GPRS Scans 175-Year-Old Church to Detect Cornerstone Artifacts
“We found something in the middle of the stone… Then we got closer to the edge. It was right on the corner… We scanned adjacent stones to rule out artifacts or false signals, and found no similar readings.”
When Field Services Manager Patrick Hughes and Area Manager Sam Hart were asked to investigate a centuries-old stone church in Doylestown Borough, Pennsylvania, they weren’t expecting to stumble upon a mystery that had remained buried for nearly 175 years.
Saint Paul’s Episcopal Church, consecrated on September 9, 1846, is the fourth-oldest borough and has long been rumored to contain a trove of historical artifacts sealed within its cornerstone. When the church’s anniversary committee contacted GPRS, they were looking for confirmation without causing damage.
Click the Video to see how GPRS helped the church solve their mystery.
Saint Paul’s team asked GPRS to verify whether such a container exists within the limestone block using Ground Penetrating Radar technology. The scan would guide next steps before attempting any intrusive exploration.
“They didn’t want to just go blindly chipping around,” Hughes said.
According to local accounts and historical records, the cornerstone may hide a box containing The Holy Bible, The Book of Common Prayer, two journals from Episcopal Church conventions in 1844, Bishop Potter’s Primary Charge and Pastoral Letter, and rare periodicals such as The Episcopal Recorder and The Banner of the Cross.
GPRS Area Manager Sam Hart inspects the cornerstone of Saint Paul’s Episcopal Church with a StructureScanTM Mini XT handheld GPR system
How Does GPR Detect Hidden Objects Beneath the Surface?
Ground Penetrating Radar (GPR) is a non-destructive testing method that allows experts to detect subsurface anomalies including utilities, structural components, and buried objects. The system works by emitting high-frequency electromagnetic waves into a material and analyzing the signals that reflect back.
Here’s how GPR functions in practical terms:
Signal Propagation: Radar pulses are transmitted into a surface such as concrete, soil, or stone. When the waves encounter materials with different dielectric properties, parts of the signal are reflected to the receiver antenna
Data Interpretation: The returning signals are mapped as subsurface variations. Metallic objects, voids, dense stone, and organic material generate distinct patterns, which skilled technicians interpret as possible targets or structural features
At Saint Paul’s, Hughes and Hart used a StructureScan™ Mini XT handheld GPR system. Its compact size and precision scanning made it particularly suited to investigate the church’s historic limestone block.
“Whether we’re scanning a slab for utilities or investigating a site of historical significance, our standards for precision don’t change,” Hughes said.
GPRS Area Manager Sam Hart inspects the cornerstone of Saint Paul’s Episcopal Church with a StructureScanTM Mini XT handheld GPR system
How Can GPR Help Contractors and Facilities Managers?
For general contractors and facilities managers, GPR offers an indispensable tool for safe and informed project planning. Its applications include:
- Concrete Analysis: Scanning for rebar, post-tension cables, and conduits before coring or drilling
- Utility Mapping: Identifying buried pipes or electrical lines to avoid costly accidents during excavation
- Structural Diagnostics: Evaluating foundation integrity in older facilities where blueprints may be missing or incomplete
- Void Location: Finding potential hidden voids that could compromise load-bearing structures
In environments where preservation matters and where construction must be minimally invasive, GPR allows operators to work with confidence and respect for underlying materials and history.
“The anomaly was consistent at the corner of the block,” Hart said. “That gave us a high level of certainty. We scanned adjacent stones to rule out artifacts or false signals, and found no similar readings.”
This illustrates how GPR results can be verified through comparative scans, ensuring accuracy in environments where even the smallest error could result in damage to critical structures or historical assets.
Confirming the Anomaly
After their initial investigation, Hughes and Hart marked a potential target approximately three inches inside the corner of the limestone block.
“We found something in the middle of the stone, but it was not very distinctive,” Hart explained. “Then we got closer to the edge. It was right on the corner. We were able to scan both corners that met together to see if they were consistent, which they were.”
The anomaly was significant, and adjacent stone scans did not show similar features. This reinforced the credibility of the original detection.
“It was jumping out at us, for sure,” Hughes said.
The church now plans to consult a structural engineer to determine how to safely access the potential chamber. GPRS will continue assisting throughout the process. Hughes and Hart intend to be on site when further investigation takes place.
“It was pretty exciting, what we were seeing,” Hart said. “I feel pretty confident that there’s something there. Whether it’s relevant or not, it’s hard to say.”
This scan is another example of GPRS helping clients visualize unseen structures with accuracy and care. Whether working with modern concrete or 18th-century limestone, the goal remains the same: to deliver reliable data without causing harm.
Said Hughes, “We just went above and beyond, by doing our standard process.”
Finding buried time capsules in church cornerstones isn’t an everyday occurrence for GPRS, but it is just one of the many ways we Intelligently Visualize The Built World® for customers nationwide.
What can we help you visualize?