In this ship ® it a single timber, al though it has been before observed this single timber is sometimes placed near the steps, or gangway. Observe, this sin gle timber is introduced to change the bo dies, as that before it is called the fore body, so that abaft it is called the after body : but this is not all ; the floors in the fore-body are placed on the fore-side of the joint, consequently their moulding edge is on their aft-side, and the floors in the after-body are placed on the aft side the joint, and their moulding edge is on their fore-side ; therefore, in both bo dies they become under bevellings hence the necessity of this single timber to effect this change, or two floors would come together at the turn of the body, and the joint at their heads not strength ened by this intermediate shift of timber. Now, as we do not mean to square up perpendiculars at the joint of every frame timber, we shall make use of as many as will suit our purpose in delineating the sheer plan. Therefore, set before the perpendicular ® 19 feet 3 inches, and then square up from the upper edge of the keel a perpendicular, and under it mark F, as that is the station for frame F; then before F square up perpendiculars at 11 feet distant, marking under that next F, K, the next 0, and the foremost one S. Then abaft, the perpendicular set off twenty 24 feet 9 inches, and then square up a perpendicular, and mark under it 6, as that will be the station for frame 6; then abaft this perpendicular set off 16 feet 6 inches five times, and square up perpendiculars at. each station, marking that next abaft 6, 12, the others in succession 18,24, 30, and the after one 36. These perpendiculars, or stations, are always referred to by those names hereafter.
Above the upper edge of the rabbit of the keel set up upon the foremost per pendicular 29 feet, the height of breadth at the stem, as both heights of breadthsare terminated at one place quite forward and aft ; next set up at S 24 feet 2 inches; at 0 22 feet 8 inches; at K 21 feet inches ; at F 21 feet 3 inches; at ® 21 feet 3 inches; at 6, 21 feet 3+ inches; at 12, 21 feet 4 inches; at 18, 21 feet 6 inches ; at 24, 22 feet 4 inches; at 30, 23 feet 9 inches ; at 36, 26 feet 5 inches ; and the after perpendicular 27 feet 10 inches. Then an elliptical curve drawn through those heights will show the lower height of breadth all fore and aft.
The rising line is the next curve to he drawn in the sheer plan, which, in a ship of this construction, gives the heights of the centres of the floor-sweeps, by the which curves the shape of the timbers at and near the floor-heads are formed in the body plan ; thus, set np, as before, at K 21 feet 4 inches; at F 14 feet 7 inch es; at ® 11 feet 6 inches; at 6, 12 feet: at 12, 14 feet ; at 18, 17 feet 6 inches; at 24, 24 feet 11 inches.
Then an elliptical curve drawn through those heights will determine the centre heights of the floor-sweeps; and although these lines may be termed imaginary lines, and not wanted' in finishing the fa bric, the necessity of drawing these lines, with their connected half breadths, &c. will appear, when we insist upon the nicety required in the formation of every line used in ship building ; and by thus representing them, the draftsman, con structor, avails himself of an opportunity of observing that the said lines make fair curves. We said above, that the rising
line in a ship of this construction gave the heights of the centres for forming the floor-sweeps ; but in full-built ships, or merchant ships in general, this rising line gives the rising or lifting of the floors towards their heads, above which one ra dius is given for limiting their curves, and from this very line the whole construction or form of the body at this place is given. Now, in the formation of this line, no un deviating rule is given ; therefore, to construct it, a general knowledge of the formation of various bodies of different vessels is absolutely necessary. But what follows may be invariably observed, that is, the lifting of this line on the sheer plan, and narrowing it on the half•breadth plan, will procure velocity and less capacity ; while lowering it on the sheer plan, and continuing its midship part parallel with the keel, and augmenting its breadth on the half-breadth, and continuing it in mid ships parallel with the middle line, will produce a full, or burthensome vessel ; but then a vessel on this construction will not sail ; hence the judgment 'required in constructing this part of the ship can only be acquired by practice.
Now the main half-breadth, and the half-breadth of the rising of this ship, may be drawn in the half-breadth plan : thus, draw a straight line, parallel to and as much below the upper side of the keel. in the sheer plan, as will admit of the depth of the keels *scale of feet and inch es, by which the whole is to be drawn, and rather more than the main-half. breadth and this line will represent the middle line of the half-breadth plan, and is so called : then square down upon this line the several perpendiculars from the sheer plan, and it will also there re present the several timbers as sections crossing the timbers in the sheer plan at right angles.
Then for the main half-breadth set up from the middle line, for S, 20 feet 4 inches ; at 0, 23 feet ; at K, 23 feet 10 inches ; at F, 23 feet 11 inches ; at e, 24 feet ; at 6, 23 feet 11} inches ; 12, 23 feet 11 inches; at 18, 23 feet 8 inches ; at 24, 22 feet 9 inches ; at 30, 20 feet 10. inches; and at 36, 17 feet 9 inches. Draw a curve through these several half breadths, and the main half-breadth line will be described, except the fore and after parts. Permit us here to observe, the best method for drawing this and all other lines partaking of the nature of curves, is by elliptical moulds ; or, what is better, when they are of any length, is by a thin pliable batton, confined down to the several spots, or dimensions, by square pieces of lead, about three or four ounces in weight ; because by this last metlual the draughtsman has an opportu nity of observing the fairness, or correct ness of the line before he draws it. Our readers will excuse this particular de scription, because it need not be repeat ed, as all lines hereafter are supposed to be drawn in the same manner.