Fred Jane's gun & armour ratings and ship classifications

Further to my recent blog post about the gun and armour ratings used by Fred Jane in the 1898 edition of JANE'S ALL THE WORLD'S FIGHTING SHIPS, here they are in great detail:

Gun ratings

• a: muzzle energy is greater than 20,000 foot/tons*
• b: muzzle energy is between 14,000 and 20,000 foot/tons
• c: muzzle energy is between 6,000 and 14,000 foot/tons
• d: muzzle energy is between 2,000 and 6,000 foot/tons
• e; muzzle energy is between 800 and 2,000 foot/tons
• z: muzzle energy is between 500 and 800 foot/tons
• *: quick-firing guns

* A foot/ton is the energy required to raise a ton (i.e., 2240 pounds) a distance of one foot against the force of gravity.

Armour ratings

• a: equal to 8-inches of Harvey nickel steel armour, 9-inches of Harvey steel armour, 11-inches of compound armour, or 17-inches of iron armour.
• b: almost equal to a; approximately 14-inches of iron armour.
• c: equal to about 5-inches of Harvey nickel steel armour, 6-inches of Harvey steel armour, 9-inches of compound armour, or 12-inches of iron armour.
• d: equal to about 4-inches of Harvey steel armour, 6-inches of compound armour, or 8-inches of iron armour.
• e: thin armour.
• 0: no armour.

Notes on different types of armour

1. Harvey nickel steel armour was Harvey steel armour that had nickel added to it to give it great resilience and strength for any given thickness.
2. Harvey steel armour was steel armour that had its front surface case-hardened using a process developed by the American engineer, Haywood Augustus Harvey. It was manufactured by the Harvey United Steel Company, a cartel owned by the Vickers, Armstrong, Krupp, Schneider, Carnegie, and Bethlehem steel companies.
3. Compound armour was made by combining steel and iron plates. The front plate of the armour was made from a hard but brittle high-carbon steel and the back plate was made from a more elastic low-carbon wrought iron. The front plate was intended to break up an incoming shell, whilst the rear plate was intended to catch any steel splinters and hold the armour together if the front plate was shattered.
4. Iron armour was made from homogenous iron plates, usually backed by a layer of teak. The teak was intended to act as a shock absorber and to reduce effect of iron splinters caused by shell impacts.

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Fred Jane also classified ships in the following way:

I: 1st class. All large modern ironclads.

II: 2nd class. Small modern ironclads, sea-going coast defence ships, old reconstructed ironclads.

III: Modern armoured cruisers.

IV: Old and obsolete ironclads, old armoured cruisers.

V: Coast defence ironclads unable to keep at sea for any period, armoured gunboats.

1: Heavily armed protected cruisers.

2: Protected cruisers with medium armament.

3: Lightly armed protected cruisers.

4: Old cruisers, or cruisers with little or no protection.

5: Coast defence gunboats carrying one or two armour-piercing guns.

6: Older ships with little or very slight fighting value.

X: Rams.

T: Torpedo depot ships, catchers, destroyers etc.

An example of one of the pages from the 1898 edition of JANE'S ALL THE WORLD'S FIGHTING SHIPS. The ship in the top right of this rather poor images is HMS Superb. She is classified as II (a 2nd class, old reconstructed ironclad) with 16D + 6Z + 14* guns and e - e armour. Bottom left is HMS Alexandra, who is likewise classified as II but which has 4c + 8d + 6e + 10* guns and e - d armour.