sq. ft. The motive power consisted of an engine with a cylinder
of three-quarter inch diameter and a two-inch stroke; between
this and the crank shaft was a bevelled gear giving three
revolutions of the propellers to every stroke of the engine; the
propellers, right and left screw, were four-bladed and 16 inches
in diameter. The total weight of the model with engine was 8
lbs. Its successful flight is ascribed to the fact that
Stringfellow curved the wings, giving them rigid front edges and
flexible trailing edges, as suggested long before both by Da
Vinci and Borelli, but never before put into practice.

Mr F. J. Stringfellow, in the pamphlet quoted above, gives the
best account of the flight of this model: 'My father had
constructed another small model which was finished early in
1848, and having the loan of a long room in a disused lace
factory, early in June the small model was moved there for
experiments. The room was about 22 yards long and from 10 to 12
ft. high.... The inclined wire for starting the machine occupied
less than half the length of the room and left space at the end
for the machine to clear the floor. In the first experiment the
tail was set at too high an angle, and the machine rose too
rapidly on leaving the wire. After going a few yards it slid
back as if coming down an inclined plane, at such an angle that
the point of the tail struck the ground and was broken. The
tail was repaired and set at a smaller angle. The steam was
again got up, and the machine started down the wire, and, upon
reaching the point of self-detachment, it gradually rose until
it reached the farther end of the room, striking a hole in the
canvas placed to stop it. In experiments the machine flew well,
when rising as much as one in seven. The late Rev. J. Riste,