264 Mr. W. Eagle Clarke—^ Month 
quite close to the tower; and thus from my elevated and 
fixed point of observation on the gallery I was enabled to 
gauge the height from which these birds dived with a degree of 
accuracy not usually attainable. I witnessed many thousands 
of dives, but in no case did the drops exceed a height of 
from 130 to 140 feet. About one-fourth of the Gannets 
seen were in immature dress, all stages being represented 
except that of the year — a fact which is worthy of note. 
The Eddystone was an excellent station for studying the 
weather conditions and their bearing upon bird-migration. 
Birds when performing long flights not unfrequently pass 
from the zone of favourable weather, which is conducive to 
their departure,, to an area in which the conditions are -more 
or less unfavourable ; and. they are consequently recorded as 
arriving on our coasts in the autumn under adverse circum- 
stances. Such inauspicious instances of immigration as 
these are apt to mislead those interested in the subject, for 
it is not always borne in mind that it is the state of the 
weather at the point of departure which affords the only 
indication of the actual conditions controlling the move- 
ments. 
At the Eddystone, owing to its contiguity to the mainland, 
one witnessed simultaneously the movements and the meteoro- 
logical conditions under which the birds elected to set out 
on their passage southwards ; or if no movements took 
place, either by day or by night, one was able, it being the 
height of the emigratory season, to determine, in some 
measure at least, what the weather-barriers were which 
arrested such migrations. Thus this station was singularly 
favourably situated — probably none more so — for observing 
the meteorological conditions which made for or against 
emigration. 
No movements were witnessed, either by day or night, on 
the part of land-birds under weather conditions which could 
be described as in the least degree unfavourable for crossing 
the Channel. 
The wind is certainly the main factor in migration- 
