84 TRANSACTIONS OF THE [pEc. 19, 
During the prevalence of any considerable wind, the frigate 
bird was invariably soaring over the fortress, and, rather singu- 
larly as we thought, over the light-tower quite accurately and 
regularly, which afforded exceedingly favorable views. 
A singular fact is that at night, either in moonlight, or when 
the sky is overcast, these birds are seen in their accustomed 
position. 
It is a well-known circumstance of this region that a gentle 
breeze prevails during most of the time in the winter months, 
always from the east. ‘This condition is pretty regularly 
interrupted, once in fourteen days, more or less, by a ‘‘north- 
er,” so-called. 
The garrison ensign in this isolated post came to be a sort of 
oracle from which satisfactory instruction was frequently drawn. 
It could be depended on to indicate an impending ‘‘norther ” 
by coming to astand a few hours in advance, the mercury then 
indicating 80 degrees. 
I do not recall an instance of the flight of a frigate bird at 
such times, excepting an occasional dash at plunder. 
The birds were then quietly roosting. This dead level of 
quiet prevails but a few hours, and is anon rudely interrupted ; 
the ensign veers quickly, and indicates a wholesale breeze ; the 
north wind is instantly in force, and the frigate birds are almost 
simultaneously at hand directly over the light-tower. In the 
one feature, the heading of the birds to windward, lies the index 
to the solution of the problem involved in the soaring of birds. 
A remarkable circumstance is the perfect repose of the birds, 
blow it ever so rudely. The heaviest gales have no effect to 
lessen the perfect balance of the bird upon the elements ; it rests 
as upon a pivot; scarcely leaving the field of the glass ; swaying 
at times but never rudely, and never pushed aside in any direc- 
tion. 
This gwast condition of rest rendered observation, aided by 
the nearness afforded by the tower and glass, nearly perfect. 
It had been claimed, in absence of a satisfactory explanation of 
the extraordinary buoyancy of such birds, that there must be 
some movement of the inner coverts which was not noticed at 
the altitude usually met with by the observer; and on such weak 
and unphilosophical subterfuge the subject has been dropped 
for many years. 
There could be nothing added to our opportunity for exact 
observation; the rather low position of the birds usually, when 
soaring, and the nearness attained, unseen by them, were all that 
could be called for, and there is no denying the fact that these 
birds rest on the wind, their wings extended to the utmost, and 
the entire mechanism in a state of seeming catalepsy. 
