176 NATURAL HISTORY OF SELBORNE. 
tall buildings, churches, and steeples, and breed only in such ; yet 
in this village some pairs frequent the lowest and meanest cottages, 
and educate their young under those thatched roofs. We remember 
but one instance where they breed out of buildings, and that is in the 
sides of a deep chalk-pit near the town of Odiham, in this county, 
where we have seen many pairs entering the crevices, and skimming 
and squeaking round the precipices. 
As I have regarded these amusive birds with no small attention, 
if I should advance something new and peculiar with respect to 
them, and different from all other birds, I might perhaps be credited, 
especially as my assertion is the result of many years exact ob- 
servation. The fact that I would advance is, that swifts tread, or 
copulate, on the wing ; and I would wish any nice observer, that is 
startled at this supposition, to use his own eyes, and I think he will 
soon be convinced. In another class of animals, viz. the insect, 
nothing is so common as to see the different species of many genera 
in conjunction as they fly. The swift is almost continually on the 
wing ; and as it never settles on the ground, on trees, or roofs, 
would seldom find opportunity for amorous rites, was it not enabled 
to indulge them in the air. If any person would watch these birds. 
of a fine morning in May, as they are sailing round at a great height 
from the ground, he would see, every now and then, one drop on the 
back of another, and both of them sink down together for many 
fathoms with a loud piercing shriek. This I take to be the juncture 
when the business of generation is carrying on. 
As the swift eats, drinks, collects materials for its nest, and, as it 
seems, propagates on the wing, it appears to live more in the air 
than any other bird, and to perform allfunctions there save those of 
sleeping and incubation. 
This hirundo differs widely from its congeners in laying invariably 
but two eggs ata time, which are milk-white, long, and peaked at 
the small end ; whereas the other species lay at each brood from 
four to six. It is a most alert bird, rising very early, and retiring to 
roost very late ; and is on the wing in the height of summer at least 
sixteen hours. In the longest days it does not withdraw to rest till 
a quarter before nine in the evening, being the latest of all day-birds. 
Just before they retire whole groups of them assemble high in the 
air, and squeak, and shoot about with wonderful rapidity. But this 
bird is never so much alive as in sultry thundry weather, when it 
expresses great alacrity, and calls forth all its powers, In hot 
mornings, several, getting together in little parties, dash round the 
