13 
To the mind of the careless observer it should seem, that this ugly 
bird had the power of ascending to almost any height in the atmos- 
phere by circular movements, and of remaining in those calm and 
pure regions for hours at a time, without any other exertion than 
that of merely expanding his wings. But this attractive and beauti- 
ful exhibition, like all the seeming mysteries in nature coming with- 
in the scope of our observation and comprehension, may be easily 
explained by simply acquiring correct knowledge of the physical 
structure of this class of birds, and duly considering all the apparent 
as well as the probable circumstances connected with its production. 
Many years ago, I discon^red that these seeming " fancy flights" 
upon " airy nothing," were chiefly efi'ected by the force of the winds 
in connection with the expanded wings ; and considering their large 
size compared with the weight of the bird, the former containing 
about three square feet area, and the latter being about six pounds, 
I suppose, that the velocity of the current of air should not exceed, 
nor fall much below, the rate of five miles per hour, (a light breeze) 
within that region of the atmosphere where these movements occur, 
in order that the animal may ascend in this manner immediately over 
a particular spot on the earth. For I have often observed, that if 
the wind happened to blow at a greater velocity than that stated, the 
birds engaged in performing these evolutions were soon blown away 
into a distant part of the heavens ; and, on the other hand, if the 
current seemed to fall short of that rate, they advanced in the direc- 
tion of the point from whence it came. 
Now, let us suppose that, whilst there is a current of air moving 
at the rate of five miles per hour from the direction of the cardinal 
point west, one of these birds starts on the wing at that point and 
makes his first circular movement around by south to east, and thence 
by north to the place of departure. 
It will be perceived that, in passing around the southern section 
of the circle, the animal floats with the current of air moving east- 
ward, the force of which, added to that of his gravitating tendency, 
imparts to his body considerable velocity with which he rounds the 
eastern point, and turning his head westward immediately comes in 
contact with the wind which, while it instantly checks his motion, in 
an equal degree gradually raises him as he moves slowly up by north 
towards the starting point. And thus, by many repetitions of these 
gyrations, making a little ascension each time in passing up the northern 
