As the construction and tests of this experimental engine had shown many places in which the weight might be safely reduced, the writer decided to construct an entirely new and larger single engine, and thereby avoid the extra weight and difficulties which would be introduced by having to use synchronizing gears where two engines were used, it being impossible, of course, to run the two propellers from the two engines independently without risk of serious disaster. [p224] It will be recalled that when the aerodrome was originally planned in 1898 it was proposed to have two engines of 12 horse-power each, and the contract for the single engine of 12 horse-power provided that a duplicate was to be supplied, if desired, immediately upon the completion and delivery of the first one. The calculations, both from the whirling-table tests and from the results with the steam-driven models in actual flight, indicated that 24 horse-power would be ample for the aerodrome, which it was then expected would not exceed 640 pounds in weight, with a supporting surface of 960 square feet. But it was found that the total weight of the machine was rapidly increasing on account of slight increases in the various details, which when added together made a considerable increase in weight. Furthermore, as it had been found difficult to keep all five of the cylinders of the experimental engine working uniformly, it was thought best to build this new engine sufficiently large to provide not only the extra power necessary because of the increased weight of the aerodrome, but also to provide for further inevitable increases in weight, and over and above all this, to provide also that the engine would furnish all the power necessary, even though one of its cylinders should absolutely fail to work and act as a dead load on the others. The writer accordingly designed this new engine to give 40 horse-power when all five of the cylinders were working, and 28 horse-power even though one cylinder should act as a dead load on the others. The various materials for the construction of this engine were ordered early in December, 1900, with the promise of delivery not later than January, 1901. Owing to various causes, however, the major portion of the materials could not be obtained until late in the spring, and, in fact, a portion of them were not obtained until the summer of 1901. During this period of delay, however, the engine for the quarter-size model was completely reconstructed and further tests were made with the experimental engine in developing accessories, such as carburetors and spark coils.