and the settlement of equilibrium while in flight had to be overcome,
and then it was possible to set about the construction of the series of
model aerodromes and make test of their 'lift.'

By the time Langley had advanced sufficiently far to consider it
possible to conduct experiments in the open air, even with these models,
he had got to his fifth aerodrome, and to the year 1894. Certain tests
resulted in failure, which in turn resulted in further modifications of
design, mainly of the engines. By February of 1895 Langley reported
that under favourable conditions a lift of nearly sixty per cent of
the flying weight was secured, but although this was much more than
was required for flight, it was decided to postpone trials until two
machines were ready for the test. May, 1896, came before actual trials
were made, when one machine proved successful and another, a later
design, failed. The difficulty with these models was that of securing
a correct angle for launching; Langley records how, on launching one
machine, it rose so rapidly that it attained an angle of sixty degrees
and then did a tail slide into the water with its engines working at
full speed, after advancing nearly forty feet and remaining in the
air for about three seconds. Here, Langley found that he had to obtain
greater rigidity in his wings, owing to the distortion of the form of
wing under pressure, and how he overcame this difficulty constitutes yet
another story too long for the telling here.

Field trials were first attempted in 1893, and Langley blamed his
launching apparatus for their total failure. There was a brief, but at
the same time practical, success in model flight in 1894, extending
to between six and seven seconds, but this only proved the need for
strengthening of the wing. In 1895 there was practically no advance
toward the solution of the problem, but the flights of May 6th and
November 28th, 1896, were notably successful. A diagram given in
Langley's memoir shows the track covered by the aerodrome on these two
flights; in the first of them the machine made three complete circles,
covering a distance of 3,200 feet; in the second, that of November 28th,
the distance covered was 4,200 feet, or about three-quarters of a mile,
at a speed of about thirty miles an hour.

These achievements meant a good deal; they proved mechanically propelled
flight possible. The difference between them and such experiments as
were conducted by Clement