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Lehigh Valley Live: Historic Bethlehem enlists Lehigh students to aid in underground Moravian settlement survey

November 29th, 2021 |

Written by Connor Lagore for Lehigh Valley Live

A Ground Penetrating Radar is exactly what it sounds like — a device that beams a radar signal into the ground. Of course, it has a purpose for penetrating the earth with said signal: the radar measures and denotes environmental disturbances and electrical properties of materials in the earth. Think a CT scan, but for the ground.

Last month, one such device and a group of Lehigh University students helped Historic Bethlehem Museums & Sites take a big step forward in uncovering an unseen chunk of Moravian history.

The Historic Bethlehem Partnership enlisted Mariah Hoskins, an adjunct professor and postdoctoral researcher, and her “Seismology: The Earth and the Environment” class to survey an open part of lawn at Bethlehem’s Colonial Industrial Quarter to help uncover precise locations of torn-down buildings that were once part of the Moravian settlement that stood centuries ago. Using the Ground Penetrating Radar, or GPR, the survey was able to find the exact location of the foundation of an old tawry, a business that made soft leather that was important in numerous 1700s industries, that was once part of the settlement.


To the uneducated observer, the surveying might have looked a bit ridiculous as the eight students and one professor stood around an empty lawn on Oct. 25. “The GPR unit is basically a box with a receiver and the radar source contained in this box that we drag across the ground” Hoskins said. It does indeed look like a small orange box — hitched to a wheel for easy movement — with a long cord connecting to an imaging device strapped to the shoulders of a student.

But to the educated observer, what the small team of seismology students (and one seismologist) were doing allowed them to look down, vertically, into the ground through hundreds of years. They dragged the box in a line stretching the length of a roped off area they were surveying, and repeated the process a half-meter to the side until the whole area had been carefully moved over with the GPR. The foundation of the tawry, likely made of stone and other materials, had different electrical properties than loose soil, so in covering that whole space, any remaining semblance of the foundation would catch the radar’s attention.

“The data we’ve collected, then, is this vertical slice down underneath each of these lines that we’ve traced out,” Hoskins said. “We have software that basically combines those slices into an image of the whole volume we were able to scan. We could see there was this linear shape that looked very different, and that’s how we deduced that this evidence of disturbance or difference in electrical property is likely the foundation.”


The students also deduced in the survey that much more time and data would be needed to uncover the rest of the foundation as well as other buildings that old records suggest are in the area, buried deep underground, like a butchery and an oil mill, according to a release from Historic Bethlehem Museums & Sites. But finding the initial foundation of one centuries-old building is quite a start.


And it couldn’t have come at a better time. The Colonial Industrial Quarter and all of the Moravian settlement is currently going through the application process of being added to UNESCO’s list of World Heritage Sites in a multi-pronged effort that also includes early Moravian settlements in Germany and Northern Ireland.


“We are so excited that the class was able to identify one of the foundation walls of the tawry through their survey analysis,” said Charlene Donchez Mowers, the president of Historic Bethlehem Museums & Sites, in a statement. “As we move closer to World Heritage, it is so important to be able to document another facet of the Colonial Industrial Quarter and have a better understanding of the location of this structure in relation to the other buildings and trades operating on the site in the mid-1700s.”

The discovery of more past buildings and aspects of the 1700s Moravian lifestyle may or may not help the application — that’s up to UNESCO. But there’s no denying the historic value of further understanding the way some the first residents of Bethlehem lived.


Lehigh students aren’t currently scheduled to make anymore trips to the Colonial Industrial Quarter for more discoveries, but it seems likely that whenever someone is able survey further, there’s plenty down there waiting.


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