The Diadem class cruiser was a class

Ship class

A ship class is a group of ships of a similar design. This is distinct from a ship-type, which might reflect a similarity of tonnage or intended use. For example, the is a nuclear aircraft carrier of the Nimitz class....

 of "First-Class" protected cruiser

Protected cruiser

The protected cruiser is a type of naval cruiser of the late 19th century, so known because its armoured deck offered protection for vital machine spaces from shrapnel caused by exploding shells above...

 built for the Royal Navy

Royal Navy

The Royal Navy is the naval warfare service branch of the British Armed Forces. Founded in the 16th century, it is the oldest service branch and is known as the Senior Service...

 during the 1890s that served in the First World War. The class consisted of eight ships, built at a cost of around £600,000 each.

They were considered "good sea boats" but criticised for their lack of a heavy calibre main armament, bulky unprotected sides, average speed and lack of manoeuvrability despite being considered large ships when completed. They were the last British first class protected cruisers; the armoured cruiser taking the large cruiser role in future."Diadem class at worldwar1.co.uk

Design

The Diadems were designed by Sir William White

William Henry White

Sir William Henry White was a prolific British warship designer and Chief Constructor at the Admiralty....

, and are typical of British design practice of the period, with high freeboard (by the standards of the time) and the use of 'double-decker' casemates, with the hull forward and aft cut away to allow fore and aft fire from the casemate guns. Casemates provided good protection for the guns and allowed a large number of guns to bear on the broadside; however, the lower (main deck) guns were almost unusable in heavy seas.Brown, p.136

According to a contemporary (1900) edition of Jane's Fighting Ships:

• Hulls were wood sheathed and coppered.
• "There are coal bunkers on the lower deck, and above and below the armour deck. The pair of 6 in guns forward and aft are served by one hoist to the pair, each casemate has its own hoist: those to the double casemates being double. The machinery weighs 1630 tons: the boilers occupy a space of about 132 feet (40 m). Working pressure is [300 to 250 psi (2.1 to 1.7 MPa
  MPA
  -Academic degrees:* Master of Professional Accountancy* Master of Public Administration* Master of Public Affairs* Master of Physician's Assistant-Chemicals:* Medroxyprogesterone acetate, also known by the brand name Depo-Provera* Morpholide of pelargonic acid...
  
  )].

• "The ships are almost absolutely identical in appearance. The Diadem and Andromeda have no steam pipes abaft the first two funnels, while all the others have steam pipes before and abaft each funnel."

History

The Diadem class was intended, like the preceding Powerful class

Powerful class cruiser

The Powerful class were first-class protected cruisers built for the British Royal Navy in the 1890s. There were two ships in the Powerful class, the lead ship Powerful and the Terrible.-Design:...

, for trade protection, and were intended to be "capable of dealing with any cruiser existing or building". The Powerfuls had proved costly and demanding in manpower, and the new class had to represent a more economical solution, that could be built and operated in greater numbers. To achieve this, the specification was reduced relative to the Powerfuls: power and speed were reduced from 25,000 ihp

IHP

IHP is a three letter acronym that can stand for:*International Hydrological Programme*Indicated horsepower*Innovations for High Performance Microelectronics, a German institute and part of the Gottfried Wilhelm Leibniz Scientific Community...

 (22 knots) to 16,500 ihp (about 20 knots), the thickness of the protective deck reduced from 6 to 4 inches (101.6 mm), and the armament simplified by replacing the single 9.2 inches (234 mm) guns fore and aft with pairs of 6 inches (152 mm) guns, mounted side by side.Conway's, 1860-1905, p.68 These changes saved about £100,000 per ship (approximately 15%) relative to the Powerful design.

