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correctness of the principle upon which he had been workings 
guided by the experiments undertaken by the Aeronautical 
Society. If the old theory was correct, he argued, the lifting 
pressure on the planes would only amount to a few ounces per 
square foot ; if the new theory was correct, the pressure would 
far exceed that of the old. It turned out that the old theory 
was wrong, and the reliability of the recent experiments was 
confirmed. The revolving planes having been set at an angle 
of 15°, the pressure was found to be exactly one pound to the 
square foot at a speed of twenty miles an hour ; and with the 
angle set at 45°, the pressure was 1^- lb. to each square foot. 
The success of the ulterior experiment, therefore, all depended 
upon whether he could obtain a sufficient speed upon the 
ground to avail himself of the lifting-pressure due to the 
angle of inclination. 
The fountain had a path round it. The diameter of the 
circle was 300 feet. A pole was erected in the centre, from the 
top of which two cords were attached, one to each end of the 
machine. Though the gravel had been rolled, the action of 
the machine under steam was so rough and unsteady that the 
experiment had to be abandoned until a suitable road could be 
constructed. 
This was eventually effected with 8,000 square feet of 
boarding, lent by the Crystal Palace authorities, when, after 
its occupation for some time by the snow, the roadway was 
ready for a further trial. Instead, however, of the necessary 
speed being attained, viz. thirty-three miles an hour, it was 
only possible to get about twelve, so that it was felt as a 
matter of regret that arrangements had not been made to run 
it upon a straight line of railway. The wheels, fitted for for- 
ward motion only, offered great resistance to running round a 
circle. 
This machine, however, weighing nearly two cwt., was im- 
pelled round a circle at twelve miles an hour by the pressure 
of two aero-plane wheels working in the air, an achievement I 
believe to be quite unprecedented. 
This first start from the ground has always presented great 
difficulties to the experimenter in aeronautics. Theory has 
generally favoured the incline as the readiest mode of accom- 
plishing the object, but it is certain that unless there is power 
sufficient to raise the weight, safety in controlling the descent 
under exceptional circumstances cannot be secured, as the 
parachute form would be out of character in any machine 
designed for rapid transit through the air. In the difficulty in 
which Mr. Moy found himself, it was natural that he should 
turn to the vertical screw. 
In the report of the Aeronautical Exhibition in 1868, drawn 
up by Mr. Wenham, the following paragraph appears : — 
