The _Grianaig's_ engines developed on trial 740 indicated horse-power at 148 revolutions per minute, with a boiler pressure of 190 lb. per square foot, and a condenser vacuum of 26.5 in. Some of the details, being typical of the practice of the firm in respect of yacht machinery, are quoted from the specification on the next page. The arrangement of cylinders is as follows: H.P. 14 in. in diameter, I.P. 22 in. in diameter, L.P. 35 in. in diameter, Stroke 24 in. The piston and connecting-rods are of steel; the guide-shoes for the crossheads are of cast iron, the ahead face having white metal, and the astern face being left plain. The back columns are of the usual cast-iron box type, the front columns, being steel, are turned. The high-pressure cylinder has a piston valve, and the intermediate- and low-pressure cylinders flat slide-valves. None of the cylinders is provided with liners. A single-stroke reversing engine is situated at the back of the main engine, but is operated from the starting platform. The condenser is of the surface type with a circular cast-iron shell; the total cooling surface is 1300 square feet. Steam is supplied to the main engine by one single-ended cylindrical boiler 13 ft. 9 in. in diameter by 10 ft. long, working at a pressure of 190 lb. per square inch. There are three furnaces, the mean internal diameter being 3 ft. 5-3/4 in. and the length 6 ft. 10 in. The grates are 6 ft. long, giving an aggregate area of 61.5 square feet. The boiler tubes are 3-1/4 in. in diameter and 6 ft. 10-3/4 in. long, the total heating surface being 1899 square feet. [Illustration: decoration] [Illustration: Plate XXVI. ENGINES OF THE YACHT "GRIANAIG."] [Illustration: Plate XXVII. DINING SALOON IN A MAIL STEAMER. (_See page 81._) DRAWING ROOM IN THE STEAM YACHT "FOROS." (_See page 81._)] [Illustration: decoration] The Twentieth Century. [Illustration: decoration] Prophecy has its allurements even in the domain of applied mechanics; and having reviewed progress during the past two centuries in naval architecture, as embodied in sailing ships, merchant steamers, warships, and yachts, there is a temptation to speculate on the prospects of the future. The possibilities of the steam turbine, for manufacturing which the Scotts are laying down a special plant; the potentialities of the producer-gas engine as applied to the propulsion of ships; and even the solution of the problems which stand in the way of the application of the universally-desired oil turbine, are all topics which would prove interesting, even although no conclusion could be arrived at. It is enough, however, to say here, that each is having careful consideration by the firm.