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    Re: Sumner's Line (Navigation question)
    From: Bill B
    Date: 2006 Feb 9, 20:40 -0500

    Ken wrote:
    
    > But someone made it (perhaps only for dramatic effect), so
    > I still want to pursue it a little further.  Several posts agreed that it
    > was not perilous since he was 31 min west of his DR, etc..  But, has
    > everyone missed this, as my reading puts him 31.8min EAST (or closer to The
    > Smalls light, and the rocks), or am I wrong?  Is it reasonable to make a
    > case that being closer than he thought was courting disaster had he not
    > discovered the LOP?
    
    Not George, but here is my two cents worth:
    
    It is a tough read, and I find it somewhat ambiguous.  Printed out the chart
    from Bowditch so I could play with it.  My measurements put his 10am DR
    approx. 41' longitude west of Small's light. What is shown as the 10am DR is
    indeed 40nm from Tusker light, and roughly 27+nm from Small's light as the
    crow flies.  The text does state that the time sight put him 15' longitude,
    or 9 miles further east than his DR, so his sight put him 31' longitude west
    (approx 19nm) of Small's light. (My comfort level would definitely be
    decreased by the time sight.)
    
    Further, it is difficult for me to tell exactly how much ground he covered
    after his 10 AM sight until the elapsed time stated to complete the leg to
    the light.  While the line of position may have become clear at "once" (once
    the calculations were done), how long did it take to make them?  All I can
    tell for sure from the account is that "...the ship was kept on her course,
    ENE,..."  So I presume she was sailing ENE after the sight and while
    calculations were being made.  Once the LOP was clear, she then made the
    light in less than an hour.
    
    Unfortunately there is not enough information in this account to do time
    time/speed/distance calculations, but a SWAG says they didn't cover 27+ nm
    in the time it took to do the calculations, plus less than an hour more of
    sailing.
    
    From the account, and the SWAG, it would appear that Ken's reasoning is
    headed in the right direction.
    
    Bill
    
    
    

       
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