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George,

The Nautical Day, 24 hours early than the Astronomical Day, was long
established and of general application -- at least in the
English-speaking world. (Smyth, for example, treated it as an
established fact, without reservations or caveats.) I'm not sure when it
entirely ended. I have a vague memory that it was still used in the
grain trade (under sail) in the 1930s, though I would be pushed to find
a reference to that.

My guess would be that mariners have been counting time noon-to-noon
since Medieval times and that they named the day by the civil day on
which they wrote up their log. Astronomers developed a different
tradition. Once mariners needed almanacs, they just had to learn to
allow for the difference in naming of the same day, until both changed
to the civil day in the 20th century.

I doubt that anyone really troubled over the extra complexity. It would
have been one of those things that a trained professional would do
without needing to think and yet would make the craft of navigation a
closed book to amateur pretenders -- a distinguishing mark that the
initiates would be very reluctant to give up.


Trevor Kenchington


You wrote:

> I had dismissed the Nautical Day as something of an early American
> aberration, but Scoresby has shown me that view was wrong.
>
> So why on Earth would mariners use yet another timescale, differing from
> both civil time and astronomical time? Were some almanacs, perhaps, printed
> with Nautical Time as their argument? How prevalent was this use of
> Nautical Time, how far back did it go, when in practice did it end? Was it
> common within the whaling community generally?


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Trevor J. Kenchington PhD                         Gadus@iStar.ca
Gadus Associates,                                 Office(902) 889-9250
R.R.#1, Musquodoboit Harbour,                     Fax   (902) 889-9251
Nova Scotia  B0J 2L0, CANADA                      Home  (902) 889-3555

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