Manuscripts/Mixed Material Article by Alexander Graham Bell, October 11, 1910
If then we build our large structure by combining together a number of small structures each light enough to fly; instead of simply copying the small structure upon a larger scale, we arrive at a compound or cellular structure in which the ratio of weight to supporting surface is the same, as that of the individual units of which it is composed, thus overcoming entirely the really valid objections of Prof. Newcomb to the construction of large flying-machines.
In my paper upon the Tetrahedral principle in Kite Structure, I have shown that a frame work having the form of a tetrahedron possesses in a remarkable degree the properties of strength and lightness. This is especially the case when we adopt as our unit structure, the form of the regular tetrahedron, in which the skeleton frame is composed of six rods of equal length, as this form seems to give the maximum strength with the minimum of material. When these tetrahedral frames or cells are connected together by their corners they compose a structure of remarkable rigidity, even when made of light and fragile material;— The whole structure possessing the same properties of strength and lightness inherent in the individual cells themselves. The unit tetrahedral cell yields the skeleton form of a solid, and it is bounded by four equal triangular faces. By covering two adjoining faces with silk or other material suitable for use in kites, we arrive at the