188 The Migration of Birds 
probably a mile or more. A telescope with a three- 
inch objective will serve every purpose, and a still, 
clear night with a full moon is necessary for good 
results. Focus the instrument upon the moon, the 
birds, as they pass, appearing quite distinctly against 
the reflecting planet. With a larger telescope it is 
possible to detect the species that have well marked 
and not too rapid wing beats. With a six-inch glass, 
under favorable conditions, as many as two hundred 
and eighty birds have been seen within three hours. 
I have observed the night flight of birds several 
times from the tower of the East Orange High School. 
Even an arc light with a good reflector is sufficient 
to attract the birds under favorable conditions, 
but with a searchlight good results were obtained. 
These night watchings have always proved most in- 
teresting to me and to friends who have been with 
me at various times, but one of the most interesting 
evenings I ever spent in the tower was on September 
23, 1890. ‘The weather conditions were perfect. 
Shortly after eight o’clock the first bird was seen, 
although others had been heard almost constantly. 
In the next half-hour two more birds were seen, but 
their call notes greatly increased as they hurried past 
us. The night was only partially clear, and as it 
advanced a threatening thunderstorm came up at 
