He raised the piece to his shoulder and took quick aim. There was a sliver of flame, a puff of smoke and a sharp report. The professor and the boys who were watching the cylinder saw it vibrate up in the air. Then there came a whistling sound. An instant later the metal body began to descend, and it and the weight fell to the earth. “I’m sorry I had to put a bullet through it, Professor,” said old Andy with a queer smile, “but it was the only way I saw of bringing it down. Hope it isn’t damaged much.” “It doesn’t matter if it is,” the scientist answered. “I can make more cylinders, but I don’t want that secret of the gas to become known. Your bullet served a good turn, Andy, for it let the compressed vapor out just in time.” “Then we may consider the experiment a success,” said Mark, as Washington went to where the cylinder had fallen, to detach it from the weight and bring both to the shed. “It seems so,” Mr. Henderson answered. “True, it was only an experiment. We have yet to test the ship itself.” “When can we do that?” asked Jack. “I hope by Monday,” the scientist answered. “Will you try it in the water or air first?” asked Mark. “I’m almost certain it will float in the water,” the aged inventor said. “It does not require much work to make a ship which will do that. But the air proposition is another matter. However, since the cylinder rose, I am pretty sure the _Flying Mermaid_ will. “But we have done enough work to-day. Let’s rest and have something to eat. Then, with Sunday to sit around and talk matters over, we will be ready for Monday’s test.” Some of the game Andy had killed was soon on the table, for Washington, in addition to his other accomplishments, was an expert cook. During the evening the boys and their friends sat in the living room of the big shed and talked over the events of the day. Sunday was spent in discussing what adventures might lie before them should they be able to descend into the big hole. Washington did not say much, but it was easy to see he had no notion of going. He even began to pack his few belongings in readiness to leave the service of Mr. Henderson, for whom he had worked a good many years. No one remained long abed Monday morning. Even Washington was up early in spite of the interest he had lost in the professor’s voyage. “I jest wants t’ see yo’ start fer that place where they buries live folks,” he said. In order to properly test the _Flying Mermaid_ it was necessary to move the craft from the shed from which place it had never been taken since it’s construction was started. It had been built on big rollers in anticipation of this need, so that all which was now necessary was to open the doors at the end, and roll the craft out. This was accomplished with no small amount of labor, and it was nearly noon before the big ship was moved into the open. It was shoved along to a little clearing in front of the shed, where no trees would interfere with its possible upward movement.