ST. MARY'S CITY -- Archaeologists excavating the remains of the Great Brick Chapel in St. Mary's City have detected a mysterious object beneath the 323-year-old Catholic church's ruins.
Ground-penetrating radar used to map disturbed earth beneath the chapel floor located the extremely dense object in August, under the north transept of the cross-shaped church. Project scientists say the object is even denser than the building's 3-foot-thick brick foundation.
"It could be something natural, like a rock," said Henry Miller, chief archaeologist for Historic St. Mary's City.
But, after clearing away the grass and topsoil that covered the spot, archaeologists have found clues suggesting a more intriguing possibility. They suspect it may be the sealed lead coffin of Philip Calvert, Maryland's first chancellor and half brother of Cecil Calvert, Lord Baltimore.
Philip Calvert died in 1682.
"He is the one man who died in Maryland, of sufficient wealth and stature -- and a Catholic -- to be buried in the church, and in a lead coffin," said Miller.
Miller and his team hope that excavations in the next few weeks will uncover the object.
"We're not going to dig it up," said archaeologist Timothy B. Riordan. "We're going to excavate just enough to find out what it is. But we'll conveniently excavate that portion where there might be a name plate."
The Great Brick Chapel at St. Mary's City was built around 1667 -- just 33 years after Maryland's founding. It replaced the original St. Maries Chapel, the first Catholic chapel in English America. The first building was a wooden structure burned in 1645 by Englishmen working for the anti-Catholic Parliament during England's Civil War.
St. Mary's City declined when the capital was moved to Annapolis. The place became a ghost town. The brick church stood until 1705. It was demolished by the Jesuits after Maryland's governor ordered it locked following the establishment of the Anglican Church as the colony's official religion.
Brick, stone, grave markers -- everything of value above the ground -- was eventually removed and reused elsewhere. Some of the distinctive chapel bricks have been identified in an early 18th century mansion in nearby St. Inigoes, Miller said.
By the 1730s, the remains of the town and its church vanished beneath pasture and cornfield, a fate which preserved for archaeologists "the only 17th century Colonial capital left in America," Riordan said. "It is an incredible resource, not only for the people of Maryland, but for the people of America as a whole."
No descriptions or drawings of the church are known to have survived. Its location was preserved in local memory by the name given to the place by farmers: Chapel Field.
Archaeologists working for Historic St. Mary's City began looking in earnest for the outlines of Maryland's "lost" capital in 1980, when the land was purchased by the state.
To their surprise, Miller said, St. Mary's turned out to be a carefully planned little "city" of the Italian Baroque design popular in Europe, with the brick church and the statehouse situated prominently at opposite ends of the main street.
Excavations since then have consistently astonished archaeologists. Survey pits dug on a 20-acre site on Mill Field across the road from Chapel Field turned up 28 significant sites, Miller said, "a remarkable density of archaeological remains."
"Every time we go to a new area to expand what we know, we're amazed," he said. "Just across the road here we found eight other 17th century sites we had no record of."
A $110,000 grant just announced by the National Endowment for the Humanities, will allow additional excavations in the Chapel Field over the next three years. Miller and his team hope to locate and study the remains of the original wooden chapel, a Jesuit Priest's House, and a "school of humane letters" built in 1677 -- the first Catholic school in the English colonies.
The remains of the Brick Chapel itself, buried for 250 years, were not fully exposed again until this past August, and its dimensions were startling.
"This is an absolutely massive building for the period; it shocked us," Miller said.
The cruciform building was 55 feet long and 58 feet wide at the transepts. The nave is about 31 feet wide. The brick foundation walls are 3 feet thick, dug more than 5 feet into the ground.
"In the Colonial period, most big brick buildings had walls 2 to 2 1/2 feet wide," Miller said. Most were dug no more than 18 inches deep.
The thick foundation walls suggest a building 30 feet high -- "an immense pile of brick" for a frontier settlement of a few hundred people, he said. "It was built to last, and also to be a very powerful symbol, a statement of the role of religious freedom in Maryland."
With the Chapel Field topsoil stripped away, the archaeologists were able to identify 30 graves beneath the nave floor, all laid out east to west. About 50 more graves were identified outside the walls, in what was once the town cemetery.
In all, Miller believes, as many as 400 graves lie in the area. No grave markers have been found. They were probably taken and used in home construction. None of the burials has been excavated.
"I'd like to identify some of them," Miller said. "The first governor of the colony, Leonard Calvert, is buried here somewhere. Finding and identifying his burial place would be a very important thing to do."
The mystery of the object under the north transept is still unraveling.
The first clue, Miller said, came with the removal of the topsoil, which revealed a large gravel-filled pit at the radar target.
The pit is 6 to 8 feet long, and 3 to 4 feet wide. The object itself lies about 4 feet below the surface.
Disturbance of the adjacent foundation brickwork and soil suggests to Miller that the colonists cut a trench through the chapel wall in order to get the object into the building, then resealed the wall.
"The best guess we can come up with is that it's a lead coffin," said Riordan. Lead coffins were not uncommon in England at the time, and two have been found elsewhere in St. Mary's.
The coffin, weighing 500 to 1,500 pounds, would have had to be moved with block and tackle. Once inside the hand-dug grave, the coffin had to be turned to an east-west position, explaining the extra-large pit.
Philip Calvert -- if that's who lies buried in the coffin, was the half brother of Cecil Calvert -- Lord Baltimore -- and uncle of Cecil's successor, Charles Calvert.
Philip served as chancellor of Maryland, an administrative post in the proprietary colony similar to today's secretary of state. He also was an astute lawyer who wrote influential legislation protecting the colony's orphans, and served as chief justice of the Provincial Court, Miller said.
His brick home a half mile from the chapel, called St. Peter's, may have been the largest in America when it was built in the 1670s. It was destroyed by a gunpowder explosion in 1695.