1 88 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 sufiicient 

 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 



