| | | Steam pressure per | 155 lb. | 300 lb. | 300 lb. square inch | | | | | | Coal consumption per | 2 lb. | 1.8 lb. | 1.8 lb. indicated horse-power | | | per hour | | | | | | Type of engine | Three- | Three- | Four- | cylinder | cylinder | cylinder | triple- | triple- | triple- | expansion | expansion | expansion | | | Piston speed in feet | 840 | 918 | 1000 per minute | | | | | | Weight of machinery per | 2-3/4 cwt. | 2 cwt. | 1.6 cwt. indicated horse-power | | | per minute | | | | | | Speed of ship | 18 | 18.25 | 23 | knots | knots | knots ------------------------+--------------+-------------+------------- [A] Battleship, _Barfleur_. [B] Battleship, _Canopus_. [C] Armoured Cruiser. The gun most in favour at the close of the eighteenth, and at the opening of the nineteenth, centuries was the cast-iron, smooth-bored, muzzle-loader: first the 32-pounder and later the 68-pounder. Carronades were used for "smashing" rather than for penetrating the skin or structure of ships. Although the 68-pounders were improved by a lining of wrought iron being inserted in the bore, whereby the energy at 1000-yards range was increased from 290 to 600 foot-tons, little progress was made until after the Crimean War, when chemists undertook the investigation of the action of explosives and metallurgists sought to produce stronger metals.