constructed of steel tubing originally one-half inch thick, which [p233] was machined to the form clearly shown in the photograph, Plate 77, where it will be seen that thin radiating ribs spaced one-quarter inch apart were formed integral with the cylinder, the combustion chambers or heads being screwed on and brazed to the cylinders. After much delay the new cylinders were completed, and upon test it was found that while the radiating ribs assisted very greatly in keeping the engine cool, yet the valves were so small that the gas was not able to get in and out of the cylinders rapidly enough to permit the engine to furnish its full power. Even at this stage it would have been better either to have made new cylinder heads with larger valves or to have made entirely new cylinders and cylinder heads, but in the effort to economize time and money it seemed best to try to overcome part of the defect by adding an auxiliary inlet valve. This was constructed, and upon test it was found that, although the engine developed 3.2 horse-power on the Prony brake at 1800 R. P. M., and even maintained 5.1 horse-power on the brake for a few seconds when running at 3000 R. P. M., the ports leading from the valve chamber to the cylinders were so small that they became heated after the engine had run for 2 minutes and premature ignition occurred, which, of course, immediately and very greatly reduced the power developed. It was decided, however, in view of the tests in which the engine had developed 3.2 horse-power at 1800 R. P. M., that there was sufficient margin of power to enable it to propel the quarter-size model, even if it was not working at its best. After concluding the Prony-brake tests on the engine, it was mounted in its proper position in the aerodrome frame and connected to the propeller shafts. Some pendulum tests were then made, showing an average lift of approximately 57 per cent of the total flying weight. But it was found that the propeller and transmission shafts and their bearings would not stand the strain due to the increased power of the engine. Newer and stronger shafts and bearings were, therefore, constructed and further pendulum tests were made. It was then found that the transverse frame which supported the shafts and bearings was too weak, and this was strengthened by substituting newer and thicker tubing where it seemed necessary. These changes and repairs were all completed by October, 1901, and the quarter-size model was at last, after months of delay, felt to be in a condition which justified the expectation that its next flight would be entirely successful. In view of the much more important work on the large aerodrome which demanded immediate attention the quarter-size model in this completed condition was put aside. Nothing more was done with it until April, 1903, when some shop tests were made preliminary to taking it to Quantico, where, on August 8, it made a successful flight, which is described in Chapter XII. [p234]