1016 ON FORM AND MECHANICAL EFFICIENCY [en. 



bridges over points or areas where pressure might be unduly con- 

 centrated or confined, adapts itself to a sudden impact or concentrated 

 stress, helps to lessen or to guard against shock, and imparts to the 

 whole structure a quality which we may call, for short, resiliency. 



The engineer finds it easiest of attainment when his principal 

 members are in tension; hence elastic movement and resilience are 

 apt to be conspicuous in a suspension-bridge. One way and another, 

 resihence shews to perfection in a bird. The S-shaped curve of the 

 neck carrying the Hght weight of the head, the zig-zag flexures of 

 the legs bearing the balanced burden of the body, the supple basket 



Fig. 489.. A woodcock's skull, in (or nearly in) the natural attitude. A, B, the 

 baMS cranii; E, auditory meatus; 0, orbit; Q, quadrate bone. 



of the ribs, each rib in two halves one flexed on the other, all these 

 are such as to make the whole framework act like an elastic spring, 

 absorbing every shock as the bird lights on or rises from the ground. 

 Bird, beast and man exhibit this resilience, each in its degree; 

 a springy step is part of the joy of youth, and its loss is one of the 

 first infirmities of age. 



Nature's engineering is marvellous in our eyes, and our finest 

 work is narrow in scope and clumsy in execution compared to her 

 construction and design. But following her example, wittingly or 

 unwittingly, our own problems evolve and our ambitions enlarge 

 towards the conception of an "organised structure." In such 



