She Pie ge Si ee a De ear TD ig cece ot ae a a a 
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7 1886] 
The Wings of Birds. vot 
scribed as situated “ near Bristol ” was in Pennsylvania. It seems 
more probable that it was located either on Burlington island or 
on the mainland near the site of the city of Burlington, in New 
Jersey. 
Twenty years ago a colony of crows roosted on Newbold’s 
island in the Delaware river, four miles north-west of Burlington 
island, and forty or fifty years ago another colony slept in a wood 
near Florence and, being disturbed, moved to another forest near 
Beverly which, within three years, has been deserted in turn for 
another site. 
There is much to warrant the conclusion that the great roost 
described by Wilson was parent to this and many others now 
Scattered over Burlington county, New Jersey. 
(To be continued.) 
10: 
THE WINGS OF BIRDS. 
BY I, LANCASTER. 
Wile engaged in ascertaining the methods employed by 
the soaring birds, on reaching a point where light began to 
break upon the obscurity, it became evident that the flight of all 
birds would be made comprehensible; that not only the day-long 
translation of frigate birds in ‘circular paths high in the air, but 
_ the homeward passage of pigeons and the migratory flight of 
wild fowl, would emerge from the realm of fancy and range 
themselves with allied phenomena on the platform of recognized _ 
mechanical activities, 
Indeed, many specimens of active wing flight have hitherto as _ : 
completely baffled the best efforts of mechanical science as has 
Soaring flight. When the weight of the bird is considered as- 
resistance to be overcome by muscular force, flapping is incompe-— 
tent to do the work required, and in spite of such effort gravity 
Would compel motion in its own direction to the surface of the 
- The area of the two wings of a duck of four pounds weight, _ 
which is effective on the air in the down stroke is not more than e 
_ two square feet. Counting one up and one down vibration as a 
Single stroke, not more than three of these would be made in one 
_ Second, and a liberal estimate would be an average of one foot of : 
Space traveled at each stroke for the entire wing surfaces. This — 
ignores loss in the upward vibration. The effective work done on 
