The Wright brothers made careful observation of the flight of birds, and fourd their observations A'aluable. It is interesting to consider the resemblance and differences of the manufactured aeroplane and the living bird. The resemblance may be simply the result of copying the bird, or it may be that similar designs have been arrived at independently by birds and men. The wings of both are roughly the same shape : of wide span, and narrow in the direction in which the bird flies ; both have concave wings with thick leading edges. In many aeroplanes hollow spars arc used like bones and like the quills of the feathers of birds. We copy plants also in this respect, for they too have learnt the economy of material in the use of hollow spars. The bodies of airships {iresimilar in shape to the bodies of swimming animals, with the greatest width towards the head. The bodies of birds are of similar form.