the linear dimension. If be greater the increase will be appropriately more rapid.
The relation could only remain constant if the value of were to sink to zero, a condition which is manifestly impossible.
It is probable that for an aerodrome the size of that chosen as an example in the preceding section the value of , is in excess of that necessary, but it is questionable whether it would be possible to construct a machine of moderate velocity capable of bearing a man, without the aerofoil considerably exceeding one-fifth of the total weight.
The question of aerofoil weight as affecting the phenomenon of flight as presented by Nature takes its place in the later portion of the work. It is only necessary here to point out that the larger birds must, in general, be more influenced than the smaller ones, just as in the case of other forms of aerodrome; and in the matter under discussion we have one of the causes, if not the most important cause, that constitute determining factors of that critical point at which Nature finds it advantageous to change from the insect mode to the avian mode of flight: that is, from the aeroplane to the pterygoid form.
Note.—Tables, etc., in present chapter relate strictly to incompressible fluid. For method of taking compressibility of air into account, see Appendix I.
