While advances were being made in naval technology, there was remarkable progress in artillery as well, both on land and on the sea. There had been no fundamental changes since the sixteenth century. At the end of the 1850s cannons were still simple muzzle-loaded cast-iron tubes that fired cannonballs. Variations, such as howitzers and carronades, appeared, and even rifling was attempted in the muzzle-loaders. But these innovations did not lead to any dramatic changes. Then in 1858-59 a British artillery committee studied a revolutionary gun design by a British civil engineer, William G. Armstrong. Instead of being cast, the gun was made of steel plates welded around a rifled iron tube; it was breech-loaded and fired a conically shaped shell a distance of some two kilometres with extraordinary accuracy. The shell even had the capacity to pierce a dozen centimetres of armour before exploding. The Armstrong gun was immediately adopted by the British navy and army. 
The appearance of such a powerful weapon significantly influenced the design of warships and fortifications; ship armour and casemates for forts had to be much more elaborate. The last great forts built by the British south of Quebec City between 1865 and 1870 reflected the influence of these new types of guns, because the Americans Thomas Rodman and Robert Parrott had invented similar guns for their army as early as 1861. The new forts were clearly designed to fend off a land attack, because on the sea the Royal Navy remained invincible, having rapidly equipped itself with an impressive fleet of steam-propelled armoured ships against which no country had a chance.