headlong to it, gripped Mark Sampson like a giant hand. He felt difficulty in breathing, although it was not the height that gave him that choking sensation. There was a mist before his eyes, still the sun was shining brightly. The startling gyrations of the flying machine for some time shook the lad to the core.
But Jack's cheerful cry of "Hang on!" spurred Mark to a new activity—an activity of hand as well as brain. He knew that something had fouled and that this accident was the cause of the machine making such sickening bounds in the air. She was overbalanced in some way.
With Jack's encouraging shout ringing in his ears, Mark came to himself. He would hang on! His friends depended upon him to control the machine and to save them from destruction, and he would not be found wanting.
One lever after another he gripped and tried. It was one controlling the rising power that was fouled. He learned this in a moment. He sought to move it to and fro in its socket and could not do so. He had overlooked this lever before.
Again the Snowbird dashed herself from a height of five hundred feet toward the earth.
They still flew over the forest. The tops of the trees intervened, and Mark managed to counteract the plunge before the prow of the machine burst through the treetops. She rose again, and using both hands, Mark jerked the wheel stick into place.
At once the flying machine responded to the change. She rode straight on, slightly rising as he had pointed her, and Mark dared touch the motor switch again. Instantly the machine speeded ahead.
"Hurrah for Mark!" shrieked Jack. "He's pulled us through."
"He has indeed," agreed the professor, and they settled into their seats and gave attention to the working of the apparatus. Mark now had the Snowbird well under control.
Jack changed places with his chum and managed the Snowbird equally well. At his touch she darted upward at a long slant until the altimeter registered two thousand feet above the sea. And the sea was actually below them, for Jack had guided the flying machine away out from the land.
"Boys," said Professor Henderson, quietly, "you have done well—remarkably well. I am certainly proud of you. Some day the people of the United States will be proud of you. I am sure that the inventor's instinct and the scientist's indefatigable energy are characteristics you both possess."
"That's praise indeed!" exclaimed Jack, smiling at his chum. "When the professor says we've won out, I don't care what anybody else says."
"Do you think the Snowbird is fit for long-distance travel?" asked Mark of Professor Henderson, now displaying more eagerness than before.
"I do indeed. I think you have a most excellent flying machine. I would not hesitate to start for San Francisco in her."
"Or farther?" asked Jack.
"Certainly."
"Across the ocean?" queried Mark, quickly.
"I do not see why any one could not take a trip to the other side of the Atlantic in your 'plane," replied the professor. "With proper precautions, of course."
They reached the land and came safely to rest before the hangar without further accident. The professor was delighted with the working of his catapult and at once made ready to call the attention of the Navy Department to his improvement in the means of launching an airship from the deck of a vessel. Ere he had written to the Department, however, he and his young friends were suddenly made interested in a scheme that was broached by letter to Professor Henderson from a fellow-savant, Dr. Artemus Todd, of the West Baden University.
Professor Henderson and Dr. Todd had often exchanged courtesies; but the university doctor was mainly interested in medical subjects, while Mr. Henderson delved more in the mysteries of astronomy and practical mechanics.
The doctor's letter to Professor Henderson read as follows:
"Dear Professor:
"I am urged to write to you again because of something that has recently come to my knowledge regarding a subject we once discussed. As you know, for some years past I have been investigating not the cause of aphasia and kindred mental troubles (for we know the condition is brought about by a clot of blood upon the brain), but the means of quickly and surely overcoming the condition and bringing the unfortunate victim of this disorder back to his normal state. In our age, when mental and nervous diseases are so rapidly increasing, aphasia victims are becoming more common. Scarcely a hospital in the land that does not have its quota of such patients under treatment—patients who, in many cases, have completely forgotten who and what they are and have assumed a totally different identity from that they began life with."
"We know that, in some cases, hypnotism has benefited the aphasia and amnesia victim. His condition is not like that of the mentally feeble; he has merely lost his memory of what and who he previously was. Believing that all disease, of whatsoever nature, can be safely treated only through the blood, this ill to which human flesh is heir particularly must be treated in that way, for we know that a stagnant state of the blood in one spot, at least, is the cause of the patient's malady. Therefore I have been experimenting botanically to discover a remedium for the state in question—something that will act swiftly upon the blood, and directly dissipate such a clot as is spoken of above."
"My dear Professor! I can announce with joy that this remedium is discovered. I obtained a specimen of a very rare plant brought back from Alaska by a miner who wandered into the fastnesses of the Endicott Range, far beyond the usual route of gold miners and in a district which, I understand, is scarcely ever crossed by whites and which is, indeed, almost impassable, even in the summer months. With the aid of this herb—Chrysothele-Byzantium (it was known to the ancients, but very rare)—I have brewed a remedium which, in one case at lest, instantly cleared the blood vessels of the patient and brought him back to a knowledge of his real self."
"But my supply of the herb is gone. It reached me in its dry state, or I should have first tried to propagate it. It seeds but once in seven years and therefore is rare and hard to grow. But I must have a supply of the Chrysothele-Byzantium seeds, plants, and all. I look to you, my dear Professor Henderson, for help. To you space and the flight of time are merely words. You can overcome both if you try. I need somebody to go to the northern part of Alaska—that is, beyond the Endicott Range—to obtain this rare plant for me. You have already flown over the North Pole and a trip which carries one only three or four degrees beyond the Arctic Circle is a mere bagatelle to you."
"Yes! it is in you I place my hope, Professor. The hopes of many, many afflicted people may be placed in you, too. I ask you to fly to this distant place and obtain for me the herb that will do humanity such great good. Under another enclosure I send you drawings of the plant in its several states and a full and complete description of how it was found. You can make no mistake in the Chrysothele-Byzantium. You know that I am a cripple, or I would offer to join with you in this search. But at least I am prepared to pay for any expense you may be under. Draw upon me for ten thousand dollars to-morrow if you so desire, and more if you need before the start. The Massachusetts Bay Trust Company, of Boston, will honor the draft. Make up the expedition as you see fit. Take as many men with you as you think necessary. Make all preparations which seem to you fit and needful. I limit you in nothing—only bring back the herb."
"Remember I shall impatiently await your return and look for your success—I expect nothing but unqualified success from your attempt. You who have achieved so much in the past surely cannot fail me in this event. I await your agreement to attempt this voyage with confidence. I must have the herb and you are the only person who can obtain it for me."
"Your friend and co-worker for the betterment of humanity,
ARTEMUS TODD, M.D., PhD."
Professor Henderson read this strange letter aloud in the evening as he and his friends were sitting before the small, clear fire of hickory logs in the big living room of the bungalow in the woods, built beside the great workshops and laboratory. With the scientist and the two boys was Andy Sudds, the old hunter, who sat cleaning his rifle, and Washington