lattice flooring over pontoons, moored at the rear end of the boat, as clearly seen in Plate 38. In order to raise the aerodrome frame from the raft to the upper works, a large, but light, mast and boom, with suitable stays were provided. As the wings, when mounted in their proper position on the aerodrome, would be interfered with by such a mast, the mast and boom were so devised as to be capable of rapid erection and dismounting, only five minutes being necessary for either operation. In Plate 38 the mast and boom are seen in position in Fig. 3, while in Figs. 1 and 2 they have been dismounted. The construction of the launching track and car was begun in November, 1899, but their completion was long delayed, as they were frequently put aside for the more immediately important parts of the work. Moreover, the arrangement of the struts and clutch of the launching car depended entirely on the form and dimensions of the frame of the aerodrome, which could not be entirely decided until a proper engine had been secured and tested in the frame to determine what modifications of it were necessary. In the spring of 1902, however, the launching car was entirely finished and a number of tests of the large engine were made in the shop with the frame mounted in position on the car. From the description of the “overhead” launching apparatus (Part I, Chapter X) which had proved so successful in the tests of the models, both in 1896 and in the later experiments of 1899, it will be recalled that the essential features of it were a track and a light car with three hinged struts which extended below the body of the car, and against which suitable co-acting bearing points attached to the frame of the aerodrome were tightly drawn by means of a clutch which gripped a special fitting fastened to the aerodrome frame near the central point of its length. After the engine of the aerodrome had been started and got to running at full speed, the car was released and moved forward along its track by the combined force of the thrust of the propellers and the pull of the coiled launching springs. Just before the car reached the forward end of the track, a cam at this point caused the clutch to open and release [p158] the aerodrome, which immediately dropped slightly, as it had purposely not quite reached a speed sufficient to cause it to soar. This slight drop of the aerodrome, even if it were only a fraction of an inch, made it possible for the hinged struts, against which it had been held by the clutch, to be folded up by their special springs against the floor of the car, thus leaving the aerodrome free in the air without danger of entanglement.