Fourthly, it was proposed to lay the decks diagonally; but this system does not appear to have ever come into general use. It should here be mentioned that the use of shelf-pieces and thick waterways in connection with the ends of the beams was first adopted by the French in very small vessels; also the system of fillings between the frames was an extension of a method which had been in use for some time, for it was customary to fill in the spaces as far as the heads of the floors, in order to strengthen the ship's bottom against the shocks and strains due to grounding. [Illustration: FIG. 64.--Sir Robert Seppings' system of construction.] Sir Robert Seppings further introduced many minor improvements into the details of the construction and the forms of ships. Amongst these may be mentioned the method of combining the frame-timbers. The old method of shaping the heads and heels of these timbers and of combining them with triangular chocks is shown on the left-hand side of Fig. 64. In the new method the heads and heels were cut square, and combined with circular coaks, as shown on the right-hand side in the same Fig.] [Illustration: FIG. 65.--The _Waterloo_.] The principal alterations in the forms of ships introduced by Sir Robert Seppings, were connected with the shapes of the bow and stern. Hitherto the bow was cut straight across at the cathead, so as to form a vertical wall extending down to the level of the upper deck portsills, and formed of thin boarding and stanchions. The old shape of the bow is clearly shown in Figs. 52 and 55. The disadvantage of this arrangement was that it exposed the ship to the raking fire of an enemy. The old form of bow was also deficient in structural strength, and was liable to cause leakage. Sir Robert Seppings carried the rounding of the bow right up to the upper deck, and made it as strong as any other part of the ship to resist either shot or stresses. This alteration also enabled him to provide for firing several guns in a line with the keel. The old square stern was also abolished and a circular one introduced, which enabled a more powerful battery to be carried aft.