regain it. This recommendation, by
the way, received ample support in the training areas of war pilots.

Man's muscles, said da Vinci, are fully sufficient to enable him to
fly, for the larger birds, he noted, employ but a small part of their
strength in keeping themselves afloat in the air--by this theory he
attempted to encourage experiment, just as, when his time came, Borelli
reached the opposite conclusion and discouraged it. That Borelli was
right--so far--and da Vinci wrong, detracts not at all from the repute
of the earlier investigator, who had but the resources of his age to
support investigations conducted in the spirit of ages after.

His chief practical contributions to the science of flight--apart
from numerous drawings which have still a value--are the helicopter or
lifting screw, and the parachute. The former, as already noted, he
made and proved effective in model form, and the principle which he
demonstrated is that of the helicopter of to-day, on which sundry
experimenters work spasmodically, in spite of the success of the plane
with its driving propeller. As to the parachute, the idea was doubtless
inspired by observation of the effect a bird produced by pressure of its
wings against the direction of flight.

Da Vinci's conclusions, and his experiments, were forgotten easily by
most of his contemporaries; his Treatise lay forgotten for nearly four
centuries, overshadowed, mayhap, by his other work. There was, however,
a certain Paolo Guidotti of Lucca, who lived in the latter half of the
sixteenth century, and who attempted to carry da Vinci's theories--one
of them, at least, into practice. For this Guidotti, who was by
profession an artist and by inclination an investigator, made for
himself wings, of which the framework was of whalebone; these he covered
with feathers, and with them made a number of gliding flights, attaining
considerable proficiency. He is said in the end to have made a flight of
about four hundred yards, but this attempt at solving the problem
ended on a house roof, where Guidotti broke his thigh bone. After that,
apparently, he gave up the idea of flight, and went back to painting.

One other a Venetian architect named Veranzio, studied da Vinci's theory
of the parachute, and found it correct, if contemporary records and even
pictorial presentment are correct. Da Vinci showed his conception of a
parachute as a sort of inverted square bag; Veranzio modified this to a
'sort of