1887. ] NEW YORK ACADEMY OF SCIENCES. 85 
The body and wings are necessarily as one piece, as much so 
practically as the component parts of a kite, with no perceptible 
movement of one part upon another. These are facts; but it is 
a noticeable circumstance that those who have, in earlier times, 
considered the subject have not taken into account the inexo- 
rable requisite, the aim of the bird to windward. 
We have in the case of the frigate bird, which is regarded as 
a typical soarer, a bird exhibiting the maximum of wing- 
spread, and a minimum of bulk. The centre of gravity is well 
forward in a small compact body; the head and neck are nearly 
buried in the feathers of the thoracic region; the feet and legs 
extremely small, and the tail reduced to insignificance, and 
forked. We have here the elements fora soarer, from which 
the typical toy kite may well have derived its principles. 
Every boy who is ingenious enough to make a kite knows how 
requisite it is to construct the frame carefully, and more than 
all to adjust the rigging, so that the several forces which the 
completed toy is to meet in the air will have been harmonized 
to anicety. The beautiful poise and nearly absolute state of 
quiet seen'in a good kite are the result of considerable at- 
tention to details. What more natural than to compare the bird 
to a kite? 
But, say the mathematicians, the familiar law of mechanics 
forestalls that. Weclaim that the intelligence of the bird un- 
consciously modifies the action of the forces in play—the wind 
and gravity—and produces equilibrium. Give the kite that in- 
telligence, and cut the string. ‘The simile is rational. We 
have a thin outline presented by the wings and body to the 
wind. So long as that outline is preserved, and the bird has 
the power to meet the requirements, it will adjust itself by 
tilting, allowing gravity to oppose the wind. ‘The result is, as 
we see, a state of comparative rest. 
We often see a piece of paper, as mooth stiff sheet, sail off 
with the wind, and, occasionally, see it rest for an instant be- 
tween the two forces, the wind and gravity. 
Of course, one force prevails eventually, but there is a point 
reached at times which exhibits the sheet of paper in an attitude 
very suggestive of the bird and the kite in their condition of 
soaring, but having neither string nor intelligence, it falls. 
During the year 1858, I wrote an account of these observations, 
which was subsequently placed on record by Dr. William Stimp- 
son, secretary of the Chicago Academy of Sciences. 
I submitted them also to several officers of the United States 
Engineer Corps. The latter met the statements with the reply 
that a familiar law of mechanics militated against them. 
I was gratified, however, by receiving from one of the officers, 
