The sounds that Tarzan heard came from a great distance and were faint even to his ears: nor at first could he definitely ascribe them to their true source, though he conceived the impression that they heralded the coming of a party of men.
Buto the rhinoceros, Tantor the elephant or Numa the lion might come and go through the forest without arousing more than the indifferent interest of the Lord of the Jungle, but when man came Tarzan investigated, for man alone of all creatures brings change and dissension and strife wheresoever he first sets foot.
Reared to manhood among the great apes without knowledge of the existence of any other creatures like himself, Tarzan had since learned to anticipate with concern each fresh invasion of his jungle by these two-footed harbingers of strife. Among many races of men he had found friends, but this did not prevent him from questioning the purposes and the motives of whosoever entered his domain. And so today he moved silently through the middle terrace of his leafy way in the direction of the sounds that he had heard.
As the distance closed between him and those he went to investigate, his keen ears cataloged the sound of padding, naked feet and the song of native carriers as they swung along beneath their heavy burdens. And then to his nostrils came the scent spoor of black men and with it, faintly, the suggestion of another scent, and Tarzan knew that a white man was on safari before the head of the column came in view along the wide, well marked game trail, above which the Lord of the Jungle waited.
Near the head of the column marched a young white man, and when Tarzan’s eyes had rested upon him for a moment as he swung along the trail they impressed their stamp of approval of the stranger within the ape-man’s brain, for in common with many savage beasts and primitive men Tarzan possessed an uncanny instinct in judging aright the characters of strangers whom he met.
Turning about, Tarzan moved swiftly and silently through the trees until he was some little distance ahead of the marching safari, then he dropped down into the trail and awaited its coming.
Rounding a curve in the trail the leading askari came in sight of him and when they saw him they halted and commenced to jabber excitedly, for these were men recruited in another district—men who did not know Tarzan of the Apes by sight.
“I am Tarzan,” announced the ape-man. “What do you in Tarzan’s country?”
Immediately the young man, who had halted abreast of his askari, advanced toward the ape-man. There was a smile upon his eager face. “You are Lord Greystoke?” he asked.
“Here, I am Tarzan of the Apes,” replied the foster son of Kala.
“Then luck is certainly with me,” said the young man, “for I have come all the way from Southern California to find you.”
“Who are you,” demanded the ape-man, “and what do you want of Tarzan of the Apes?”
“My name is Jason Gridley,” replied the other. “And what I have come to talk to you about will make a long story. I hope that you can find the time to accompany me to our next camp and the patience to listen to me there until I have explained my mission.”
Tarzan nodded. “In the jungle,” he said, “we are not often pressed for time. Where do you intend making camp?”
“The guide that I obtained in the last village complained of being ill and turned back an hour ago, and as none of my own men is familiar with this country we do not know whether there is a suitable camp-site within one mile or ten.”
“There is one within half a mile,” replied Tarzan, “and with good water.”
“Good,” said Gridley; and the safari resumed its way, the porters laughing and singing at the prospect of an early camp.
It was not until Jason and Tarzan were enjoying their coffee that evening that the ape-man reverted to the subject of the American’s visit.
“And now,” he said, “what has brought you all the way from Southern California to the heart of Africa?”
Gridley smiled. “Now that I am actually here,” he said, “and face to face with you, I am suddenly confronted with the conviction that after you have heard my story it is going to be difficult to convince you that I am not crazy, and yet in my own mind I am so thoroughly convinced of the truth of what I am going to tell you that I have already invested a considerable amount of money and time to place my plan before you for the purpose of enlisting your personal and financial support, and I am ready and willing to invest still more money and all of my time. Unfortunately I cannot wholly finance the expedition that I have in mind from my personal resources, but that is not primarily my reason for coming to you. Doubtless I could have raised the necessary money elsewhere, but I believe that you are peculiarly fitted to lead such a venture as I have in mind.”
“Whatever the expedition may be that you are contemplating,” said Tarzan, “the potential profits must be great indeed if you are willing to risk so much of your own money.”
“On the contrary,” replied Gridley, “there will be no financial profit for anyone concerned in so far as I now know.”
“And you are an American?” asked Tarzan, smiling.
“We are not all money mad,” replied Gridley.
“Then what is the incentive? Explain the whole proposition to me.”
“Have you ever heard of the theory that the earth is a hollow sphere, containing a habitable world within its interior?”
“The theory that has been definitely refuted by scientific investigation,” replied the ape-man.
“But has it been refuted satisfactorily?” asked Gridley.
“To the satisfaction of the scientists,” replied Tarzan.
“And to my satisfaction, too,” replied the American, “until I recently received a message direct from the inner world.”
“You surprise me,” said the ape-man.
“And I, too, was surprised, but the fact remains that I have been in radio communication with Abner Perry in the inner world of Pellucidar and I have brought a copy of that message with me and also an affidavit of its authenticity from a man with whose name you are familiar and who was with me when I received the message: in fact, he was listening in at the same time with me. Here they are.”
