ST. MARY'S CITY -- A pattern of brass tacks on a coffin lid may hold a clue to the identity of at least one of the three Maryland colonists buried here 300 years ago.
"It may be a decorative pattern, a date, or it may be the initials of the individual," Dr. Henry Miller, chief archaeologist for Historic St. Mary's City, said yesterday.
The pattern won't be decipherable until the lead coffin is opened during the second week of November. The tacks, with domed heads about the size of a dime, were spotted late last week during a fiberoptic examination of the lid of the largest lead coffin's wooden inner box.
Archaeologists think the coffin may contain the remains of Philip Calvert, youngest son of Sir George Calvert, the first Lord Baltimore. Philip, the colony's first chancellor, died in 1682.
"We could see at least six or seven [tacks], but we know there are a lot more," Dr. Miller said. "The brass looked to be in wonderful shape."
He said the tacks were driven into the coffin lid about an inch apart, in a pattern rather than in a straight line. A straight line of tacks would suggest they had merely held down fabric. The fiberoptic camera's limited perspective made the pattern impossible to read, Dr. Miller said.
Scientists are now in the fourth week of their seven-week, high-technology study of the lead coffins and their contents. They hope their work on the rare and well-preserved burials will provide the identities of those buried beneath the Colonial capital's Great Brick Chapel.
They also hope it will shed light on the lives and health of Maryland's first colonists, and yield information on the environment in which they lived.
Yesterday, NASA scientists working on Project Lead Coffins said they will need two to four weeks to determine if the largest coffin holds a long-sought sample of preindustrial air.
In contrast to the first two coffins tested last week, the third and largest coffin was airtight when sampled. However, the air extracted from inside has proved to be a puzzle.
"There was a . . . significant amount of decomposition in that casket," said Dr. Wesley R. Cofer 3rd, an atmospheric scientist with NASA's Langley Research Center.
Gases generated by decomposition produced a complex "soup" of organic compounds in the sample that have so far frustrated efforts to measure the amount of Freon in the coffin. Because Freon was not manufactured until the late 1940s, scientists are using it as a "marker" for the presence of modern air in the coffin.
Still, Dr. Cofer said, "It's only a matter of weeks before we can [measure] the Freon."
Less certain is whether the sample will ever yield useful data on the amounts of methane, carbon dioxide, nitrous oxide and other "greenhouse gases" in the 17th-century atmosphere. Such information would help scientists measure the impact of man's activities on the atmosphere since the Industrial Revolution.
Many of the same "greenhouse gases" also are given off by the decomposition of the body in the coffin. Carbon dioxide in the coffin's air was four times the level of modern air, nitrous oxide levels were 25 percent higher, methane levels also were higher, said Dr. Cofer.
"There are ways maybe to untangle this thing," he said. "But I don't think anybody has ever studied decay over a 300-year period. I don't know if the microbes then are the same as the microbes we would study today."
He cautioned there is "a real possibility" scientists will never sort the coffin's original air from the decomposition gases given off by the body.
Whatever the results, NASA scientists will keeping looking for a sample of preindustrial air, said Dr. Joel Levine, a senior scientist at NASA's Langley center. He said his team had received an invitation from an undisclosed source "outside the United States" to conduct a similar study on another lead coffin. He declined to identify the location but said the coffin was at least a century older than those at St. Mary's City.
"Eventually," said Dr. Levine, "someone will find a sample of preindustrial air, and I hope we find it. I think we have written an important chapter in this search."
Also yesterday, scientists scrambled to stabilize the remains in the largest of the lead coffins. Mark Moore of the Armed Forces Radiobiology Institute said that while installing insulation to cool the coffin Sunday, he got "a real nose-full" of decomposition odor.
Experts said the odor is not unexpected and not necessarily a sign that decomposition has accelerated since the coffin was drilled last week. Nevertheless, Mr. Moore said, "It panicked me."
The coffin already was being flooded with inert argon gas to halt any decomposition. But yesterday, scientists used dry ice to better regulate and cool the argon flow and to ward off any further decomposition.