If you are interested in Hornblower and other Royal Navy stuff, here are some links:

Short History of the 18th c. Royal Navy

18th c. Navy Ranks

Wiki- Naval Officer Ranks

Wiki – Royal Navy

Wiki – Hornblower

The Hornblower Pages

That’ll get you started. “Clicking-thru” and “Googling” will, of course, bring up other interesting history and trivia… 😉