With eight ships, each of 11,000 tons and costing £600,000, the Diadems were an important class. However, they proved controversial. The naval journalist Fred Jane characterised them as "much-discussed" and complained that "all the weak points of the Powerfuls were exaggerated in them".Jane, The British Battlefleet, p. 284 In particular, contemporary critics raised objections to their indifferent speed, poor manoeuvrability, and lack of heavy guns, and the fact that, while most of the armament was well protected in casemates, the fore and aft pairs of guns, which commanded the greatest fields of fire, were protected only by gunshields.worldwar1.co.uk; Conway's, 1860-1905, p.68

Although the powerplant used Belleville boilers, which were of the then-new water-tube

Water-tube boiler

A water tube boiler is a type of boiler in which water circulates in tubes heated externally by the fire. Fuel is burned inside the furnace, creating hot gas which heats water in the steam-generating tubes...

 type, most of the ships enjoyed the reputation of good steamers; the exception was Niobe, whose engines gave persistent trouble. The first four ships were troubled by vibration; to remedy this, the engine rooms of the last four was rearranged; the new configuration also provided a 1500 hp increase in power.Brown, op cit All eight ships exceeded their design power on trials (for details, see below); the first four averaged 20.5 knots (40.2 km/h) in service, the later four 21 knots (41 km/h).

In general the Diadems served most of their careers in home waters, although there were some deployments to China Station

China Station

The China Station was a historical formation of the British Royal Navy. It was formally the units and establishments responsible to the Commander-in-Chief, China....

, the Mediterranean and the Caribbean

Caribbean

The Caribbean is a crescent-shaped group of islands more than 2,000 miles long separating the Gulf of Mexico and the Caribbean Sea, to the west and south, from the Atlantic Ocean, to the east and north...

. Niobe was sold to Canada

Canada

Canada is a North American country consisting of ten provinces and three territories. Located in the northern part of the continent, it extends from the Atlantic Ocean in the east to the Pacific Ocean in the west, and northward into the Arctic Ocean...

 in 1910. After 1906, they were only occasionally in commission, and by 1914 the class had for the most part been relegated to training ship and depot ship duties. However, with the outbreak of the First World War, several of them were reactivated, initially for patrol duties with the 9th Cruiser Squadron in the Eastern Atlantic. In 1917 Amphitrite and Ariadne were converted into minelayer

Minelayer

Minelaying is the act of deploying explosive mines. Historically this has been carried out by ships, submarines and aircraft. Additionally, since World War I the term minelayer refers specifically to a naval ship used for deploying naval mines...

s, for service with the Dover Patrol

Dover Patrol

The Dover Patrol was a Royal Navy command of the First World War, notable for its involvement in the Zeebrugge Raid on 22 April 1918. The Dover Patrol formed a discrete unit of the Royal Navy based at Dover and Dunkirk for the duration of the First World War...

. Ariadne was the only war loss, being torpedoed by the German submarine UC-65 on 26 July 1917. By the end of the war the survivors had again been withdrawn from active service, and all of them had been sold for scrap by 1932, with the exception of Andromeda, which served as a boys’ training ship until 1956.Conway's, 1906-1921, p.10

Building Programme

Standard British practice at that time was for building costs to exclude armament and stores.Brassey's Naval Annual (BNA)

Brassey's Naval Annual

The Naval Annual was a book that sought to bring together a large amount of information on naval subjects, which had hitherto been obtainable only by consulting numerous publications and chiefly from foreign sources...

 gave costs for these ships that were on average £25,600 greater in the 1904 and 1905 editions than in the 1906 and subsequent editions. Brassey's Naval Annual 1914 (p200) only lists two of the Diadems and quotes the same cost as the 1906 edition. Niobe is listed under Canada (page 207) but no cost is given.

