MAST, a long round piece of timber, elevated perpendicularly upon the keel of a ship, to which are attached the yards, the sails, and the rigging. A mast, with regard to its length, is either formed of one single piece, which is called a pol-mast, or composed of several pieces joined together, each of which retains the name of mast separately. The lowest of these is accordingly named the lower-mast, a fig. 1.; the next in height is the top-mast, b, which is erected at the head of the former; and the highest is the top-gallant-mast, c, which is prolonged from the upper end of the top-mast. Thus the two last are no other than a continuation of the first upwards.
The lower-mast is fixed in the ship by an apparatus described in the articles HUIK and SHEERS: the foot, or heel of it rests in a block of timber called the step, which is fixed upon the keelson; and the top-mast is attached to the head of it by the cap and the truss-tree.
The latter of these are two strong bars of timber, supported by two prominences, which are as shoulders on the opposite sides of the mast, a little under its upper end: athwart these bars are fixed the cross-trees, upon which the frame of the top is supported. Between the lower mast-head and the foremost of the cross-trees, a square space remains vacant, the sides of which are bounded by the two truss-trees. Perpendicularly above this is the foremost hole in the cap, whose after hole is solidly fixed on the head of the lower-mast. The top-mast is erected by a tackle, whose effort is communicated from the head of the lower mast to the foot of the top-mast; and the upper end of the latter is accordingly guided into and conveyed up through the holes between the truss-trees and the cap, as above mentioned. The machinery by which it is elevated, or, according to the sea phrase, swayed up, is fixed in the following manner: the top rope d, fig. 3. passing through a block e, which is hooked on one side of the cap, and afterwards through a hole, furnished with a sheave or pulley f, on the lower end of the top-mast, is again brought upwards on the other side of the mast, where it is at length fastened to an eye-bolt in the cap g, which is always on the side opposite to the top-block e. To the lower end of the top-rope is fixed the top-tackle h, the effort of which being transmitted to the top-rope d, and thence to the heel of the top-mast f, necessarily lifts the latter upwards, parallel to the lower-mast. When the top-mast is raised to its proper height, fig. 4. the lower end of it becomes firmly wedged in the square hole above described, between the truss-trees. A bar of wood or iron called the fid, is then thrust through a hole i in the heel of it, across the truss-trees, by which the whole weight of the top-mast is supported.
In the same manner as the top-mast is retained at the head of the lower-mast, the top-gallant-mast is erected, and fixed at the head of the top-mast.
Besides the parts already mentioned in the construction of masts, with respect to their length, the lower masts of the largest ships are composed of several pieces united into one body. As these are generally the most substantial parts of various trees, a mast, formed by this assemblage, is justly esteemed much stronger than one consisting of any single trunk, whose internal solidity may be very uncertain. The several pieces are formed and joined together, as represented in the section of a lower-mast of this sort, fig. 5. where a is the shaft, or principal piece into which the rest are fixed, with their sides or faces close to each other. The whole is secured by several strong hoops of iron, driven on the outside of the mast, where they remain at proper distances.
The principal articles to be considered in equipping a ship with masts are, 1st, the number; 2d, their situation in the vessel; and, 3d, their height above the water.
The masts being used to extend the sails by means of their yards, it is evident, that if their number were multiplied beyond what is necessary, the yards must be extremely short, that they may not entangle each other in working the ship, and by consequence their sails will be very narrow, and receive a small portion of wind. If, on the contrary, there is not a sufficient number of masts in the vessel, the yards will be too large
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CCCXV.