A pipe? A log? A hazard to the oil tankers docking nearby?

No one was sure until a diver was sent down weeks later and found a strange pointed object buried in the muck about 40 feet down.

This week, Cox identified it as the business end of a cheval-de-frise, an iron-tipped log once embedded in the river, along with many others, to gore the hulls of British warships menacing Philadelphia in the mid-1770s. It had been silently resting not far from where oil-laden Sunoco tankers have berthed since Philadelphia's industrial age.

The cheval-de-frise was in excellent condition, a rare historic find after more than two centuries in the river.

"I had never seen one up close," Cox said yesterday as he gazed at the relic at Sunoco Logistics' Fort Mifflin Terminal. "This is great."

The company donated the cheval-de-frise to the Independence Seaport Museum, which plans to conserve it over the next year and make it the cornerstone of its growing Revolutionary War collection.

Museum officials yesterday picked up the 11-foot, 2-inch object by van and transferred it to the Penn's Landing museum, where experts will take about a year to conserve it.

The relic will be placed in a tank of polyethylene glycol, which will permeate and preserve the wood.

"It's in fabulous shape," said museum curator Craig Bruns.

"Wow!" said Michele DiGirolamo, a museum spokeswoman, as she got her first look. "That's scary-looking."

The yellow pine log, with its heavy iron tip, was once bolted into a wooden-framed box anchored with rocks. Poised on the river bottom with scores of other chevaux-de-frise, it was a formidable defense against British ships.

Bruns said the newly discovered relic was probably placed in the river in 1775, at a time when the Pennsylvania Council of Safety, under the direction of Benjamin Franklin, was overseeing the colony's defense.

After the Revolution started, the chevaux-de-frise were used by Continental forces - in conjunction with Fort Mifflin and Fort Mercer, across the river in New Jersey - to oppose the British resupply of troops occupying Philadelphia in the winter of 1777-78. Not coincidentally, that was the winter that Washington and the Continental Army spent at Valley Forge.