548 MIGRATION 
term of years; but, though we may safely predict that if they 
appear at all they will do so at a certain season, it is impossible to 
make a forecast as to the year in which an example will arrive, or 
whether in one year some half-dozen may or may not occur. The 
matter thus becomes a matter of averages, and like all such is open 
to the influence of many perturbants, not that such may not well 
be subject to some law of which we are ignorant. JBeside this, the 
average is hard to strike, depending as it must on the existence of 
favourably-placed and watchful observers. Moreover if we consider 
that the number of competent observers, though possibly as great 
in England as anywhere, has been at all times small, it is not sur- 
prising that little has been effected towards the compassing of any 
definite notion on this head. At present we can but attribute the 
appearance of some foreign stragglers on our shores, and no doubt 
the same may be said of other countries, to the influence of storms 
which have driven the wanderers from their course, and though 
other more remote causes may possibly be assigned, there seems to 
be none but this on which we can safely rely. Consequently until 
the periodicity of storms is brought within our knowledge we must 
be content to abide in our ignorance of the laws which govern the 
appearance of the strangers. Still confining our remarks to the 
British Islands, the effect of these laws is in some degree constant. 
Singular as it may appear, the greatest number of North-American 
Birds—and especially of the Limicolx, which are recorded as having 
occurred in this country have been met with in the eastern part of 
England or Scotland. There are two ways of accounting for this 
fact, the first of which is the comparative scarcity of observers in 
Treland and on its western coast especially, and this is by no means 
to be overlooked; but it may be remarked that in no part of the 
United Kingdom is the profession of the gunner more enthusiastically 
followed than in the sister-island, and the men who pursue that 
vocation are all alive to the mercantile value of any strange bird 
which may fall in their way. Of course they have no means of 
knowing what it is, yet as their spoils are sent for sale to the 
nearest market, it cannot but happen that if many examples of 
North-American species were procured by them, some proportion 
of these would find their way to the notice of the amateur naturalist 
and by him be recorded in the public prints. Now, as compared 
with Great Britain, this so rarely occurs in Ireland that it is by no 
means unfair to draw the inference that Transatlantic Birds are 
there far less frequently met with. The second mode of account- 
1 It seems also not unlikely that the very scarcity of rare birds in Ireland is 
one reason why there are so few ornithologists in that country, for here it is not 
uncommon for a man to have his attention first called to zoology by meeting 
with some strange animal—be it beast, bird, beetle, or butterfly, and for such a 
man afterwards to become no mean field-naturalist. 
