476 POPULAR SCIENCE MONTHLY. 



lar flap with the hase forming the front edge of the wing and the apex 

 lying in the elbow joint. 



The wing of the frigate bird, too, is quite the opposite of that of 

 the hummer, for it is the inner portion of the wing, the upper arm and 

 forearm, which is elongated, and instead of the six feeble secondaries of 

 the humming-bird there are no less than twenty-four; instead of a short, 

 stiff, rounded wing we have one that is long, flexible and pointed. In- 

 stead of a wing driven at the rate of several hundred strokes a minute 

 there is a wing that may be held outstretched and apparently motion- 

 less for minutes at a time, the muscles of the frigate bird being almost 

 as constantly in repose as those of the other are perpetually in motion. 



If the frigate bird represents the highest type of soaring flight two 

 more familiar birds, the turkey buzzard and albatross, are not far be- 

 hind, and these represent two methods of sailing flight and two distinct 

 modifications in the type of wings. The albatross is continually on the 

 move, ever quartering the water as a well-trained setter does the ground, 

 and yet with all this movement rarely mounting higher than fifty feet 

 above the water and never wheeling in great circles in mid-air. This 

 bird has that type of wing which best fulfills the conditions necessary 

 for an aeroplane, being long and narrow, so that while a fully grown 

 albatross may spread from ten to twelve feet from tip to tip, this wing 

 is not more than nine inches wide. This spread of wing, like that of 

 the frigate bird, is gained by the elongation of the inner bones of the 

 wing and by increasing the number of secondaries, there being about 

 forty of these feathers in the wing of the albatross. 



The turkey buzzard is emphatically a high flyer, wheeling slowly 

 about, half a mile or a mile above the earth, while his cousin, the 

 condor, so Humboldt tells us, has been seen above the summit of 

 Chimborazo. If any bird knows how to utilize every breath of wind 

 to the utmost that bird is the albatross, and it is equally a delight and 

 a marvel to see this bird apparently setting at naught all natural laws 

 as he sails with outstretched pinions almost into the eye of the wind or 

 hangs just off the lee quarter of a ship reeling off ten or twelve knots 

 an hour. In this last trick, however, the gull is almost equally expert, 

 evidently making use of the draft from the sails as well as of the 

 eddies caused by the passage of the vessel. 



It has long been evident that if man is to navigate the air it must 

 be done after the method of the albatross rather than that of the hum- 

 ming-bird, by the aeroplane and not by any device to imitate the strokes 

 of a bird's wings, for not only do the largest birds and those of the 

 longest flight for the most part sail or soar, but it is apparent that the 

 limit of size in a vibrating wing must soon be reached, since in a strong 

 wind with its varying eddies it would be quite out of the question to 

 manipulate such a piece of mechanism. 



