“It’s a storm in the upper regions!  We’ll find it calm below!” cried the professor above the howling of the gale.  He opened the gas outlet wider and the ship fell more rapidly.

“Are you sure we’re over the ocean?” asked Mark.

“Positive!” the professor called back.  “We have been traveling straight south over the Atlantic for the last week.  We will land in the midst of the waters and float safely.”

Lower and lower went the Mermaid.  The wind was now blowing with the force of a tornado, and, as the craft had to slant in order to descend, it felt the power of the gale more than if it had scudded before it.  But, by skilful use of the directing tube, the professor was able to keep the boat from turning over.  As they came further down toward the earth the force of the wind was felt less and less, until, as they came within two hundred feet of the water which they saw below them in the gathering dusk, it died out altogether.

“Now we are free from it,” said the professor as the Mermaid came down on the waves like an immense swan.

“Are you going ahead or going to stop here?” asked Mark

“We’ll keep right on,” Mr. Henderson answered.  “No telling when the storm may strike down here.  We’ll go as far as we can to-night.”

CHAPTER VII

 A queer sail

Now that the fear and worriment was over they all began to feel hungry, and, while Mark and Jack took charge of the conning tower Washington got breakfast.  The professor seemed preoccupied during the meal, and several times, when Mark spoke to him, he did not reply.

“I wonder if he is worried about something, or is thinking of something which seems to be concealed in the storeroom,” the boy thought.

But, after a while, the professor seemed to be more like himself.  He was busy over several maps and charts, and then announced the ship would try air-sailing again for a while.

“We can make better time above than we can on the water,” he said, “and I am anxious to get to the mysterious island and learn what is in store for us.”

Perhaps if the professor had been able to look ahead, and see what was soon going to happen, he would not have been so anxious for it to occur.

It was shortly after dinner when, the gas container having been filled, the ship rose in the air, and began sailing over the ocean, about a mile up.  The day was a fine one, and, as they were moving south, it was constantly growing warmer.  Down on the water, in fact, it was quite hot, but in the air it was just right.

Like some immense bird the Mermaid went flying through the air.  The boys and the professor sat upon the deck in easy chairs.  It was like being on the top of some tall “sky-scraper” building which, by some strange power, was being moved forward.  Below them the ocean tumbled in long, lazy swells.