174 THE REIGN OF LAW. 



slight elevation of one side of the whole body, and 

 a slight depression of the other. The depression is 

 always on that side towards which the bird is turn- 

 ing. On the opposite side, that from which the 

 bird is turning, there is of course a corresponding 

 elevation. Sometimes this is very obvious ; but 

 in general it is so slight as to require close ob- 

 servation to detect it. In the Albatross, when 

 sweeping round, the wings are often pointed in a 

 direction nearly perpendicular to the sea* The 

 effect of this, of course, is to expose the two 

 vanes at different angles to the aerial currents 

 — and it must be remembered that in flight the 

 balance of all the forces employed is so ex- 

 tremely fine that the most minute alteration 

 in the degree in which they bear upon each 

 other, will produce an immense change in the 



* See a very interesting account of the flight of the Albatross by 

 Captain T. W. Hutton, in the "Ibis" for July 1864. Captain 

 Hutton says, "If he wishes to turn to the right, he bends his head 

 and tail slightly upwards, at the same time raising his left side and 

 lowering the right in proportion to the sharpness of the curve he 

 wishes to make, the wings being kept rigid the whole time." This 

 is the only paper I have seen on the flight of birds in which obser- 

 vation of the facts is not vitiated by some false preconceived theory 

 on their cause. Captain Hutton has thoroughly seized the true 

 mechanical principles of flight. 



