WINDLASS, in a ship, is an instrument, in small ships placed upon the deck, just abaft the foremast. It is made of a piece of timber six or eight feet square, in form of an axletree, whose length is, placed horizontally upon two pieces of wood at the ends, and upon which it is turned about by the help of handspikes put into holes made for that purpose. This instrument serves for weighing anchors, or hoisting of any weight in or out of the ship, and will purchase much more than any capstan, and that without any danger to those who heave for if in heaving the windlass about any of the handspikes should happen to break, the windlass would pall of itself.

WINDMILL, a machine turned by the power of the wind, which is caused to act upon vanes or sails, and give them a rotary motion. The external structure of the common windmill is well known to every person, but the interior mechanism not being so generally understood, we have given (in plate 175) a vertical section of a whole mill, which is upon the best construction. The four sails are fixed to an iron axis AA, by serewing them to an iron cross at one end of it. Two of these sails are marked BB; upon the axis within the mill a cog wheel D is fixed, and this turns a wheel C, on the upper end of a vertical shaft, EE, extending from the top to the bottom of the mill, to turn the machinery: on the lower end of it is a large wheel F, which turns two pinions a a, upon the spindles of the mill-stones bb; these are on the same construction as those described in our article FLOUR-MILL, to which we refer. At G is a wheel upon the main axis, giving motion to a pinion on an horizontal shaft H, which has one or more wheels upon it, to receive an endless rope for turning the bolting and dressing machines; for a description of which see BOLTING-MILL.

We will now enter more fully into the inechanism of the upper part of the mill, which is called its head or cap, marked II, and contains the axis A A. This is supported upon bearings, one near the sails and the other at its extreme end, as is shewn in fig. 2, plate 176, which is an horizontal section of the head, shewing the circular kirb or wooden ring K, and the framing which is bolted upon it to support the axis.

The construction of the axis is shewn in figs. 3 and 4 of plate 176. It consists of an octagonal iron shaft with two cylindrical necks at c and d, where it rests upon its bearings. At the end it has a kind of box e, which has two mortices through it in perpendicular directions to receive the sails B B. At the back of one of these mortices, and the front of the other, a projecting arm is left in the casting to receive screw bolts, which hold the sails fast in the mortices: the cog wheel is fitted on at D, its arms being bolted against a flaunch, cast

on the axis. The sails are braced by an iron stay f to each arm, proceeding from the end of a pole g, which is fixed at the end of the cast iron axis. The sails are formed of a sail cloth, spread upon a kind of lattice-work or framing, composed of rails morticed into the arms of the sails B B. The plane of these frames is inclined to the plane of the sails' motion, at such an angle, that the wind blowing in the direction of the axis, acts upon them as inclined planes, and turns them about, with a power proportionate to the size of the sails and force of the wind. It is necessary as the wind changes its direction to turn the sails about, that the axis may be always in the direction of the wind; this motion is effected by turning the head of the mill round upon the walls or frame LL, composing the body of the mill. At the top of this is a circular kirb, upon which a number of rollers are placed, and the kirb K of the cap lies upon these rollers, which are kept equidistant from each other by their centre pins being fitted into a circular hoop. By this means, though the head with the wheels and sails weigh many tons, they can be turned round to face the wind by a slight power; but in the best kind of windmill, such as is represented in our plate 175, the head is contrived to turn itself about whenever the wind changes. This is done by a small pair of sails M, fixed up in a frame projecting from the back of the head; it has a wheel upon its axis turning an other upon an inclined axis h, and this has a pinion turning a wheel i upon a vertical axis, at the lower end of which is a pinion working in a range of cogs, fixed round in the outside of the kirb. By this means, whenever the vane M is turned it moves the head of the mill slowly round, and with proportionate power. Now if ever the wind varies in the least from the direction of the axis, it acts obliquely upon the vanes M, and turns them round, at the same time setting the head right again. But when the axis is right, the wind blows in the plane of the vanes, and has no effect upon them. The head of the mill is kept firmly in its place by rollers, figs. 5 and 6; the frames of these are bolted to the lower side of the framing of the head, and then the rollers apply to the inside of the kirb K: there are eight of thes rollers, four of each kind. The pivot at the upper end of the vertical shaft E is supported in a bearing bolted to a cross beam in the framing of the head of the mill, and this is precisely in the centre of the head, that it may not vary as the head turns round. Many other things are so evident in the drawings as to need little explanation. Such are the walls NN, the different floors 00: at PP is a circular gallery all round the mill for the miller to go round, to take the cloth off the sails in high winds, or when the mill is to stop; this is done by untying the cloth at the extremity of the sails, and twisting it up like a rope, and tying the end of it again, in which state it presents no surface to the wind. At Q is a roller torn ed round by a wheel on the vertical shaft E;