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Often considered the prototypes of the modern cruiser, HMS Iris and Mercury were speedy avisos with steel hulls and a few breech-loading guns. The first steel-hulled ships in the Royal Navy, they sported an advanced steam plant for the day, consisting of twelve Scotch boilers. Two-shaft horizontal compound engines delivered 7,700 hp for a speed of 17.7 knots, dazzling for the 1870s; the machinery occupied an unprecedented amount of the ships' interiors. They were made with a double bottom and comparatively advanced watertight subdivision.
Both sisters were constructed at the Royal Pembroke Dockyard; as befit their purpose as messengers, they carried a broadside armament of 6-inchers and no armor to slow them down. Mercury was distinguishable from her sister by her plumb stem; Iris had a clipper bow and so was 15 feet longer over all (330 vs. 315 feet). Completed with a light barquentine rig, largely for reasons of fuel economy, these two ships were essential components of the Portsmouth Reserve fleet for more than 20 years, also serving in China waters in the Nineties. Mercury began a long and honored semi-retirement in 1903, serving as instructional and depot ship through the end of WWI. Iris was hulked finished her career serving for two years as a tender to the stationary training ship St. Vincent, a wooden-walled three-decked launched in 1815. She was sold for scrapping in 1905 along with the St. Vincent, as part of Jackie Fisher's sweeping modernization of the Royal Navy.
For a dramatic cutaway view of the Mercury, click here.
Specifications for the Iris class:
Dimensions: 333' OA x 46'x 22' Displacement: 3,730 tons. Crew: 278. Armament (1882): (2) 64-pdr, (4) 6"/26 Mk II BLR, (4) 5" BLR. Fuel capacity: 780 tons coal. Propulsion: 12 coal-fired boilers: 4 cylindrical and 8 oval; (2) Maudslay horizontal compound engines developing 7,330 ihp; twin screw. Sail rig: 3-mast barquentine. Speed: 17.7 kts. Crew: 275. Cost: £234,860.NOTE: These ships were widely admired in the service and were rearmed three times during their active duty years.
Metric specs:
Dimensions: 101m OA x 14m x 6.7m . Displacement: 3,730 tons. Crew: 278. Armament (1882): (2) 29-kg, (4) 152 mm/26 Mk II BLR, (4) 127 mm BLR. Fuel capacity: 780 tons coal. Propulsion: 12 coal-fired boilers: 4 cylindrical and 8 oval; (2) Maudslay horizontal compound engines developing 9.8 mW; twin screw. Sail rig: 3-mast barquentine. Speed: 32.8 km/hr. Crew: 275. Cost: £234,860.
The source of their blinding speed: twin horizontal compound engines delivering 7,300 hp. Horizontal mounting was used to keep all the machinery below the waterline, safe from enemy shellfire. This resulted in the staggered positioning and the port shaft being much shorter than the starboard. Textured craquelure along sides indicates coal bunkers.
In the 1890s both ships appeared with reduced rig: Mercury with bowsprit removed and no yards crossed, but with gaff mainsail furled to the mast.
Leander and the four ships of her class were pioneering protected cruisers: speedy warships with steel hulls and breech-loading guns. Completed with a light barquentine rig, they were closely modeled on the dispatch vessels Iris and Mercury (1879). Amphion was built at the Royal Pembroke Dockyard, while the remaining three of the class were constructed at Napier's in Glasgow. Somewhat burlier fighting ships than the Irises, the Leanders combined greater coal storage and moderate armor protection (3" belt, 1-1.5" deck) with a still-impressive service speed of 16.5 knots.
Having an armor belt on the hull classified these ships among the first belted cruisers, while the internal armored deck protecting the ships' vitals was uniformly adopted for light cruisers in the Royal Navy and its many imitators, creating the protected cruiser type of which the Leander is considered the prototype. As with the Iris class as modified soon after commissioning, the main armament was ten 6-inch BL guns, fitted with 1½" armored splinter shields to protect the gun crews. Their sail rig -- somewhat lighter than the Irises -- was removed in the late 1890s. These were among the last Royal Navy vessels to be fitted with a full sail rig. The vessels' endurance under steam alone was an impressive 11,000 miles at 10 kts. Leander lasted until 1920, while Amphion survived until 1947, much of that time as a hulk.
Specifications for the Leander class:
Dimensions: 315' long OA x 44' beam x 19'7" draft. Displacement: 4,300 tons. Armament: (10) Mk II 6"/26 cal BLR, (8) 1" Nordenfeldt, (2) 5-barrel and (2) 2-barrel 0.45" Gardner MG; 7-pdr and 9-pdr boat and field guns for landing parties; (4) 14" TT. The ships also carried two second-class TBs. Armor: 3" belt; 1½"/1" deck, shields. Coal capacity: 750 tons normal; 1,000 tons maximum. Propulsion: 12 coal-fired cylindrical boilers providing steam at 85.35 psi; (2) horizontal compound engines developing 5,574.88 ihp; twin screw. Sail rig: 3-mast barquentine. Speed: 18.7 kts trials, 16.5 kts. service. Endurance: 11,000 nm @ 10 kts. Crew: 278. Mean cost: £193,701.
