502 
SWALLOW. 
raises a buttress under each shell, before he ventures 
to form his nest on it.” 
In the autumn, when the time approaches for the 
swallows to leave this country, they assemble in vast 
numbers, and generally occupy the tops of houses, 
the steeples of churches, or the sides of cliffs, where 
we have seen them, at Dover, collected in large 
flocks, and making a continual noise till they have 
suddenly taken their departure. The subject of 
the migration of these birds has occasioned much 
controversy among naturalists, who have been com- 
pletely divided in their opinions ; one party con- 
tending for their submersion in rivers and lakes 
during the winter ; the other insisting, with more 
propriety, on their migration to foreign countries. 
Both sides of the question have been too much 
canvassed to make it necessary for us to enter par- 
ticularly upon the subject: we shall therefore only 
observe with Mr. Pennant, that Olaus Magnus, arch- 
bishop of Upsal, very gravely informs us, that these 
birds are often found in clustered masses at the bot- 
tom of the northern lakes, mouth to mouth, wing 
to wing, foot to foot ; and that they creep down 
the reeds in autumn to their subaqueous retreats. 
That when old fishermen discover such a mass, 
they throw it into the water again ; but when 
young inexperienced ones take it, they will, by 
thawing the birds at the fire, bring them indeed 
to the use of their wings, which will continue but 
for a short time, being owing to a premature and 
forced revival. But the good archbishop does not 
