The tense silence was shattered by a loud sneeze from Tubby, whose nostrils had become filled with the irritating dust. At the same instant an unearthly howl rang through the rocky corridors--a cry so terrible that it set Rob's heart to beating fiercely. He pulled the trigger more by instinct than anything else, and six spurts of flame leaped from the barrel of his automatic. With a howl more ear-piercing than the first, the points of fire vanished, and there was the sound of a heavy body falling. "Dead! whatever it is," was Rob's thought, but nevertheless he proceeded cautiously. It was well that he did so, for as he held his candle aloft, the huge, dun-colored body, which lay on the ground directly in front of him, made a convulsive spring. Rob, on the alert as he was, leaped back, and avoided it by a hair's breadth. "A mountain lion!" cried Harry. "That's what, and a whumper, too," exclaimed Merritt. "I guess we've laid the ghost all right. In the moonlight a light-colored creature like this would look white against the cliff face." "I wonder if that last sneeze of mine killed it?" remarked Tubby, who had leisurely sauntered up. There was now no doubt that the great tawny creature was dead. Its final spring must have been a purely convulsive act, for Rob's bullets had pierced its skull in three places. "Say, fellows," exclaimed Rob suddenly, "the fact that this brute was in here proves a mighty interesting fact." "And that is, that it's dead." "Please be quiet for two consecutive minutes, Tubby, if you can do it without injuring yourself. It means that there is another entrance to this place somewhere." "How do you make that out?" asked Jeb Cotton. "By applying a little scout lore. There are no tracks at the mouth of the cave, yet this lion is fat and well-fed, so that it must get its food outside somewhere. Therefore, there must be another entrance to the cave." "Quod erat demonstrandum," quoth Tubby learnedly. "Which is all the Euclid you know," teased Merritt. "Well," asked Rob, while Harry Harkness skillfully skinned the lion, "shall we go on or turn back?" "We'll go on!" shouted everybody. "If you guarantee no more scares," amended Tubby. With the tawny pelt slung over Harry's broad shoulder, the little party therefore pressed on into the darkness. "We'll have to hurry," said Rob suddenly, regarding his candle, of which not much was left. "How far do you guess it is from the entrance?" questioned Harry. "I've no idea," was Rob's rejoinder. "I half believe now we were wrong to try to find a way out this way." He said this in a low voice, so as not to alarm the others, who were behind the leaders. It did indeed begin to look as if the young explorers had placed themselves in a predicament.