"Of course the would-be thief may be among those we warned," said Mark, on returning to his own tent. "But if so, he'll realize that we will stand for no more such treachery." Several days passed, including Sunday, which was spent in resting up and in looking over their clothing. The boys also took a bath, in a pool of spring water back of the camp, which was both healthful and refreshing. Monday afternoon found Mark and Bob working at the bottom of a deep sand hole near the end of the gulch. Si and Maybe Dixon were not far away. Each of the party had found some small nuggets, but nothing of great value. "We must be careful here," said Mark, as he got to the bottom of the hole. "This sand is none too firm." "Oh, I reckon it will hold," cried Bob, who was scraping away industriously with his shovel. "But we can't go much further, to my way of thinking. We have about reached bed rock." "That is so. And I think--Oh! help!" Mark got no further, for at that instant the sand began to crumble down on one side of the hole. He made a wild spring for the other side and caught hold of a rope which they had been using for hoisting sand that they wanted to wash. As he went up, the whole hole caved in, burying him up to his knees. Bob was completely covered and could do absolutely nothing to save himself. Mark continued to call for aid, and soon Si and Maybe Dixon came running to the spot. "Hullo, Mark is caught in the sand hole!" cried the former farm boy. "Save me, and save Bob!" gasped Mark, who was trying his best to get away from the sand which held him. "Where is Bob?" "At the bottom of the hole." "You don't say!" exclaimed Maybe Dixon. "Boys, we've got to dig him out an' do it quick, or maybe he'll be smothered!" It was an easy task to drag Mark from the top of the opening, and this done they set to work to dig the sand from the hole. Mark and Maybe Dixon worked with their hands until Si brought up some shovels. In the meantime they called to two other miners who were not far away. "A cave-in, eh?" said one of the miners, running up. "Worse," said Mark. "Bob Billings is at the bottom of the hole." "Gee shoo! Ye don't tell me!" cried the miner. "We must git him out." "Thet's the talk, Jim," said his partner, and they pitched in with a will, and soon all on top of the ground were making the sand fly in all directions. It was no easy matter to keep the sand from caving in again and one of the miners ran off and soon brought back several short boards, with which one side of the hole was shored up. Then, a few seconds later, Mark uttered a cry as he uncovered the top of the handle of a pick. "Bob had hold of that when the cave-in came." "Maybe he has hold of it still," suggested Maybe Dixon. Mark took hold of the pick handle and pulled upon it. "Bob! Bob!" he called out loudly. "Here!" came faintly through the hole made by the moving of the pick handle. "Hold fast, can you?" "I'll try."