WATER LINES are, as we have explained above, supposed to be drawn on the surface of a ship's bottom by the surface of the water on which she floats. They are generally drawn with green ink, and are represented in the sheer draught by straight lines. If parallel to the keel, they will be represented on the body plan by horizontal lines; but if the vessel is to be constructed so as to draw most water abaft, the water lines will not, of course, be parallel to the keel, but, owing to their varying heights, will form curves upon the body plan; and, in the half breadth plan they will be described by curves which limit the half breadth of the ship at the height of their corresponding lines in the sheer plan.

RIBBAND LINES are those curved lines, in the half breadth plan, by which moulds are made for the ribbands and harpins; and the use of the ribbands and harpins is, to keep the timbers which compose the body of the ship to their true stations, so as to preserve its true form until the plank is brought on. For this purpose they are skilfully arranged with regard to their heights and distances from each other. It is evident that the ribbands will partake of a double curve, owing to the convexity of the bottom of the ship. The curve, in the sheer plan, will increase perpendicularly on approaching the stem and stern post: and it will be clear that, by deviating from the middle line of the ship's length, as they approach the extreme breadth, the ribbands will also form an horizontal curve, as upon the half breadth plan. From this double curve it results, that the ribbands will appear in different points of view, when drawn upon different plans of the same ship. To conceive this, suppose a model of a ship upon the stocks completely framed as represented in the frontispiece. If we were placed in a line prolonged from the keel, facing either the stem or stern, we should only view the projection of the ribbands on the plane of the midship frame, in which the horizontal curve is scarcely seen, but we shall discover part of the perpendicular curve which rises gradually from the extreme breadth towards the stem and stern post, so that they must be drawn on the body plan as diagonal lines, which terminate on the midship frame, and, at the heights designed on the stem and stern-post. But, if we were placed considerably above the ship, on a line perpendicular to the middle of the keel, we should discern the horizontal curve as drawn in the half breadth plan, without perceiving the perpendicular curve as drawn in the sheer plan.

SWEEPS. The different sweeps or segments of circles which successively and connectively form a bend, or frame of timbers, have already been clearly described under the article FRAMES, in the Explanation of Terms. Of these, the segment which is called the FLOOR-SWEEP is that which forms the body at the floor-head, particularly along the midships. It is limited by a horizontal line above the keel in the body-plan, and its distance above the keel at the midship timbers is called the Dead-Rising.

The LOWER BREADTH SWEEP forms that part of the body immediately below the lower height of breadth. Its centre is found in a horizontal line, in the body plan, at the height of the lower breadth of its corresponding timber in the sheer plan, upon which line is set off the main half breadth of the ship, and from which the radius is taken that describes the sweep downwards.

The RECONCILING Sweep connects the lower breadth and floor sweeps

in such a manner as to intersect neither, but to come exactly over the back of each, so that the whole form a fair curve from the lower height of breadth down to the rising or floor sweep; and, by drawing a line from the back of the floor sweep down to the keel, we shall have the whole form of the timber below the lower height of breadth line.

The UPPER BREADTH SWEEP forms part of the body above the upper height of breadth. The centre of this sweep is in a horizontal line, in the body plan, corresponding with the upper height of breadth of the same timber in the sheer plan; to which line the corresponding main half breadth of each timber is squared up. Within this half-breadth is set off the radius or length of the sweep which gives the centre for describing as much of a circle upwards as is required. The lengths of all the upper breadth sweeps are to one radius.

The TOP-TIMBER SWEEP OF HOLLOW, is a sweep inverted with its back to the back of the upper breadth sweep; its upper part intersects a spot at the top-timber half breadth at the height of the top-timber line. By this sweep, as we have before shewn, the form of the timber is completed.

The RISING OF THE FLOOR, is a curve drawn in the sheer-plan and limited at the midships by the dead-rising. In flat floored or burthensome ships it runs nearly parallel to the keel for some distance afore and abaft the midships. All the timbers where the rising is parallel with the keel are termed flats.

The HALF BREADTH of the RISING is a curve line in the half breadth plan which limits the distance of the centres of the floor sweeps from the middle line in the body plan.

