NavList:

Don you wrote:

I am mostly in agreement, but wish to clarify that in the early 19th century navies Master's Mates were not petty officers. They were the most senior of midshipmen and had to demonstrate navigational skills to earn that rating.

I think we’re talking at crossed purposes here.  Certainly, up to the start of 19^th Century, there was a Royal Navy (RN) career stream which went from keen and promising AB, to Master’s Mate, to Boatswain, to Master, and eventually, if desired, and with a lot of luck to Lieutenant. 

Such Master’s Mates had authority over ordinary ABs but did not hold warrants, and so could be promoted and demoted upon the Captains authority alone.  Therefore, the broad Petty Officer bracket seems a very appropriate place to put them and is used by such writers as N.A.M Rodger The Wooden World, Alan Villiers Captain Cook the Seamen’s Seaman, and Rear Admiral C.H. Layman The Wager Disaster. 

There were of course alternative routes.  Cook transferred from a coastal command in the Merchant Service to AB (RN) and within weeks to Master’s Mate in HMS Eagle, (60), Capt Hamer.  Bligh transferred from Midshipman with four years experience HMS Crescent (28) through force of circumstances to AB HMS Ranger and became Master’s Mate after one year.  Some senior Midshipmen took Master’s Mates posts simply because the pay was better.  However, the downside was that the time to an eventual Lieutenancy, if it occurred at all, frequently took longer than the straight Midshipman route.  I don’t believe it was possible to be a Midshipman and a Master’s Mate at the same time because a ship would have a laid down established number for each.  

It would appear from what you say, I’ve not Nordhoff Senior yet, that as the 19th Century progressed the proportion of Passed Midshipmen, i.e. experienced Midshipmen qualified and awaiting a vacancy as a commissioned Lieutenant, who took Master’s Mates posts in order to receive more pay increased.  Such Master’s Mates might well have been accepted as ‘gentlemen’ and have privileges not normally available to many in the broad Petty Officer category.  Over which time period would you say the balance changed, and which would be the best Nordhoff Senior book available at less than $10 to read about it in?  DaveP