Two centuries of shipbuilding by the Scotts at Greenock

60 Improvements in Ordnance.
advantages of fibre were thus secured for resisting circum-
ferential strain. The bore was rifled to give the shot that
rotatory motion which prevents irregularity in flight and
conduces to accuracy of fire at long range. The smooth-bore
gun was effective up to only 1000 yards range, as compared
with the 18,000 yards and 20,000 yards for the modern weapon.
Breechloading was first introduced into the Navy in the
'sixties, but discarded because the details for closing the breech
end proved unsatisfactory. Finally, it was reintroduced in
1878, a satisfactory breech block and operating mechanism
having been devised.
These various improvements gradually increased the
power of the gun. The length and weight had enormously
grown, as is shown by the particulars of successive large Naval
guns, shown in Table TV, on the next page ; but the increase
in energy up till the 'eighties was not commensurate with the
augmentation of the weights of the projectile and charge.
The advance from the 38-ton gun of 1870 to the HOj-ton
gun in 1887 involved the multiplying by five of the charge of
powder, which quadrupled the energy of the gun, but the
carrying power of the shot was still deficient. The velocity
had increased in twenty years from 1600 to 2000 ft. per second,
slower-burning powder having been introduced.
Attention was further directed to the improvement of
explosives ; and ultimately, instead of gunpowder having
a potential energy of 480 foot-tons per pound, modified gun-
cotton was introduced, with an energy of 716 foot-tons per
pound, and still later there were evolved explosive compounds
of which the potential energy per unit of weight was fourfold
greater than in the case of gunpowder, namely, 1139 foot-tons
per pound. Finally, the explosive has taken the form of
nitro-compounds, which ensure slow burning, great expansion,
and, consequently, augmented propelling power behind the
projectile, without material addition to the maximum strain
upon the weapon. But in any case the constructional strength