xxxvi INTRODUCTION 



natural than that he should fancy that these late stragglers 

 are birds which have retired to their place of hibernation 

 somewhere at hand, and which are only enticed out of it once 

 more by genial sunshine in late October or early November ? 

 A glance at the letters just mentioned will show that when- 

 ever White noticed these late parties, his preconception woke 

 to new life, and interrupted his usually clear mental vision. 

 He took them for the birds of his own village which had gone 

 into hiding and then reappeared. This happened to him on 

 November 3, 1772 (Letter XXVIII. to Pennant), on_ No- 

 vember 4, 1771 (Letter XII. to Barrington), and again in 

 October and November, 1780 (Letter LV. to Barrington). 

 On this last occasion his preconception became so strong that 

 he affirms his belief that the whole body of martins of his 

 district might be found in " secret dormitories " in some 

 shrubby ground not more than three hundred yards fi'om the 

 village, where he had observed that they were in the habit of 

 roosting in October. Thus a preconception, based on the false 

 tradition handed down to him by Olaus and his followers, led 

 to a misinterpretation of the facts before him ; and as those 

 facts were limited for the most part to the range of his 

 observation in his own parish (see above, p. xxiv), it is 

 hardly to be wondered at that the true explanation of them 

 was beyond his reach. 



