100 TRANSACTIONS OF THE [JAN. 16, 
Pror. ALLEN replied that, according to anatomists, the bird’s 
wing was constructed to guard against any rotation. He stated 
that the emargination could not be the result of wear, as it 
was present while the feathers were still in their sheaths; 
also, that the interlocking of the feathers, or crossing of the 
vanes, would cause a permanent crumpling or wrinkling of the 
vane, but that hundreds of wings of hawks in the American 
Museum showed the edges of the emarginated vanes smooth, 
straight, and perfect; that where they had been crossed by ac- 
cident, the wrinkling indicated it. 
PRESIDENT NEWBERRY briefly reviewed the debate, ex- 
plained some misunderstandings, and pleasantly closed the dis- 
cussion. 
January 16, 1888. 
STATED MEETING. 
The President, Pror. J. 8. NEWBERRY, in the chair. 
Forty-two persons present. 
The PRESIDENT exhibited a large specimen of Hdestus, and 
photo-engravings of the same. He reviewed the discussion over 
the character of the fossils, and stated his belief that they were 
spines. He read by title a paper 
ON THE GENUS EDESTUS. 
(Published in the Annals, Vol. IV.) 
Mr. W. Gootp LeEvISoN read a paper 
ON A METHOD FOR THE ABSOLUTE MEASUREMENT OF THE 
SHUTTER-SPEED IN INSTANTANEOUS PHOTOGRAPHIC 
EXPOSURES. 
(Illustrated with lantern views and results of experiments. ) 
An accurate yet simple method for determining the duration 
of instantaneous exposures has long been desired by those in- 
terested in photography, especially in its astronomical applica- 
tions; and an experience of this necessity has led me to contrive 
