"That's what I was afraid of!" cried the old elephant hunter, catching up his gun. "Some black scout has seen us and is summoning his tribesmen. Hurry, Tom, send up the ship, and we'll take care of the savages." "But I CAN'T send her up!" cried Tom. "You can't? Why not?" "Because the gas machine won't work until I put in a new cylinder, and that will take at least a half a day." "Go up as an aeroplane then!" cried Mr. Damon. "Bless my monkey wrench, Tom, you've often done it before." For answer Tom waved his hand toward the thick jungle all about them. "We haven't room to get a running start of ten feet." he said, "and without a start the airship can never rise as a mere aeroplane. The only way we can get up from the jungle is like a balloon, and without the gas--" He paused significantly. The sound of the war drums became louder, and to it was added a weird singing chant. "The natives!" cried Mr. Anderson. "They're coming right this way! We must fight them off if they attack us!" "Where's the electric rifle?" asked Ned. "Get that out, Tom!" "Wait!" suggested Mr. Durban. "This is serious! It looks as if they were going to attack us, and they have us at a disadvantage. Our only safety is in flight, but as Tom says we can't go up until the gas machine is fixed, he will have to attend to that part of it while we keep off the black men. Tom, we can't spare you to fight this time! You repair the ship as soon as you can, and we'll guard her from the natives. And you've got to work lively!" "I will!" cried the young inventor. "It's luck we have a spare cylinder!" Suddenly there was a louder shout in the jungle and it was followed by a riot of sound. War drums were beaten, tom-toms clashed and the natives howled. "Here they are!" cried Mr. Anderson. "Bless my suspenders!" shouted Mr. Damon. "Where is my gun?" "Here, you take mine, and I'll use the electric rifle," answered the elephant hunter. As he spoke there was a hissing sound in the air and a flight of spears passed over the airship. The defenders slipped outside, while Tom, with Ned to help him, worked feverishly to repair the break. They were in a serious strait, for with the airship practically helpless they were at the mercy of the natives. And as Tom glanced momentarily from the window, he saw scores of black, half-naked forms slipping in and out among the trees and trailing vines. Soon the rifles of his friends began to crack, and the yells of the natives were changed to howls of anguish. The electric weapon, though it made no noise, did great execution. "I only hope they don't puncture the gas bag," murmured Tom, as he began taking the generating machine apart so as to get out the cracked cylinder. "If they do, it's all up with us," murmured Ned.