86 IN BIRD LAND. 



of warblers. These figures are given to show the 

 heterogeneous composition of the migrant army. 



Mr. Brewster also found that no birds came about 

 the lantern except on densely cloudy or foggy 

 nights, and that they came in the greatest numbers 

 when the first hour or two of the evening had been 

 clear and was succeeded by fog or storm. These data 

 would seem to prove that the birds began their noc- 

 turnal journey with the expectation of having pleas- 

 ant weather, and when the fog or storm rose later in 

 the evening, they flew lower and got bewildered by 

 the glare of the lighthouse. 



Many theories of bird migration have been pro- 

 posed and argued at length, but, on the whole, I 

 incline to Mr. Brewster's theory that the old birds, 

 having learned the advantage of these semi-annual 

 expeditions, and having also determined the route by 

 means of certain landmarks, act as aerial pilots to 

 the army of young birds to whom the way is still 

 unknown. Mountain ranges, river valleys, coast 

 lines, and sheets of landlocked water doubtless serve 

 the purpose of guide-posts to these airy travellers. 

 Much as has been written on the subject, however, 

 there still remains a large field for original research. 