Ships in class: Leander · Phaėton · Amphion · Arethusa
Metric specs:
Dimensions: 96m x 13.4m x 6m Displacement: 4,300 tons. Armament: (10) Mk II 152 mm/26 cal BLR, (8) 25 mm Nordenfeldt, (2) 5-barrel and (2) 2-barrel 12 mm Gardner MG; 7-pdr and 9-pdr boat and field guns for landing parties; (4) 35 cm TT. The ships also carried two second-class TBs. Armor: 76 mm belt; 38/25 mm deck, shields. Coal capacity: 750 tons normal; 1,000 tons maximum. Propulsion: 12 coal-fired cylindrical boilers providing steam at 588.5 kPa; (2) horizontal compound engines developing 4,157 kW; twin screw. Sail rig: 3-mast barquentine. Speed: 34.6 km/hr trials, 30.6 km/hr service. Endurance: 20,372 km @ 18.5 km/hr. Crew: 278. Mean cost: £193,701.
The performance of the following class of protected cruisers, the Impérieuse and Warspite (launched 1883-84), under sail was so atrocious that after trials their captains advised the Admiralty that the sail rig was so much dead weight. Their lordships conceded the point and replaced the ships' heavy brig rig with a single steel pole mast amidships used to hoist signal flags and lanterns, with an unprotected gun emplacement in the top, an arrangement known as "military rig." With an internal armored deck but no armor belt on the hull, these two ships were classified protected cruisers. Note the moderate tumble-home amidships, a testimony to French influence on the design, with its single shielded 9.2" barbette mounting at either end and on each beam (in the "diamond pattern" universally adopted by French battleships and cruisers through about 1900), plus 6" guns in casemates. With barbettes and tumble-home hulls, these ships reflected a passing trend of the 1880s in the British fleet; their French influence avoided the extremism which made the Marine Nationale Française such a showcase of sculptured freaks.
Specifications for the Impérieuse class:
Dimensions: 315' x 62' x 27'4" Displacement: 4,600 tons. Armament: (4) 9.2" and (6) 6" guns; (6) 14" torpedo tubes. Armor: Deck 3"; barbettes 8"; CT: 9". Propulsion: (2) horizontal compound engines developing 5,000 hp, shafted to twin screw; sail rig: Brig. Speed: 16.75 kts.
Metric specifications:
Dimensions: 96m x 18.9m x 8.33m Displacement: 4,600 tons. Armament: (4) 234 mm and (6) 152 mm guns; (6) 35 cm torpedo tubes. Armor: Deck 76 mm; barbettes 254 mm; CT: 229 mm. Propulsion: (2) horizontal compound engines developing 3,728.5 kW, shafted to twin screw; sail rig: Brig. Speed: 31 km/hr.
Warspite was a familiar feature of the Irish Sea, serving for many years as the guard ship at Queenstown (now Cobh). Later she was converted to a destroyer depot ship. Impérieuse served as flagship of the China Station from 1889-1894, and of the Pacific Fleet from 1896-99. Both were struck off the roster and sent to the breakers post 1905 in First Sea Lord Jackie Fisher's slashing purge of obsolete ships.
The Royal Navy abandoned sail altogether in its next build of cruisers, the Mersey class, launched 1887-89. Seen here is the Chatham-built name ship of the class in a popular print by the Royal Navy's faithful chronicler, W.F. Mitchell. Propelled by the new and reliable triple-expansion engines, these were ordinary-looking steamers with fine lines, counter stern, ram bow, and main guns in shielded single mounts fore and aft. The 6-in secondary armament was mounted in sponsons and along the sides in a disposition similar to that of mid-size French cruisers of the time. The Mersey class combined a sloped, armored deck with a 3" vertical belt, thus expressing elements of both the protected and belted cruiser; they were considered to belong the former category. With a single funnel and little more superstructure than shown in the Leanders, they reverted to a mixed 8" and 6" armament. Although they were regarded as very successful ships, but led unexceptional lives. All four were sold for breaking up around 1905, as part of Lord Fisher's purge of superannuated and obsolescent ships.
Specifications for the Mersey class:
Dimensions: 315' x 46' x 19'6" Displacement: 4,050 tons. Armament: (2) 8"/30 BLR, (10) 6"/26 BLR, (3) 6-pdr QF, and (8) 3-pdr QF guns; (4) 14" TT (2 submerged and 2 above water). Armor: 3" belt, 6" conning tower, 2" shields, 1.5" deck. Fuel capacity: 500 tons of coal normal; 900 tons maximum. Propulsion: (2) 3-cyl vertical triple expansion engines developing 4,500 hp, shafted to twin screw. Speed: 18 kts trials; 15 kts 1903. Mean cost: £210,411.
Ships in class: Mersey · Severn · Thames · Forth
Metric specifications:
Dimensions: 96m x 14m x 5.94m Displacement: 4,050 tons. Armament: (2) 203 mm/30 BLR, (10) 152 mm/26 BLR, (3) 6-pdr QF, and (8) 3-pdr QF guns; (4) 35 cm TT (2 submerged and 2 above water). Armor: 76 mm belt, 156 mm conning tower, 5 cm shields, 38 mm deck. Fuel capacity: 500 tons of coal normal; 900 tons maximum. Propulsion: (2) 3-cyl vertical triple expansion engines developing 3,355.65 kW, shafted to twin screw. Speed: 33.3 km/hr trials; 27.8 km/hr 1903. Mean cost: £210,411.
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