+---------+--------------------------------------------+ |Velocity | Horse-Power. | |in Miles +--------+--------+--------+--------+--------+ |per Hour.| 60 | 70 | 80 | 90 | 100 | | +--------+--------+--------+--------+--------+ | | Thrust in Pounds. | +---------+--------+--------+--------+--------+--------+ | 1, |22,500 |26,250 |30,000 |33,750 |37,500 | | 5, | 4,500 | 5,250 | 6,000 | 6,750 | 7,500 | | 10, | 2,250 | 2,625 | 3,000 | 3,375 | 3,750 | | 15, | 1,500 | 1,750 | 2,000 | 2,250 | 2,500 | | 20, | 1,125 | 1,312·5| 1,500 | 1,687·5| 1,875 | | 25, | 900 | 1,050 | 1,200 | 1,350 | 1,500 | | 30, | 750 | 875 | 1,000 | 1,125 | 1,250 | | 35, | 642·8| 750 | 857·1| 964·3| 1,071·4| | 40, | 562·5| 656·3| 750 | 843·8| 937·5| | 45, | 500 | 583·3| 666·7| 750 | 833·3| | 50, | 450 | 525 | 600 | 675 | 750 | | 60, | 375 | 437·5| 500 | 562·5| 625 | | 70, | 321·4| 375 | 428·6| 482·1| 535·7| | 80, | 281·3| 328·2| 375 | 421·9| 468·8| | 90, | 250 | 291·7| 333·3| 375 | 416·7| | 100, | 225 | 262·5| 300 | 337·5| 375 | +---------+--------+--------+--------+--------+--------+ [Illustration: Fig. 72_b_.--When an aeroplane is driven through the air, it encounters stationary air and leaves it with a downward trend. With a thick curved aeroplane, as shown, the air follows both the top and the bottom surfaces, and the direction that the air takes is the resultant of these two streams of air. It will be seen that the air takes the same direction that it would take if the plane were flat, and raised from _a_ to _c_, which would be substantially the same as shown at _f_, _h_, _g_. It has, however, been found by actual experiment that the curved plane is preferable, because the lifting effect is more evenly distributed, and the drift is less in proportion to the lift.] [Illustration: Fig. 72_c_.--Aeroplanes experimented with by Mr. Horatio Philipps. In the published account which is before me, the angles at which these planes were placed are not given, but, by comparing the lift with the drift, we may assume that it was about 1 in 10. Fig. 5 seems to have been the best shape, and I find that this plane would have given a lifting effect of 2·2 lbs. per square foot at a velocity of 40 miles per hour.] PHILIPPS’ EXPERIMENTS.