[Illustration: Fig. 82.--The condition of the machine after the accident. One of the broken planks that formed the upper track is shown. It will be observed that the wheels have sunk directly into the ground without leaving any tracks, showing that the machine did not run along the ground, but came directly down when it stopped.] In my experiments with the small apparatus for ascertaining the power required to perform artificial flight, I found that the most advantageous angle for my aeroplane was 1 in 14, but when I came to make my large machine, I placed my aeroplanes at an angle of 1 in 8 so as to be able to get a great lifting effect at a moderate speed with a short run. In the experiments which led to the accident above referred to, the total lifting effect upon the machine must have been at least 10,000 lbs. All the wheels which had been previously painted and which engaged the upper track were completely cleaned of their paint and had made an impression on the wood, which clearly indicated that the load which they had been lifting was considerable.[10] Moreover, the strain necessary to double up the axle-trees was fully 1,000 lbs. each, without considering the lift on the forward axle-trees which did not give way but broke the upper track. [10] The latest form of outrigger wheels for engaging the upper track is shown in Fig. 84. [Illustration: Fig. 83.--This shows the screw damaged by the broken planks; also a hole in the main aeroplane caused by the flying splinters.] The advantages arising from driving the aeroplanes on to new air, the inertia of which has not been disturbed, are clearly shown in these experiments. The lifting effect of the planes was 2·5 lbs. per square foot. A plane loaded at this rate will fall through the air with a velocity of 22·36 miles per hour, according to the formula √(200 × P) = V. But as the planes were set at an angle of 1 in 8, and as the machine travelled at the rate of 40 miles an hour, the planes only pressed the air downwards 5 miles an hour (40 ÷ 8 = 5). A fall of 5 miles an hour without advancing would only exert a pressure of ·125 lb. per square foot, according to the formula (V² × ·005 = P).[11] [11] This is the old formula used by Haswell. The account of this experimental work was written in the autumn of 1894 and Haswell’s formula was used. I have thought best to make no changes. [Illustration: Fig. 84.--This shows a form of outrigger wheels which were ultimately used.]