Ship	Builder	Date of			Cost according to
		Laid Down	Launch	Completion	(BNA Brassey's Naval Annual The Naval Annual was a book that sought to bring together a large amount of information on naval subjects, which had hitherto been obtainable only by consulting numerous publications and chiefly from foreign sources...  1904 & 1905)	(BNA 1906)
Diadem HMS Diadem (1896) HMS Diadem was the lead ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Fairfield Shipbuilding & Engineering Co Ltd, Govan and launched on 21 October 1896. She served in the First World War with her sisters. In 1914 she was a stokers' training ship, and was...	Fairfield, Govan Govan Govan is a district and former burgh now part of southwest City of Glasgow, Scotland. It is situated west of Glasgow city centre, on the south bank of the River Clyde, opposite the mouth of the River Kelvin and the district of Partick....	23 Jan 1896	21 Oct 1896	19 July 1898	£582,662	£554,863
Amphitrite HMS Amphitrite (1898) HMS Amphitrite was a ship of the Diadem-class of protected cruisers in the Royal Navy. She was built at Vickers Limited, Barrow in Furness and launched on 5 January 1898. She served in the First World War with her sisters. In 1914 she was part of the Ninth Cruiser Squadron, serving in the Atlantic...	Vickers, Barrow	8 Dec 1896	5 Jan 1898	17 Sep 1901	£575,300	£552,795
Andromeda HMS Andromeda (1897) HMS Andromeda was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Pembroke Dockyard and launched on 5 January 1898. In 1913 she was converted to a training ship and renamed Powerful II on 23 September 1913...	Pembroke Dockyard	2 Dec 1895	30 Apr 1897	5 Sep 1899	£601,356	£574,916
Argonaut HMS Argonaut (1898) HMS Argonaut was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built by Fairfield Shipbuilding and Engineering Company, Govan and launched on 24 January 1898....	Fairfield, Govan Govan Govan is a district and former burgh now part of southwest City of Glasgow, Scotland. It is situated west of Glasgow city centre, on the south bank of the River Clyde, opposite the mouth of the River Kelvin and the district of Partick....	23 Nov 1896	24 Jan 1898	19 Apr 1900	£573,704	£545,756
Ariadne HMS Ariadne (1898) HMS Ariadne was a Diadem-class protected cruiser of the Royal Navy. She was built by J&G Thompson of Clydebank and launched on 22 April 1898. In March 1913, she was converted to a stokers' training ship and in 1917 was converted to a minelayer and assigned to the Nore Command...	J&G Thompson John Brown & Company John Brown and Company of Clydebank was a pre-eminent Scottish marine engineering and shipbuilding firm, responsible for building many notable and world-famous ships, such as the , the , the , the , the , and the... , Clydebank Clydebank Clydebank is a town in West Dunbartonshire, in the Central Lowlands of Scotland. Situated on the north bank of the River Clyde, Clydebank borders Dumbarton, the town with which it was combined to form West Dunbartonshire, as well as the town of Milngavie in East Dunbartonshire, and the Yoker and...	29 Oct 1896	22 Apr 1898	5 Jun 1902	£565,464	£541,927
Europa HMS Europa (1897) HMS Europa was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built by J&G Thompson, of Clydebank and launched on 20 March 1897...	J&G Thompson John Brown & Company John Brown and Company of Clydebank was a pre-eminent Scottish marine engineering and shipbuilding firm, responsible for building many notable and world-famous ships, such as the , the , the , the , the , and the... , Clydebank Clydebank Clydebank is a town in West Dunbartonshire, in the Central Lowlands of Scotland. Situated on the north bank of the River Clyde, Clydebank borders Dumbarton, the town with which it was combined to form West Dunbartonshire, as well as the town of Milngavie in East Dunbartonshire, and the Yoker and...	10 Jan 1896	20 Mar 1897	23 Nov 1899	£589,835	£564,690
Niobe HMS Niobe (1897) HMS Niobe was a ship of the Diadem-class of protected cruiser in the Royal Navy. She served in the Boer War and was then given to Canada as the first ship of the then newly-created Royal Canadian Navy as HMCS Niobe. After patrol duties at the beginning of the First World War, she became a depot...	Vickers, Barrow	16 Dec 1895	20 Feb 1897	6 Dec 1898	£574,878	£548,283
Spartiate HMS Spartiate (1898) HMS Spartiate was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Pembroke Dock and launched on October 27, 1898. She was a stokers' training ship in 1914 and was renamed Fisgard in June 1915. She survived the War and was sold in July 1932. She returned to...	Pembroke Dockyard	10 May 1897	27 Oct 1898	17 Mar 1903	£680,188	£654,661

