I am trying to track down the title of a children's series shown on British TV in the late 60s/early 70s.
As memory serves i recall it being a sort of spy/secret agent series set during the Napoleonic war, there were two stories, one was centered on the French developing an airship, and the other they were developing an early submersible.
OK then, I can put you out of your misery, but only to a degree. I do not, alas, know the name or anything much else about this series, but I do remember it, so it definately happened. The only useful bits that remain in my mind were sequences involving the submarine, and the idea that the scientist behind it was the American, Robert Fulton, who really was a submarine pioneer and really did interest the French in building submarines during the Napoleonic period.
I don't recall anything at all about an airship - which is odd as I am a bit enthusiastic about airships generally - but it would make sense as France was very much to the forefront of lighter-than-air development at the time.
I've started doing a bit of research but nothing yet; it may be impossible to get a result as getting info on childrens tv of that period is always a bloody pain.
I don't know why I didn't think of this the first time - I just now thought of putting in 'Robert Fulton' as a character name in the IMDB search and the result gives me "TRITON" a BBC series from 1968 which fits the description very well if not perfectly. Perhaps a little later than I had imagined myself, but nevertheless probably correct.
However ... and isn't it always exciting when there's a 'however'... when doing a bit of googling to see if there was more about this I discovered that there had been a previous version of this story done by the BBC in 1961! Which is why I remember it as being older.
This does rather show up alarming defects in the IMDB search which had *not* given me both instances of 'Robert Fulton' as a character name in the first search. If you simply use the title - TRITON - both versions appear.
(I am guessing that they changed the name of Fulton's actual experimental submarine built for Napoleon from 'Nautilus' to 'Triton' to avoid confusion with the Verne usage.)
Anyway, my prodding around revealed that the 1968 version had a sequel, 'PEGASUS', with the same characters including Fulton, and this time featured an experimental balloon or primitive airship, which handily answers the other part of the original question.
The bad news is that none of this survives - a shame, I'd pay money to see it.