![[Larger image]](#1952277324285608797_i_p018a.jpg.id-2065624376032442982.wrap-0.html.html){kind=link}
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.
PROGRESSIVE TYPES OF WARSHIP MACHINERY, AND THEIR ECONOMY, 1840 to 1905.
| 1840 to 1855. | 1855 to 1875. | 1875 to 1890. | 1890 to 1895.[A] | 1895 to 1900.[B] | 1900 to 1905.[C] | |
| Type of boiler ... ... | Rectangular | Rectangular | Single-ended cylindrical | Single-ended cylindrical | Belleville water-tube | Water-tube |
| Steam pressure per square inch | 3 lb. to 4 lb | 25 lb. | 90 lb. | 155 lb. | 300 lb. | 300 lb. |
| Coal consumption per indicated horse-power per hour | 7 lb. | 4 lb. to 5 lb. | 2-1/2 lb. | 2 lb. | 1.8 lb. | 1.8 lb. |
| Type of engine ... ... | Geared screw | Simple horizontal surface condensing | Three-cylinder compound | Three-cylinder triple-expansion | Three-cylinder triple-expansion | Four-cylinder triple-expansion |
| Piston speed in feet per minute | 220 | 500 to 600 | 750 | 840 | 918 | 1000 |
| Weight of machinery per indicated horse-power | 10 cwt. | 3 cwt. to 5 cwt. | 3 cwt. | 2-3/4 cwt. | 2 cwt. | 1.6 cwt. |
| Speed of ship ... ... | 8 to 9 knots | 14 knots | 16 knots | 18 knots | 18.25 knots | 23 knots |
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.
The general idea as regards the powder used as a propellant was that the ignition was instantaneous, and that the more violent the explosion the greater would be the velocity of the projectile. Under such conditions short weapons naturally found favour; and indeed, with a light, spherical, ill-fitting projectile, there was very little advantage to be gained by lengthening the bore. But with the introduction of rifled cannon, much heavier and better-fitting shot became possible, and a rapid-burning powder gave rise to dangerous pressures in the gun. It was then realised that it was not an explosion that was wanted, but a continuous pressure acting on the base of a shot for a relatively considerable period. This needed a slow-burning explosive, and led to the manufacture of powder as pebbles or prisms; the enlargement in the late 'seventies of the chamber of the gun, and the provision of air spaces for the expansion of the powder, greatly added to the velocity with which the shot left the gun, and therefore augmented its carrying power.[62]