VI INTRODUCTION. 



pared to a half circle or bent bow, the Lin- 

 colnshire and Yorkshire wolds forming the bow, 

 the coast-line the string ; whilst the great river 

 itself is like an arrow placed in the string and 

 across the bow, dividing the district into two 

 nearly equal divisions*. 



The migratory birds visiting this district in the 

 autumn and winter, almost without an exception, 

 come from the direction of the sea, arriving on 

 the coast in lines of flight varying from full N. to 

 E. The only exception to this rule is that of 

 the Grey or Winter Wagtail (Motacilla boarula), 

 which reaches us from the W. or N.W. In the 

 spring also, I am strongly inclined to think, the 

 greater portion of our little summer visitors, in- 

 cluding the delicate Warblers and Willow-wrens, 

 arrive from the sea, coming from S.E. to E., ap- 

 pearing first in the warmer and low- lying country 

 between the coast and the foot of the wold range, 

 and gradually extending inland across the high 

 wolds, a cold backward district, to the interior 

 of the county. A series of carefully kept registers 

 or calendars of the times of arrival of our spring 

 migratories, as lately recommended and set forth 



* See ' Geological Map of England and Wales/ Prof. 

 Kamsay. 



