Evening star. [volume] (Washington, D.C.) 1854-1972, 1903-05-30
that u.s. into supporting surfaces and
steadying surfaces.
Another Feature Described.

that u.s. into supporting surfaces and
steady1ng surfaces.
Another Feature Described.
Another feature of the triangular-celled
Kite that is referred to by Prof Bell is
that the separate cells are admir- ably adapt
ed for combination into compound struc-
ture, in which the aeroplane surfaces do
not interfere with one another. After ex-
planning fully the advantages of the tri-
angular over the rectangular cells. Prof.
Bell passes on to his experiments, and
tells of the construction of cells that were
triangular in every direction, longitudinal
ly as well as transversely. This he re-
CARDS az a clear realization of the funda-
mental Importance Of the skeleton of the
tetrahedron element of the structure
or framework of a kite or flying machine.
With such a construction the aeroplanes
are triangular and suggestive of pair OF
birds wings raised at an angle and con-
nected together tip to tip by a cross bar.
A tetrahedron. 1t Is explained for the
benefit of the unscientifc, is form OF
solid bounded by four triangular surfaces.
In the regular tetrahedron the boundaries
consist of four equilateral triangles and six
equal edges. In the skeleton form the
edges alone are represented and the skele-
ton of regular tetrahedron is produced
by Joining together six equal rods end to
end so as to form four equilateraI triangles.
Most persons are familiar with the conf
mon puzzie-how to make four triangieS
Win SIX matcheS. Ine lies IN the
unconscious assumption of the expert
menter that the four triangles should all
be in the same plane. The moment he
realizes that they need not be in the same
plane the solution of the problem becomes
easy. Place three matches the table 50
as to form triangle, and stand the other
three up over this like the three legs of
tripod stand. The matches then form the
skeleton of regular tetrahedron.
"A framework formed upon this model
says Prof. Bell. ''of six equal rods fastened
together at the ends constitutes a terra
hedral cen possessing the qualities OF
strength and lightness in an extraordinary
degree. 1t is not simply braced in two di-
rections in space like a triangle, but in
three directions like solid. If | may coin
| a word, it possesses three-dimensionaP
| strength; not .two-dimensionaF strength
| like a triangle, or 'one-dimensionaH
strength like a rod. 1t is the skeleton Of a
| solid, not of a surface or line"
A Tetrahedral Kite.
When a tetrahedral frame is provided
| with aero-surfaces of silk or other material
suitably arranged, it becomes a tetrahedral
kite, or kite having the form Of terra
hebron. The kite Is composed of four
winged cells of the regular tetrahedron va
riety connected together at the corners
Upon this mode of construction an empty
space of octahedral form is left in the mid
die of the kite which seems to have the
same function as the space between the
two cells of the Hargrave box kite. The
tetrahedral kites that have the largest CEN
trail spaces preserve their equilibrium best
in the air.
OF the extreme utility of the method of
construction that has been described and
its adaptability under almost all condi-
tons Prof Bell says:
My own experiments with compound
kites composed of triangular cells connect
ed corner to corner have amply demon
strated the fact that the dimensions of
such a kite may be increased to very
considerable extent without materially in
creasing the ratio of weight to supporting
surface; and upon the tetrahedral plan the