? 
498 PROCEEDINGS OF SCIENTIFIC SOCIETIES. 
ANSWERS TO CORRESPONDENTS. 
Can you inform me what is the use of the comb-like formation on 
the inside of the middle claw of the Night-heron, the Night-hawk, and 
Whippoorwill? Is it peculiar to night birds? I find it-on those men- 
tioned, and have not noticed it on any bird of the day that I have 
shot, or is in my collection. — BALDWIN COOLIDGE, Lawrence. 
We referred these questions to Dr. T. M. Brewer, who thus writes: 
I have shown your letter to Mr. G. A. Boardman, and have secured & 
very satisfactory explanation from him of the purpose and use of the 
“formation” in question. It.is used by the birds to clean their heads, 
and such portions of their neck, back, etc., as they cannot reach with 
their bills. He often finds them containing feathers, down, dead 
skin, etc. 
H. W., Massachusetts.—The Fern, from Genesee, N. Y., en- 
Z is mg nothing but a poor ites: of Aspleniuva aon 
teroides Mic 
PROCEEDINGS OF SCIENTIF IC SOCIETIES. 
a er 
AMERICAN ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE 
accumulation of snow and ice as the glacial hypothesis supposes to 
have once existed. 
The author called attention to the extremely broken gondie of 
the northern border of the continent, and to the probable effect of & 
snow line by a depression of the summer temperature. A large ex- 
tension of the area of perennial snow would result from this. But 
every one hundred feet of snowy accumulation would be more than 
equivalent in climatic effect to a hundred feet of continental eel 
introduced. We should thus have a great snow and ice plateau, cov- 
_ ering the northern portions of the maent without resorting to & 
: very extended upward mo movement of the s 
