The general plan for the large aerodrome was never a matter of uncertainty. At the time when the first general designs were made there had been in the history of mankind only one type of machine, that of the steam-driven Langley models, which had proved capable of flight for any considerable distance. Furthermore, the selection of this type had been the result not of sudden fancy or of purely theoretical consideration, but of years of the most careful experimentation, in the course of which nearly every conceivable style of machine had been tested with some form of power. It would have been worse than folly, therefore, if the one clear path had been left to seek some unknown way. It was fully realized from the first, however, that the increase in size alone would make necessary in the design for the large aerodrome a great many modifications from the designs of the steam-driven models. It was not possible here, as in nearly every other kind of structure, simply to magnify uniformly the parts and proportions of the small machine in order to obtain a successful large one. This is particularly true in the case of the aerodrome, because the rapid increase of weight in the larger structure is out of all proportion to the increase in strength, while it is very desirable that the more expensive machine which is designed to carry a human being shall be relatively even stronger than the easily replaced model. This problem of increasing size without sacrificing strength and stability, it was known from the beginning, would be encountered in a particularly difficult form in designing the frame of the large machine, and was to be solved not by the discovery of some new and wonderfully strong material, but by improvements both in the general plan and the details of the machine. Here, as is often the case, it was not the large changes in the design but the improvements in small and sometimes seemingly unimportant details which demanded the most careful consideration and, as a whole, contributed most to the final result. For this reason, as well as because the large changes, when pointed out, are usually easily understood, the present chapter is for the most part a description of the improvement of details.