82 BRITISH BIRDS. [vol. vi. 



south-west Europe and a cyclonic centre to the north of us, 

 causes unsettled conditions in the North Sea and a south-west 

 type of wind, and so unfavourable for jiassage of migrants to 

 or from the north-east or north, but favoural)le for ])assage 

 from south Europe to us, or vice versa. The north-easterly and 

 north-westerly types of weathei- are similaily explained and 

 their influences on migration, while four maps of these main 

 types render the letterpress much clearer. To criticize these 

 conclusions would be out of place here, as a large amount of 

 fresh statistics would have to be gone over, and it must be 

 left to future workers to corroborate or modify his views ; 

 but it may be here remarked that the types of weather 

 considered are what may be called simple types, and that the 

 question of the presence of secondarj^ disturbances in western 

 Europe might profoimdly alter the expectations which Mr. 

 Clarke has enunciated. 



Mr. Clarke has come to the conclusion, with which we 

 concur, that the direction of the wind in itself has no influence 

 on migration ; fog, he finds, is an unfortunate and unforeseen 

 event for migrants, and it often prevails in areas otherA\'ise 

 favourable for movements ; high wind from any quarter acts 

 as a deterrent ; a fall or rise in temperature at the oiigin of 

 the migration, acts as a direct incentive to start in autumn 

 and spring respectively. 



As ty^sical examples of the different classes of migrants, 

 Mr. Clarke has taken the same species as those embodied in 

 the third to sixth interim reports of the British Association 

 Committee, viz. Swallow, Fieldfare, White Wagtail, Song- 

 Thrush, Skylark, Lapwing, Rook, and for the most part these- 

 accounts are reprints of those papers ; little of importance has 

 been added, and so requires little notice here. In a few cases 

 further proofs have come to hand of migrations which were 

 then surmised, such for instance as the passage of the White 

 Wagtail, this si^ecies passing north numerously along our 

 west coast-line, and in smaller numbers along the east, while 

 it is shown to be a common migrant in Orkney and Shetland. 

 We note that the Song-Thrush has been established as an 

 autumn immigrant on the east coast from Central Europe, 

 and we think the Fieldfare might be put in the same 

 category. Mr. Clarke has succeeded in unravelling the tangled 

 skein of these migrant types, and states his conclusions with 

 great clearness, Avhile added to each type is a list of those 

 species which perform similar migrations ; it must be left 

 for future workers to corroborate and, we think, in places- 

 amplify or modify his views. 



