1 The six divisions into which warships of almost all sailing navies were grouped according to the number of guns carried. The system was introduced in Britain by Anson during his first term as First Lord of the Admiralty between 1751 and 1756, but some naval writers have antedated it for the sake of convenience in describing earlier warships. For example, HMS Resolution, launched in 1610, is frequently described as a first rate of 80 guns, meaning that she was one of the largest ships of her time in the British Navy and could therefore be considered a first rate. Later, first-rate ships were those that carried from 100 or 110 guns upwards, the change from 100 to 110 coming in 1810. Second rates carried from 84 (later 90) to 100 (110); third rates 70 (80); fourth rates 50 (60) to 79 (80); fifth rates 32 to 50 (60); and sixth rates, any number of guns up to 32 if commanded by a post-captain. Such ships when commanded by a commander were rated as sloops. Only ships of the first three rates were considered to be sufficiently powerful to be in the line of battle in actions between main fleets. Ships of the fifth and sixth rates were generally known as frigates; fourth-rate ships, of which very few were built, did not lie in the line of battle, except occasionally in the smaller fleets. It was not until 1817 that carronades, first introduced into the Royal Navy in 1779, were included in the number of guns which decided the rating of a ship.
2 The rate, or rating, used to describe a seaman in a warship, but more accurately the status of seamen, corresponding to rank with officers. Men hold rates according to their abilities, the normal chain of lower-deck promotion in the British Navy being ordinary seaman, able seaman, leading seaman, petty officer, chief petty officer, with similar steps in most other navies.