It is hard to say into what field of inquiry Edison has not dipped. He told me once that whenever he travelled he carried a note-book with him, in which he jotted down suggestions for experiments to be made. Railway journeys, at a time when Edison was a constant traveller, were productive of much material of this kind, for the inventor never sleeps when travelling, and his brain works, going over, even in a doze, the thousand and one aspects of his work, and evolving theories to be dismissed almost as soon as evolved. His mind, when at rest, reviews his day's work almost automatically, just as a chess player's brain will, after an exciting game, go over every situation in a half dream-like condition and evolve new solutions. He has great respect for even what appear to be the most inconsequential observations, provided they are made by a competent person, and a large force in his splendid laboratory at Orange is always employed in studies that appear to the outsider to be aimless; for instance, the action of chemicals upon various substances or upon each other. Strips of ivory in a certain oil become transparent in six weeks. A globule of mercury in water takes various shapes for the opposite poles of the electric-battery upon the addition of a little potassium. There is no present use for the knowledge of such facts, but it is recorded in voluminous note-books, and some day the connecting-link in the chain of an invaluable discovery may here be found. My next visit to Menlo Park was a few months later, when I found Edison in bed sick with disappointment. The lamps had again taken to antics for which no remedy or explanation could be discovered. There was an air of desolation over the place. The laboratory was cold and comfortless. Upon every side were signs of strict economy. Most of the assistants were young men glad to work for little or nothing. For the last month Edison had been working in the direction of a general improvement of all parts of the lamp instead of devoting himself to one feature. Expert glass-blowers were brought to Menlo Park, the air-pumps were made more perfect, new substances were tried for carbons. All this had taken time, during which outsiders freely predicted failure. The stock in the enterprise fell to such a price that it was hard to raise money for the maintenance of the laboratory. It was argued, and with some truth, as I have had occasion to remark, that Edison had really discovered nothing new; he had attempted to do what a dozen famous men had tried before him and he had failed. The quotations of New York gas stocks rose again.