They all agreed that they would rather work than sleep, and soon the entire force was busy in the engine room. There was much to be done, and the most important things were attended to first. The motive power was overhauled and found to be in need of several new parts. These were put in and then the gas generator, and the negative gravity machine, were put in shape. It would have taken something very substantial to have awakened any one on board the _Mermaid_ that night. They all slept soundly and awoke to find the strange colored lights shining in through the glass covered port holes. “Well, the sun, or what corresponds to it, is up,” observed Jack, “and I guess we had better do as the little boy in the school reader did, and get up, too, Mark.” Soon all the travelers were aroused, and the sound of Washington bustling about in the kitchen, whence came the smell of coffee, bacon and eggs, told the hungry ones that breakfast was under way. After the meal work was again started on repairing the ship, and by noon the professor remarked: “I think we shall try a little flight after dinner. That is, if one thing doesn’t prevent us.” “What is that?” asked Jack. “We may be held down, as were those stones,” was the grave answer. CHAPTER XXI THE FISH THAT WALKED It was with no little apprehension that the professor prepared to take his first flight aboard the ship in the realms of the new world. He knew little or nothing of the conditions he might meet with, the density of the atmosphere, or how the _Mermaid_ would behave under another environment than that to which she was accustomed. Yet he felt it was necessary to make a start. They would have to attempt a flight sooner or later, and Mr. Henderson was not the one to delay matters. So, the last adjustment having been made to the repaired machinery, they all took their places in the ship. The boys and the professor went to the conning tower to direct matters, while Washington and the others were in the engine room to see that the machinery worked properly. Mark gave a last look outside as he closed the big steel cover over the hole through which admission was had to the craft. He thought he might catch a glimpse of the queer shadow, but nothing was in sight. It was like a beautiful summer’s day, save for the strange lights, shifting and changing. But the travelers had become somewhat used to them by this time. The professor turned the valve that allowed the gas to enter the holder. There was a hissing sound and a sort of trembling throughout the entire ship. The dynamos were whizzing away and the negative gravity machine was all ready to start. For several minutes the travelers waited until the big lifting tank was filled with the strong vapor. They watched the gages which indicated the pressure to be several hundred pounds.