"The area lost," continued Rawolle, "was about one hundred thousand square miles; the volume nearly one hundred and seventy-five trillion cubic feet. The water-shed of the Ohio produced ten billion cubic feet per day, all of which flowed into the Central Sea. The first two years the Mississippi discharged a like amount into the sunken area. It was estimated that over ninety trillion cubic feet of water were pushed up, so to speak, from the strata of the earth by the subsidence of the upper crust. Thus, one hundred trillion cubic feet of water rushed into the doomed basin of the Ohio in the first two years, making inundation very rapid during that time, and frightfully rapid during the first week. The Ohio water-shed supplied nearly four trillion cubic feet per year, which, to complete the seventy-five trillion necessary to fill the sea, took twenty-one years."
"This is a most wonderful occurrence, and did I not have ocular proof of its reality, I admit I should be loath to believe it a possibility;" and Cobb seemed lost in a reverie of the marvelous events which had transpired during his long sleep on Mt. Olympus.
The tinkling of a bell caused Lieutenant Sibley, who had been writing at his desk, to look up and say:
Then, going to the tube, he answered Mr. Irwin, in the pilot-room, and was informed that the vessel was then over the city of Louisville.
The Tracer was soon brought to a rest, and Cobb witnessed the peculiar arrangements made for descending to the bottom of the sea. He watched every movement and noted every detail, and saw with what wonderful facility a thousand-ton ship could be made to obey a man's will.
The mast of the Tracer was dropped until its top rested upon the deck of the vessel, its top closing automatically to prevent the ingress of water. A large circular float containing air-valves, and attached to a long hose, was loosened from its fastenings on the deck. The water cylinders were opened, and as they partially filled, the vessel lost its superiority of displacement and began to sink; the large float, with its air-valves, and attached to the hose, remained upon the top of the water, permitting air to be drawn down into the vessel by suction. Thus a constant supply of fresh air was obtained without recourse to the compressed air in store. In fact, the latter was never used except in emergencies or when it was desired, as in the case of war, to keep the approach of the vessel a secret.