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    Re: David Thompson's Navigational Technique
    From: Bruce Stark
    Date: 2004 May 31, 18:33 EDT
    Thanks, Fred.

    You say:
    "Yes indeed, the famous error that Bowditch took much credit for
    correcting (and still takes, 203 years later!).

    BTW, I wonder if someone could refresh our memories on Bowditch's
    contribution to methods of clearing the lunar distance.  Was he one of
    the first to present an "approximate" method such as Frank Reed
    recently described?"

    As to Bowditch's contribution, it was in devising the first "approximate" method of clearing that was easy to learn and easy to use without making a blunder. Approximate methods had been around a long time, and had been improved and revised over the years. But the rules were complicated. Ken Muldrew recently gave the version of Witchel printed in Moore. I didn't bother to read through it because it's probably still in my memory—somewhere. It was one of the methods I was using a quarter century ago. Anyway, if you've read through it you'll see how easy it would be to take the wrong road at one of the forks, and subtract rather than add, or vice-versa. Also, Bowdich understood how much easier it is to add than subtract, and worked out ways to make everything additive.

    Bowditch himself made no overblown claims as to his lunar method. Other Americans did.

    Like practically everyone else, Bowditch felt it was in his interest to point out the failings of his competitors, and Moore was the standard of the time. Moore had combined his own tried and true dead reckoning and piloting manual with Maskelyne's Requisite Tables. Just about everything a navigator needed was put into one convenient book. It was a success.

    There were no international laws against "pirating," so the "New Practical Navigator" was printed and sold by publishers outside England. In an effort to control this, Moore had a copperplate of himself put in his book. This would be hard to counterfeit. But apparently the copperplate didn't solve the problem. I've seen five or six "Moores." As I recall, one was without the picture and, though the others had pictures, only two pictures were identical. Can you imagine what a printer, with his focus on the bottom line, setting up print the way they had to in those days, would have done to something like a navigation manual? Especially the tables?

    Well, that's what happened, and Moore took the hit. This isn't to say the "true" Moore didn't have plenty of errors. But it served mariners well.

    The American publisher, Blunt, was more responsible than the other "pirates." Instead of adding errors, he did his best to get rid of them. That's where Bowditch (and others) came in. As I recall, most of the errors Bowditch found had to do with the difference of rounding down from eight or ten places instead of five or six and would, as he himself pointed out, be of no consequence in practical navigation.

    There has been a lot of chauvinistic puffery about Bowditch. But I don't believe he had any part in it. In any event, the puffery shouldn't obscure the fact that his "Navigator" was top notch. Bowdich deserves all the credit he got. It's just that he sometimes gets credit for the wrong reasons.

    I'm no historian. These remarks are dependent on a perhaps faulty recollection of the view I picked up years ago, reading the old navigation manuals. Perhaps others will look into the history more carefully.

    Bruce







       
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