vi PREFACE 



distribution of Birds generally, I have been enabled to 

 propound what I believe to be a Law of Dispersal, 

 The present volume is the development and applica- 

 tion of that Law. I may here remark that this Law 

 has been gradually developed from a vast number 

 of accumulated facts, and is not a result of any pre- 

 conceived theory, 



I have selected British Birds for this application, 

 chiefly because our knowledge of their distribution, and 

 of the past physical changes in the areas they inhabit, 

 is not only extensive but fairly reliable. We are often 

 told that there is nothing new to be said about British 

 Birds. I offer the present volume as an answer to that 

 hackneyed remark, and desire specially to call attention 

 to our lack of information on many important subjects 

 connected with British ornithology, indicated here and 

 there in the following pages, as a possible field of very 

 fruitful research. 



I am aware that much in the present volume is 

 opposed to the general views held by naturalists, and 

 even to those expressed by myself in former works. 

 For such portion of my work, a patient perusal and an 

 impartial judgment are asked. I am quite prepared to 

 meet with some amount of hostility from specialists 

 whose views are not in harmony with this new Law of 

 Dispersal. I have no fear for the results so far as Birds 

 are concerned ; and I await with profound interest, and 

 yet with every confidence, the results of its application to 

 other branches of biology, to which only specialists are 

 competent to apply it. On its important bearing on the 

 Distribution of Floras I have already dwelt at some 

 length in my closing chapter. 



