working in a chamber in the upper cylinder; f, g, are tubes passed through the piston, one of which tubes opens in the upper cylinder beneath the chamber, e, the other opens above. There is a valve in the tube, g, opening into the chamber, e, for admitting the air when the piston rises, and a valve in the tube, f, for discharging the air from the chamber when the piston descends.

h.

In the centre of the plate, b, a short tube extends downwards, at the lower end of which is a conical disc, Immediately under this disc is a table, i, supported by the rod, j, and passed through the lower end of the cylinder. As it is necessary that the interior of the cylinders should be exhausted of air previously to performing the operation of freezing, it is requisite that all its joints should be air tight; and for the purpose of more conveniently effecting this, the bottom of the cylinder is made to slide in; and round the edge there is a trough, k, k, to be filled with mercury, which when the interior of the cylinder is in a state of vacuum, is, by the pressure of the external air, forced up the spaces between, and the joint is thereby rendered tight.

From the upper part of the upper cylinder a pipe or tube, l, extends to the lower part of the vessel, m, and from the top of the same vessel another pipe or tube, z, extends to the lower cylinder, a. This vessel, m, is divided at the part, n, by an iron plate perforated with small holes, from which small pipes descend, and this plate is covered with sheet lead, also perforated with small holes immediately over the pipes, partly for the