Topaze-class cruiser

HMS Amethyst
Class overview
Operators	Royal Navy
Preceded by	Pelorus class
Succeeded by	Town-class (1910)
Subclasses	Amethyst
Built	1903–1905
In commission	1905–1921
Planned	8
Completed	4
Cancelled	4
Scrapped	4
General characteristics
Class & type	Topaze-class protected cruiser
Displacement	3,000 long tons (3,048 t)
Length	360 ft (109.7 m) (p/p)
Beam	40 ft (12.2 m)
Draught	16 ft (4.9 m)
Installed power	9,800–12,000 ihp (7,300–8,900 kW) 10 water-tube boilers
Propulsion	All except Amethyst: 2 Shafts, 2 triple-expansion steam engines Amethyst: 3 Shafts, steam turbine set
Speed	21–22 knots (39–41 km/h; 24–25 mph)
Complement	318
Armament	12 × QF 4-inch (102 mm) guns 8 × QF 3-pounder (47-mm) guns 2 × 18-inch (450 mm) torpedo tubes
Armour	Deck: 0.75–2 in (19.1–50.8 mm) Gun shields: 1 in (25 mm) Conning tower: 3 in (76 mm)

The Topaze-class cruisers (often referred to as the Gem class) were a quartet of third-class protected cruisers built for the Royal Navy in the first decade of the 20th century (four additional ships of the class were cancelled before their keels were laid). HMS Amethyst of this class was the first warship larger than a destroyer to be powered by turbine engines.

As well as a significant historical 'first' this class also embodied many 'lasts' and, despite being units of the Edwardian-period Royal Navy, represented the end of the Victorian-period lineage of protected cruisers in many ways. Amongst the many cruiser classes of the Royal Navy to have been rated as

Perhaps most significantly of all, the Gems were the very last third-class cruisers to be so rated in the Royal Navy: the following classes of scout cruisers which featured internal protective decks instead of armour belts were of similar type, but were faster & weaker and intended for a very specialist role; they were accordingly assigned their new official type designation. When the later small turbine-propelled cruisers of the Arethusa class appeared (combining the features of scouts & second-class cruisers, to provide for greater utility & fighting power more in line with the Third Class), the new ships were designated from the outset as 'light armoured cruisers, thus dispensing with the third-class rating entirely.

Discussions had been ongoing for several years about a successor to the previous

The first small cruisers designed for the Royal Navy by the new

Amethyst was fitted with a Parsons steam turbine set that drove three shafts using the same number of boilers as her sisters. They delivered enough steam to allow the engines to reach 12,000 ihp (8,900 kW) and her designed speed of 22.5 knots (41.7 km/h; 25.9 mph). She also easily exceeded her designed power and speeds during her sea trials, reaching 23.4 knots (43.3 km/h; 26.9 mph) from 14,300 ihp (10,700 kW). The turbine proved to be more economical at high speeds than the reciprocating engines of her sisters, but less so at slow speeds, only having an endurance of 5,500 nautical miles (10,200 km; 6,300 mi) at 10 knots, but 3,000 nautical miles (5,600 km; 3,500 mi) at 20 knots.^[2]

The main armament of the Topaze class consisted of a dozen

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• Friedman, Norman (2012). British Cruisers of the Victorian Era. Barnsley, South Yorkshire, UK: Seaforth.
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• Friedman, Norman (2011). Naval Weapons of World War One. Barnsley, South Yorkshire, UK: Seaforth.
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• Gardiner, Robert & Gray, Randal, eds. (1985). Conway's All the World's Fighting Ships 1906–1921. Annapolis, Maryland: Naval Institute Press.
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• Viscount Hythe (1912). The Naval Annual 1912. Portsmouth, UK: J Griffin and Co.

Wikimedia Commons has media related to Topaze class cruiser.

• The Topaze or "Gem" class at battleshipscruisers.co.uk