Ship of the line

A ship of the line was one powerful enough to take a place in the line of battle. (The term "battleship" has a similar etymology.) Generally, this meant a 3rd Rate or larger ship, with guns on two or more decks. Rated ships smaller than this were frigates, and carried all their guns on a single upper deck.

Rate	Guns	Men
1st Rate	100 or more	875 to 850
2nd Rate[?]	90 to 98	700 to 750
3rd Rate	64 to 80	500 to 650
4th Rate[?]	50 to 60	320 to 420
5th Rate[?]	32 to 40	200 to 300
6th Rate[?]	20 to 28	140 to 200
Sloops	16 to 18	90 to 125
Gun-Brigs & Cutters	6 to 14	5 to 25

The number of crew on a 1st Rate was increased by 25 when used as an Admiral's flagship, by 20 with a Vice Admiral and 15 with a Rear Admiral.

Originally from http://www.cronab.demon.co.uk/gen1.htm, with the author's permission.