Number of rib. Deflection. Inches. 1 (Heavy end rib) 5.5 2 9.5 3 11.75 4 12.25 5 12.5 6 12.75 7 12.9 8 13.0 9 12.0 10 (Heavy end rib) 9.75 The weight of sand put on the wing in this test was 1.5 times as great as the pressure which at this time it was expected would be imposed upon it in flight, and was in fact 1.2 times as great as the normal pressure when supporting the aerodrome as finally constructed. Even under this weight the greatest deflection noted in terms of the total length of the rib was less than 0.10, showing that the elastic limit of the rib was far from being reached. [p204] As this test seemed to indicate that the wings constructed in this manner were certainly strong and rigid enough for use on the aerodrome, and that immediate further improvement could hardly be made, three similar wings were at once constructed to complete the set. Somewhat later two additional wings were provided, so that when the large aerodrome was taken to Widewater on the Potomac in 1903 one and a half complete sets of wings were on hand, which seemed to be ample to provide for any emergencies that might arise. Each of these wings had, as is clearly shown in the drawings, Plates 53 and 54, two main ribs, which formed the main strength of the framework and gave the wing longitudinal rigidity. To the main front rib were attached the cross-ribs and the pieces for the curved extension later described. The mid-rib extended across the cross-ribs, parallel to and about 5 feet behind the front rib, this being approximately the line in which lay the center of pressure of the wing. It was upon this rib, therefore, that the greatest strain would fall. The mid-rib, Plate 66, Fig. 2, was 731.5 cm. (24 ft.) long, having at the butt an outer diameter of 38 mm. (1.5 in.) and an inner diameter of 25 mm. (1 in.), the walls being, therefore, approximately 6.5 mm. (0.25 in.) thick. From the butt to the middle point the section was uniform, but from this point it had a taper of one-twenty-fourth of an inch to the foot, so that at the tip it had an outer diameter of 25 mm. (1 in.), the thickness of the wall being unchanged. At the butt end a wooden block 8 inches long was glued inside the rib, and at uniform distances of 75 mm. (30 in.) 10 smaller blocks were glued in where the cross-ribs were attached. The main front rib was of the same form and size, except that it was some 2 inches shorter and had no blocks, except the long one at the butt, glued in it.