But it was not the size of the great hole in the ground, not its fearful gloom, that attracted their attention. What did was a great natural or artificial bridge of stone that was thrown across the middle of it from edge to edge. A bridge of stone that spanned the abyss; a roadway, fifty feet wide, which reached into some unknown land, connecting it with the desolate country in which our friends had been wandering.
"A bridge of stone across the cavern," said Jack, "but see. Here is a house of stone. This was the guard-house, I'll wager--the guardhouse at the entrance to some city, and that bridge is the means by which the inhabitants entered and left. Maybe we are at the edge of the inhabited part of the moon!"
His words thrilled them. They pressed forward to the beginning of the bridge across the crater. They looked into the stone hut. Clearly it had been made by hands, for it was composed of blocks of stone, neatly fitted together. Jack's theory seemed confirmed.
Mark peered into the house, and uttered a cry of alarm.
"There's a petrified man in there!" he gasped.
Jack and Andy looked in at the open window. They saw, sitting at a table, which was also of rock, a man, evidently a soldier, or rather he had been, for he was nothing but stone now, like the hut in which he dwelt.
The wanderers looked at each other with fear on their faces. What dreadful mystery were they about to penetrate? "Let's cross the bridge," suggested Jack, in a low voice. "Maybe this marks the end of desolation. Perhaps we may find life and food across the crater."
"But--but the petrified man!" gasped Mark.
"What of it? He won't hurt us. Maybe there are live men, who will take care of us, beyond there," and Jack pointed across the bridge of stone.
There was nothing to keep them where they were--in the land of desolation. They could not live much longer there, with no food and water. To pass on over the crater seemed the only thing to do.
"Come ahead," called Jack boldly. They followed him. They kept in the middle of the road, for to approach the edge, where there was a sheer descent of so many feet that it made them dizzy to think of it, filled them with terror. On they hurried until, in a short time, they had crossed the great chasm.