upward, but also pulls forward in the direction from which the wind blows, thus overcoming both gravity and the speed of the wind. We tried the same experiment with a man on it, but found danger that the forward pull would become so strong, that the men holding the ropes would be dragged from their insecure foothold on the slope of the hill. So this form of experimenting was discontinued after four or five minutes’ trial. ‘In looking over our experiments of the past two years, with models and full-size machines, the following points stand out with clearness:-- ‘1. That the lifting power of a large machine, held stationary in a wind at a small distance from the earth, is much less than the Lilienthal table and our own laboratory experiments would lead us to expect. When the machine is moved through the air, as in gliding, the discrepancy seems much less marked. ‘2. That the ratio of drift to lift in well-shaped surfaces is less at angles of incidence of 5 degrees to 12 degrees than at an angle of 3 degrees. ‘3. That in arched surfaces the centre of pressure at 90 degrees is near the centre of the surface, but moves slowly forward as the angle becomes less, till a critical angle varying with the shape and depth of the curve is reached, after which it moves rapidly toward the rear till the angle of no lift is found. ‘4. That with similar conditions large surfaces may be controlled with not much greater difficulty than small ones, if the control is effected by manipulation of the surfaces themselves, rather than by a movement of the body of the operator. ‘5. That the head resistances of the framing can be brought to a point much below that usually estimated as necessary. ‘6. That tails, both vertical and horizontal, may with safety be eliminated in gliding and other flying experiments. ‘7. That a horizontal position of the operator’s body may be assumed without excessive danger, and thus the head resistance reduced to about one-fifth that of the upright position. ‘8. That a pair of superposed, or tandem surfaces, has less lift in proportion to drift than either surface separately, even after making allowance for weight and head resistance of the connections.’ [Illustration: The Wrights’ first power-driven machine, 1903.]