Ironclads and Gunboats
This wonderful photograph, captioned "The 38 ton gun and the 7lbr Abysinnian gun", taken in the north court of the Armstrong gun factory, sums up the applications of ordnance in the mid-1870s. The power of the Ironclad, and the range of the Gunboat, were both decisive in the later nineteenth century. The small bronze Naval-service gun (1) was probably made in the Brass Foundry, the large gun was made in the building in the background.
The story really started about a quarter of a century earlier. HMS Pallas (on the right) was built at Woolwich Dockyard in 1865. An ironclad screw-driven steamship, she shows two distinctive features; the form of a ram at the bow, and a forward-facing armoured central battery. She usefully represents the transition between the broadside-firing, square rigged sailships that the Navy had used from the time of the Henri, and the deck-mounted revolving turrets of the all-steam battleships that we are more familiar with.
The Crimean War of 1854-1856 first proved the worth of armouring ships. Sailing ships were used in this war by the British and French to bombard Russian fortifications. France then decided to build a sea-going ship, the Gloire, completely armoured with wrought-iron plates. Britain responded to this Naval challenge by building HMS Warrior. It was the American civil war that conclusively proved how useless the older type cannon were against this type of ship; the old round cannonballs would simply bounce off the hulls.
Major (later Sir William) Palliser of the 18th Hussars developed an iron shell at the Arsenal with a hardened head that could penetrate the thick wrought iron and timber armour used at the time. As armour became thicker, guns became more powerful. Improvements in steam engines allowed the Navy to dispense with sail power altogether, and with the masts gone, the new large guns could be mounted in revolving turrets on the deck.
The Woolwich 38 ton guns mounted in HMS Thunderer on the left were protected by thick armour at the sides (but not overhead). At this stage still muzzle-loading, they had short stubby barrels that allowed them to be reloaded inside the turret. The accuracy that longer barrels would give could only be achieved with breech-loading weapons. When a gun exploded in practice on the Thunderer in 1879, tests at the Arsenal proved that this had been caused by accidental double-shotting. As this could not happen with breech-loading guns, the end of the old muzzle loaders was signalled.
The composite screw steel gunboat Dwarf [NMM photo] was built at the Dockyard in 1867. One of the last vessels built here, she followed a line of steam ships built at Woolwich from 1831 onwards. The steam engine factory in the dockyard, built in 1839 (when the Arsenal's Brass Foundry was still using horses to power the lathes), was of national importance.
Fragments of the 38-ton gun reassembled at Woolwich
Until the age of steam, the heavy fire power of warships was restricted to coastal regions. Initially, steam tugs were used to tow warships into inland waters, but the shallow-draught, steam powered gunboat was soon developed. The power of British imperialism could now reach into the heart of Asia. The Chinese (opium) and Burmese wars of the nineteenth century demonstrated the power of the steam gunboat. Together with the breech-loading rifle and quinine prophlaxis, it was a tool of empire that would enable the "Scramble for Africa" and the establishment of a British empire that covered a quarter of the globe.

(1) The 7lbr bronze Mk II 200lb "Abysinnian Gun" for Naval Service had a Land Service equivalent in the 7lbr steel Mk III. The Land Service gun was 50lbs lighter [PFS]

The Arsenal's big guns in the Victorian period
16" Mk I 81 tons From 1878. Used aboard H.M.S. Inflexible.
12.5" Mk I 38 tons From 1875. Used aboard H.M.S. Dreadnought, H.M.S. Agamemnon, & H.M.S. Ajax. Used by the Army as a Coastal Defence Gun.
12" Mk I&II 35/25 tons From 1870. Used aboard H.M.S. Monarch, H.M.S. Captain, H.M.S. Glatton, H.M.S. Hotspur, H.M.S. Devastation, H.M.S. Thunderer, H.M.S. Neptune, H.M.S. Belleisle & H.M.S. Orion..
11" Mk II 25 tons From 1867. Used aboard H.M.S. Alexandra & H.M.S. Temeraire. Used by the Army as a Coastal Defence Gun.
10" Mk II 18 tons From 1868. Used aboard H.M.S. Sultan, H.M.S. Hercules, H.M.S. Alexandra, H.M.S. Temeraire, H.M.S. Superb, H.M.S. Cerebus, H.M.S. Magdala, H.M.S. Abyssinia, H.M.S. Rupert, H.M.S. Cyclops, H.M.S. Gorgon, H.M.S. Hecate, H.M.S. Hydra, H.M.S. Shannon, H.M.S. Nelson, & H.M.S. Northumberland. Used by the Army as a Coastal Defence Gun.
9" Mk IV ~12 tons From 1865. Used aboard H.M.S. Achilles, H.M.S. Minotaur, H.M.S. Agincourt, H.M.S. Northumberland, H.M.S. Prince Consort, H.M.S. Royal Alfred, H.M.S. Lord Clyde, H.M.S. Lord Warden, H.M.S. Bellerophon, H.M.S. Audacious, H.M.S. Invincible, H.M.S. Iron Duke, H.M.S. Vanguard, H.M.S. Sultan, H.M.S. Swiftsure, H.M.S. Triumph, H.M.S. Hercules, H.M.S. Royal Sovereign, H.M.S. Prince Albert, H.M.S. Scorpion, H.M.S. Wivern, H.M.S. Neptune, H.M.S. Shannon, H.M.S. Nelson, & H.M.S. Northumberland. Used by the Army as a Coastal Defence Gun at Cliffe Fort (Thames) & Plymouth.