Buried in a field near Carleith Primary School in West Dunbartonshire in Scotland is a piece of history that eluded archaeologists for hundreds of years. In 1707, antiquarian Robert Sibbald described a Roman fortlet in the area, but attempts to find it during the 1970s and 1980s were futile. Now, thanks to advances in technology, archaeologists have been able to find the structure that was once believed lost to time.
“Archaeology is often partly detective work, and the discovery at Carleith is a nice example of how an observation made 300 years ago and new technology can come together to add to our understanding,” Riona McMorrow, deputy head of world heritage at Historic Environment Scotland (HES), says in a statement.
To find the fortlet, which isn’t visible above ground, archaeologists employed gradiometry, a geophysical survey technique that uses small variations in Earth's magnetic field to find objects buried underground without excavation. Through this method, they have located the structure’s stone base, on which turf would have been stacked to create a more than six-foot-tall rampart.
During its use in the second century, the fortlet would have been occupied by roughly a dozen Roman soldiers who would stay a week at a time before being replaced by another detachment of soldiers from a larger nearby fort. The structure would have had two small wooden buildings to house these soldiers during their duty.
The newly discovered structure is the tenth known fortlet in the area, but there had been as many as 41 such structures along the Antonine Wall, once the northernmost frontier of the Roman Empire. The almost 40-mile-long wall was built shortly after 140 C.E. on the orders of Emperor Antoninus Pius. Unlike Hadrian’s Wall to the south, the Antonine Wall was made of turf ramparts, rather than stone.
Historians believe Pius built the Antonine Wall to serve as a military victory credited to his rule, John Reid, a historian and archaeologist who is the chairman of the Trimontium Trust, which investigates Roman archaeology in Scotland, says to Live Science’s Tom Metcalfe. “He had no military experience, and we think he was looking for a win that he could pretty much guarantee,” Reid explains. Fortlets were built along the Antonine Wall to control the Indigenous populations in the area at the time.
Though the wall was used for just two decades before being abandoned, it is now included in one of Scotland’s six UNESCO World Heritage Sites. Its significance stems not only from being a physical manifestation of Roman policy, but also illustrating the technological skill of the Roman army in frontier areas, according to the HES.
Questions still remain about the wall, including why exactly Roman forces abandoned it. The new discovery may help historians and archaeologists better understand the wall’s short history, David Breeze, former chief inspector of ancient monuments for HES, tells the Scotsman’s Lucinda Cameron. “The Antonine Wall was the most sophisticated frontier of the Roman Empire and inspite of over 100 years of excavation it still has many secrets to reveal,” he says. “We believe that there are many more of these to discover and finding these will help us understand the original plan for the frontier.”