548 THE BIRDS OF HELIGOLAND 



summei" months by far the larger majority of these are old indi- 

 viduals in snow-white plumage. At such times the scene presented 

 to the eye of an onlooker is truly wonderful. Over a surface of sea 

 a thousand paces or so in extent, and close to shore, vast numbers 

 of the birds spread themselves in a motley crowd, at all heights 

 above the sea up to two or three hundred feet ; they soar about 

 confusedly among each other, crossing each other's paths, ascending 

 and descending, amid frequent utterance of their loud clear-sound- 

 ing 'kli-ou — kli-ou — kli-ou' (kliau — kliau — kliau). Still more beauti- 

 ful is the scene when, momentarily disturbed by a boat, the 

 whole flock rises in circling flight above the cliff, and there, in 

 the calm clear atmosphere, soars about on motionless expanded 

 wings, neither sinking nor ascending, but revolving in beautiful 

 curves and circles, until, the boat liaving disappeared, the birds 

 once more return to their previous occujiations. 



In the first part of this work, when dealing with the altitude of 

 the migration flight, I have expressed the conviction that these 

 gulls, and in fact the majority of birds, are endowed with qualities 

 and capacities by means of which they are enabled, according to 

 their needs, to neutralise and overcome the general laws of gravity, 

 without thereby making use of the mechanical powers of their 

 wings, or being supported by atmosphei'ic currents. In this con- 

 viction I remain unshaken ; and progressive observations, combined 

 with the most severe criticism of my own views, on my own part, 

 have only served to further confirm me in my previous con- 

 clusions. Not only ai'c these gulls able to soar in a calm atmo- 

 sphere in a direction straight forwards, or sideways, on calmly 

 outspread wings, but, as has been more fully discussed in the case 

 of Buzzards, they can also, in a manner similar to theirs, soar 

 upwards to any desirable altitude. The gulls are able to perform 

 their soaring movements on the same plane in all phases of the 

 weather, during the most violent storm as well as in a perfect 

 calm, progressing forwards or sideways at the most variable rates 

 of velocity ; now darting along with the swiftness of an arrow, no^v 

 merely gliding, as it were, at the slowest pace imaginable. In the 

 latter case, indeed, we are frequently, even against our will, forced 

 to the conclusion that these birds must have at their command 

 some unknown means or mechanism which prevents their sinking ; 

 for neither is the surface-area of their wings large enough, nor are 

 these organs sufficiently concave in form, to allow of their support- 

 ing the bird after the manner of a parachute. I have been able to 

 make these observations for a long series of years, in all manner of 

 ways, and under the most favourable conditions, at the end of the 

 landing-stage on this island, where hundreds of the birds have been 



