POWER OF FLYING. 547 



condly, be sufficient muscular power to give 

 these instruments a very great velocity. Both 

 these advantages are found combined in the an- 

 terior extremities of birds, and no animals be- 

 longing to any other class possess them in the 

 same perfection. No quadruped, except the bat, 

 has sufficient muscular power in its limbs, how- 

 ever aided by an expansion of surface, to strike 

 the air with the force requisite for flight. No 

 refinement of mechanic ingenuity has ever 

 placed the Daedalian art of flying within the 

 reach of human power ; for even if the lightest 

 possible wings could be so artificially adapted to 

 the body as to receive the full force of the ac- 

 tions of the limbs, however these actions might 

 be combined, they would fall very far short of 

 the exertion necessary for raising the body from 

 the ground. 



Examples, however, occur in every one of 

 the classes of vertebrated animals, where an 

 approach is made to this faculty. In the Exo- 

 ccBtus, or flying-fish, the pectoral fins have been 

 enormously expanded, evidently for the purpose 

 of enabling the animal to leap out of the water, 

 and support itself for a short interval in the air : 

 but its utmost efforts are inadequate to sustain 

 it beyond a few moments in that element, and 

 it can never rise to more than five or six feet 

 above the surface of the water. 



A species of lizard, called the Draco Volans, 



