PROGRESSION IN OR THROUGH THE AIR. 



129 



without diminishing the power of flight. Compare with 

 experiments 5 and 6. 



If the mutilation be carried further, flight is laboured, and 

 in some cases destroyed. 



Exp, 15. When the front edges of the first and second pairs 

 of wings are notched or when they are removed, flight is com- 

 pletely destroyed. Compare with experiments 3, 4, and 9. 



This shows that a certain degree of stiffness is required for 

 the front edges of the wings, the front edges indirectly sup- 

 porting the back edges. It is, moreover, on the front edges 

 of the wings that the pressure faUs in flight, and by these 

 edges the major portions of the wings are attached to the 

 body. The principal movements of the wings are communi- 

 cated to these edges. 



Bidterfly. — Exp. 1 6. Removed posterior halves of the first 

 pair of wings of white butterfly. Flight perfect. 



Exp, 17. Removed posterior halves of first and second 

 pairs of wings. Flight not strong but still perfect. If addi- 

 tional portions of the posterior wings were removed, the 

 insect could still fly, but with great effort, and came to the 

 ground at no great distance. 



Exp, 18. When the tips (outer sixth) of the first and 

 second pairs of wings were cut away, flight was in no wise 

 impaired. When more was detached the insect could not fly. 



Exp, 19. Removed the posterior wings of the brown but- 

 terfly. Flight unimpaired. 



Eipp. 20. Removed in addition a small portion (one-sixth) 

 from the tips of the anterior wings. Flight still perfect, as 

 the insect flew upwards of ten yards. 



Exp. 21. Removed in addition a portion (oiie-eighth) of 

 the posterior margins of anterior wings. The insect flew 

 imperfectly, and came to the ground about a yard from the 

 point where it commenced its flight. 



House Sparrow, — The sparrow is a heavy small-winged 

 bird, requiring, one would imagine, all its wing area. This, 

 however, is not the case, as the annexed experiments show. 



Exp. 22. Detached the half of the secondary feathers of 

 either pinion in the direction of the long axis of the wing, 

 the primaries being left intact. Flight as perfect as before 

 7 



