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From: Frank Reed (no email)
Date: Wed Apr 19 2006 - 08:22:11 EDT
Hello Jan K.
It is wonderful to see you again. How long has it been... a year... two??
You wrote:
"Nevertheless, Thomson's table was unique by its small steps and in the
consequence, by many thousands of calculations that were needed for constructing
it. One secret remains - how Thomson could find time for calculating it
throughout his life of a mainline mate and later the captain of the brig?"
As you know, many similar tables existed but Thomson's were the most
extensive. Thomson's were unique for including thousands of entries which saved the
sea-going navigator the effort of interpolation. But that means only that the
creator of the tables had to do the interpolation himself, or hire someone
to do it. He didn't necessarily have to do each calculation from scratch
(though he could have if time permitted).
And you wrote:
"Thomson's method was the FIRST Bowditch's method in his first editions.
Only later Bowditch moved his own (first) method from the appendix into the main
text and made it the chief lunar method in his compendium."
That's not quite right. I think if you check your own postings on this
matter from a few years back you'll find that you had it right back then.
Thomson's method was the last of the four added to the Navigator (it was listed as
method #2 from 1837 to 1880). It appeared first in the edition of 1837 --the
year before N. Bowditch died. It's interesting to note that prior to this, in
1826, Bowditch had extended his own Table XX to include the effect of the
"quadratic cross-term" which is the only real extension in Thomson's tables. It's
a minor thing, but it does help in some cases. Unlike Thomson's, Bowditch's
version was a brief table with rather large steps so interpolation would
often be required.
And you wrote:
"I tried to download Zach's article on Thomson' table from the adress that
Frank hints at, but I got the paper from the year 1830, not 1829 I asked"
I can send you a copy. It's a brief note.
I'll say again, it's wonderful to see you posting here.
-FER
42.0N 87.7W, or 41.4N 72.1W.
www.HistoricalAtlas.com/lunars
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