THE PROBLEM OF THE SOARING BIRD. 55 
solution of the matter, that of the surging head, was given 
provisionally. 
I was not prepared to deny any of the solutions given, and 
not more ready to admit them, being conscious of very much 
ignorance of the entire matter. Meanwhile my interest in the 
subject, constantly increasing, had, in 1876, overshadowed all 
others, and being disengaged from business, I devoted the ensuing 
five years to the birds on the Gulf Coast of South Florida, where 
the soaring varieties were found in abundance, fully intending to 
unravel the case before leaving it. The task was a hard one, and 
the final solution was found in a totally unexpected direction. 
The predominant feeling I have since experienced in regard to it 
is one of surprise—surprise that in this ceaselessly active age 
mechanical possibilities of the most important character could 
exist in the atmosplieric spaces all about us, with many of the 
largest species of existing birds putting them in daily practice 
before our eyes, and we still remaining completely ignorant of 
them! I propose in this paper to present, first, a few of the 
most significant facts exhibited by the soaring birds; next, to 
offer an explanation of the phenomenon; and finally, to examine 
the bearing of what has been said on the problem of artificial 
air-navigation. 
I mean by a “ soaring bird” one which habitually travels the 
air on motionless wings. All birds flap their pinions at times, 
and many of the smaller kinds, such as Rooks, Kestrels, Crows, 
and Gulls can maintain flight on fixed wings when the conditions 
are favourable. But I would never think of observing them for 
lessons in soaring. ‘They are too light to average the inequalities 
in the air current, and there are frequently long intervals of 
active wings before the fixed conditions occur. ‘The soaring 
varieties are at it all the time. The Frigate-birds live in the air 
night and day for a week at a time without touching a roost. 
Their congeners, the Buzzards, spend the day in the same style. 
The various Cranes common to the coast often spend hours 
resting in the air, while the Gannet is an admirable soaring bird 
with a heavy body and relatively small expanse of wings. 
When I speak of “fixed” or ‘‘ motionless” wings the meaning 
is that no muscular power is used to either overcome weight or 
air resistance. It is not meant that the pinions are absolutely 
rigid, like a board, for they are moved to accomplish change 
