The sun., 1894-05-13

| and Il is pronounced possible that = similar
! texture Of surface may prove Of advantage In
| nyinR machines. but this probably will not be
| determined until partial success has been
achieved with an apparatus Of Sufficient size
to sustain the weight ofs man.
W.
The problem Of the maintenance Of soui-
llbrium 10 in Mr.. Chsnutes view the most
dlfhcult now remaining In be solved. Almost
every failure In actual experiments has re-
suited from lack OF equilibrium. This Is the
capital requisite. for manifestly safety is the
supreme test OF successes In aerial naviga-
tion-safety In starting up. In sailing. and in
coming down. II flying machine were only
required to sail at one unvarying angle Of in
cidence In calm air. the problem here pro-
pounded would be much easier OF solution.
The centre OF gravity would be so adjusted as
TO coinclde with the centre OF pressure at the
particular angle OF flight desired and the
speed would be kept as regular as possible;
but the flying machine. like the bird. must
rise and must fall, and 1t must encounter
whirls. eddies and gusts OF wind. The bird
meets these By constantly changing his cen
tire Of gravity; he is an acrobat and balances
himself by instinct; but the problem is very
much more difficult for an inanimate ma
chine: and the latter requires an epuipoise-
automatic II poesible-which shall be more
stable than that OF the bird. Experiments
described In the body Of this book have shown
that transverse stability may be secured In two
ways; frat. by placing the two halves Of the
sustaining surfaces at q diedral angle to each
other: and. secondly. by adding longitudinal
keel to the apparatus. as In the case OF MIR.
Boynton's I'm kites. The mode OF action is
practically the same for both devices. and con-
sists in producing increased air pressure upon
the side which tends to dip downward. The
two devices may he employed coniointly. but
the keel will produce less head resistance to
forward motion than the dledral angle. which
resistance. however. may be diminished By
turning upward only the outer ends of the
sustaining surfaces in q manner similar to the
upbending primary feathers OF the soaring
birds. Longitudinal stability may he pro-
NOTED In three ways; first. by additional sur
faces at . slight angle to the main aus
tanning surface: secondly. BY placing several
surfaces behind each other; and. thirdly.
By causing the centre Of gravity always to CO.
incids with the centre OF pressure. Tho first
way corresponds to the just mentioned
method for procuring transverse stability by
means OF surfaces at diedral angle: It Is IL
lustrsted by Maxim's aeroplane. In which two
such surfaces are afllxed. front and rear: and
by Penaud's asroplans. in which but one Is
affixed. at the rear. The second way Is ex-
empifsd In Browns bi-planes and By Har-
graves cellular kites. and the third 10 the
method universally employed By the birds.
For an artificial apparatus the method last re-
ferred to constitutes 40 yet an unsolved
problem. Several inventors have proposed
methods OF shifting weights to change the DO
sition Of the centre Of gravity as the ap-
paratus changes its angle OF incidence. but
mono OF these is automatic. and none has been
tested