798 Mr. brown’s Defer iption of 
thin intervening membrane fo rigid, that it is difficult to 
expand them without violence, at the fame time that the 
motion of the whole wing backward and forward is no- 
thing impaired ; this circumftance, which only happens 
after the fifh has been aconfiderable time out of the water, 
may have given rife to the common tradition amongft 
fea-faring people, that it can fly no longer than its 
wings are wet, and that in its flight it Ikims along the 
furface and dips, fkims and dips again, with no other 
purpofe than to moiften and keep them in a flying trim. 
That in the courfe of one flight, at leaft once, twice, 
or perhaps thrice, it flightly touches the water is certain ; 
but the whole is performed in fo fmall a fpace of time, 
and its continuance in the air is of fo fhort duration, that 
even in the dryeft, warmeft weather little is to be appre- 
hended from the too great rigidity of the wings. In my 
opinion, though this circumftance of moiftening them 
may be of fome ufe, and a fecondary advantage, yet they 
feem to touch the water for a more important purpofe, 
for the fame reafon that a diver or fwimmer, when be- 
low the furface of another element, is very frequently 
obliged to emerge into his own. It may alfo be of fome 
ufe in giving the animal new force and vigour for ano- 
ther departure. 
But as flying is only a fudden expedient, in order to 
efcape the jaws of their enemies, and by no means their 
natural 
