180 
THE NATURAL HISTORY 
[LETT. 
while they have young, discover a lump of insects in their 
mouths, which they pouch and hold under their tongue. In 
general they feed in a much higher district than the other 
species ; a proof that gnats and other insects do also abound to 
a considerable height in the air : they also range to vast dis- 
tances ; since locomotion is no labour to them, who are endowed 
with such wonderful powers of wing. Their powers seem to 
be in proportion to their levers ; and their wings are longer in 
])roportion than those of almost any other bird. When they 
mute, or ease themselves in flight, they raise their wings, and 
niake them meet over their backs. 
At some certain times in the summer I had remarked that 
bvvifts were hawking very low for hours together over pools 
and streams ; and could not help inquiring into the object of 
their pursuit tliat induced them to descend so much below their 
usual range. After some trouble, I found that they were taking 
pJiryfjaneir, cpliemcrcv and lihcUulw (caddis-flies, may-flies, and 
dragon-flies) that were just emerged out of their aurelia state. I 
then no longer wondered that they should be so willing to stoop 
for a prey that afforded them such plentiful and succulent 
nourishment. 
They bring out their young about the middle or latter end of 
J idy : but as these never become perchers, nor, that ever I could 
discern, are fed on the wing by their dams, the coming forth 
ol the young is not so notorious as in the other species. 
On the .*^Oth of last June I untiled the eaves of a house 
where many pairs build, and found in each nest only two squab, 
naked ^m//^,- on the 8th of July I repeated the same inquiry, 
and found they had made very little progress towards a fledged 
state, but were still naked and helpless. From whence we may 
conclude that birds whose way of life keeps them perpetually 
on the wing would not be able to quit their nest till the end 
of the month. Swallows and martins, that have numerous 
families, are continually feeding them every two or three 
minutes ; while swifts, that have but two young to maintain, 
are much at their leisui'e, and do not attend on their nests for 
liours togetlier, 
Sometimes they pursue and strike at havrks that come in 
