"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."