tability they
depended entirely on end curtains between the upper and lower
surfaces of both the main planes and biplane tail surfaces. They, like
Santos-Dumont, fitted a wheeled undercarriage, so that the machine
was self-contained. The Voisin machine, then, was intended to be
automatically stable in both senses; whereas the Wrights deliberately
produced a machine which was entirely dependent upon the pilot's
skill for its stability. The dimensions of the Voisin may be given for
comparative purposes, and were as follows: Span 33 feet with a chord
(width from back to front) of main planes of 6 1/2 feet, giving a total
area of 430 square feet. The 50 horse-power Antoinette engine, which
was enclosed in the body (or 'nacelle ') in the front of which the pilot
sat, drove a propeller behind, revolving between the outriggers carrying
the tail. The total weight, including Farman as pilot, is given as 1,540
lbs., so that the machine was much heavier than either of the others;
the weight per horse-power being midway between the Santos-Dumont
and the Wright at 31 lbs. per square foot, while the wing loading was
considerably greater than either at 3 1/2 lbs. per square foot. The
Voisin machine was experimented with by Farman and Delagrange from about
June 1907 onwards, and was in the subsequent years developed by Farman;
and right up to the commencement of the War upheld the principles of
the box-kite method of construction for training purposes. The chief
modification of the original design was the addition of flaps (or
ailerons) at the rear extremities of the main planes to give lateral
control, in a manner analogous to the wing-warping method invented by
the Wrights, as a result of which the end curtains between the planes
were abolished. An additional elevator was fitted at the rear of the
fixed biplane tail, which eventually led to the discarding of the front
elevator altogether. During the same period the Wright machine came into
line with the others by the fitting of a wheeled undercarriage integral
with the machine. A fixed horizontal tail was also added to the rear
rudder, to which a movable elevator was later attached; and, finally,
the front elevator was done away with. It will thus be seen that having
started from the very different standpoints of automatic stability and
complete control by the pilot, the Voisin (as developed in the Farman)
and Wright machines, through gradual evolution finally resulted in
aeroplanes o