The direct-acting vertical engine, with inverted cylinders, almost as we know it to-day, and as illustrated in connection with the work of the twentieth century, was introduced in the late 'fifties. The compound engine, introduced in 1854, was developed into the triple-expansion system in 1882, and later into the quadruple-expansion type; but this latter has not been much adopted, only some 3 per cent. of the vessels registered at Lloyds being so fitted. This is in a large measure due to the satisfactory economy attained with triple-expansion engines. As to the progress made, Table II., giving average results at different periods, is instructive.[51] TABLE II.--PROGRESS IN THE ECONOMY OF THE MARINE ENGINE, 1872 TO 1901. -------------------------------------------+-----+-----+------+------ |1872.|1881.|1890. | 1901. -------------------------------------------+-----+-----+------+------ Boiler pressure in pounds per square inch |52.4 |77.4 |158.5 | 197 Coal consumption in pounds per indicated | | | | horse-power per hour | 2.11| 1.83| 1.52 | 1.48 Consumption on prolonged sea voyages in | | | | pounds per indicated horse-power per hour |... | 2 | 1.75 | 1.55 Piston speed in feet per minute |376 |467 |529 | 654 -------------------------------------------+-----+-----+------+------ The advance of the century may be popularly expressed by stating that, whereas in the first coasting steamships built by the Scotts the fuel consumed in carrying 1 ton of cargo for 100 miles was 224 lb., the expenditure to-day is from 4 lb. to 5 lb. The economy of the steam engine has accounted, as is shown in the Table, for a considerable part of this improvement. But, at the same time, the growth in the size of ships has enabled the normal speed of 10 knots to be realised, with an addition to engine power of much less ratio than the increase in the capacity of the steamer. As to speed, recent progress has been most marked in the Navy, and it is therefore fitting that here we should direct our attention to Naval work. [Illustration: decoration] [Illustration: Plate XIV. MODEL OF H.M.S. "PRINCE OF WALES," 1803.] FOOTNOTES: [17] Woodcroft's "Steam Navigation," page 20, etc. [18] Woodcroft's "Steam Navigation," page 54. [19] Deas' "Treatise on the Improvements and Progress of Trade on the River Clyde" (1873), page 24. [20] Muirhead's "Life of Watt," pages 428 and 429. [21] Williamson's "Clyde Passenger Steamers," pages 348 to 351. [22] James Napier's "Life of Robert Napier," page 21. [23] This was the second of the name--a favourite one after the Duke of Wellington's great victory, and gave rise to the following poetic effusion:--