They were minutes away from using up the oxygen."
The crowd grouped around the amplifier was stunned by the announcement. But as the news sank in, relief spread across every face, and the ancient stone city echoed with cheers and applause. Miller turned away as if wiping tears from his eyes while Giordino smiled and smiled.
Down in the chamber Pitt motioned that he could not remove his full face mask and converse. He indicated they would have to communicate through hand signals. Shannon and Rodgers nodded, and then Pitt began to describe visually the procedure for their escape.
Since the lost divers had dropped all of their useless dive gear, except for face masks and buoyancy compensators, Pitt felt confident the three of them could be pulled back through the narrow shaft against the current and into the main pool by his phone and safety line without complications. According to the manufacturers' specs, the nylon line and phone cable could support up to almost six thousand pounds.
He signaled Shannon to wrap one leg and one arm around the line and lead off, breathing through her pony bottle. Rodgers would repeat the step and follow, with Pitt bringing up the rear close enough for the spare regulator to reach Rodgers's mouth. When Pitt was sure they were stable and breathing easy, he alerted Giordino.
"We're positioned and ready for escape."
Giordino paused and stared at the young archaeology students, their hands gripping the safety line, poised as if ready for a tug-of-war. He studied their impatient expressions and quickly realized he would have to keep their enthusiasm and excitement in check or they might haul the divers through the rock passageway
like so much meat through a jagged pipe. "Stand by. Give me your depth."
"I read slightly over seventeen meters. Much higher than the bottom of the sinkhole. We were sucked into a passage that sloped upward for twenty meters."
"You're borderline," Giordino informed him, "but the others have exceeded their time and pressure limits. I'll compute and advise you of decompression stops."
"Don't make them too long. Once the pony bottle is empty, it won't take long for the three of us to use up what air I have left in my twin tanks."
"Perish the thought. If I don't hold these kids by the collar, they'll jerk you out of there so fast you'll feel like you were fired from a cannonball."
"Try to keep it civilized."
Giordino held up his hand as a signal for the students to begin pulling. "Here we go."
"Bring on the jugglers and the clowns," Pitt answered in good humor.
The safety line became taut and the long, slow haul began. The rush of the surge through the shaft was matched by the gurgling of their exhaust bubbles from the air regulators. With nothing to do now but grip the line, Pitt relaxed and went limp, allowing his body to be drawn against the flow of the underground current that gushed through the narrow slot like air through a venturi tube. The lighter silt-clouded water in the pool at the end of the passage seemed miles away. Time had no meaning, and he felt as if he'd been immersed for an age. Only Giordino's steady voice helped Pitt keep his grip on reality.
"Cry out if we haul too fast," ordered Giordino.
"Looking good," Pitt replied, hearing his air tanks grinding against the ceiling of the shaft.
What is your estimate of the current's rate of speed?"
"Close to eight knots."
Small wonder your bodies are causing severe resistance. I've got ten kids up here, pulling their hearts out."
"Six more meters and we're out of here," Pitt informed him.
And then a minute, probably a minute and a half, struggling to hold on to the safety line as they were buffeted by the diminishing force of the torrent, and they broke free of the shaft into the cloud of silt swirling around the floor of the sacrificial pool. Another minute and they were pulled upward and clear from the drag of the current and into transparent, unclouded water. Pitt looked up, saw the light filtering through the green slime, and felt a wondrous sense of relief.
Giordino knew they were free of the suction when the tension on the safety line suddenly diminished.
He ordered a halt to the ascent operation as he rechecked his decompression data on a laptop computer.
One stop of eight minutes would take Pitt out of any danger of decompression sickness, but the archaeology project divers would need stops of far longer duration. They had been down over two hours at depths ranging from 17 to 37 meters (67 to 122 feet). They would require at least two stops lasting over an hour. How much air was left in Pitt's tanks to sustain them? That was the life-or-death dilemma.
Enough for ten minutes? Fifteen? Twenty?
At sea level, or one atmosphere, the normal human body contains about one liter of dissolved nitrogen.
Breathing larger quantities of air under the pressure of water depth increases the absorption of nitrogen to two liters at two atmospheres (10 meters, or 30 feet of water depth), three liters at three atmospheres (30 meters, or 90 feet), and so on. During diving the excess nitrogen is rapidly dissolved in the blood, carried throughout the body, and stored in the tissues. When a diver begins to ascend, the situation is reversed, only this time far more slowly. As the water pressure decreases, the overabundance of nitrogen travels to the lungs and is eliminated by respiration. If the diver rises too quickly, normal breathing can't cope and bubbles of nitrogen form in the blood, body tissue, and joints, causing decompression sickness, better known as the bends, a condition that has crippled or killed thousands of divers over the past century.
Finally, Giordino set aside the computer and called Pitt. "Dirk?"