From a portfolio he took a letter which he handed to Tarzan and a bulky manuscript bound in board covers.
“I shall not take the time to read you all of the story of Tanar of Pellucidar,” said Gridley, “because there is a great deal in it that is not essential to the exposition of my plan.”
“As you will,” said Tarzan. “I am listening.” For half an hour Jason Gridley read excerpts from the manuscript before him. “This,” he said, when he had completed the reading, “is what convinced me of the existence of Pellucidar, and it is the unfortunate situation of David Innes that impelled me to come to you with the proposal that we undertake an expedition whose first purpose shall be to rescue him from the dungeon of the Korsars.”
“And how do you think this may be done?” asked the ape-man. “Are you convinced of the correctness of Innes theory that there is an entrance to the inner world at each pole?”
“I am free to confess that I do not know what to believe,” replied the American. “But after I received this message from Perry I commenced to investigate and I discovered that the theory of an inhabitable world at the center of the earth with openings leading into it at the north and south poles is no new one and that there is much evidence to support it. I found a very complete exposition of the theory in a book written about 1830 and in another work of more recent time. Therein I found what seemed to be a reasonable explanation of many well known phenomena that have not been satisfactori1y explained by any hypothesis endorsed by science.”
“What, for example?” asked Tarzan.
“Well, for example, warm winds and warm ocean currents coming from the north and encountered and reported by practically all arctic explorers; the presence of the limbs and branches of trees with green foliage upon them floating southward from the far north, far above the latitude where any such trees are found upon the outer crust: then there is the phenomenon of the northern lights, which in the light of David Innes’ theory may easily be explained as rays of light from the central sun of the inner world, breaking occasionally through the fog and cloud banks above the polar opening. Again there is the pollen, which often thickly covers the snow and ice in portions of the polar regions. This pollen could not come from elsewhere than the inner world. And in addition to all this is the insistence of the far northern tribes of Eskimos that their forefathers came from a country to the north.”
“Did not Amundson and Ellsworth in the Norge expedition definitely disprove the theory of a north polar opening in the earth’s crust, and have not airplane flights been made over a considerable portion of the hitherto unexplored regions near the pole?” demanded the ape-man.
“The answer to that is that the polar opening is so large that a ship, a dirigible or an airplane could dip down over the edge into it a short distance and return without ever being aware of the fact, but the most tenable theory is that in most instances explorers have merely followed around the outer rim of the orifice, which would largely explain the peculiar and mystifying action of compasses and other scientific instruments at points near the so-called north pole—matters which have greatly puzzled all arctic explorers.”
“You are convinced then that there is not only an inner world but that there is an entrance to it at the north pole?” asked Tarzan.
“I am convinced that there is an inner world, but I am not convinced of the existence of a polar opening,” replied Gridley. “I can only say that I believe there is sufficient evidence to warrant the organization of an expedition such as I have suggested.”
“Assuming that a polar opening into an inner world exists, by just what means do you purpose accomplishing the discovery and exploration of it?”
“The most practical means of transportation that exists today for carrying out my plan would be a specially constructed rigid airship, built along the lines of the modem Zeppelin. Such a ship, using helium gas, would show a higher factor of safety than any other means of transportation at our disposal. I have given the matter considerable thought and I feel sure that if there is such a polar opening, the obstacles that would confront us in an attempt to enter the inner world would be far less than those encountered by the Norge in its famous trip across the pole to Alaska, for there is no question in my mind but that it made a wide detour in following the rim of the polar orifice and covered a far greater distance than we shall have to cover to reach a reasonably safe anchorage below the cold, polar sea that David Innes discovered north of the land of the Korsars before he was finally taken prisoner by them.
“The greatest risk that we would have to face would be a possible inability to return to the outer crust, owing to the depletion of our helium gas that might be made necessary by the maneuvering of the ship. But that is only the same chance of life or death that every explorer and scientific investigator must be willing to assume in the prosecution of his labors. If it were but possible to build a hull sufficiently light, and at the same time sufficiently strong, to withstand atmospheric pressure, we could dispense with both the dangerous hydrogen gas and the rare and expensive helium gas and have the assurance of the utmost safety and maximum of buoyancy in a ship supported entirely by vacuum tanks.”
“Perhaps even that is possible,” said Tarzan, who was now evincing increasing interest in Gridley’s proposition.
The American shook his head. “It may be possible some day,” he said, “but not at present with any known material. Any receptacle having sufficient strength to withstand the atmospheric pressure upon a vacuum would have a weight far too great for the vacuum to lift.”
“Perhaps,” said Tarzan, “and, again, perhaps not.”
“What do you mean?” inquired Gridley.
“What you have just said,” replied Tarzan, “reminds me of something that a young friend of mine recently told me. Erich von Harben is something of a scientist and explorer himself, and the last time that I saw him he had just returned from a second expedition into the Wiramwazi Mountains, where he told me that he had discovered a lake-dwelling tribe using canoes made of a metal that was apparently as light as cork and stronger than steel. He brought some samples of the metal back with him, and at the time I last saw him he was conducting some experiments in a little laboratory he has rigged up at his father’s mission.”
