478 Artificial Flight. [ J uly, 
long, with about 16 square feet of surface. By this arrange- 
ment of loose waving surface I have had the smaller model 
(5 x 8) fly from my hand perfectly horizontally to the extent 
of 6o feet. 
What has assured me that there is a necessary relation 
between the arc of vibration, the velocity, the weight, and 
the surface, is the fact that through breakage I had to review 
the parts, and I have never since regained that chance rela- 
tionship ; but the model appears to descend until the loose 
fabric is seen to hold the air, so that if the ballast is behind 
the centre of effort the surface is forced outward at an angle 
of perhaps io°. Upon stoppage of the motive power there 
would then be no parachute action, but the machine would 
descend tail first. The ballast, however, properly arranged, 
the velocity of the model is increased, and the head being 
heavier, and power ceasing, onward motion continues under 
the concave extension of the surface. 
All this would be at the command of a man with a power 
upon which he could depend. It is probable that if this 
wave-action were used in addition to a wing about a foot 
wide, a greater impact upon the air at starting might assist 
the supporting effort. 
I perhaps need scarcely say that the judgment must be 
formed not upon the duration of flight or the distance tra- 
velled, but upon the effedt observed in any part of its short 
flight which with my limited power I am enabled to give the 
model. It then becomes evident that we should only require 
a continuance of the power. 
I think that after fourteen years’ study of the subject by 
the members of the Aeronautical Society we are now in a 
far more favourable position than we have ever yet been to 
form a fair estimate of the probabilities of success. 
The conditions necessary for flight are pretty well under- 
stood. There remain but the mechanical difficulties. How 
far those difficulties have now been minimised can only be 
satisfactorily determined by actual experiment upon a scale 
commensurate with the importance of the subject. And 
with respect to the model which illustrates this wave-action 
we may predicate for it that — largely constructed with 
power, strength, and surface — there would be as much 
difference in the effect as between a child’s halfpenny toy, 
with four paper vanes pinned to the end of a stick, and the 
windmill whose larger vanes grind our corn. 
