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    Re: Sobel and Longitude.
    From: George Huxtable
    Date: 2010 Mar 22, 15:52 -0000

    It may be that Frank and I  differ somewhat less than either of us is keen
    to admit, about aspects of the practice of lunar distance navigation.
    
    I can accept his researches as providing evidence of the state of
    East-coast US navigation in the period he has studied. Where we differ is
    in extrapolation, from that evidince, to the wider and more sophisticated
    art of navigation that was then being practised by European navigators.
    
    He wrote- "History is what navigators actually did, and there is ample
    evidence of their practice in the logbooks. For the American whaling fleet
    which dominated the Pacific (from New England!) in the mid-19th century,
    there are 15,000 logbooks extant. This is a massive store of information
    that has only barely been mined for navigational information. I've studied
    just over a hundred logbooks from the 19th century. Lunars were typically
    used for a few days every two weeks around First Quarter and Last Quarter.
    They were typically Sun-Moon lunars. This wasn't exclusive by any means.
    Something like 80-90% of lunars were Sun-Moon lunars. I have, in fact,
    described some of those less common star lunars in NavList posts in the
    past few years. These lunars were used in support of "longitude by account"
    from about 1800-1835, roughly, and to support "longitude by chronometer"
    from 1835-1850, roughly. After that, they're gone. And by the way, on
    American vessels, I haven't found any evidence of lunars before 1800, but I
    haven't looked much. I know of letters from that period stating that they
    are "new" to Nantucket or "new" to Salem c.1800, but that's all. "
    
    First, to star lunars. I agree that given the choice, where a Sun lunar was
    available, it would be used by most mariners, in preference to a star
    lunar, because that was easier. And when a Sun lunar wasn't available, but
    an observation could be delayed without danger until it was, then it was
    very likely to be so delayed. That applies to the mid-ocean phase of a
    crossing, and also applies where a lunar was being used as backup only. So
    if the claim is that 80 to 90% were Sun lunars, then taking the 80% figure,
    I would not disagree. Indeed, it fits in rather well with the percentage of
    Sun lunars in that 1768 Cook passage from Plymouth to Rio, which I quoted.
    What was important was that the mariner was capable of handling a star
    lunar, when that became necessary, at a crucial point in the proceedings.
    In the voyages Frank has followed, were there vessels who took Sun lunars,
    and nothing but Sun lunars?
    
    I think Frank and I are likely to agree that lunar observations called for
    the precision and wider range of the brass sextant , and use of a wooden
    octant for that purpose was an inadequate make-do. Although Davis quadrants
    were still being produced in the colony, Bedini, in "Early American
    scientific instruments and their makers" (1986), found few octants, no
    sextants. Did Frank find evidence of ownership of brass sextants, home or
    imported,  in  the logs he has followed, prior to 1800? Did that relate to
    his failure to find any evidence of American lunars prior to 1800?
    
    I wonder whether that may have been one of the side-effects of the War of
    Independence, the disruption of the import of the instroments that were so
    vital to improved navigation.
    
    Bedini, in "Thinkers and Tinkers", of 1975, wrote (page 334), about the
    period of introduction of mechanisation-
    
    "There were nevertheless frustrating deterrents to the modernisation of
    navigational practices made necessary by the rapid advancement of maritime
    enterprise. Primary among these was the American seaman's reluctance, and
    frequently inability as well, to accept and apply new navigational
    procedures and aids, as well as the concurrent inability of the American
    instrument makers to produce new instrumentation of adequate precisiion in
    sufficient quantity. These factors contributed materially to the long delay
    in the adoption of the sextant and the chronometer."
    
    One could add that this reluctance to change could apply to mariners the
    World over, but I see a connection with Frank's absence of American lunars
    prior to 1800.
    
    So, I see Frank's archive of ships' logs as deriving from something of a
    navigational backwater, in World terms. Conclusions from that work may well
    be applicable to other parts of America, but great care has do be taken in
    applying them to the practice of other nations. Note that those comments
    relate only to those years, and that later in the 19th century a
    significant catch-up could well have occurred.
    
    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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