The figures in the Table are average results rather than highest attainments during the periods. For 1890-95 we have taken the _Barfleur_, the engines of which were constructed by the Scotts in 1894; whilst the particulars for 1895-1900 refer to the _Canopus_, engined by them in 1900. In 1902 they also supplied the machinery for the battleship _Prince of Wales_, and commenced the construction of the armoured cruiser _Argyll_. But before referring in detail to these latter ships, we may briefly review the advances in applied mechanics, metallurgy and chemistry, which have contributed largely to the perfection of these modern fighting ships in respect of offensive and defensive qualities. TABLE III. PROGRESSIVE TYPES OF WARSHIP MACHINERY, AND THEIR ECONOMY, 1840 TO 1905. ------------------------+-------------+-------------+-------------- |1840 to 1855.|1855 to 1875.|1875 to 1890. | | | ------------------------+-------------+-------------+-------------- Type of boiler | Rectangular | Rectangular | Single-ended | box | box | cylindrical | | | Steam pressure per | 3 lb. | 25 lb. | 90 lb. square inch | to 4 lb | | | | | Coal consumption per | 7 lb. | 4 lb. | 2-1/2 lb. indicated horse-power | | to 5 lb. | per hour | | | | | | Type of engine | Geared | Simple | Three- | screw | horizontal | cylinder | | surface | compound | | condensing | | | | Piston speed in feet | 220 | 500 to 600 | 750 per minute | | | | | | Weight of machinery per | 10 cwt. | 3 cwt. | 3 cwt. indicated horse-power | | to 5 cwt. | per minute | | | | | | Speed of ship | 8 to 9 | 14 | 16 | knots | knots | knots ------------------------+-------------+-------------+-------------- ------------------------+-------------+-------------+-------------- |1890 to 1895. |1895 to 1900.|1900 to 1905. | [A] | [B] | [C] ------------------------+--------------+-------------+------------- Type of boiler | Single-ended | Belleville | Water-tube | cylindrical | water-tube |