The RISING LINE is a curve in the sheer draught which contains the heights of the centres of the floor sweeps, taken from the body-plan; but, if the whole height of those centres was set off upon corresponding timbers in the sheer plan, they would interpose with the upper lines in the draught; the rising line is, therefore, so contrived as to come to the lower part of the sheer-plan, by taking all the heights of the centres in the body-plan, from a horizontal line, at the height of the centre which sweeps dead-flat; and, setting them off on their corresponding timbers in the sheer-plan, from the upper edge of the rabbet of the keel, by which means the rising line in the midships breaks in fair with the upper edge of the rabbet of the keel. When the body is constructed by a rising floor, the floor sweeps are all of one length.

The CUTTING DOWN LINE is a curve line, in the sheer-plan, which limits the height of every floor timber at the middle line; and, likewise, the height of the upper side of the deadwood afore and abaft, which must be sufficiently high to allow for the siding of the keelson, and leave sufficient strength in the rising floors.

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ROOM-AND-SPACE, or Timber and Room, is the distance between the moulding edges of all the timbers; or, rather, the siding of every two timbers and opening between: the timber being considered as the Space and the opening between as the Room. The Room-and-Space accordingly varies with the size of the ship; and, it must always be contrived, in draughting, so as to contain the siding of two timbers and the opening between, agreeably to the definition. In all ships of war, the breadth of the ports must here be always considered. It may be observed, that one

mould serves for two timbers, the foreside of the one being supposed to unite with the aftside of the other, and so forming only one line, which is called the joint of the frame or timbers. The midship timber, or broadest part of the ship, is called dead-flat, and distinguished by this character. The timbers before the midship are distinguished by the letters A, B, C, &c. and those abaft the midship by the figures 1, 2, 3, &c. Those timbers following dead-flat, both afore and abaft, where there is no rising, are called flats, and are distinguished by the characters (A), (B), &c. in the fore body, and (1), (2), &c. in the after body. It may be generally observed, that all particulars in the fore body are distinguished by letters of the alphabet, and all those in the after body by figures. Thus the cant timbers in the fore body are commonly distinguished by a, b, c, &c. and those in the after body by small figures.

As, in all ships of war, there is a fixed height for the lower sill of the midship port above the load-water line, with six months stores, provisions, &c. on board, their capacity should be simply adequate for this purpose, neither more nor less; it should not be more, to avoid superfluous expense in construction and the additional number of men required to navigate; nor should it be less, from an obvious general insufficiency to answer the required purposes; the bias should rather tend to the increase than the diminution of capacity.

If we observe what draught of water a ship draws when she is laden, with every thing on board, and supposed to be immersed to her deep water mark, or load-water line, we shall have only to find a method whereby we may come at the true number of cubic feet contained in the ship below that line; which, consequently, will be the number of cubic feet in the bulk of water displaced by the ship in that position : whence, by calculating the weight of so many cubic feet of water, we may obtain the true weight of the ship with every thing on board, and all that leans or presses upon her.

Now, as ships of the same number of guns and tons, are nearly of the same dimensions, we may, by knowing the weight of such a ship, compare it with the estimated weight of a ship, the plans of which we have constructed, by examining the draught of water, and computing the weight therefrom. If the weight be found to agree with the known weight of that of similar size, the load water line may be considered as rightly placed; and, we shall know, to a certainty, how much water she will draw when brought down to her load-water mark; in consequence, we may determine on the height of the lower-deck, ports, by which the . true placing of the decks, &c. must be regulated.

But, if the weight, as laid down in the draught, exceeds the weight first mentioned for ships of a similar size, the load-water line in the draught is placed too high, and must be lowered till both the weights are found to agree: for the same reason, if the weight of the ship, in the draught, appears to be less than the weight first mentioned, the water line will then be too low, and must be raised accordingly.

The ship may be laid down in the draught either so as to sail on an even keel or so as to draw most water abaft; but the larger classes, in general, are recommended to be constructed for an even keel, as we have before noticed, having thus the advantage both with respect to strength and velocity. For, if a ship constructed to sail by the stern, be brought

down to her load-water mark so as to sail on an even keel, her strength and sailing qualities will be considerably diminished; and, the fore part being brought down lower than it should be, the middle of the ship maintaining its proper depth in the water, the after part must be, by these means, lifted, and will press downwards with a strain which may continue until the ship's sheer is entirely broken. It is probable, that, from this reason, we see so many ships, after having sailed a little while, with broken backs (as it is termed ;) that is, with their sheers altered in such a manner, that the sheer rounds up, and the highest part is in midships.

