The Professor was a man of some forty-seven years, tall and thin and with that slight stoop of the shoulders peculiar to the student. The face was clean-shaven and pale, with a marked puff of the flesh above each eye where the brows were wont to contract in the intensity of thought. When the firm, well-cut features lighted in a smile, the face became positively handsome. One of the Professor’s hobbies, which he was fond of discussing with Mr. Kearns, was the question of the economic condition of the masses of the people. The Professor contended--and it pained his kindly nature that such was the case--that the great mass of the people were not as well-off as they should be; that the true happiness and well-being of the great body of mankind had not advanced in proportion to the world’s progress in other directions. Another pet subject of discussion with the Professor was his theories of aërial navigation. In fact, he declared that he had fully and satisfactorily solved the problem and was prepared in the near future to produce a craft with which the air could be navigated at will, both in safety and at high speed. His plans for this work, he explained, were fully perfected and the completed invention would have been an accomplished fact some time before had he not been hampered by lack of means. But with the funds received from the sale of his electrical device to the cable company he was in possession of sufficient means to put through the work properly, and he intended to devote himself actively to this matter as soon as his present vacation was over. In the meantime, he had written on the subject of aërial navigation sundry pamphlets which had attracted attention in scientific circles. At first, Mr. Kearns was disposed to regard Professor Dean’s projects in this connection as partaking of the visionary, but as he grew to know him better, the Professor’s clear-headedness and conservatism made more and more of an impression upon him and he came to regard aërial navigation, with Professor Dean as its introducer, as not such an unlikely possibility in the near future. Another acquaintance made by Mr. Kearns was that of Dr. Raoul Jaquet. Dr. Jaquet was not a guest of Dr. Belden’s famous establishment, but lived in a cottage of his own some little distance away. He was on friendly terms with Dr. Belden, who spoke of him as a man of remarkable attainments in certain branches of scientific research, notably in chemistry and toxicology. Dr. Jaquet cultivated friendly relations with Professor Dean and Mr. Kearns, and his visits to Dr. Belden’s establishment became more frequent than ever. All three were fond of exercise on foot and they took long rambles together over the surrounding country.