with vertical webs of holland two feet apart, thus
virtually giving a length of wing of ninety-six feet and
one hundred and twenty square feet of supporting surface.
The man was placed horizontally on a base board
beneath the spar. This apparatus when tried in the wind
was found to be unmanageable by reason of the fluttering
motions of the fabric, which was insufficiently stiffened
with crinoline steel, but Mr. Wenham pointed out that
this in no way invalidated the principle of the apparatus,
which was to obtain large supporting surfaces without
increasing unduly the leverage and consequent weight
of spar required, by simply superposing the surfaces.

This principle is entirely sound and it is surprising that
it is, to this day, not realized by those aviators who are
hankering for monoplanes.

Experiments by Stringfellow.

The next man to test an apparatus with superposed
surfaces was Mr. Stringfellow, who, becoming much impressed
with Mr. Wenham's proposal, produced a largish
model at the exhibition of the Aeronautical Society in
1868. It consisted of three superposed surfaces aggregating 28
square feet and a tail of 8 square feet more.
The weight was under 12 pounds and it was driven by a
central propeller actuated by a steam engine overestimated
at one-third of a horsepower. It ran suspended
to a wire on its trials but failed of free flight, in
consequence of defective equilibrium. This apparatus has