line-of-flight elevation. The gliding angle of this model is good, being approximately 9°.
Fig. 13 is a form due to Hele Shaw, and exhibited by him to the Royal Society in May, 1907; it also obviously derives its inspiration from nature, being a close representation of the plan-form of a swallow; it is quite stable, and also shows the flight path oscillation to a pronounced degree ; this glider is simply cut from a sheet of paper and ballasted by means of split shot. The gliding angle of this form is also very good.
As far as the author has been able to judge, none of the forms above given are superior to the simple ballasted rectangular plane,
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Fig. 12.
and the only obvious reason for the adoption of fancy shapes, such as those of Weiss and Hele Shaw, appears to be found in their common origin as imitations of forms presented by nature.
§ 10. Author's Experiments, 1894.—In 1894 the author commenced the practical investigation of stability in flight, some preliminary theoretical work having shown that it should be possible to obtain automatic equilibrium with a suitably designed apparatus.
At the date in question, although Mouillard's "L'Empire de l'Air" had been published several years, the author was not aware of the automatic equilibrium possessed by the ballasted
17
