Point of Weight application Absolute in terms Deflection of weight weight in of in terms in terms of grammes. greatest of length. length. weight. 0.39 1050 1.0 .38 0.445 605 0.58 .38 0.56 405 0.39 .38 0.75 210 0.20 .38 0.95 77 0.075 .38 HOLLOW SPRUCE RIB. Weight, 120 grammes; length 153 cm.; section, rectangular; tip, 17 cm. above butt. Point of Weight application Absolute in terms Deflection of weight weight in of in terms in terms of grammes. greatest of length. length. weight. 0.39 15,000 1.0 .11 0.445 11,400 0.76 .11 0.56 7,900 0.53 .11 0.75 4,000 0.27 .11 0.95 2,000 0.135 .11 In each case the unit of length was the portion extending beyond the clamp; the unit of weight, the greatest weight employed to produce the deflection. It should be noted, however, that the relative deflection was quite different in the two comparisons. In the case of the quill the deflection was 17 cm. in 45 cm., or 38 per cent; in the case of the rib it was 17 cm. in 153 cm., or 11 per cent. In the case of the rib at the point 0.39 the absolute weight was 15,000 grammes, the relative weight unity and the deflection in terms of length 0.11. While no rigorous comparison can be instituted, since the rib was not deflected nearly as much proportionately as the quill, yet the general inference is that while the rib was not intended to be, and was not as elastic proportionately as the quill, it was probably at least as strong in proportion to its weight. Briefly summarizing these results it will be noted that the spruce rib was about 3.3 times the length and 30 times as heavy, while it was 15 times as stiff near the butt and 26 times as stiff at the tip, as the quill. As this test on the rib for the large wings had apparently shown that the plan of constructing the ribs in the form of a hollow square secured maximum strength for minimum weight, it was decided to construct a few sample ribs after the same plan for the wings of the new quarter-size model of the large aerodrome, and to test, these ribs in a similar manner. The following table shows the results of the test on one of these ribs: