happened to eight Confederate sailorsaboard the H.L. Hunley after it became the first submarine in historyto sink an enemy warship?

Theirhand-cranked sub rammed a spar with black powder into the Unionblockade ship Housatonic off Charleston on a chilly winter night in1864 but never returned.

Its fate has been thesubject of almost 150 years of conjecture and almost a decade ofscientific research since the Hunley was raised back in 2000. But thesubmarine has been agonizingly slow surrendering her secrets.

"Shewas a mystery when she was built. She was a mystery as to how shelooked and how she was constructed for many years and she is still amystery as to why she didn't come home," said state Sen. GlennMcConnell, R-Charleston and chairman of the South Carolina HunleyCommission, which raised the sub and is charged with conserving anddisplaying it.

Scientists hope the next phaseof the conservation, removing the hardened sediment coating the outsideof the hull, will provide clues to the mystery.

McConnell, who watched the sub being raised more than eight years ago, thought at the time the mystery would be easily solved.

"Wethought it would be very simple ... something must have happened at thetime of the attack," he said. "We would just put those pieces togetherand know everything about it."

But what seemedso clear then seems as murky now as the sandy bottom where the Hunleyrested for 136 years. When the Hunley was raised, the design wasdifferent from what scientists expected and there were only eight, notnine, crewmen, as originally thought.

The firstphase of work on the Hunley consisted of photographing and studying theoutside of the hull. Then several iron hull plates were removedallowing scientists to enter the crew compartment to remove sediment,human remains and a cache of artifacts.

Thousandsof people, many re-enactors in period dress, turned out in April 2004when the crew was buried in what has been called the last Confederatefuneral.

With the inside excavated, the outsideof the hull will now be cleaned before the sub is put in a chemicalbath to remove salts left by years on the ocean floor. The Hunley willeventually be displayed in a new museum in North Charleston.

ArchaeologistMaria Jacobsen said the Hunley is like a crime scene except that,unlike on television shows, there is no smoking gun.

"Ifwe compare this crime site investigation with, say, a tragic planecrash in the mountains, that investigation would be a lot easier," shesaid. "You can go to the crash you can see the metal pieces and theyhave the fingerprints of the crash site."

Inthe case of the Hunley, some of those fingerprints may be covered withthe encrusted sediment on the hull that scientists refer to asconcretion.

When the sub was found there was nowindow in the front conning tower, suggesting it had been shot out,perhaps by Union sharpshooters.

But no glasswas found inside the sub and the remains of the captain, Lt. GeorgeDixon, showed no injuries to his skull or body consistent with beingshot while looking through the window, McConnell said.

Thecrew's bodies were found at their duty stations, suggesting there wasno emergency resulting in a scramble to get out of the sub. And thecontrols on the bilge pump were not set to pump water from the crewcompartment, suggesting there was no water flooding in.

Afterthe attack both Confederates on shore and Union ships reported seeing ablue light, believed to be the Hunley signaling it had completed itsmission.

A lantern with a thick lens that would have shifted the light spectrum and appeared blue from a distance was found in the wreck.

Butafter the attack, the USS Canandaigua rushed to the aide of theHousatonic and there is speculation that the light could have come fromthat ship instead.

Could the Canandaigua havegrazed the Hunley, disabling her so the sub couldn't surface? A goodlook at the hull in the coming months may provide the answer.

Historians also know the Hunley needed to wait for the incoming tide to return to shore.

"Were they waiting down there and miscalculated their oxygen and blacked out?" said McConnell.

Hesaid a grappling hook, believed to serve as an anchor of the Hunley,was found near the wreck. Cleaning the hull may produce evidence of arope showing the sub was anchored, perhaps waiting for the tide tochange.

Then there is the mystery of Dixon'swatch, which stopped at 8:23 p.m. Although times were far from uniformin the Civil War era, the Housatonic was attacked about 20 minuteslater, according to federal time, McConnell said.

Onetheory is the concussion of the attack stopped the watch and knockedout the sailors on the sub. Or the watch simply might have run down andwas not noticed in the excitement of the attack. That could have led toa miscalculation of the time they were under water.

Uniontroops reported seeing the Hunley approaching and the light through thetower window "like dinosaur eyes or a giant porpoise in the water,"McConnell said.

If the Hunley crewmiscalculated and surfaced too close to the Housatonic on their finalapproach they would not have had enough time to replenish their oxygenbefore the attack, he said.

The clues now seemto indicate the crew died of anoxia, a lack of oxygen, and didn'tdrown. "Whatever happened, happened unexpectedly, with no warning,"McConnell said.

Running out of oxygen can quickly cause unconsciousness.

"One you reach that critical stage, it's like you flick a switch," he said. "It's that fast, like on an airplane."