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4 September 08: You know what this is . . .
It's a celebration, BRIDGES!
Greetings again, friends. So as to not confuse, let's reiterate up front that Philly Skyline's Summer of the Delaware follows the Philly
Skyline Gregorian calendar, from solstice to equinox. Besides, this latest addition to the series has 13 editions unto itself.
Today we begin our journey downstream, following the tidal Delaware River from the New Jersey capital -- and Capitol -- to the state where the Delaware River becomes
the Delaware Bay: Delaware. Delawhat? DELAWARE.
The Delaware River is tidal from the Atlantic Ocean up to Trenton, a journey of 130 miles or so. It's here that exists what is known as the fall line -- where two
geologic provinces meet. This creates not only a change in topography, but also in the performance in a river like the Delaware. Here's a map project I did in 1998
of
Pennsylvania's geologic provinces, which may help to give this some context.
(Apparently this map was made before the concept of anti-aliasing; no really, it looked good printed out!)
If you follow the line just below "Triassic Lowlands" on the right, where it meets the eastern border is what's known as the "Falls of the Delaware" -- the portion
of
the river between Morrisville PA and Trenton NJ that's rocky at low tide and deep at high tide, an average of about eight feet in difference. (Check out this site for more on the tides.) This is also indicative
of the shift in geology: above the falls (within the Piedmont -- soft rolling hills in which the fertile farmland in Lancaster County is also located), the river is
more rocky and shallow; below the falls (within the flatter Coastal Plain, in which most of Philadelphia, including all of its Delaware Riverfront, lies), the bed is
softer, sandier, and the river is more navigable because of it.
The fall line helps to explain Trenton's location (it's as far north as early ships could travel), and in turn explains Washington's crossing just north of Trenton
in
1776. He couldn't attack the Hessians and British directly at Trenton, or he'd have been pummeled. He couldn't do it south of there because there were too many men
to
cross competing against the tides.
With all this in mind, we're going to set sail tomorrow morning on this Summer of the Tidal Delaware and take a look at each of the 13 bridges from Trenton to the
Bay.
Cue up the Action News theme song ("the Delaware Valley's leading news program"), because this series examines the Delaware Valley at its truest sense.
To kick it off, let's begin without any bridges at all, instead opting to have a look at our launchpoint, the Philly Trenton Skyline. This was taken
from the dike at Williamson Park in Morrisville, about 32 miles from Center City.
B Love
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SUMMER OF THE DELAWARE ARCHIVES:
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