1920.] of the Miyralonj Fliykt of Birds. 921 



mioratiou to be normal. Gaetke is careful to explain that 

 bv normal migration be only means those large extensive 

 movements which carry birds in one uninterrnpted, and for 

 the most pai-t nocturnal flight, from their starting point to 

 their destination. He farther considers that the height of 

 normal migration is at lea.-.t 20,000 I'eet. it must be 

 remembered that Graetke's observations were confined to 

 Heligoland, and that ha occasionally allows his enthusiasm 

 to outrun his facts, but this does not in the least lessen the 

 charm of his delightful book. 



AVhitlock ('Migration of Birds,' 189 7, pp. 56-88) challenges 

 Gaetke's statements and notes the unsatisfactory evidence 

 on which his theories are based. But sound theories can be 

 arrived at by conviction if bused on a wide experience, 

 even thonoh such theories cannot be scientificallv proved. 

 Gaetke's theory is non-proven, but is based on experience 

 such as no other ornithologist can claim. Whitlock gives us 

 no evidence to enable us to arrive at the truth, though he 

 produces much destructive criticism. 



Now let us turn to some very definite evidence. On 

 October 19, 1880, at Princeton in New Jersey, W. E. D. 

 Scott (Bull. Niittall Ornith. Club, vi. pp. 97-100) saw large 

 numbers of liirds passing across the face of the moon, 

 when ol)serving through an astronomical telescope. It was 

 estimated that these birds were at an altitude of between 

 5000 and 10,000 feet. On April l(i, 1881, lurther obser- 

 vations were made at the same })lace, but only some low- 

 flying Swallows were seen on the northward passage. 



Chapman (Auk, 1888, pp. 37-39), also in New Jersey, 

 watching for nearly three hours on the evening of Sept. 3, 

 1887, observed 2^2 birds cross the face of the moon. Of 

 these, 233 were estimated to be at a height of from 1500 to 

 15,100 feet. It was observed that the lower-Hying birds 

 seemed to be Hying u[)wards and were seeking " tb.e proper 

 elevation at which to continue their flight."' Among the 

 birds recognised were five Carolina Hails, of which three 



