1850 Coastal Survey Marker in the South Carolina Scrub [March 6, 2016]

Hidden away in a palmetto and pine scrub forest in Edisto Beach SC is a granite marker of great historical and scientific importance.  It is one of 14 such makers that were put up during the 19^th century as benchmarks for the first coastal survey of the Gulf of Mexico and the Atlantic Ocean.

Surveyors would find a straight area along the coast of a certain distance.  In Edisto Beach it is 6.68 miles.  They would measure that distance and mark it at each end with one of these markers.  They would then use that line between the markers as one side of a triangle that they would then use to triangulate and derive other distances (yes, geometry in action).  Each triangle would provide information for the next triangle as the surveyors moved up and down the coast from that location.

There were 7 of these locations (Epping ME, Kent Island MD, Bodie Island NC, Edisto Beach SC, Key Biscayne FL, Cape Sable FL, Dauphin Island AL), and Edisto Beach has the only set of both markers still in existence today.  The second marker at Edisto Beach is in the Botany Bay Plantation Wildlife Management Area.

To make the initial measurement in 1850, surveyors hacked a 20 foot wide path through the scrub land the whole the length of the area to be measured.  They then measured the distance using “bars of invariable length” invented by Prof A D Bache.  They would position a bar, move a second bar to the end of the first bar and then move the first bar to the new end of the second bar, leapfrogging for 6.68 miles.  Modern scientists re-measured the distance using satellite technology, and found that the old measurement was accurate to within 2.5 inches.  Imagine that!

Imagine hacking through this scrub!

Prof Bache was the great grandson of Benjamin Franklin.  He was also a scientist of note, and was involved in the creation of the National Academy of Scientists and the Smithsonian.

You can get to the trail to the marker, which has very interesting and informative signs along the way, at the Environmental Education Center at Edisto Beach State Park.