The two surfaces were kept apart by two struts or vertical
posts with a few guy wires, but the connecting joints were weak and
there was nothing like trussing. This eventually cost his most useful
life. Two weeks before that distressing loss to science, Herr Wilhelm
Kress, the distinguished and veteran aviator of Vienna, witnessed a
number of glides by Lilienthal with his double-decked apparatus. He
noticed that it was much wracked and wobbly and wrote to me after the
accident: "The connection of the wings and the steering arrangement were
very bad and unreliable. I warned Herr Lilienthal very seriously. He
promised me that he would soon put it in order, but I fear that he did
not attend to it immediately."

In point of fact, Lilienthal had built a new machine, upon a different
principle, from which he expected great results, and intended to make
but very few more flights with the old apparatus. He unwisely made one
too many and, like Pilcher, was the victim of a distorted apparatus.
Probably one of the joints of the struts gave way, the upper surface
blew back and Lilienthal, who was well forward on the lower surface, was
pitched headlong to destruction.

Experiments by the Writer.

In 1896, assisted by Mr. Herring and Mr. Avery, I experimented with
several full sized gliding machines, carrying a man. The first was a
Lilienthal monoplane which was deemed so cranky that it was discarded
after making about one hundred glides, six weeks before Lilienthal's
accident. The second was known as the multiple winged machine and
finally developed into five pairs of pivoted wings, trussed together at
the front and one pair in the rear. It glided at angles of descent of 10
or 11 degrees or of one in five, and this was deemed too steep. Then
Mr. Herring and myself made computations to analyze the resistances. We
attributed much of them to the five front spars of the wings and on
a sheet of cross-barred paper I at once drew the design for a new
three-decked machine to be built by Mr. Herring.

Being a builder of bridges, I trussed these surfaces together, in order
to obtain strength and stiffness. When tested in gliding flight the
lower surface was found too near the ground. It was taken off and the
remaining apparatus now consisted of two surfaces connected together
by a girder composed of vertical posts and diagonal ties, specifically
known as a "Pratt truss." Then Mr. Herring and Mr. Avery together
devised and put on an elast