he failures of others.

Legend and doubtful history carries up to the fifteenth century, and
then came Leonardo da Vinci, first student of flight whose work endures
to the present day. The world knows da Vinci as artist; his age knew him
as architect, engineer, artist, and scientist in an age when science was
a single study, comprising all knowledge from mathematics to medicine.
He was, of course, in league with the devil, for in no other way
could his range of knowledge and observation be explained by his
contemporaries; he left a Treatise on the Flight of Birds in which are
statements and deductions that had to be rediscovered when the Treatise
had been forgotten--da Vinci anticipated modern knowledge as Plato
anticipated modern thought, and blazed the first broad trail toward
flight.

One Cuperus, who wrote a Treatise on the Excellence of Man, asserted
that da Vinci translated his theories into practice, and actually flew,
but the statement is unsupported. That he made models, especially on
the helicopter principle, is past question; these were made of paper and
wire, and actuated by springs of steel wire, which caused them to lift
themselves in the air. It is, however, in the theories which he put
forward that da Vinci's investigations are of greatest interest; these
prove him a patient as well as a keen student of the principles of
flight, and show that his manifold activities did not prevent him from
devoting some lengthy periods to observations of bird flight.

'A bird,' he says in his Treatise, 'is an instrument working according
to mathematical law, which instrument it is within the capacity of man
to reproduce with all its movements, but not with a corresponding
degree of strength, though it is deficient only in power of maintaining
equilibrium. We may say, therefore, that such an instrument constructed
by man is lacking in nothing except the life of the bird, and this life
must needs be supplied from that of man. The life which resides in the
bird's members will, without doubt, better conform to their needs than
will that of a man which is separated from them, and especially in the
almost imperceptible movements which produce equilibrium. But since we
see that the bird is equipped for many apparent varieties of movement,
we are able from this experience to deduce that the most rudimentary
of these movements will be capable of being comprehended by man's
understanding, and that he will to a great extent be a