“Where is this man?” demanded Gridley.
“Dr. von Harben’s mission is in the Urambi country,” replied the ape-man, “about four marches west of where we now are.”
Far into the night the two men discussed plans for the project, for Tarzan was now thoroughly interested, and the next day they turned back toward the Urambi country and von Harben’s mission, where they arrived on the fourth day and were greeted by Dr. von Harben and his son, Erich, as well as by the latter’s wife, the beautiful Favonia of Castrum Mare.
It is not my intention to weary you with a recital of the details of the organization and equipment of the Pellucidarian expedition, although that portion of it which relates to the search for and discovery of the native mine containing the remarkable metal now known as Harbenite, filled as it was with adventure and excitement, is well worth a volume by itself.
While Tarzan and Erich von Harben were locating the mine and transporting the metal to the seacoast, Jason Gridley was in Friedrichshafen in consultation with the engineers of the company he had chosen to construct the specially designed airship in which the attempt was to be made to reach the inner world.
Exhaustive tests were made of the samples of Harbenite brought to Friedrichshafen by Jason Gridley. Plans were drawn, and by the time the shipment of the ore arrived everything was in readiness to commence immediate construction, which was carried on secretly. And six months later, when the O-220, as it was officially known, was ready to take the air, it was generally considered to be nothing more than a new design of the ordinary type of rigid airship, destined to be used as a common carrier upon one of the already numerous commercial airways of Europe.
The great cigar-shaped hull of the O-220 was 997 feet in length and 150 feet in diameter. The interior of the hull was divided into six large, air-tight compartments, three of which, running the full length of the ship, were above the medial line and three below. Inside the hull and running along each side of the ship, between the upper and lower vacuum tanks, were long corridors in which were located the engines, motors and pumps, in addition to supplies of gasoline and oil.
The internal location of the engine room was made possible by the elimination of fire risk, which is an ever-present source of danger in airships which depend for their lifting power upon hydrogen gas, as well as to the absolutely fireproof construction of the O-220; every part of which, with the exception of a few cabin fittings and furniture, was of Harbenite, this metal being used throughout except for certain bushings and bearings in motors, generators and propellers.
Connecting the port and starboard engine and fuel corridors were two transverse corridors, one forward and one aft, while bisecting these transverse corridors were two climbing shafts extending from the bottom of the ship to the top.
The upper end of the forward climbing shaft terminated in a small gun and observation cabin at the top of the ship, along which was a narrow walking-way extending from the forward cabin to a small turret near the tail of the ship, where provision had been made for fixing a machine gun.
The main cabin, running along the keel of the ship, was an integral part of the hull, and because of this entirely rigid construction, which eliminated the necessity for cabins suspended below the hull, the O-220 was equipped with landing gear in the form of six, large, heavily tired wheels projecting below the bottom of the main cabin. In the extreme stern of the keel cabin a small scout monoplane was carried in such a way that it could be lowered through the bottom of the ship and launched while the O-220 was in flight.
Eight air-cooled motors drove as many propellers, which were arranged in pairs upon either side of the ship and staggered in such a manner that the air from the forward propellers would not interfere with those behind.
The engines, developing 5600 horsepower, were capable of driving the ship at a speed of 105 miles per hour.
In the O-220 the ordinary axial wire, which passes the whole length of the ship through the center, consisted of a tubular shaft of Harbenite from which smaller tubular braces radiated, like the spokes of a wheel, to the tubular girders, to which the Harbenite plates of the outer envelope were welded.
Owing to the extreme lightness of Harbenite, the total weight, of the ship was 75 tons, while the total lift of its vacuum tanks was 225 tons.
For purposes of maneuvering the ship and to facilitate landing, each of the vacuum tanks was equipped with a bank of eight air valves operated from the control cabin at the forward end of the keel; while six pumps, three in the starboard and three in the port engine corridors, were designed to expel the air from the tanks when it became necessary to renew the vacuum. Special rudders and elevators were also operated from the forward control cabin as well as from an auxiliary position aft in the port engine corridor, in the event that the control cabin steering gear should break down.
In the main keel cabin were located the quarters for the officers and crew, gun and ammunition room, provision room, galley, additional gasoline and oil storage tanks, and water tanks, the latter so constructed that the contents of any of them might be emptied instantaneously in case of an emergency, while a proportion of the gasoline and oil tanks were slip tanks that might be slipped through the bottom of the ship in cases of extreme emergency when it was necessary instantaneously to reduce the weight of the load.
This, then, briefly, was the great, rigid airship in which Jason Gridley and Tarzan of the Apes hoped to discover the north polar entrance to the inner world and rescue David Innes, Emperor of Pellucidar, from the dungeons of the Korsars.