With the widening of the maritime interests and the intensification of competition there was awakened a general desire to increase the strength of ships. In this respect, as in others, there had been little advance either in the Navy or in the mercantile marine. It was exceptional for a ship of the eighteenth century to continue in service for more than twelve or fifteen years. This was due partly to defective constructional details, and partly to the ineffective methods of preserving timber.

A TYPICAL EAST INDIAMAN. [(See page 12.)]

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Ships were then built up[12] of a series of transverse ribs, connected together by the outside planking and by the ceiling. There was no filling between the ribs. The ship's structure thus suffered severely from hogging and sagging stresses. The French tried to improve this by introducing oblique iron riders across the ceiling, or by laying the ceiling and the outside planking diagonally, while in other instances the whole was strengthened with vertical or diagonal riders; but none of these systems gave complete satisfaction. The Sepping system was introduced about 1810, and was early adopted by the Scotts. The bottom of the ship was formed into a solid mass of timber. The beams were connected with the side of the ship by thick longitudinal timbers below the knees, and by other stiffening members. A trussed frame was laid on the inside of the transverse frame in the hold of the ship, and the decks were laid diagonally. These members bound the ship in all directions, so as to resist the stresses due to the ship working in a seaway.

The method of preserving the timber adopted at the beginning of the eighteenth century was to char the inner surface of the log, while the outer surface was kept wet; but this was superseded early in the century by the stoving system, which consisted in placing timber in wet sand, and subjecting it to the action of heat, for such time as was necessary to extract the residue of the sap and bring the timber to a condition of suppleness. This process continued until 1736, after which the timber itself was steamed. Copper sheathing was first employed on warships in 1761; prior to this lead had been used, but only occasionally.

American shipbuilders held an important position, even in the British trade, for some time after the Declaration of Independence; but there was then developed a pronounced spirit of emulation amongst the British firms, which had a marked effect on competition in western seas. At the beginning of the nineteenth century much of the oversea work done by the Scotts was for the West Indian trade. The vessels were not often of more than 600 tons, but the firm continued steadily to develop their business.

Plate VI.