SO 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. 
en Oe ee ee eee 