Such are the disadvantages arising from not paying a due attention to those points in the construction of a draught; therefore, when the load water line is found to be situated of a proper height on the draught, according to the weight given, and likewise drawn parallel to the keel, as supposing that to be the best sailing trim, the next matter will be to examine whether the body is constructed suitably thereto, in order to avoid the bad consequences which we have noticed.

For this purpose we must, in the first place, divide the ship equally in two, lengthwise, between the fore and after perpendiculars described on the draught; and, the exact number of cubic feet in the whole bottom beneath the load water line being known, we must find whether the number of cubic feet in each part so divided is the same; if they prove to be so, the body of the ship may then be said to be constructed in all respects suitably to her swimming on an even keel, let the shape of the body be whatever it may, and which will be found to be her natural position at the load water line.

But, if one of the parts should contain a greater number of cubic feet than the other, that part which is the heaviest will sink the deepest, supposing the ship in her natural position. Then, in order to render the ship suitably constructed to the load water line in the draught, (which is parallel to the keel) we must subtract the number of cubic feet contained in the lesser part, from the number contained in the greater part, and then fill out that part of the body which contains the lesser quantity, till it has accumulated half the sum of the difference, and draw in the other part of the body proportionably, so as to make both parts equal. Thus will the ship's body be so constructed as to swim on an even keel.

Also, if we propose that a ship, to be laid down, shall not swim on an even keel, but draw more water abaft than afore, we must then, by comparing the fore and aft parts of the ship's body together, swell out the one part of the body and reduce the other; so that the ship shall have her natural position when brought down to the load water mark, as required.

It has sometimes been supposed that, to construct a draught is no more than to draw the several lines which compose the whole, and form the representation of the sheer draught, half-breadth and body plans at discretion, shaping them in such a manner as only to answer particular purposes, as 'stowage, dispatch, &c. without the least attention to some considerations which are most essential to every class of shipping. A ship thus constructed, if put together as strongly as possible, and by the most skilful workmen, and likewise with the best materials, would not, unless by mere chance, answer the wished-for purposes so well as one

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put together in a more unskilful manner, and with more unsound materials, but constructed agreeably to the dictates of theory and experience. Because the latter would always wear easy, by being kept in her natural position and free of compulsion; whereas, on the contrary, the former might, by continual strains, in consequence of her body being irregularly formed, be wearing herself to pieces, and trying every part to the greatest degree; and, by the time that the strength of the latter began to decline, the first would not be in value equal to one half of that of the other ship.

INSTRUCTIONS FOR DELINEATING THE SEVERAL
DRAUGHTS AND PLANS OF A SHIP.

GENERAL OBSERVATIONS ON THE PROPORTIONAL DIMENSIONS, &c. PREPARATORY TO THE CONSTRUCTION OF A DRAUGHT.

In order to fix upon the proportions for a ship of any class, it will be necessary, in the first place, to determine on the length between the foremost and after perpendiculars; as, when that determination is once fixed, it becomes a standard whereby all the proportions are calculated, and every particular regulated, with respect to proportion, strength, and beauty.

The proportions will, of course, be regulated upon the principles established by experience. These teach that a ship should not be too long with respect to breadth, nor too short with respect to depth. Length, although highly desirable to a certain degree, if carried to excess, will, as we have shewn, be prejudicial; and, when ships are extremely long, they must have an extraordinary allowance of timber and planking to make them equal in strength to those which are shorter.

The LENGTH BETWEEN THE PERPENDICULARS, in most ships of war, is the length on the gun or lower deck, taken from the aftside of the rabbet of the stem to the foreside of the rabbet of the stern-post at the height of the lower deck: and, in merchant-ships, from the aftside of the sternpost, at the height of the wing transom, to the foreside of the stem at the same height. (See Table of Dimensions and Scantlings, folio I.)

In ships of war the length is regulated by the number of ports intended to be made on the Gun-deck; and the disposition of the timbers by the situation of the ports. The latter should be so disposed as to weaken the ship as little as possible, and so as to avoid cutting off any of the principal timbers, &c. and, in placing them, we must consult the situation of the frames, which is every other bend throughout the ship, and of which the joints are represented by perpendicular lines in the square body, and by ticked lines in the cant bodies, agreeably to their thwartship appearance. (See Sheer Draught, Plate I.)

The foremost and aftermost ports being determined upon, the intermediate ports will be at equal distances asunder, according to the rooin-and