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    Re: Sumner's Line (Navigation question)
    From: George Huxtable
    Date: 2006 Feb 11, 22:45 -0000

    On 9 Feb, Ken Gebhart wrote-
    
    "However, it did not answer the second part which asked why disaster was
    averted.  You pointed out that Bowditch did not include that comment which
    is good to know.  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?"
    
    Ken is correct. Sumner says that if he had adopted his DR latitude (which at 51deg 37'N was 8
    minutes South of where his true position eventually turned out to be; not bad going for DR after 600
    miles!) then his calculated longitude would have been too far West by 31 minutes. Or conversely,
    that his ship was actually 31' East, and 8' North, of that calculated position. If anyone said the
    opposite (hope not me ...), they were wrong. Sumner was very conscious of the dangers of his
    reckoning being wrong. He says that at 10 am "... the latitude by D. R. was 51deg 37' North, but
    supposed liable to error of 10 miles either side, N. or S."
    
    But the danger was not that of getting to the Smalls before he expected to. No doubt, he had most of
    the watch-on-deck straining their eyes ahead, to port and starboard, looking for that lighthouse,
    and had been doing so for some hours. The danger was in being off the direct line to the lighthouse,
    so it might pass, out of sight, to one side or the other, and land him in the rocks.
    
    A square-rigged vessel always had the chance to heave-to, or to jill about tacking to and fro, to
    wait for the visibility to improve, and no doubt Sumner was weighing up such a course of action when
    he had his inspiration.
    
    No doubt Ken has, by now, had the chance to raid his own stocks and acquant himself with Sumner's
    actual words, in Vanvaerenbergh and Ifland's book.
    
    By the way, my copy of Bowditch (2vols) in vol.1 (1977) section 131, has a page about Sumner, with
    some quotations, which does NOT include those inauthentic words "The result to the ship might have
    been disasterous had this wrong position been adopted". It must have been (wisely) dropped. I wonder
    when.
    
    That edition of Bowditch, in fig 131, does include a plot of St George's channel, supposedly showing
    Sumner's track, but it differs from Sumner's own plate III in many important details. For example,
    it does not show Sumner's 10 AM position which he marked as- "True position as afterwards proved".
    
    This takes me to Bill's recent mailing. He is clearly peeved at my comments, but I do not retract
    them. Unless he has read Sumner's own account (rather than a precis, with inaccuracies, in Bowditch)
    he is simply unqualified to judge whether "It is a tough read, and I find it somehat ambiguous".
    
    He asks- "My question is, at the time of his 10 AM sighting was his DR position in fact 40 miles
    from Tusker lighthouse, (approximately 51d 32'N on Bowditch's figure 110) in your texts?"
    
    No, not according to Sumner's Plate III. If Bill chose to examine Sumner's own account, he would
    likely answer his own questions.
    
    Bill concludes-
    "If you are frustrated that I have not had the time to read all the history books to date--well so I
    am."
    
    If Bill hasn't the time to acquire and read that information, when it's so readily available, that's
    up to him. But in that case, he really shouldn't pontificate about what he hasn't read.
    
    George.
    
    contact George Huxtable at george@huxtable.u-net.com
    or at +44 1865 820222 (from UK, 01865 820222)
    or at 1 Sandy Lane, Southmoor, Abingdon, Oxon OX13 5HX, UK.
    
    
    

       
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