Soon they discovered that the larger the machine they made the less it flew, and in pondering this fact they gradually evolved for themselves the theory which is now known as Langley's unyielding mathematical law, referred to a few pages back. The problem of human flight had not been considered by them at this time, and it was not until the news of Lilienthal's death startled the world that they entered the field of invention in earnest. Then they began constructing gliding machines, modifications of those of Lilienthal and Chanute, and began making long flights, studying defects and overcoming adverse conditions as they presented themselves. By 1901, they had surpassed the performances of all predecessors, yet, as they tell us, "we saw that the calculations upon which all flying-machines had been based were unreliable, and that all were simply groping in the dark. Having set out with absolute faith in the existing scientific data, we were driven to doubt one thing after another, till finally, after two years of experiment, we cast it all aside, and decided to rely entirely upon our own investigations. Truth and error were everywhere so intimately mixed as to be indistinguishable. Nevertheless, the time expended in preliminary study of books was not misspent, for they gave us a good general understanding of the subject, and enabled us at the outset to avoid effort in many directions in which results would have been hopeless." From mere gliding machines without self-contained power the brothers progressed through the various stages of achievement until in the fall of 1903 they had created the type of flying-machine now made so familiar to everyone through the pictorial publications. Incidentally they had invented and constructed their own gasoline motor for furnishing the power--an accomplishment of no mean importance in itself. On December 17th, 1903, in the presence of a small company of witnesses who had braved the cold, the Wright machine, carrying one of the brothers, made a short but successful flight--the first ever accomplished in which a machine carrying a passenger had raised itself by its own power, sailed a certain distance in free flight, yet subject to guidance, and landed itself and its passenger safely. Mr. Hiram Maxim's machine had, indeed, lifted itself and its passengers, but it sailed unguided through the air, and it could in no sense be said to have made a flight comparable to that of a bird or a bat. The Wright machine, on the other hand, progressed through the air under guidance of its passenger, rising or settling, or turning to right or left as he wished. Its progress constituted, in other words, a veritable flight. Yet the problem of perfectly controlled flight under all ordinary conditions was by no means completely mastered. The principle was correct, but there were endless details to be worked out. The embodiment of these is the Wright flying-machine of the present time.