io~ THE ZOOLOGIST. 
To account for the appearance of North American birds in this 
country is not so easy. I was at one time inclined to believe that 
the majority of them must find their way here from Greenland wid 
Iceland,* but the investigations of Professor Spencer Baird have 
led me to alter this opinion, and to concur for the present in his 
own view that their appearance here is due principally, if not 
entirely, to the agency of the winds at the period of their migrations. 
Prof. Baird’s remarks on this subject are so extremely interesting 
and at the same time so instructive, that they may be here appro- 
priately quoted. After some pertinent observations on zoological 
geography and the general principles of distribution to which hejhas 
been led by an examination of the large collection of specimens in 
the Museum of the Smithsonian Institution, he proceeds to deal 
in detail with the migration of North American birds, and referring 
to the species which are reported to have occurred in England, 
he says :— 
“ 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 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 direction 
* In support of this view, it may be observed that out of the forty-two species of 
North American birds which are stated to have occurred in this country, sixteen, on 
the authority of Professor Reinhardt, haye been found in Greenland. 
