86 TRANSACTIONS OF THE - [pxc..19, 
Colonel Walter McFarland, a second letter, in which he said 
that, upon reflection, he must admit the theory as correct. 
It chanced that his charge as engineer officer at Tortugas 
i given him similar opportunities for observing the frigate 
irds. 
Mr. Darwin, in his pleasant account of the ‘‘ Voyage of the 
Beagle,” says of the condor: ‘*‘ Except when rising from 
the ground, I do not recollect ever having seen one of these 
birds flap its wings. Near Lima I watched some for nearly 
half an hour, without once taking off my eyes. ‘They moved in 
large curves, sweeping in circles, descending and ascending, 
without giving a single flap. 
“* As they glided close over my head, Lintently watched from 
an oblique position the outlines of the separate and great ter- 
minals of each wing; and these separate feathers, if there had 
been the least vibratory movement, would have appeared as if 
blended together ; but they were seen distinctly against the 
clear sky. 
‘‘The head and neck were moved frequently, and apparently 
with force ; and the extended wings seemed to form the fulcrum 
on which the movement of the neck, body, and tail acted.” 
I wrote to Mr. Darwin, detailing the particulars of my ob- 
servations. In reply I received a letter in which he says: 
‘‘The same thought about the soaring of the condor formerly 
passed through my mind, but on consulting with mathemati- 
cians I am assured that it will not hold good.” 
Doubtless, had he subsequently turned the matter over in his 
mind, he would have come to the present theory. 
The result of my observations was published in Harper’s 
Monthly of that period, and also in the Sportsman, which was 
afterwards merged in the Forest and Stream. 
On coming to New York in 1869, I submitted the same to 
President Barnard, of Columbia College, who claimed the su- 
premacy of the law of mechanics as before applied. He did, 
however, think that, with very delicate instruments, which pos- 
sibly some one might hereafter invent, the true explanation 
would be forthcoming. 
The Duke of Argyll has, among many truisms, and after quot- 
ing some hitherto appropriate lines from Solomon, ‘‘ ‘ The way of 
an eagle in the air,’ he knew it not,” reached nearly the correct 
conclusion, as have several other late writers. 
There are many interesting phases of bird flight which I be- 
lieve may be better understood by using intelligently the simile 
of a sailing ship—the ‘sailing in the eye of the wind,” 
“tacking,” ‘‘ jibing,” ‘‘coming in stays,” etc., but particularly 
