As she came into the open her pumps commenced to expel the air from the three lower tanks, and at the same time a portion of her excess water ballast was slowly discharged, and almost immediately the huge ship rose slowly and gracefully from the ground.
The entire personnel of the ship's company during the test flight was the same that had been selected for the expedition. Zuppner, who had been chosen as captain, had been in charge of the construction of the ship and had a considerable part in its designing. There were two mates, Von Horst and Dorf, who had been officers in the Imperial air forces, as also had the navigator, Lieutenant Mines. In addition to these there were twelve engineers and eight mechanics, a negro cook and two Filipino cabin-boys.
Tarzan was commander of the expedition, with Jason Gridley as his lieutenant, while the fighting men of the ship consisted of Muviro and nine of his Waziri warriors.
As the ship rose gracefully above the city, Zuppner, who was at the controls, could scarce restrain his enthusiasm.
"The sweetest thing I ever saw!" he exclaimed. "She responds to the lightest touch."
"I am not surprised at that," said Hines; "I knew she'd do it. Why we've got twice the crew we need to handle her."
"There you go again, Lieutenant," said Tarzan, laughing; "but do not think that my insistence upon a large crew was based upon any lack of confidence in the ship. We are going into a strange world. We may be gone a long time. If we reach our destination we shall have fighting, as each of you men who volunteered has been informed many times, so that while we may have twice as many men as we need for the trip in, we may yet find ourselves short handed on the return journey, for not all of us will return."
"I suppose you are right," said Hines; "but with the feel of this ship permeating me and the quiet peacefulness of the scene below, danger and death seem remote."
"I hope they are," returned Tarzan, "and I hope that we shall return with every man that goes out with us, but I believe in being prepared and to that end Gridley and I have been studying navigation and we want you to give us a chance at some practical experience before we reach our destination."
Zuppner laughed. "They have you marked already, Hines," he said.
The Lieutenant grinned. "I'll teach them all I know," he said; "but I'll bet the best dinner that can be served in Berlin that if this ship returns I'll still be her navigator."
"That is a case of heads-I-win, tails-you-lose," said Gridley.
"And to return to the subject of preparedness," said Tarzan, "I am going to ask you to let my Waziri help the mechanics and engineers. They are highly intelligent men, quick to learn, and if some calamity should overtake us we cannot have too many men familiar with the engines, and other machinery of the ship."
"You are right," said Zuppner, "and I shall see that it is done."
The great, shining ship sailed majestically north; Ravensburg fell astern and half an hour later the somber gray ribbon of the Danube lay below them.
The longer they were in the air the more enthusiastic Zuppner became. "I had every confidence in the successful outcome of the trial flight," he said; "but I can assure you that I did not look for such perfection as I find in this ship. It marks a new era in aeronautics, and I am convinced that long before we cover the four hundred miles to Hamburg that we shall have established the entire air worthiness of the O-220 to the entire satisfaction of each of us."
"To Hamburg and return to Friedrichshafen was to have been the route of the trial trip," said Tarzan, "but why turn back at Hamburg ?"
The others turned questioning eyes upon him as the purport of his query sank home.
"Yes, why?" demanded Gridley.
Zuppner shrugged his shoulders. "We are fully equipped and provisioned," he said.
"Then why waste eight hundred miles in returning to Friedrichshafen ?" demanded Hines.
"If you are all agreeable we shall continue toward the north," said Tarzan. And so it was that the trial trip of the O-220 became an actual start upon its long journey toward the interior of the earth, and the secrecy that was desired for the expedition was insured.
The plan had been to follow the Tenth Meridian east of Greenwich north to the pole. But to avoid attracting unnecessary notice a slight deviation from this course was found desirable, and the ship passed to the west of Hamburg and out across the waters of the North Sea , and thus due north, passing to the west of Spitzbergen and out across the frozen polar wastes.
Maintaining an average cruising speed of about 75 miles per hour, the O-220 reached the vicinity of the north pole about midnight of the second day, and excitement ran high when Hines announced that in accordance with his calculation they should be directly over the pole. At Tarzan's suggestion the ship circled slowly at an altitude of a few hundred feet above the rough, snow-covered ice.
"We ought to be able to recognize it by the Italian flags," said Zuppner, with a smile. But if any reminders of the passage of the Norge remained below them, they were effectually hidden by the mantle of many snows.
The ship made a single circle above the desolate ice pack before she took up her southerly course along the 170th East Meridian .
From the moment that the ship struck south from the pole Jason Gridley remained constantly with Hines and Zuppner eagerly and anxiously watching the instruments, or gazing down upon the bleak landscape ahead. It was Gridley's belief that the north polar opening lay in the vicinity of 85 north latitude and 170 east longitude. Before him were compass, aneroids, bubble statoscope, air speed indicator, inclinometers, rise and fall indicator, bearing plate, clock and thermometers; but the instrument that commanded his closest attention was the compass, for Jason Gridley held a theory and upon the correctness of it depended their success in finding the north polar opening.
For five hours the ship flew steadily toward the south, when she developed an apparent tendency to fall off toward the west.
"Hold her steady, Captain," cautioned Gridley, "for if I am correct we are now going over the lip of the polar opening, and the deviation is in the compass only and not in our course. The further we go along this course the more erratic the compass will become and if we were presently to move upward, or in other words, straight out across the polar opening toward its center, the needle would spin erratically in a circle. But we could not reach the center of the polar opening because of the tremendous altitude which this would require. I believe that we are now on the eastern verge of the opening and if whatever deviation from the present course you make is to the starboard we shall slowly spiral downward into Pellucidar, but your compass will be useless for the next four to six hundred miles."
Zuppner shook his head, dubiously. "If this weather holds, we may be able to do it," he said, "but if it commences to blow I doubt my ability to keep any sort of a course if I am not to follow the compass."
"Do the best you can," said Gridley, "and when in doubt put her to starboard."
So great was the nervous strain upon all of them that for hours at a time scarcely a word was exchanged.
"Look!" exclaimed Hines suddenly. "There is open water just ahead of us."
"That, of course, we might expect," said Zuppner, "even if there is no polar opening, and you know that I have been skeptical about that ever since Gridley first explained his theory to me."
"I think," said Gridley, with a smile, "that really I am the only one in the party who has had any faith at all in the theory, but please do not call it my theory for it is not, and even I should not have been surprised had the theory proven to be a false one. But if any of you has been watching the sun for the last few hours, I think that you will have to agree with me that even though there may be no polar opening into an inner world, there must be a great depression at this point in the earth's crust and that we had gone down into it for a considerable distance, for you will notice that the midnight sun is much lower than it should be and that the further we continue upon this course the lower it drops—eventually it will set completely, and if I am not much mistaken we shall soon see the light of the eternal noonday sun of Pellucidar."