MIGRATION 563 
consists chiefly of the abortive or unsuccessful attempts at its 
accomplishment, when birds are checked in their course, and being 
unable to proceed present themselves to our sight and hearing. H 
this be so, the aid of “land-bridges” and river-valleys, the importance 
of which is so strongly pressed by certain writers (mostly theorizers) 
becomes insignificant. 
Now that birds can and do fly at elevations far beyond those 
which most people are accustomed to think possible, we have some 
indication. Mr. J. Tennant states (Stray Feathers, iii. p. 419) that 
at Roorkee on the 23rd Sept. 1875, while looking through a 
telescope at the sun, he saw birds, apparently Kites, frequently 
pass over its face, some of which were in focus with the sun itself 
and must therefore have been several miles high, while the nearest 
must have been quite a mile above the earth’s surface. These 
birds indeed were only soaring, on the look-out for prey, and not 
migrating ; but a stronger case in point is the curious and valuable 
observation recorded by Mr. W. E. D. Scott (Bull. Nuttall Orn. 
Club, vi. pp. 97-100) when on the night of the 19th Oct. 1880, 
he saw through an astronomical telescope, at Princeton, in New 
Jersey, great numbers of birds passing across the face of the moon. 
Computation shewed that these birds, which were on their autumnal 
Migration, must have been travelling at heights varying from a 
mile to two miles. Some time later, 16th April 1881, the same 
gentleman, in company with Mr. Allen, made some further observa- 
tions (tom. cit. p. 188) at the same place; but on this occasion the 
birds seen—Swallows, and on their northward journey—were flying 
comparatively low. They were also much less numerous, for only 
13 passed in three-quarters of an hour, whereas on the former 
occasion the average was 4°5 per minute. Again Mr. F. M. 
Chapman (4uk, 1888, pp. 37-39), also in New Jersey, watching 
for nearly three hours on the evening of the 3rd Sept. 1887, saw 
in like manner 262 birds cross the moon’s face. Of these 233 
were computed to be at a height of from 1500 to 15,100 feet; 
but an especially remarkable thing is that the lowest birds were 
“flying upward,” as if they had risen from the immediate neigh- 
bourhood and “were seeking the proper elevation at which to 
continue their flight.” 2 
1 “Most of the birds were the smaller land-birds, among which were plainly 
recognized Warblers, Finches, Woodpeckers and Blackbirds [Jcteridx].. . 
Among the Finches I would particularly mention Chrysomitris tristis, which 
has a very characteristic flight ; and the Blackbirds were conspicuous by the 
peculiar shape of the tail, from which characteristic I feel most positive in my 
identification of Quiscalus purpureus.” 
2 Among the birds recognized on this occasion were 5 Carolina RAtrts, 
of which 3 are computed to have been between the limits of 1900 and 10,200 
feet, one between 2000 and 11,000, and one between 2600 and 13,500. 
