INTRODUCTION 19 



we know must have taken place, as the records 

 of palaeontology unquestionably demonstrate, and 

 there can be little or no doubt is in actual progress 

 around us now; but the process is so gradual, and 

 the difficulties of direct observation and calculation 

 so immense, that we entirely fail to perceive it. 

 Some slight indication of the exterminating force 

 of unfavourable natural conditions may be derived 

 from the effects, say, of a severe winter, or an 

 abnormal season of drought or wet, or unusual 

 lowness of temperature, upon birds, for instance ; 

 but these adverse circumstances are never 

 sufficiently prolonged for us to remark the 

 absolute decimation of a species, and apply but 

 to a circumscribed area. On the other hand, the 

 extermination due to man's interference with the 

 balance of nature is immeasurably more rapid, and 

 its results in the majority of cases are only too 

 sadly apparent. Many, indeed, are the instances 

 which might be quoted in support of these state- 

 ments. Uncivilised man, so long as he uses 

 primitive weapons, apparently makes little or no 

 evil impression upon continental fauna), the slight 

 tax upon them being amply met by the normal in- 

 crease of the species concerned, but in islands the case 

 has been different, as will be seen in future pages. 



