178 THE REIGN OF LAW. 



seem to be achieved : yet not by knowledge only, 

 except as the guide of Power. For here, as every- 

 where else in Nature, we see the same mysterious 

 need of conforming to imperative conditions, side 

 by side with absolute control over the forces 

 through which this conformity is secured. When 

 any given purpose cannot be attained without the 

 violation of some law, unless by some new power, 

 and some new machinery — the requisite power 

 and mechanism are evolved — generally out of old 

 materials, and by modifications of pre-existing 

 forms. There can be no better example of this 

 than a wing-feather. It is a production wholly 

 unlike any other animal growth — an implement 

 specially formed to combine strength with light- 

 ness, elasticity, and imperviousness to air. Again, 

 the bones of a bird's wing are the bones of the 

 Mammalian arm and hand, specially modified to 

 support the feathers. The same purpose is effected 

 by other means in connexion with precisely the 

 same bones in the flying Mammalia — the Bats. 

 In these animals the finger-bones instead of being 

 compressed or soldered together to support fea- 

 thers, are separated, attenuated, and greatly length- 



