THE ZooLtocistT—OcToBER, 1875. 4641 
true cause of the movements of birds; and, so far as I know, no one 
in this country has ever attempted to trace the routes by which 
birds migrate—a subject which has of late been very fully and ably 
treated by a Finnish naturalist, Herr Palmén *—though I must add 
that I don’t think he has succeeded in proving all he advances. 
Indeed, how should he? In his opinion, the British Islands form a 
spot, in or around which converge no less than four very important 
lines of traffic, yet his materials gathered from British sources are 
scanty in the extreme, and, but for the light reflected on them by 
continental naturalists, would be utterly useless. Yet, I take it, that 
the out-of-door ornithologists of England alone in numbers much 
exceed those of Norway, Sweden, Denmark, Holland and Belgium 
put together; but since the observers in those countries try to in- 
form themselves as to the points on which information is desirable, 
the results of these observations immeasurably exceed those of our 
countrymen in value. It is true that a very considerable step in 
advance was taken by an excellent out-of-door observer, Mr. Knox,} 
but that was a good deal more than twenty years ago, and I may say 
that almost nothing has since been done in this direction by British 
ornithologists. Many of them, indeed, do not keep up to the ground 
that Mr. Knox won for them, but (saving that they regard migration 
as an admitted fact, and I believe that they all do that) they have 
made no progress since Gilbert White’s time. Well, then, the sum 
of it all is, that we have an enormous quantity of scattered statistics, 
which might lead to something if any one would be at the trouble of 
working them up. We suspect that there is much partial migration, 
but have little definite acquaintance with it. We know from Mr. 
Knox that there is an essential difference between the manner in 
which birds arrive on our shores in spring, and quit them towards 
autumn; but as to the routes which birds take while passing through 
the country, we are of ourselves entirely ignorant; we can only guess 
at the cause of migration, and not even guess at the faculty by means 
of which it is, as a rule, so unerringly performed. This I have left 
to the last, because it is the most important and mysterions feature 
of the subject. Dr. von Middendorff has thrown out a hint that 
birds on their voyages know where the magnetic pole is situated, 
and steer their course accordingly. Improbable—impossible we 
* «Om Foglarnes flyttningsvagar.’ Helsingfors, 1874. 
+ ‘Ornithological Rambles in Sussex.’ Letter vii. London, 1849, 
