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Corallina offered us a useful link to a digitised copy of Norie's Tables of 
1805.

This was an early edition of the famous navigational classic, which was 
often issued as two companion volumes, Norie's Epitome of Navigation (up to 
1900 or so) and Nories Nautical Tables (still in print; last edition was 
2007). They were often bound together in an unwieldy 1000-page volume, 
"Norie's Navigation". Mine is the 1900 edition of the Epitome, bound with a 
1914 edition of the Tables.

Such a copy is likely to cost you £50 or $75, and if you can find one less 
than that, snap it up. Mine was a lucky strike in my local secondhand 
bookshop at £2.50, so it can be done. It contains everything (from its 
period) that you could possibly wish for.

However, Corallina asked about Norie's Nautical Tables for the purpose of 
looking up log trig functions. Bravo!, I say. That is doing the job with 
full authenticity. All the necessary tables are there. We were asked about a 
modern edition. I can only speak for my 1970 edition of the Tables. That 
also contains tables of log trig functions, in a form that's significantly 
less precise (5 decimal places, rather than 6), but has a great advantage 
over earlier editions, in which log trig functions were only tabulated to 
45º. Above that, you had to read off a complementary function , at a 
complementary angle, up from the foot of the page rather than down from the 
top. I have always found this totally confusing. The newer editions have a 
page for each degree up to 90º , which is much more straightforward.

Books of tables used to be very robustly bound, to handle all the multiple 
page-shufflings that they have to put up with. In that respect, my 1970 
edition has been disappointing, as its binding is already giving way 
("shaken", as a bookseller would call it).

Of course, you can always bypass such lookup tables by using a scientific 
calculator or a computer, but it's not that simple. First, you have to 
convert arc-minutes to decimals of a degree, and add them in. Then, many 
computer programs work trig functions, not in degrees but in radians, in 
which case you have to multiply by pi / 180. Then get the trig function, 
such as tan, of that angle. Then take its log (to base 10). The if the 
result is negative, which it often is for log trig functions, convert to 
"nautical logs" convention by adding 10.0  Quite a business. Using a 
calculator, you can simplify the whole thing by calculating directly without 
using logs at all.

George.

contact George Huxtable, at  george@hux.me.uk
or at +44 1865 820222 (from UK, 01865 820222)
or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK. 


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