Andrew passed on a question from the rec.arts.sf.written newsgroup about the use of dreadnought in His Majesty's Dragon: this is not actually hinting at any historical change; HMS Temeraire, the ship Laurence names Temeraire after, was a member of the Dreadnought/Neptune class of ships (of which the contemporary HMS Dreadnought, predecessor of the more famous WWI-era ship, was also a member). I used this excuse to cheat and use the term a bit anachronistically here because the more historically accurate description, "second-rate," reads so completely wrong to a modern reader -- I of course did not want to convey the idea that Laurence was naming his dragon after some sort of inferior ship!

One of the best online references about ships, Houghton-Mifflin's Ships of the World: An Historical Encyclopedia, is no longer freely accessible, I'm sorry to say, but you can still take a peek at the entry for HMS Temeraire at the Wayback Machine.