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From: George Huxtable (no email)
Date: Sat Sep 11 2004 - 16:04:35 EDT
Gordon Talge wrote, in the thread "Cotter - copy located"
>I have read and have tried to work my way through Cotter
>and have found quite a few errors.
================
If Gordon can identify any errors that don't appear on our website-
www.huxtable.u-net.com/cotter01.htm
Jan and I would be pleased to hear about them.
>
>What I have found is to get a copy of say, "A Complete Epitome
>of Practical Navigation" by J.W. Norie 1840 or so or "The
>Complete Navigator" by Andrew Mackay ( mine is an 1807 American
>rip-off of a British Edition ) Or maybe something by John
>Hamilton Moore's "Practical Navigation" ( mine is 1798 although
>it has several errors and one procedure that is simply wrong ).
>
>My books, although old, are not in pristine condition and really
>did not cost that much, but are very much still readable.
============
I take a similar attitude. Some of my sets of nautical tables are browned
and smell of strong tobacco and coal-dust, and fingerstained in the
most-used pages such as the refraction and dip tables. That doesn't worry
me; indeed it adds some historical charm, as long as the information is all
readable and complete. But I find that nautical tables before, say, 1850,
tend to be pricey now, and outside my buying-range (which is normally well
below $100). I wish I could pick up a copy of a 1798 Moore, as Gordon has.
I'm fortunate, though, to be within striking distance of the Bodleian
Library in Oxford. This was, and still is, a Copyright Library, which
implies that any publisher seeking UK copyright has to send a copy to the
Bod and the four (or so) other copyright libraries, free of charge. As a
result, it has a copy of just about everything ever published in Britain,
though not quite such comprehensive cover of stuff from abroad.
Gordon adds-
>Norie's is very clear, but practical. It does not give you
>formulas for things, but gives you directions in words. So
>instead of sin(x) = sin(y)+ cos(z), it would say "take y
>and z go to table VII or something and extract the sine and
>cosine of x and y. Add the two quantities together and then
>return to table VII and extract the inverse that gives the ..."
>
>To get the formula you have to piece it together from the
>directions.
>
>The trig is done in an entirely different, but equivalent way
>that is kind of neat. Norie also has a section on "Longitude by
>Observation" (Lunar Distance) along with a couple of different
>methods and several examples.
>
>So my idea is get the "who did what when, and what book they wrote
>or what method they used" from Cotter, but get the nitty gritty
>pencil and paper methods from some books like Norie or Mackay, the
>books that the people that actually navigated during that
>period used.
==========
I agree with Gordon's view. The trouble with the old nautical manuals is
that they would give you a recipe, just as Gordon describes. This fulfilled
two purposes-
1. It provided a form of words which you could remember and exactly recite,
parrot-fashion, when being examined for your "ticket".
2. That recipe, deeply embedded into the brain, became a procedure that a
navigator, at sea, could work through exactly, whether he understood it or
not, and then if he made no arithmetical errors he would get the right
answer.
But I think that many Nav-L users, including Gordon and me, have a deeper
interest, in understanding what's behind these directions, and how they
work. Unfortunately, the basic trig. was always thoroughly mangled to put
the equations into a form where logs could be applied (so negative
quantities had to be avoided). It's often quite hard to "reverse engineer"
the procedures to arrive at the underlying trig. This is where Cotter often
comes in useful, in spite of his deficiencies.
If pocket calculators had been available in the 18th century, there would
have been no need to call for logs, and the formulae would have been much
easier to understand. And if only the sexagesimal system had been left with
the Babylonians, and replaced, for angles and times, by decimal quantities,
much of the arithmetic, and the looking-up of tables, could have been
discarded. But then, that's just an old hobby-horse of mine.
George.
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contact George Huxtable by email at , by phone at
01865 820222 (from outside UK, +44 1865 820222), or by mail at 1 Sandy
Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
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