excerpts from the original message with miscellaneous notes
added

--- In BoundaryPoint@yahoogroups.com, "Lowell G. McManus"
<mcmanus71496@m...> wrote:

> Below is the reply by Mr. William S. Schenck of the
> Delaware Geological Survey in answer to my inquiry regarding

the

> under-measurement of the twelve-mile arc at its lower

crossing of the Delaware

> River.
>
> The figure from the Perry article to which he refers can be

found at this direct

> link:
> http://www.udel.edu/dgs/graphics/IS06FIG2.jpg .

> ----- Original Message -----
> From: "William S. Schenck"
> To: "Lowell G. McManus"
> Sent: Wednesday, February 16, 2005 7:38 AM
> Subject: RE: 12-mile circle in Delaware River
>
>
> > Mr McManus
> >
> > I know just enough about the history of the Delaware -

Pennsylvania 12-Mile

> > Circular Boundary to make me dangerous.

i must say this was very considerate & fair of him to say
& of course it is true of all of us too & even of the real experts
if indeed there are any to be found anywhere

but the delaware boundary monument data base he maintains &
personally runs all around the state to update etc
http://rdms.udel.edu/dgs/boundaryMap.html
is the best & only known such in the usa
& has been on line for years so is far ahead of the field if any

& despite some minuscule flaws & errors & other shortcomings
it is really quite commendable on just about every level
& a valuable resource
& a pleasure to use

I do know that the boundary is

> > composed of 2 compound curves, not one arc of a 12-mile

circle. The radius

> > of both curves constantly increases from west to east.

this is true
& i have just checked it carefully using his coords

The reason for the

> > compound curves is that the 1701 survey of the line had

problems with their

> > chains getting worn and longer and longer as they

progresses from west to

> > east.

it all makes perfect sense
except it is still hard for me to believe they did survey from west to
east in 1701 when civilization was mainly concentrated along the
coast & advancing slowly & with difficulty inland

& i am pretty sure perry indicates otherwise too

& where in the west would they have begun anyway

neither of the m&d lines existed yet

moreover please see schencks own contradiction below

clearly more research is needed on this point

& happily the historical account of hodgkins the 1892 surveyor is
still out there waiting to be heard from in his own words

At DE-PA #10 they made a correction and you can actually see
that is

> > the line today.

well it is true you can see a little wiggle on the topo in that vicinity
but you can also see one on the artificial island arc
which we know has no wiggle in reality
so that in itself is inconclusive

& his coords dont support this assertion either
i just learned
as the mathematical gradient of the curve remains remarkably
constant all around milepost 10 & its near neighbors in both
directions

he may well have been thinking about the 1850 transition point
between the 2 arcs of the compound curve he mentions tho
which in fact occured near milepost 11
& did create a wiggle that may be perceptible on the topo
for whatever that is worth

> > The best reference I can direct you to is an article that

appeared in the

> > journal of Civil Engineering. The reference for it is:
> >
> > Perry L., 1934, The circular boundary of Delaware, Civil

Engineering: v. 4,

> > no. 11, p. 576-580.
> >
> > You can see one of the figures from that article in my

information pamphlet

> > about Delaware's boundaries on our web site at
> > http://www.udel.edu/dgs/Publications/pubsonline/info6.html

this article contains many more inaccuracies than the data base
& some of them are rather flagrant

& it is noteworthy that he contradicts his above assertion when
he says in the essay that the 1701 survey proceeded westward
from the delaware river

> > That's about all I know.

etc

other recent findings based on his data & perry include a fairly
good hypothetical position for the long lost original 1701
precourthouse center point shown in figure 2 to be in the river as
of 1934 tho i would make it quite a bit farther out in the river now

still refining this however
& doing a lot of other number crunching too
which i will eventually report on
but there are still some slight uncertainties i need to nail down
before i do

like i just noticed the perry diagram shows the wedge arc with a
radius of 12 miles & 108 feet at its south end but exactly 12
miles at its north end
a geometric impossibility in need of some explanation