Fortunately they had knives with big, strong blades, and as Tom had said, the stone was comparatively soft. But, after several hours' work they only had a small depression under the stone door.
"At this rate it will take a month," sighed Ned.
"Say!" cried Tom, "we're foolish. We should try to cut through the stone slab itself. It can't be so very thick. And another thing. I'm going to play the flames from the gas torches on the stone. The fires will make it brittle and it will chip off easier."
This was so, but even with that advantage they had only made a slight impression on the solid stone door after more than four hours of work, and Eradicate came back, with a hopeless look on his face, to report that he had been unable to find water.
"Then we've got to save every drop of what we've got," declared Tom. "Short rations for everybody."
"And our lights, too," added Mr. Damon. "We must save them."
"All out but one!" cried Tom quickly. "If we're careful we can make them gas torches last a week, and the electric flashes are good for several days yet."
Then they laid out a plan of procedure, and divided the food into as small rations as would support life. It was grim work, but it had to be done. They found, with care, that they might live for four days on the food and water and then--
Well--no one liked to think about it.
"We must take turns chipping away at the stone door," decided Tom. "Some of us will work and some will sleep--two and two, I guess."