.')24 THE MECHANICAL FUNCTIONS. 



any other class of animals. Birds, in their annual 

 migrations, are known to traverse whole seas and 

 continents in the course of a very few days. Many 

 continue for weeks constantly on the wing : Frigate- 

 birds (Pelicanus aquilus, Linn.) are seen hovering 

 over the sea, in search of their prey, at the greatest 

 distances from land, without ever taking rest : and 

 their lives may almost be said to be passed in one 

 continued flight. 



END OF VOL. I. 



C. WHITTINGIIAM, TOOKS COl'RT, CHANCERY LANE. 



