There must be some other outlet. When the other side of the crater had been reached, they were surprised at its immensity. When in the center they had imagined the diameter of the almost circular crater to be some fifty or sixty feet, but as they pushed their boat round, they discovered that it must be more than three times that distance. Another thing puzzled them. Were fish and lizards constantly petrified as they floated or swam into the vortex, or was it only during an eruption? “Shall we go on or wait here?” asked Ibrahim. “We will go on after we have had something to eat.” “Happy thought that, Max, for I am hungry.” A package of food was opened out, and Max commenced eating; but he made such a grimace that Ibrahim laughed heartily. “Stop that. The echo will drive me mad!” exclaimed Max, who recalled that terrible time in the tomb near Cairo. “Stop making faces then.” “You will make a worse one when you taste----” “What?” “Your lunch.” “Why?” “It is strong with sulphur.” Alas! all their food had become impregnated with sulphur fumes and almost turned them sick, but they could get no other and hunger is a tyrannic master. They ate heartily, notwithstanding the sulphur, Max telling them how civilized people will travel many miles and spend large sums of money in order to drink water impregnated with sulphur. “Had we better commence to limit our rations?” asked Ibrahim, when he had eaten all he possibly could. They had not thought of that. It was becoming serious. They might be a long time before they could obtain a fresh supply of food. “We will start to-morrow,” Max decided. The water began to be agitated again and it was deemed advisable to get away from the crater. After a short journey through another tunnel they reached daylight. The river ran sluggishly along between two high cliffs. “I am sure we are the first to navigate this river.” “I think so, too, Max.” “I am sure of it. It is not on any map, for I have always been interested in African deserts.” “You have?” “Yes, I think a wonderful people are to be found in Sahara--white people whose knowledge is greater than ours.” “Fact?” “Yes, Ib. I have often thought that the ancient Egyptians knew many engineering secrets which are lost to us; they certainly had power of divination and many other things which puzzle the brains of our best men to-day. Why should not these old fellows have left Egypt and founded a new country where they would be free from the incursions of other nations?” “But they died thousands of years ago.” “Of course they did, but we didn’t. And their descendants may be living.” “Don’t say a word to Uncle Sherif, or he will make us start off in search at once.” “Seriously, do you ever expect to see your uncle or Girzilla again?” It was a cruel question to ask, but Max was in the same boat, and he had but little hope of escape. “I hope so. Why not?” “Because---- Hello! we are in the dark again.”