°jg I Recent Literature. 4^3 



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 Giitke'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 G^tkean. Space 

 will not permit us to follow Mr. Whitlock's critical analysis of Herr 

 Giitke'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 difticult. 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 Gatke's own statements. 

 After an extended discussion of the subject he says (p. 39) : "It is difficult 

 to see on ^hat grounds Herr GJitke 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 Gatke'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 Gatke's theories of 



