f the 'kite-carriage,'
on the helicopter principle, W. H. Phillips constructed a model machine
which weighed two pounds; this was fitted with revolving fans, driven
by the combustion of charcoal, nitre, and gypsum, producing steam which,
discharging into the air, caused the fans to revolve. The inventor
stated that 'all being arranged, the steam was up in a few seconds, when
the whole apparatus spun around like any top, and mounted into the
air faster than a bird; to what height it ascended I had no means of
ascertaining; the distance travelled was across two fields, where, after
a long search, I found the machine minus the wings, which had been
torn off in contact with the ground.' This could hardly be described as
successful flight, but it was an advance in the construction of machines
on the helicopter principle, and it was the first steam-driven model of
the type which actually flew. The invention, however, was not followed
up.

After Phillips, we come to the great figures of the middle nineteenth
century, W. S. Henson and John Stringfellow. Cayley had shown, in
1809, how success might be attained by developing the idea of the plane
surface so driven as to take advantage of the resistance offered by
the air, and Henson, who as early as 1840 was experimenting with model
gliders and light steam engines, evolved and patented an idea for
something very nearly resembling the monoplane of the early twentieth
century. His patent, No. 9478, of the year 1842 explains the principle
of the machine as follows:--

In order that the description hereafter given be rendered clear, I will
first shortly explain the principle on which the machine is constructed.
If any light and flat or nearly flat article be projected or thrown
edgewise in a slightly inclined position, the same will rise on the
air till the force exerted is expended, when the article so thrown or
projected will descend; and it will readily be conceived that, if the
article so projected or thrown possessed in itself a continuous power or
force equal to that used in throwing or projecting it, the article
would continue to ascend so long as the forward part of the surface was
upwards in respect to the hinder part, and that such article, when the
power was stopped, or when the inclination was reversed, would descend
by gravity aided by the force of the power contained in the article, if
the power be continued, thus imitating the flight of a bird.

Now, the first part