He further increased the speed of the propellers, and the gas machine was set to make vapor at its fullest capacity, and force it into the bag. Still the craft was held to the earth. "Maybe the gas has no effect in this climate," called Ned. "It can't be that," replied Tom. "The gas will operate anywhere. It worked all right today." Suddenly she airship moved up a little way, and then seemed to be pulled down again, hitting the ground with a bump. "Something is holding us!" cried Tom. "We're anchored to earth! I must see what it is!" and, catching up his electric rifle, he dashed out of the cabin. CHAPTER XII AMONG THE NATIVES For a moment after Tom's departure the others stared blankly at one another. They could hear the throbbing and hum of the machinery, and feel the thrill of the anchored airship. But they could not understand what the trouble was. "We must help Tom!" cried Ned Newton at length as he caught up his rifle. "Maybe we are in the midst of a herd of elephants, and they have hold of the ship in their trunks." "It couldn't be!" declared Mr. Durban, yet they soon discovered that Ned's guess was nearer the truth then any of them had suspected at the time. "We must help him, true enough!" declared Mr. Anderson, and he and the others followed Ned out on deck. "Where are you Tom?" called his chum. "Here." was the answer. "I'm on the forward deck." "Do you see anything?" "No, it's too dark. Turn the search-light this way." "I will," shouted Mr. Damon, and a moment later the gleam of the powerful lantern brought Tom clearly into view, as he stood on the small forward observation platform in the bow of the Black Hawk. An instant later the young inventor let out a startled cry. "What is it?" demanded Mr. Durban. "An immense snake!" shouted Tom. "It's wound around a tree, and partly twined around the ship! That's why we couldn't go up! I'm going to shoot it." They looked to where he pointed, and there, in the glare of the light, could be seen an immense python, fully twenty-five feet long, the forward part of its fat ugly body circled around the slender prow of the airship, while the folds of the tail were about a big tree. Tom Swift raised his electric rifle, took quick aim, and, having set it to deliver a moderate charge, pressed the button. The result was surprising, for the snake being instantly killed the folds uncoiled and the ship shot upward, only, instead of rising on an even keel, the bow pointed toward the sky, while the stern was still fast to the earth. Tilted at an angle of forty-five degrees the Black Hawk was in a most peculiar position, and those standing on the deck began to slide along it. "There's another snake at the stern!" cried Mr. Damon as he grasped a brace to prevent falling off. "Bless my slippers! it's the mate of the one you killed! Shoot the other one, Tom!"