"Go ahead, my lads."
They began to throw up, within a circle of three yards in circumference, a soil consisting of vegetable mold in which, in twenty minutes' time, they had dug a hole five feet deep. Here they came upon a layer of stones cemented together; and their work now became much more difficult, for the cement was of incredible hardness and they were only to break it up by inserting their picks into the cracks. Paul followed the operations with anxious attention.
After an hour, he told them to stop. He himself went down into the hole and then went on digging, but slowly and as though examining the effect of every blow that he struck.
"That's it!" he said, drawing himself up.
"What?" asked Bernard.
"The ground on which we are standing is only a floor of the big buildings that used to adjoin the old keep, buildings which were razed to the ground centuries ago and on the top of which this garden was laid out."
"Well?"
"Well, in clearing away the soil, I have broken through the ceiling of one of the old rooms. Look."
He took a stone, placed it right in the center of the narrower opening which he himself had made and let it drop. The stone disappeared. A dull sound followed almost immediately.
"All that need now be done is for the men to widen the entrance. In the meantime, we will go and fetch a ladder and lights: as much light as possible."