“I wonder where we are?” asked Jack, who with Mark had come back from the tower.

“We’ll have to guess at it,” replied Andy.  “It would be as much as a man’s life is worth to go outside and take an observation.”

“Don’t hab to do dat,” broke in Washington.  “See here!”

He stooped over and pulled on an iron ring that was fastened in the floor of the dining-room cabin.  A section of a board came up.

“Look!” exclaimed the negro pointing down.  All leaned forward and saw that a heavy plate glass had been set over a hole cut through the floor of the ship.  By means of this strange window one could look directly down toward the earth.  Jack kneeled and peered through the glass.  He rose to his feet with a cry of fear.

“What’s the matter?” asked Andy.

“We are right over the ocean!” exclaimed the boy.  “I can see immense waves not three hundred feet below!  The airship must be falling and we’ll be dashed into the sea!”

At these words Washington ran to the engine room.  He looked at the height indicator.

“We’s four hundred feet in de air, an’ a—­we’s agoin’ down!” he muttered.

Jack, who had followed him, saw by the instrument what the dreadful truth was.  Blown from her course, the Monarch was now over an open polar sea, into which she might be dashed at any moment.  The tornado still howled and roared outside, making it impossible to inflate the gas bag, so strong was the pressure of wind on it.  And without a fresh supply of gas, the ship must fall.

There was no abatement to the tornado.  The ship was tossed more violently than ever.  Jack peered through the floor-window again.

“We are nearer the water!” he exclaimed as he arose.  “The sea is covered with icebergs.  They are crashing together in the big waves.  If we fall the ship will be ground to pieces in the floes!”

“Try the gas machine again!” urged Andy.  “Maybe the wind has lessened.”

Washington started the machine.  He kept one eye on the needle of the indicator that told the gas pressure in the bag, and the other on the height register.  The black pointer of the latter went lower and lower.  It was now at one hundred, and kept on going down slowly, until it stood at seventy-five.  Soon only sixty-five feet stood between the airship and her passengers, and the angry, swirling water beneath, where the icebergs crashed and ground together.

Then Washington, who was ready to faint with fear and despair, gave a cry of joy.  He had noticed that the height indicator stopped.  At the same time the gas register showed that the vapor from the machine was entering the bag.

“Glory!  Glory!” cried the negro.  “We’s saved now.  De ship is goin’ up, and the gas is workin’ in.  De wind must be goin’ down!”

Then, while all save Professor Henderson, who was still unconscious, crowded into the engine room, they saw that what Washington said was true.  The pressure of the wind had lessened, permitting the bag to fill with the gas.  This served to lift the ship, and the pointer on the height indicator began to move upward.  Higher and higher went the craft, until in a few minutes the register showed six hundred feet.  They had been saved from death in the sea.