on the Eddy stone. 24-9 



during my visit was dependent to an extraordinary degree 

 upon the weather. This was especially the case as regards 

 night movements ; for it must be borne in mind that con- 

 ditions which are eminently favourable for migration may be, 

 and indeed in most cases are, quite unfavourable for its 

 observation. Successful night observation I found to be 

 entirely dependent upon a combination of meteorological 

 conditions which, while being favourable for emigration, 

 also rendered the lantern attractive to the migrants— a com- 

 bination which, though not very uncommon, is yet one of 

 which the comparative infrequence results in the great 

 majority of movements being unobserved. The lantern of a 

 light-station is simply a decoy. It is one that I found to 

 "work'^ only under peculiar conditions, whi(;h were dependent 

 upon the amount of moisture (rain, haze, cloud) present in 

 the atmosphere. When moisture is disseminated through 

 the air as a liquid in a state of minute subdivision, the 

 mixture becomes more or less opaque, while the powerful 

 beams streaming out from the lantern upon it become 

 luminous and brilliant to a very remarkable degree, and 

 exert extraordinary attractive powers over the migrants that 

 pass within their sphere of influence. On such occasions 

 the twelve slowly revolving rays from the Eddystone lantern 

 presented a very singular and mystifying appearance, and 

 small wonder was it that the emigrants could not resist their 

 seductions. 



My visit included a period when the nights were brilliantly 

 moonlit and cloudless, during which, no doubt, great passage- 

 movements were performed, but they were beyond the range 

 o£ observation. Gales were not infrequent and arrested 

 emigration. 



The first emigratory movement performed during the 

 hours of darkness which I was to witness set in at 3 a.m. on 

 September 23rd. I say "set in," because just previously to 

 its advent the weather was of such a description as to render 

 migration impossible, owing to the prevalence of a south- 

 easterly gale with a velocity of from -10 to 48 miles an hour. 



