Another mystery was the valve attached to a short length of pipe on top of the dome. The pipe was plugged at the end but had an opening cut in one side. It made no sense.
What, then, was the function of the brazier and the conventional bellows below the dome? Obviously, to heat the fuel in the dome to operating temperature. But why? Neither Shef nor Steffi had any word to express the concept “volatile,” but they had seen water boil, had seen kettles boil dry. Shef, too, remembered the experiments of his former shipmate Udd with distilling a kind of winter ale. “Some things boil with less heat than water,” he explained to Steffi. “It may be that this stuff in the tank is one of them. What comes out of the nozzle when you turn the valve, then, is the lighter stuff, like the drink that Udd makes out of the steam from ale.”
“Isn’t steam just water?” queried Steffi.
“Not if you heat ale or wine,” said Shef: “The stronger stuff comes off first, before the water. The opposite of winter wine. Water freezes first in the cold, boils last in the heat.” As he said the words he stiffened, the words of Loki coming back to him. What was it he had said, had offered him as a token? “It is best on a winter morning.” He did not understand, but it had something to do with this problem. He would remember it. If it worked… Then he would owe Loki something. Put into practice the plan he had considered. It would be a fair test, a fair return.
All their actions had been watched with tight-lipped scorn by the Greek siphonistos taken from the captured galley.
“We’re going to try it,” said Shef to Skaldfinn. “All those who aren’t necessary had better leave the boat.” The Greek turned immediately, reached for the painter of their dinghy.
“He understands our language a bit, then,” said Shef. “Ask him why he will not help us.”
“He says you are barbarians.”
“Tell him barbarians would lash him to the dome so that he would feel the fire first if anything went wrong. But we are not barbarians. He will see. He will stay with us, take the same chances that we do. The rest of you—over the side with you all, and lay off ten strokes. Now—” Shef turned back to Steffi and his three-man gang with a confidence he did not feel. “Light the match! Bellows-man, stand by and start when the flame is alight.”
“It’s this pump that worries me,” muttered Steffi in an undertone. “I can see what it does, but I don’t know what it’s for.”
“Me neither. We still have to try it. Start pumping on the handle.”
The Greek edged away, watching the preparations with increasing fear. The very thought of the fire exploding made his bowels cringe within him. He had seen several demonstrations of what happened when an apparatus was overheated. They had turned the safety-valve closed, without realizing what it was for. He knew, if the barbarians did not, that they were not far enough off to be safe.
Competing with the personal fear was fear for his faith and his country. The barbarians seemed strangely sure about what they were doing. They had spent a long time observing, making simple trials, doing very little and nothing roughly—not like the barbarians of his imagination, but like skilled men. Could it be that they would solve the problem? Even if they did, a voice within him reminded him, there was one thing no ingenuity could find: the strange seepages of Tmutorakan far beyond the Black Sea, where the oil welled up out of the ground.
The fire was burning, the pump was operating, the barbarian with the squint sweating as he worked. In his bones the siphonistos could feel the pressure increasing, building up. It had to build up, it must not be allowed to grow too great, heat and pressure had to be balanced just so.
Observing carefully out of the corner of his one eye, Shef watched the signs of tension grow in the captive Greek. He feared the fire perhaps more than they did. And he knew, as they did not, when the likely moment of disaster would be. Had he the resolution to face death unmoved? Shef felt sure that he would make some sign of betrayal. If he did, he and Steffi and the others would be over the side and into the water in a moment. But the Greek did not know that.