digging this message 12321 out of the archive has also rattled
my brain enough to completely reconstruct the puzzle
& then also to recall that tho i cant put my hands on the really
authoritative 1934 article by perry
i can still recollect it fairly well
& have dug up the paper topos from which i can crib all the
necessary coords & then compute independently with a great
circle arc calculator exactly where on the mason & dixon west
line the original 1701 arc would have had to cross it
if not precisely at modern demdpa
aha
& what fun
all of which i ought to be able to do with the help of messages
12156 & 614
but especially message 644 for the exact measurements
so first the coords of the new castle county courthouse spire
aka the center of the original 1701 depa arc
as partially recovered in 1892
nad83 nlat 39d29m35s x wlong 75d33m52s
& then the latitude of the mason&dixon line at demdpa
nad83 nlat 39d43m20s
& next the radius of the 1701 depa arc
67637 feet
yes i know almost 13 miles but thats what she really wrote
& finally the coords of denjpa
at the opposite end of the original 1701 arc sweep
just as a double check
nad83 nlat 39d48m07s5 x wlong 75d24m53s
but anyway let me really go out on a limb & post this much first
& i will proceed with the great circle calculations after an
appropriate pause for fanfare & drumroll
& dinner
unless someone beats me to them
--- In
BoundaryPoint@yahoogroups.com, "acroorca2002"
<orc@o...> wrote:
> we know from pre1849 maps that the depa arc was originally
tangent to
> demd at modern demdpa
> or at least it appears to have been so
> &
> we understand that the wedge was created in 1849 as a
prolongation of
> the demd arc
> which had a smaller radius than the depa arc as well as a
different
> center
> &
> we know that the western part of the depa arc was shaved
back at that
> time
> in order to feather these 2 or 3 slightly different arcs together
> into a single continuous curve from the delaware river to the
m&d
> tangent point
> etc
>
> but how was it possible that the original 1701 depa arc & the
> original 1764 m&d north line from the demd tangent point
could both
> have struck the m&d west line at precisely the same point
> modern demdpa
>
> or at least how can they appear to have done so
>
> for it seems to me one or the other of these 2 chance
intersections
> would have produced & become the definitive demdpa
> while the other would have had to miss the mark
>
> the intersections were independently conceived & generated
> one being supposedly 12 miles from the horse dike at new
castle
> & the other 15 miles south of the southernmost point of philly
as
> well as due north of the more famous tangent point
>
> neither position was derivative of the other
> yet both apparently agree
>
> so i am thinking
> m&d
> or at least someone prior to graham in 1849
> might already have done some fudging of the westernmost
end of the
> depa arc here just to make everything line up
>
> of course in 1849
> whatever slight previous fudging may also have been done
was
> completely obliterated by the much greater fudging produced
by graham
>
> so this is a question only for ghost pointing
> & perhaps only to be answered in some dusty archive if at all
>
> but it titillates my sense of & desire for precision