with the thick edge to the wind, and 0·42 lb. with the thin edge to the wind; _c_ showed a drift of 0·23 lb. with the thick edge to the wind, and 0·59 lb. with the thin edge to the wind; and _d_, which was the same thickness as the others and 12 inches wide, both edges being alike, showed a drift of only 0·19 lb. These experiments show in a most conclusive manner the shapes that are most advantageous to use in constructing the framework of flying machines. Aeroplane _e_, Fig. 26, when placed on the machine in a horizontal position showed neither lift nor drift, but upon placing it at an angle of 1 in 20, as shown at _f_, the lift was 3·98 lbs. and the drift 0·30 lb. with a wind velocity of 40 miles per hour. At this low angle the blade trembled slightly. Upon placing the same plane at an angle of 1 in 16 as shown at _g_, the lift was 4·59 lbs. and the drift 0·53 lb. It will be observed that the underneath side of this plane is perfectly flat. The next experiment was with planes slightly curved, as shown in Fig. 27. The aeroplane _a_ was 16 inches wide, very thin, and only slightly curved. When set at a very low angle, it vibrated so as to make the readings very uncertain, but when set at an angle of 1 in 10 it lifted 9·94 lbs. with a drift of 1·12 lbs. By slightly changing the angle it was made to lift 10·34 lbs. with a drift of 1·23 lbs., the wind velocity being 41 miles per hour. Aeroplane _b_, 12 inches wide, Fig. 27, when placed at an angle of 1 in 14 with an air blast of 41 miles per hour, gave a lift of 5·28 lbs. with a drift of 0·44 lb.; at an angle of 1 in 12 the lift was 5·82 lbs. and the drift 0·5 lb.; at an angle of 1 in 10 the lift was 6·75 lbs. and the drift 0·73 lb.; with an angle of 1 in 8 the lift was 7·75 lbs. and the drift 1 lb.; with an angle of 1 in 7 the lift was 8·5 lbs. and the drift 1·25 lbs.; at an angle of 1 in 6 the lift was 9·87 lbs. and the drift 1·71 lbs. Aeroplane _c_, Fig. 27, which had more curvature than _b_, when run in a horizontal position, gave a considerable lift, and when raised to an angle of 1 in 12 it gave a lift of 6·12 lbs. with a drift of 0·54 lb. In another experiment at the same angle, it gave a lift of 6·41 lbs. with a drift of 0·56 lb.; at an angle of 1 in 16 it gave a lift of 5·47 lbs. with a drift of 0·37 lb.; at an angle of 1 in 10 it gave a lift of 6·97 lbs. and a drift of 0·70 lb.; at an angle of 1 in 8 it gave a lift of 8·22 lbs. with a drift of 1·08 lbs.; at an angle of 1 in 7 it gave a lift of 9·94 lbs. with a drift of 1·45 lbs.; at an angle of 1 in 6 it gave a lift of 10·34 lbs. and a drift of 1·75 lbs. This plane was then carefully set so that both the forward and aft edges were exactly the same height, and with a wind blast of 41 miles per hour it gave a lift of 2·09 lbs. with a drift of 0·21 lb. It was then pitched 1 in 18 in the wrong direction, and at this point, the lifting effect completely disappeared, while the drift was practically nothing.