ing machine which allowed for alteration of
the angle of incidence of the wings in the manner that was subsequently
carried out by the Wright Brothers. It was not until 1883 that any
attempt was made to put this patent to practical use, and, as the
inventor died while it was under construction, it was never completed.
D'Esterno was also responsible for the production of a work entitled
Du Vol des Oiseaux, which is a very remarkable study of the flight of
birds.

Mention has already been made of the founding of the Aeronautical
Society of Great Britain, which, since 1918 has been the Royal
Aeronautical Society. 1866 witnessed the first meeting of the Society
under the Presidency of the Duke of Argyll, when in June, at the Society
of Arts, Francis Herbert Wenham read his now classic paper Aerial
Locomotion. Certain quotations from this will show how clearly Wenham
had thought out the problems connected with flight.

'The first subject for consideration is the proportion of surface to
weight, and their combined effect in descending perpendicularly through
the atmosphere. The datum is here based upon the consideration of
safety, for it may sometimes be needful for a living being to drop
passively, without muscular effort. One square foot of sustaining
surface for every pound of the total weight will be sufficient for
security.

'According to Smeaton's table of atmospheric resistances, to produce
a force of one pound on a square foot, the wind must move against the
plane (or which is the same thing, the plane against the wind), at the
rate of twenty-two feet per second, or 1,320 feet per minute, equal to
fifteen miles per hour. The resistance of the air will now balance the
weight on the descending surface, and, consequently, it cannot exceed
that speed. Now, twenty-two feet per second is the velocity acquired at
the end of a fall of eight feet--a height from which a well-knit man or
animal may leap down without much risk of injury. Therefore, if a man
with parachute weigh together 143 lbs., spreading the same number of
square feet of surface contained in a circle fourteen and a half feet
in diameter, he will descend at perhaps an unpleasant velocity, but with
safety to life and limb.

'It is a remarkable fact how this proportion of wing-surface to weight
extends throughout a great variety of the flying portion of the
animal kingdom, even down to hornets, bees, and other insects. In some
instances, however, as in the ga