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 

 he in proportion to their levers ; and their wings are longer in 

 proportion than those of almost any other bird. When they 

 mute, or ease themselves in flight, they raise their wings, and 

 make them meet over their backs. 



At some certain times in the summer I had remarked that 

 swifts were hawking very low for hours together over pools 

 and streams; and could not help inquiring into the object of 

 their pursuit that induced them to descend so much below their 

 usual range. After some trouble, I found that they were taking 

 phryganecc, ephemera and libellulce (caddis-flies, may-flies, and 

 dragon-flies) that were just emerged out of their aurelia state. I 

 then no longer wondered that they should he 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 

 July : but as these never become perchers, nor, that ever I could 

 discern, are fed on the wing by their dams, the coming forth 

 of the young is not so notorious as iu the other species. 



On the 30th of last June I untiled the eaves of a house 

 where many pairs build, and found in each nest only two squab, 

 naked pulli : 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 leisure, and do not attend on their nests for 

 hours together. 



Sometimes they pursue and strike at hawks that come in 



