The following is a slightly modified version of a posting I made on the Honor Harrington Discussion Board in March, 1998.

Ships of the Line, Ships of the Wall

The recent discussions about Honor Harrington and Horatio Nelson and the Alliance-Haven War period as compared to the era of the Napoleonic Wars brought another area of comparison to mind: the RMN's Wall of Battle and the RN's Line of Battle, and the ships therein.
I went back to my naval and historical reference books to do a bit of checking, and found an unusual degree of agreement between the different authorities cited, so I decided to put the following chart up for those who might be interested.

Unrated Classes in the old Sail Navies included:
(1) Sloops-of-War (usually 14-22 6-lb guns); either Ship Sloops (3 masts) or Brig Sloops (2 masts)
(2) Brigs-of-War (usually 10-14 6-lb guns); always Brig Sloops
(3) Cutters, Ketches (Bombs), Schooners, and other seagoing sailing warships, often TUCE (Taken Up from Civilian Economy) and modified, rather than purpose-built vessels.
(4) Small Cutters, etc. and gunboats (LACs).
These classifications were apparently in general use for the Royal Navy and the U.S. Navy once it was formed. The number of guns refers to the ship's main broadside armament, its "Great Guns," half of which would be mounted to fire to port and half to starboard. Smaller-calibre guns mounted elsewhere (such as the "fighting tops" of the masts) and chase armament of any size are not counted.

There were two primary requirements for the Royal Navy to call a ship a "Ship of the Line": first it had to be "ship-rigged," i.e., three masts with square sails, and second it had to be commanded by a "Post Captain" (an officer with the official rank of Captain). The RMN seems to follow the same practice with its BCs and CAs.

There were occasional vessels which had as many or more guns than a Sixth Rate ship, but either not commanded by a Post Captain for some reason, or with a different rig.

It is interesting to note that from the middle of the 18th Century, ships of the Fourth Rate and smaller were not considered large or tough enough to stand in the Line of Battle—sounds like the PN's Battleships, doesn't it? Also interesting is the fact that the Royal Navy called the ships of the Fourth through Sixth Rates "cruisers" because they were often assigned to long, independent cruises, especially as convoy escorts.

The famous Royal Navy "frigates" were ships of the Fifth and Sixth Rates—and occasionally a smaller Fourth Rate—who had all their Great Guns mounted on a single deck. Like the RMN's BCs and CAs, they also served as the "eyes of the fleet" and as flags for squadrons of smaller vessels.

My two main sources for the above information were To Shining Sea by Stephen Howarth (Random House, NY; 1991), a history of the U.S. Navy, and A Sea of Words by Dean King with [introductory material by] John B. Hattendorf and J. Worth Estes (Henry Holt & Co., NY; 1995), a companion volume to Patrick O'Brien's Aubrey-Maturin novels.

As a last note, the "KT" above is a corvette—in the RMN's terms, a very small frigate.