THE BIRDS OF HELIGOLAND 549 



soaring immediately around me; so that there is absolutely no 

 possibility of my having been in any way mistaken in my state- 

 ments on this question. Up to the present time, indeed, the nature 

 of this phenomenon lacks every kind of adequate explanation ; but 

 the same may be said in regard to another process of a similar or 

 closely related nature, though expressed in an exactly opposite 

 manner : I mean the slow immersion not by diving of the body 

 of swimming birds in a specifically heavier medium like water ; no 

 one can refute the actual performance of such an act, but we are as 

 little able to explain it as we can the opposite action of the soaring 

 upward of the avian body in the specifically lighter atmosphere. 



It has been conjectured in several quarters that this upward 

 soaring flight of birds is accomplished by vibratory movements of 

 the separate feathers ; I am, however, able to state most definitely, 

 from observations made in the closest proximity to the birds them- 

 selves, that no such vibrations of the feathers really take place. 

 Both myself as well as the youngest of the Aeuckens brothers 

 now, I am sorry to say, no longer living have spent many 

 summer hours lying in the sunshine close to the edge of the cliff, 

 watching the hundreds of old Herring Gulls which were flying, 

 unconscious of our presence, along the face of the rock, and soar- 

 ing upwards over the cliff edge, a few paces from us so near, in 

 fact, that we could plainly distinguish the dark pupils of their 

 clear lustrous eyes ; but we were never able to discern the 

 least trace of this supposed vibratory movement of the feathers, 

 although the birds were so near to us that anything of this descrip- 

 tion could not have possibly escaped our observation. All that 

 seemed to happen on such occasions, was, that the birds, suddenly 

 seeing two persons so unexpectedly near them, drew up their 

 plumage somewhat tighter, but, otherwise undisturbed, soared up- 

 wards, without any wing-movements, calmly but with a fair speed 

 into the still clear atmosphere. 



In order to obtain a safe and reliable result from such observa- 

 tions, it is necessary to keep the eye on one particular bird out of 

 the many hundreds swarming about in search of food ; we shall 

 see it roving over the surface of the water where any fish offal 

 happens to be drifting, on calmly outspread wings, and, sweeping 

 round in a fairly large curve, once more re-traverse the same 

 space ; if in the course of these movements the bird happens to spy 

 a morsel at some distance, it at once slackens its speed, its horizontal 

 progress having, by the time it arrives near the object in pursuit, 

 become so slow that it would unavoidably drop if it were not able 

 to sustain itself by other means than its calmly expanded wings. 

 In this manner it will glide along for about ten paces past its spoil, 



