"Fire again!" cried Dave, and blazed away, bringing his game to its knees. Bob also fired, but missed his mark. Then on they went again, over rocks and stubble and through a mass of trailing vines, to where Dave's goat had gone down. The animal was dead. "Good for you!" cried Bob. "Now I must do as well!" and away he went again, with Dave at his heels, anxious, if possible, to add the kids to his bag. At the top of the second line of hills the wounded goat made a sharp turn to the left. On went the young hunters after him, never dreaming of the pitfall into which they were rushing. They were now side by side, and Bob was on the point of blazing away at the wounded goat, in full view before him, when Dave clutched his arm. "Back!" "What's up?" "Nothing's up, but we'll be down if we don't take care!" "What do you mean?" Before Dave could reply, Bob saw what had caused the young diver to become alarmed. They were walking over some moss and brushwood, and the mass under their feet was shaking like so much jelly. Both started to retreat, but it was too late! Down went the mass of brushwood, at first slowly and then swifter and swifter. They tried to clutch at the sides of the opening, but in vain. Everything they grasped gave way--sticks, moss, stones, bushes, vines. Nothing could stop that downward course. The moss was dry and the dust filled their eyes, almost blinding them. "We are lost!" gasped Bob, and then the dust got into his throat and he began to cough as though choking. In the excitement of the moment, Dave's shotgun went off, the charge passing directly between him and his companion. After falling about twenty feet, the mass of brushwood became wedged tight for a moment, and stopped descending. "Oh!" came from Dave. "Now we are in a pickle. How are we to get out?" For the moment they scarcely dared to move. Then Bob took a step forward and the young diver did the same. Instantly the mass began to sink once more, at first slowly and then as rapidly as ever. Down they went--thirty feet, forty, fifty, sixty--a hundred, until the top of the hole was lost to sight and they found themselves they knew not where. Again the brushwood and moss became wedged fast. But now they did not dare to move for fear of dislodging it once more. "We are lost!" came from the engineer. "We'll never get out of this alive!" "Don't give up yet," answered Dave, bravely, yet his heart felt like a lump of lead in his bosom. "Where can we be?" "Down in a mighty deep hole." "I know. But is this the bottom?" "There's no telling. We might--we are going down again!" It was true. They were again descending, but now slowly, as if the passage below was growing smaller. "Shall we ever stop!" groaned Dave. "It's all up with us!" came from Bob. "We won't be able--gracious! Water!" The young engineer was right. The mass of brushwood had reached the level of some water at the bottom of the hole.