As rapidity in answering the helm was a most important element in tacking, and therefore in speed, the firm about this time prepared full-rigged models, about 5 ft. long, for experimental trials as to the ship's form and rudder, on Loch Thom, on the hill above Greenock, in an exposed place where the conditions of wind were analogous to those at sea. The results proved satisfactory. In fact, in these years, when the _Minerva_, _Acbar_, and other noted clippers were built, the care used in design and construction was almost as great as that now devoted in the case of racing yachts. [Illustration: Plate VII. THE "ARCHIBALD RUSSELL." (_See page 14._)] The Scotts, in the first half of the nineteenth century, continued to produce a long series of successful sailing ships, while at the same time taking a creditable part in the evolution of the steamship. Steam, however, was not possible in long-distance voyages until pressures had been increased, and coal consumption reduced to moderate limits; and thus it came that, although the steam engine was used in the early years of the nineteenth century in river, and later in coasting, craft, the sailing ship continued supreme almost until the middle of the century. We do not propose, however, to refer to all of the later sailing ships built by the Scotts, but it may be interesting to give some details of the construction. American rock elm was largely used. The frames were in three sections with scarfed joints, bolted together, the scantlings being reduced towards the top, so as to lower the centre of gravity. Inside the frames there were at various heights longitudinal timbers, to add to the fore-and-aft strength. The top sides were of greenheart, the beams of oak or greenheart, with wrought-iron knees; the height between the beams was made to admit of two hogsheads of sugar being placed in the hold. There were side-stringers, sometimes 10 in. thick, between the floor and the beams, which were half-checked into the stringers. On the top of the beams there were deck-stringers. There was a most effective transverse and longitudinal binding, brass bolts being extended right through the knee, stringer, frame, and skin of the ship. The decks were of yellow or Dantzig white pine. An 800 or 1000-ton West Indiaman occupied about nine months in construction. The last wooden ship built in Greenock was the _Canadian_, completed by the Scotts in 1859.[14]