et Vv Recent Literature. 423 
special department of ornithological science, for the study of which Heli- 
goland is so pre-eminently adapted, will naturally have the greatest 
weight with all, and some in their admiration for the veteran observer 
have formed the opinion, that all, or nearly all of our previous concep- 
tions, as to the direction, altitude and velocity of the migratory flight, will 
have to be greatly modified or altogether abandoned in favour of those 
he sets before us.” 
After a few pages of introductory remarks, Mr. Whitlock takes that 
part of Herr Gatke’s ‘Heligoland’ treating of the ‘Migration of Birds’ 
(pp. 3-148, English ed.), to which he chiefly confines his remarks, syste- 
matically taking up the various points that are especially Gitkean. Space 
will not permit us to follow Mr. Whitlock’s critical analysis of Herr 
Gitke’s many extraordinary statements regarding plain matters of fact, to 
say nothing of his astonishing inferences and assumptions. As to the 
former, our author says, with an evident feeling of kindness: “It will be 
readily admitted that to arrive at an accurate result in calculating the 
numbers of rapidly moving objects is very difficult. It is equally difficult 
to arrive at a proper estimate of the value we are to place on the author’s 
computations. In particular instances the reader can hardly fail to be 
struck by evidence of the grossest, though no doubt unintentional, 
exaggeration. This must perhaps be attributed to the artistic element in 
Herr Gatke’s nature.” (p. 11.) 
Mr. Whitlock combats at length Gatke’s theory of a general east and 
west migration, and migration by a ‘broad front’ as against fly lines, 
bringing much evidence against it from even Gitke’s own statements. 
After an extended discussion of the subject he says (p. 39): “It is difficult 
to see on what grounds Herr Gitke has based his theory that the general 
course of migration tends from east to west.” 
The absurdity of many of Gatke’s theories and assumptions is mercilessly 
exposed by Mr. Whitlock’s simply bringing to bear upon them a little 
common sense and well-known physical laws, especially on the supposed 
‘altitude’ and ‘velocity’ of migration flight and the assumed influence 
thereon of certain meteorological conditions. 
In regard to Gitke’s objections to current views on the “cause of 
the migratory movement,” and on ‘what guides birds during their 
migrations,” Mr. Whitlock says of the former (p. 114): “It has been 
previously pointed out that so far from enunciating any theory of his 
own... Herr Gatke frankly avows himself disinclined to undertake the 
task. The chapter in his work he devotes to the question is, therefore, 
nothing but a statement of his objections to the theories of others. .. . 
It is, perhaps, not to be wondered that he should feel disinclined to put 
forth any theory of his own, committed as he already is to the statements 
on the direction, altitude and velocity of migration flight as detailed in 
previous pages. No theory that could be devised would be likely, in all 
its details, to fit in with such various speculations, and he may well look 
upon the task as hopeless.” Later on (p. 120) Herr Giitke’s theories of 
