Dear Frank all,
On the meaning of PI Long:
Waugh uses the symbol P in his computational treatment of the declining
dial on p. 80. The P values for each hour line in table 10.2 are what
Holwell (in Clavis Horologiae, London 1712) calls the polar angles. The
polar angle for noon equals the
Dear Frank et al,
I note that the letters 'PI' (as well as PII and PW) appear as one of the
centres of Oughtred's Horizontal Instrument. They are actually engraved on the
instrument made by Elias Allen.
Perhaps this is another red herring.
Regards,
John D
Thinking of the canting of the dial, I wonder if it was moved from a
different location. Could then the PI refer to Previous Installation; or if
at one time it was PL, Previous Location?
I know it is really stretching it, but could the 'PI Long' somehow refer to
the co-latitude of the
Frank Evans wrote:
He [Keith Scobie-Youngs] unfortunately had no information or theory on
what the PL Long [Now known to be PI Long] meant, nor indeed as to
why the dial is canted to no apparently significant declination!
On the matter of the dial being designed as a declining dial yet also
A new hypothesis :- )
If we move a dial holding it parallel to itself, we can bring it in a point on
the Earth's surface in which it is horizontal (Equivalent Point)
The longitude of the equivalent point of a vertical declining plane (longitude
related to the place in which is the
