on the Eddy stone. 249 
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-statiqn is simply a decoy. It is one that I found to 
"work" only under peculiar conditions, which 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 Eddy stone 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 
of 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 40 to 48 miles an liour. 
