The next instant there came an appalling sound, an onrush like the voice of a hundred waterfalls. The wind puffed in their faces in sharp blasts, and something swept by them in the darkness with a strange, muffled shriek. CHAPTER X. THE GHOST OF THE CAVE DWELLING. "L-l-let's get out of here--_quick_!" Tubby gasped the exclamation, as with a resounding rush the mysterious sounds swept by. "Ouch, somebody hit me in the face!" howled Jeb Cotton suddenly. "Me, too!" yelled Bill Simmons. "Say, fellows," shouted Rob suddenly, as the noise lessened, "be quiet, will you, till I light a candle. I've an idea what that noise was, and it was nothing to get scared at." "Oh, it wasn't, eh?" protested Tubby angrily. "Well, something hit me a bang on the nose." "And me on the ear," chimed in Jeb Cotton. "And me----" Bill Simmons was beginning, when Rob checked him. "Let up a minute, will you, and give me a chance? All that racket was caused by nothing more than a lot of old bats." "Cats, you mean, or flying rats," said Tubby scornfully. "No, bats. Look here. I knocked down one." Rob held his candle high above his head, and the astonished boys saw lying under a projecting bit of rock one of the leathern-winged cave-dwellers. "Huh," remarked Tubby, "and I thought it was ghosts. The ghost of the cliff. The one the cow-puncher said he saw." "I guess that ghost has leather wings and a furry body, if the truth were known," laughed Rob, as he flung the bat he had knocked down into the air, and the creature flapped heavily off toward the cave mouth. "Yes, ghosts are----" began Merritt, when he broke off suddenly. His mouth opened to its fullest extent, and his eyes grew as round as two big marbles. "Great hookey--what's that?" His frightened expression was mirrored on the rest of the countenances in the candle-lit circle, as a strange sound was borne to the ears of the Boy Scouts. "It's footsteps," gasped Jeb Cotton. "Coming this way, too," stuttered Tubby, edging back. "Nonsense," said Rob sharply, but nevertheless loosening his revolver in its holster. "It's the wind or something." "The funniest wind I ever heard," interrupted Tubby scornfully. "It's got feet--hark!" Nearer and nearer came the mysterious sound. They could now hear it distinctly--a soft "phut-phut" on the dusty floor of the passage. "Wow-oo, I see two eyes!" yelled Tubby, suddenly taking to his heels. His toe caught on a hidden rock, and he fell headlong in the choking dust. Scarcely less startled than the fat boy was Rob, as he made out, glaring at them from beyond the friendly circle of light, two big green points of fire. "Who's there?" he cried sharply. There was no answer, but the two green globes never moved. "Speak, or I'll fire!" cried the boy. "A-choo-oo-o--o-o-o-o-o!"