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Explorer delivers relic for CT scan

| Saturday, Aug. 24, 2013, 8:21 p.m.
Steve Libert of Great Lakes Exploration Group accompanies a nearly 20-foot-long timber slab as it gets a CT scan at Otsego Memorial Hospital in Gaylord, Mich., on Saturday Aug. 24, 2013.

GAYLORD, Mich. — Technicians at a northern Michigan hospital used a CT scan machine Saturday to take X-rays of a wooden beam that could be part of the Griffin, a ship commanded by the French explorer La Salle that has been missing for more than three centuries.

The procedure was the latest twist in a decades-old quest by diver and history buff Steve Libert to locate the vessel, which disappeared in 1679 while setting sail from an island near Lake Michigan's Green Bay with a crew of six and a cargo of furs. A dive team retrieved the timber in June while discovering to their disappointment that it wasn't attached to buried wreckage.

They hope the CT scan, which produced images of tree rings inside the beam, will help determine whether it was cut down about the time the Griffin was built. A Cornell University expert in dendrochronology — a scientific technique that uses ring patterns to date trees — has agreed to analyze the images, which were recorded on compact discs.

“It's very important,” Libert said. “Now this comes down to science.”

He said the timber could be the Griffin's bowsprit — a spur or pole that extends from a vessel's stem. Michigan's state archaeologist, Dean Anderson, has said he isn't convinced the beam is part of a ship and contends it could be a stake from a “pound net,” a type of fishing gear used in past centuries.

A small crowd watched, many snapping photos, as crewmen with Libert's Great Lakes Exploration Group unloaded the nearly 20-foot-long timber from a trailer at Otsego Memorial Hospital in Gaylord, about 225 miles northwest of Detroit.

The oak beam has been submerged in water and preservative chemicals. One end is split, and three peglike pieces of wood protrude from the side. Libert said they are “tree nails” and provide further evidence the beam was fashioned by humans.

For the scan, it was wrapped in a permeable fabric and placed inside a cradle made of PVC pipe. Eight men lowered the slab, which weighs about 400 pounds, onto dollies and wheeled it down a hallway to the hospital's radiology section, maneuvering carefully around corners and through doorways. Then they donned rubber gloves and hefted it into the room with the scanning machine.

There, it was placed on an examining table usually occupied by patients being X-rayed to detect cancerous tumors, blockages in blood vessels or other internal ailments. The mechanical table eased one end of the timber — a nearly 5-foot-long section — into the doughnut-shaped scanning machine, where a spinning X-ray camera recorded cross-section images of the interior. Readings were taken about an inch apart for 10 minutes.

The crew then lugged the timber into the hallway, turned it around and took it back for a scan of the other end.

A computer read the images and projected them onto screens in an adjacent room. Tree rings were clearly visible, and radiology director Andy Lanway said technicians counted at least 29. Carol Griggs, the Cornell specialist, has said 50 or more might be needed to determine when the tree was felled by matching ring patterns with those of other trees in the university's archive.

“I'm not sure it's going to be enough,” Libert acknowledged. But he added, “There might be more rings. They might be so tight that we couldn't see them with the naked eye.”

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