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    Gunter's Scale
    From: Gordon Talge
    Date: 1999 Jun 03, 7:58 PM

    Wonder if anyone has or has read about the "Gunter's Scale".
    
    I am reading about it in Moore's "Practical Navigator" (1798) and in Andrew
    Mackay's "The Complete Navigator" (1807). Very clever device.
    
    I quote from Mackay.  "The ruler in general use in navigation, is that known
    by the name of "Gunter's Scale".  The length of this scale is usually two
    feet, and about an inch and a half broad.  One side of this scale contains lines
    for constructing geometrical figures; and the lines upon the other side are call
    "artificial", or "logarithmic" lines, being intended to resolve the questions
    in the several sailings, and to perform other mathematical operations."
    
    The scale on side 1 are:
    
     Scales of equal parts
     Chords, marked CHO
     Rhumbs  RHU
     Sines SIN
     Secants SEC
     Tangents TAN
     Semi-Tangents S.T.
     Longitudes M.L.
    
     On side 2 are:
    
     Sine rhumbs  S.R.
     Tangent T.R.
     Numbers NUM
     Sines SIN
     Versed sines  V.S.
     Tangents TAN
     Meridioinal parts MER.
     Equal Parts  E.P.
    
    -------------------------------------------------
    
    The chapter goes on to describe how to contruct a gunter's scale mathematically.
    Very very clever device!
    
    It seems that the Gunter's scale is a precursor to the slide rule. You use
    it by measuring off distances and values with a pair of dividers or compasses.
    
    The trig functions are defined in an equivalent, but different way, then
    they are usually defined today;  as lengths of lines rather than ratios
    of lengths of lines.
    
    --- Gordon
    
    
    
    
                                         ,,,
                                        (. .)
             +-----------------------ooO-(_)-Ooo----------------------+
             |  Gordon Talge WB6YKK            e-mail: gtalge{at}pe.net  |
             |  Department of Mathematics      QTH: Loma Linda, CA    |
             |  Notre Dame High School         Lat.  N  34� 03.1'     |
             |  Riverside, CA 92506            Long. W 117� 15.2'     |
             |  http://www.pe.net/ND                                  |
             +--------------------------------------------------------+
    

       
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