"There must be a cavern beyond, the entrance to which is at the foot of the cliff."
"And in which it is probable that animals take shelter during the night," added Gordon.
"That is it," said Donagan. "And to-morrow we must try and find it."
At this moment a bark was heard, and then a howling. The sound came from the interior of the rock.
"Can Fan be there?" asked Wilcox, "and fighting with some animal?"
Briant went back into the tunnel and listened with his ear against the wall. But there was nothing more. Whether Fan was there or not, it was evident that there must be a second opening which ought to communicate with the exterior, probably by some gap in the thicket of brushwood.
The night passed without either barking or howling being again heard.
Next morning the search was begun at break of day, but with no more result than the day before. Fan, sought for and shouted for all over the neighbourhood, did not come back.
Briant and Baxter took turns at the digging. Pickaxe and shovel were kept constantly at work. During the morning the tunnel was made two feet longer. From time to time the boys stopped to listen, but nothing could they hear.
After dinner the digging began again. Care was taken in case a blow of the pickaxe knocked through the wall and gave passage to an animal. The younger boys were taken out to the bank of the river. Gun in hand, Donagan, Wilcox, and Webb stood ready for anything that might happen.
About two o'clock Briant suddenly exclaimed. His pickaxe had gone through the limestone, which had fallen in and left a good-sized hole.
Immediately he returned to his comrades, who could only think — But before they had time to open their mouths, an
