It is obvious that a ship constructed on this prin ciple, may sustain the loss of certain planks of the bot tom, and also the keel, (which has frequently been found to have happened to ships of war on their be ing taken into dock,) and still reach the place of her destination, when the loss of either would be the de strnction of a ship built on the present mode. It will be evident also, that a ship constructed as now recom mended, possesses greater stowage and more space for leakage than by the old plan, by the omission of the useless inner planking, and by laying the kentlage on dunnage, leaving a space for the water, which was formerly occupied by the inner lining. This dunnage in the bilge may be found in the iron kentlage, and thereby serve as ballast, for which it is well calcula ted from its situation, and by its occupying a space heretofore forming part of the fabric of the ship, will give an increase of stowage, as before stated.
The best method of closing the openings between the timbers, is by filling the intermediate space with pieces of wood, about three inches in depth, of such lengths as the inferior conversions will supply, abund ance of which may be procured from the offal. These fillings are to be well caulked, after which the exterior plank is to be brought on. When the works are going on within board, similar pieces are to be fitted inter nally, and afterWards taken out for the purpose of fill ing the spaces between the pieces so fitted with a mixture of Parker's Roman cement and drift sand, in the following proportions, viz.
previously paying the opening well with coal tar. Where there is sufficient space, a brick, or part of one, may be int-oduced, provided there is room for cement between it and the timbers. When filled in to within about two inches of the surface of the frame, the pieces of three inches already fitted and taken out, are to be well driven in and caulked, and by so doing, no space will be left unoccupied. if considered de sirable, these pieces may be driven below the surface of the timber, thereby leaving water courses to con vey the leakage to the pumps in channels. And prior to launching or undocking of ships built on this prin ciple, it has been the practice to inject the part filled in with mineral tar by means of a simple forcing pump, boring holes in the joints of the timbers for the introduction of the pipe. By following this me thod the air will be excluded, which, as experience has shown, tends much to the durability of the fabric. If what is here recommended be attended to, says Sir Robert Seppings, and mercantile ships were built un der roofs, as ships of war now are, durability would be obtained in addition to safety from the mode of their construction.
The beams are to be attached to the sides, as shown at 0, Plate D. Figure 5, rendering wood knees un necessary, and requiring only a small number of those of iron.
Plate DI. Figure 1, marked P, describes the old principle of framing the stern with transoms. Q re presents the new principle, with timbers similar to the bow, omitting the transoms below the wing or upper transom; and by introducing the new principle on which the floors are made, the necessity of using valuable compass, or crooked timber, hitherto re quire(' and with difficulty procured for these purposes, is avoided. Uniform support will thus be given, and also an increase of room for stowage.
In large mercantile ships above 500 tons, Sir Ro bert Seppings would recommend that plate iron be laid diagonally, as shown in Plate DI.
The principle thus recommended will cause a de crease in the consumption of materials, and the diffi culty of procuring the necessary curvature will be ob• viated. It also affords protection from worms exter nally, and vermin internally. Leaks may be more easily discovered and stopped than by the old method; and in point of additional strength there can be no doubt. If farther proof were required, Sir Robert Seppings refers to the case of the Malabar of 74 guns, built at Bombay, and which arrived at Portsmouth, loaded to her upper deck with timber, and during her passage encountered four heavy gales of wind, without showing a symptom of weakness, as will appear by the following extract from the survey made by the officers of the Plymouth yard, on that ship, by order of the Lords Commissioners of the admiralty.
" When we consider the nature of the lading that this ship has brought home, with the temporary se curity to the beams of all the decks, except the orlop, and that on her passage she encountered four very se i vere gales of wind, it must, we presume, be very gratifying to your honourable board to find, that she does not indicate any past symptoms of weakness or straining in any part." This ship had no other attachment for her beams than the internal hoops and thick water ways; the remainder of her security, the iron knees, being omitted (from the difficulty of procuring them in India) until her arrival in this country; thus support ing her cargo without the aid of knees, either of wood or Having delivered these general observations on the best method for constructing the hulls of merchant ships, we close this part of the article with a few ob servations on the proportions of their masts and yards.