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mast, lower, trestle-trees, masts, top and levers

FID. A short and thick bar of wood or iron, which, passing through a hole cut in the lower part of the topmast or top-gallant mast, and resting upon the trestle trees, serves to support those masts. A most important improvement upon this part of a ship's apparatus, is the patent lever fids, invented by Mr. Rotch, by means of which ships may strike their topmasts, or top-gallant masts, at any moment, in less than one minute, and fid them again in less than five minutes. The lever fids consist of two powerful levers of the first class, resting upon iron plates or carriages, bolted upon the upper surface of the trestle-trees, and carrying the gudgeons or trunnions which form the fulcrums of the levers; these gudgeons pass through circular notches cut in the upper side of the levers, and that part of the levers which rests upon the plate being formed into the arc of a circle, of which the gudgeons are the centre, the whole weight of the masts is sup ported upon the carriages, instead of upon the fulcrum, which merely serves as a centre of motion. The operation of fidding a mast is as follows :—The mast being swayed high enough for the short arms of the levers to enter the fid-hole (which is defended by a very stout iron plate), the longer arms are depressed by tackles hooked to their extremities until they attain a horizontal position, when they are secured by lashings. To strike a mast (the top rope being rove and made fast below), all that is necessary is to slack the lashings until the strain is brought upon the top rope, and then to lower away. These patent lever fids may be applied to any ship without any alteration in her tops, mast, or fid holes; and from the rapidity and certainty of their operations, are calculated to render most important service to navigators in the most trying situations, where despatch in striking a mast may be of essential consequence, as in the case of a sharp ship grounding upon a rapidly falling tide, in gales of wind at sea in a dark night. In the case of springing a topmast just above the cap, when in chase, the lever fids will be found invaluable, as the topmast may be instantly lowered until the part which is sprung is below the cap, by just shaking the vessel in the wind for half a minute, when all will be safe, and she may be kept on her course again. So sensible were the Lords of the Admi

ralty of the utility of this invention, that they paid to Mr. Botch a large sum for the use of it in the Royal Navy.

Mr. Botch has subsequently taken out a patent for a prop for supporting masts, by which the strain is transferred from the trestle trees to the lower mast, just beneath the top, and acts in a direction nearly vertical. The cut on the followingpage represents an outline sketch of' the apparatus. a is the top. mast; b the lower mast ; c the fish (which is a strong piece of timber fixed to the lower mast to strengthen it) shown in dotted lines ; d the cheeks of the lower mast, on which are fixed the trestle-trees e; f the fid of the top mast ; g a bolt stay to the topmast; h, the new patent prop, bolted to the heel of the top-mast by means of an iron plate, connected with the hinge joint upon which it turns, the other end rest ing in an angular cavity made to receive it in the fish of the lower mast ; i shows the position which the prop takes when the top-mast is being raised or lowered; the curved dotted lines o o represent the form into which the trestle-trees ordi narily become bent by the action of the top-mast. This latter effect is owing to the trestle-trees having to support the whole weight of the top-mast, with its ends resting upon the trestle-trees. To the weight is to be added the force of the wind, which has a tendency to in crease that effect in a tenfold degree, especially when the inclined position in which the masts of most ships are placed is taken into consideration. If instead of the fid and the trestle-trees having to withstand all this force, the little prop h be put into the cavity of the fish, it will be seen that nearly the whole of it is thereby thrown diagonally upon the lower mast, which is well able to sustain it.