Trials

Ship	Date	8 hours full power natural draught 30 boilers			4 hours forced draught 24 boilers			30 hours natural draught 30 boilers			Source
Diadem HMS Diadem (1896) HMS Diadem was the lead ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Fairfield Shipbuilding & Engineering Co Ltd, Govan and launched on 21 October 1896. She served in the First World War with her sisters. In 1914 she was a stokers' training ship, and was...	1897	17262 ihp	20.65 knots (40.5 km/h)		15861 ihp	19.9 knots (39 km/h)		12791 ihp	19.8 knots (38.8 km/h)		Jane's 1900
Amphitrite HMS Amphitrite (1898) HMS Amphitrite was a ship of the Diadem-class of protected cruisers in the Royal Navy. She was built at Vickers Limited, Barrow in Furness and launched on 5 January 1898. She served in the First World War with her sisters. In 1914 she was part of the Ninth Cruiser Squadron, serving in the Atlantic...	1900	18229 ihp	20.78 knots (40.7 km/h)					13695 ihp	19.5 knots (38.2 km/h)		Jane's 1900
Andromeda HMS Andromeda (1897) HMS Andromeda was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Pembroke Dockyard and launched on 5 January 1898. In 1913 she was converted to a training ship and renamed Powerful II on 23 September 1913...	1898	16751 ihp	20.41 knots (40 km/h)					12621 ihp	19.3 knots (37.8 km/h)		Jane's 1900
Argonaut HMS Argonaut (1898) HMS Argonaut was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built by Fairfield Shipbuilding and Engineering Company, Govan and launched on 24 January 1898....	1899	18894 ihp	21.17 knots (41.5 km/h)					13815 ihp	19.86 knots (38.9 km/h)		Jane's 1900
Ariadne HMS Ariadne (1898) HMS Ariadne was a Diadem-class protected cruiser of the Royal Navy. She was built by J&G Thompson of Clydebank and launched on 22 April 1898. In March 1913, she was converted to a stokers' training ship and in 1917 was converted to a minelayer and assigned to the Nore Command...	1899	19156 ihp	21.5 knots (42.1 km/h)					14046 ihp	20.1 knots (39.4 km/h)		Jane's 1900
Europa HMS Europa (1897) HMS Europa was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built by J&G Thompson, of Clydebank and launched on 20 March 1897...	1898	17137 ihp	20.4 knots (40 km/h)		16298 ihp	19.9 knots (39 km/h)		12739 ihp	19.33 knots (37.9 km/h)		Jane's 1900
Niobe HMS Niobe (1897) HMS Niobe was a ship of the Diadem-class of protected cruiser in the Royal Navy. She served in the Boer War and was then given to Canada as the first ship of the then newly-created Royal Canadian Navy as HMCS Niobe. After patrol duties at the beginning of the First World War, she became a depot...	1898	16834 ihp	20.59 knots (40.4 km/h)		16834 ihp	20.5 knots (40.2 km/h)		12961 ihp	19.27 knots (37.8 km/h)		Jane's 1900
Spartiate HMS Spartiate (1898) HMS Spartiate was a ship of the Diadem-class of protected cruiser in the Royal Navy. She was built at Pembroke Dock and launched on October 27, 1898. She was a stokers' training ship in 1914 and was renamed Fisgard in June 1915. She survived the War and was sold in July 1932. She returned to...

The Diadem (Dec 1898) did a mean of 19.27 knots (37.8 km/h) in a 69 hour run from Gibraltar

Gibraltar

Gibraltar is a British overseas territory located on the southern end of the Iberian Peninsula at the entrance of the Mediterranean. A peninsula with an area of , it has a northern border with Andalusia, Spain. The Rock of Gibraltar is the major landmark of the region...

 to the Nore

Nore

The Nore is a sandbank at the mouth of the Thames Estuary, England. It marks the point where the River Thames meets the North Sea, roughly halfway between Havengore Creek in Essex and Warden Point in Kent....

with 14,268 horsepower (10.64 MW). For 60 hours with 24 boilers with 12,791 ihp (9.538 MW), she made 19.3 knots (37.8 km/h) on trial. Andromeda did a sea trip at 800 ihp = 16 knots (31 km/h).

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