HMS Iris (1877)
A Greyhound of her time, the Royal Navy’s first steel ship
When writing about the past it’s easy to overlook the importance of achievements that seem unspectacular by today’s standards, overtaken as they are by the march of technology. In their own time however such achievements invoked awe and admiration, and sometimes had significant bearing on the politics or military strategies of the time. Several such technological breakthroughs occurred in the naval sphere in the late nineteenth century – armour, turrets, large calibre guns, torpedoes, come to mind. On some occasions the combination of several major innovations in a single ship resulted in a revolutionary development which established standards for later ships to meet – HMS Warrior in 1860 immediately comes to mind. Another such vessel which is largely forgotten today was of equal significance. This was HMS Iris.
Launched in 1877, HMS Iris was first all-steel ship to serve with the Royal Navy and her speed, 17.89 knots over the measured mile, was the highest attained up to that time. Though usually employed a fast despatch vessel, her armament made her well suited to cruiser duties such as merchant protection and hunting down “corsairs”. The success of the CSS Alabama in the American Civil War had highlighted just how serious such threats could be to a maritime trading nation.
Displacing 3750 tons, this revolutionary vessel was 300 ft. between perpendiculars, with 46 ft. beam and a draught just under 20 feet. The use of steel, in place of the iron previously employed for metal ships, resulted in considerable weight-saving and it was this, combined with her efficient machinery, which secured her high speed. She was propelled by direct-acting, horizontal, compound, four-cylinder Maudslay engines driving twin screws and they produced 7300 Horse Power at 95 rpm. Steam was provided by twelve boilers in two separate boiler rooms. Iris carried no armour but did have a double-bottom, and like many unarmoured vessels of the period coal bunkers located in wing-compartments to either side of the engine room, as can be seen from the plan and cross-section diagrams below. Maximum coal storage was 780 tons, giving an amazing endurance of 6000 nautical miles at 10 knots, or 2000 at full speed. Given this, it is understandable that her barque sailing-rig was removed early in her career. She required a crew of 275, an indication of just how manpower-intensive warships could be at that time.
Note the placement of coal bunkers to give a degree of protection (not much!) against shell-fire
The importance attached to Iris when new was such that The Times newspaper covered her trials, and those of her only sister HMS Mercury, in very considerable detail. Complete with tables and a mass of statistics related to horsepower, boiler pressure, revolutions, speed and propeller design, The Times account, as reprinted in Brassey’s “The British Navy” of 1882, runs to seven closely-printed pages. It is impossible to imagine such detailed coverage being provided in a mass-circulation newspaper to any such developments today.
HMS Iris in drydock at Malta, circa 1880
Iris’s armament consisted of ten 64-pounder muzzle-loaders, four on each broadside and one on a revolving mount at both forecastle and poop. The broadside weapons were carried on the open deck, the only protection being the 3/8” plating of the bulwarks. Soon after completion these antiquated weapons were replaced by four 6” and four 5” breech-loader rifles (BLRs) s and an even more powerful armament was provided in 1886/87 – thirteen 5” BLRs. At the same time Iris, and her close sister Mercury, were classified as second-class cruisers. Iris was sold off in 1905 but Mercury became a submarine depot ship at the same time and survived as a hulk during WW1 up to 1919.
The Iris class, small though it was, played a crucial role not just in cruiser development, but in exploring, and proving, the advantages of steel construction. As such they deserved to be remembered regarded in their own right as being as significant as HMS Warrior in 1860 and HMS Dreadnought in 1905.