142 Miscellaneous. 
duces the following generalizations in regard to the interchange of 
birds between America and Europe. 
European birds, especially the land species, reach Greenland and 
return to the continent by way of Iceland, the Faroe Islands forming 
a stepping-stone from Great Britain and Scandinavia. In very rare 
instances species seem to proceed direct to Greenland, without stop- 
ping in Iceland, although this may be due to the fact that while 
visiting Iceland they have not yet been noted there by any naturalist. 
The European birds found on the continent of North America 
reach it by autumnal movement from Greenland in company with 
strictly North American species. 
Birds of North America rarely, if ever, reach England from 
Greenland by direct spontaneous migration by way of Iceland, as 
shown by the fact that only three of the American birds occurring 
in Greenland are found in Iceland, and that few of the American 
species observed in Europe are found in Greenland at all. 
Most specimens of American birds recorded as found in Europe 
were taken in England (about fifty out of sixty-nine), some of them 
in Heligoland ; very few on the continent (land birds in only five 
instances). 
In nearly all cases these specimens belonged to species abundant 
during summer in New England and the eastern provinces of British 
America. 
In a great majority of cases the occurrence of American birds in 
England, Heligoland, and the Bermudas has been in the autumnal 
months, 
The clue to these peculiarities attending the interchange of species 
of the two continents will be found in the study of the laws of the 
winds of the northern hemisphere, as developed by Prof. Henry and 
Prof. Coffin. These gentlemen have shown (see Prof. Henry’s 
articles on Meteorology, ‘Report of Commissioner of Patents for 
1856,’ p. 489) that the ‘‘resultant motion of the surface atmosphere, 
between latitudes 32° and 58° in North America, is from the west, 
the belt being twenty degrees wide, and its greatest intensity 
in the latitude of 45°. This, however, must oscillate north and 
south, at different seasons of the year, with the varying declination 
of the sun. South of this belt, in Georgia, Louisiana, &c., the 
country is influenced, at certain seasons of the year, by the north- 
east trade-winds, and north of the same belt by the polar winds, 
which, on account of the rotation of the earth, tend to take a direc- 
tion towards the west. It must be recollected that the westerly 
direction of the belt here spoken of is principally the resultant of 
the south-westerly and north-westerly winds alternately predomi- 
nating during the year.” 
From these considerations and facts, therefore, we are entitled to 
conclude that the transfer of American birds to Europe is principally, 
if not entirely, by the agency of the winds, in seizing them during 
the period of their migration (the antumnal especially), when they 
follow the coast or cross its curves, often at a considerable distance 
from land, or a great height above it. Carried off, away out to sea, 
