312 PROCERDINGS OP PROVINCIAL SOCIETIES. 



which becomes, however, gradually absorbed, to make room for the 

 admission of air. The air passes into the lungs by a communication 

 with the windpipe, and is conveyed into a number of membranous 

 cells, which lie in various bones. Could a man move at the pace 

 of the swiftest bird, as he is not furnished with internal reservoirs 

 similar to those possessed by birds, the actual resistance of the air 

 would soon suffocate him. The act of flying is performed by the 

 bird leaping from the ground or droj)ping from a height, and raising 

 its wangs at the same time ; and the velocity with which the bird 

 ascends is proportioned to the velocity with which the strokes of the 

 wings are repeated upon the air. When birds fly in a horizontal 

 direction their motion is not in a straight line, but inclining up- 

 wards, and the body then comes down to a lower level before ano- 

 ther stroke is made ; so that they move in a succession of curves. 

 With regard to migration, the lecturer observes, '^ About twenty- 

 five kinds of birds regularly visit this country in the spring, and 

 about seventeen in the autumn. The Wryneck and Lesser Willow 

 Wren, or ChiiFchaff', our earliest spring visitors, arrive here gene- 

 rally towards the end of March ; the Flycatcher, which is the latest, 

 about the middle of May. All our autumn visitors arrive much 

 nearer together. The periods of migration are greatly influenced 

 by the seasons. This spring, for instance, birds were generally very 

 late in arriving : and yet we sometimes find anomalies in this as in 

 other things ; for I saw a Swallow on the 5th of April, nearly a 

 fortnight earlier than they usually appear in this neighbourhood — a 

 clear proof, too, that one Swallow does not make a summer. On 

 the same day I saw a flight of Fieldfares, which had not yet left us — 

 an unusual assemblage of spring and autumn visitors." After notic- 

 ing the doubts of some naturalists as to the migration of our short- 

 winged spring visitors, he continues, " But, notwithstanding all 

 these difliculties, certain it is that many of the least of birds, and the 

 most timid and inefficient of flyers, do migrate, many of them to 

 Italy and the coast of the Mediterranean. They take advantage of 

 a favourable breeze, and are doubtless lost by hundreds in the sea, 

 should the wind become adverse. I will allow that a few instances 

 have occurred of migrating birds being found in this country during 

 winter in a torpid state, but these are only rare exceptions to the 

 general rule. By some instinctive power, birds are enabled to se- 

 lect the narrowest channels of the sea, and also to traverse regions 

 which, to our eyes, would present no mark or guide, and to arrive 

 at the self-same spot which, each successive year, is the scene of 

 their habitation. The eyes of birds are peculiarly quick and pierc- 

 ing, and it is supposed that they are guided by the appearance of 

 the atmosphere, the clouds, and direction of the wind ; these vary- 

 ing and uncertain causes, however, appear to me quite insufficient 

 for the purpose. It is evident that practice is a great assistant to 

 instinct ; in the case of Carrier Pigeons, for instance, they are first 

 taken a short distance from home — a quarter of a mile, perhaps — 

 which distance is gradually increased, till at last these extraordinary 



