Flight of Albatrosses. 



S7 



moving faster than the lower stratum of wind and will again 

 develop new energy if its inertia is sufficient to prevent its 

 attaining the new velocity of the wind at once. So that the 

 bird must fly against the wind when ascending and with it 

 when descending. Thus the energy constantly lost by the 

 friction of the air is partially renewed by these manoeuvres. 

 This explains why the birds can sail longer in a high wind 

 than in a calm. It is because in a high wind and with a high 



1m-. 10. 



Albatross descending and making a broad curve to tbe left. 



sea there is much greater difference between the velocities of 

 the wind near the surface and a short distance above it; and 

 this, again, is an explanation of why an Albatross keeps so 

 close to the surface of the sea, only just topping the waves 

 and occasionally rising high in the air. 



The foregoing sketches (figs. 7-10) are copied from enlarged 

 photographs, the only good ones nut of many failures. The 



