REVOLVING BALLAST.

THE system of raising a portion of the ballast, by means of a powerful screw apparatus for drawing the ballast up to the deck beams, so as to alter the centre of gravity at pleasure, is another of Mr. Shuldham's inventions; the plan is very useful for steadying vessels in a sea-way, and preventing them from rolling so much as when all the ballast is under the floor. It should only be hove up when running before the wind; but as this method is better explained by illustration than profusion

Section of Boat, showing Screw, with Ballast partly raised.

of words, the diagram above will more clearly elucidate the subject.

The lump of lead or iron ballast, thus moveable, should be secured in a strong wooden or iron case, the screw passing through both. This method of raising the ballast enables a vessel to run lighter and faster before the wind, particularly in a heavy sea; when on a wind, it must be lowered. There is a model of a revenue cutter in the Society of Arts Repository, for which Mr. Shuldham was awarded a silver medal, for an ingenious method similar to this, but so contrived that, when the vessel heeled over thirty degrees, the ballast lowered itself. The revolving lead keel answers every purpose of raising and lowering ballast, and is in some respects superior to, and more simple in contrivance, than the revolving ballast.

CENTRE-BOARD SAILING-BOATS.

(See the Engraving on opposite page.)

CENTRE-BOARD sailing-boats have been common in England since the year 1852, when a little boat, of about three and a half tons admeasurement (named the 'Truant '), was sent over to this country from New York to compete with our English sailing-boats; and on so doing showed such a superior capacity for working to windward and scudding, that she became an object of considerable attraction and observation.

This celebrated little clipper was fitted with a centre-board keel; (1) and as regards the form of the boat, it was constructed upon the most approved lines of the New York boat-builders, which were totally different to those of any kind of boat which had previously been seen in English waters.

Since the period alluded to, centre-board sailing-boats have become popular in this country. The form of the American boat is very broad and very shallow, with a wide and powerful stern, and sharp hollow bow. Some of these boats were so shallow that, when on the river Thames, they were termed mere 'skimming dishes.'

For boats of a deep and narrow form of hull, the centreboard keel is unsuited; it is, in fact, best adapted for boats of a broad and shallow form.

The form and rig of the centre-board boat of the present day are purely of American invention. English boat-builders improved upon it, and in the result they turned out some very excellent boats, in which the American 'skimming-dish' style of hull is considerably modified; and boats of a less shallow form have been constructed with remarkable success.

The rapidity with which an American centre-board boat may be tacked and turned up to windward in narrow channels, and the facility with which it may be run over shallow waters, are truly astonishing; but it is best adapted for smooth water. One of the great advantages in a shallow-bottomed boat is, (1) See a description of centre-board keels, and the mode of working them, ante, page 83.

that in shallow tidal waters there is seldom any risk of running aground; whereas, with a sharp, deep-keeled boat, it is sometimes impossible to avoid the risk of being left on the shallows in that ludicrous predicament in which the poet Moore found a sailing-boat and crew, when he penned the beautiful couplet :

'I saw from the beach, when the morning was shining,
A bark o'er the waters move gloriously on,

I came when the sun o'er that beach was declining,
The bark was still there, but the waters were gone.'

An American centre-board boat, although very broad and shallow, has fine lines both fore and aft. The bow is sharp and even hollow, both above and under water, and the stern is neatly rounded, but nearly as broad as the midship section. There is very little keel, except the centre-board keel, which, as regards the part hanging below the keelson when let down, is triangular in shape, or like the fin of a fish.

The whole fabric of the boat is so broad and shallow that the middle part is nearly flat-bottomed, although the bow is sharp and fine at the entrance.

The rudder is of necessity very broad at the lower part.

As to the inner part of the boat, it is decked nearly all over, leaving only a sort of well, or steering place, at the broadest part round about the keel-case, where also there are thwarts or benches for the crew.

The case containing the centre-board keel is fitted at about one-third of the boat's length from the stern. There were formerly many objections to centre-board keels, such as their .liability to get out of order by being choked with sand, mud, or seaweed, the room they occupied in the boat, dividing the open part into two longitudinal halves, and the difficulty experienced in keeping the keel-case water-tight; but these and other such objections have been overcome by the mechanical ingenuity of modern boat-builders.

There are various ways of rigging these boats, such as cutter, sloop, yawl, and otherwise; but the most usual is the sloop rig, with the mast stepped very far forward-in fact, close to