g at the first descent. But, neglecting the fact that the
inevitable final collapse rendered them impossible, the weight of the
flying machines gave them this theoretical advantage, that they could
go through the air against a wind, a necessary condition if aerial
navigation was to have any practical value. It is Filmer's particular
merit that he perceived the way in which the contrasted and hitherto
incompatible merits of balloon and heavy flying machine might be
combined in one apparatus, which should be at choice either heavier or
lighter than air. He took hints from the contractile bladders of fish
and the pneumatic cavities of birds. He devised an arrangement of
contractile and absolutely closed balloons which when expanded could
lift the actual flying apparatus with ease, and when retracted by the
complicated "musculature" he wove about them, were withdrawn almost
completely into the frame; and he built the large framework which these
balloons sustained, of hollow, rigid tubes, the air in which, by an
ingenious contrivance, was automatically pumped out as the apparatus
fell, and which then remained exhausted so long as the aeronaut desired.
There were no wings or propellers to his machine, such as there had been
to all previous aeroplanes, and the only engine required was the compact
and powerful little appliance needed to contract the balloons. He
perceived that such an apparatus as he had devised might rise with frame
exhausted and balloons expanded to a considerable height, might
then contract its balloons and let the air into its frame, and by an
adjustment of its weights slide down the air in any desired direction.
As it fell it would accumulate velocity and at the same time lose
weight, and the momentum accumulated by its down-rush could be utilised
by means of a shifting of its weights to drive it up in the air again
as the balloons expanded. This conception, which is still the structural
conception of all successful flying machines, needed, however, a vast
amount of toil upon its details before it could actually be
realised, and such toil Filmer--as he was accustomed to tell the
numerous interviewers who crowded upon him in the heyday of his
fame--"ungrudgingly and unsparingly gave." His particular difficulty was
the elastic lining of the contractile balloon. He found he needed a new
substance, and in the discovery and manufacture of that new substance he
had, as he never failed to impress upon the interview