1887. | NEW YORK ACADEMY OF SCIENCES. 19 
Pror. W. C. TROWBRIDGE announced 
A DISCOVERY BY C. C. TROWBRIDGE REGARDING THE PURPOSE 
OF THE EMARGINATION IN THE PRIMARY WING-FEATHERS 
OF CERTAIN BIRDS. 
My son, C. C. Trowbridge, astudent in the Hopkins Grammar 
School at New Haven, called my attention recently to a fact 
which he had observed, viz., that the emarginate cuttings of 
the primary feathers of certain birds are designed to enable the 
birds to interlock, at will, these feathers in an extended position, 
in order, presumably, to relieve the muscles of the tip of the 
wing from prolonged or continuous exertion during flight. 
From my own examination of the specimens which he brought 
GY 
to my notice I am quite sure of the truth of his observations ; but 
although the facts were quite new to me, and especially inter- 
esting in connection with the mechanism of flight, I hesitated 
to make any announcement of the discovery until I could con- ' 
sult those who were likely to know whether the facts observed 
had been before noticed or described. 
The results of my inquiries were that, while ornithologists 
have, of course, known and described the peculiar cuttings of 
the feathers, the purposes subserved by the shape thus given to 
them have hitherto escaped observation. 
I accordingly requested my son to make such drawings from 
wings in his possession as would serve to explain or illustrate 
the mode by which the primaries are interlocked. The figures 
