372 



Microscopical Essays. 



then feparated, by blowing between them with a final I tube.. 

 The vellels, or ribs, lie between thefe fkins. 



As the wings of the moth and butterfly are light, they can flip- 

 port thernfelves for a long time in the air ; their manner of flying 

 is ungraceful, mounting and defcending alternately, fo that they 

 generally move in a zigzag line, to the right and to the left, up 

 and down ; by this means they often efcape the birds who chace 

 them, as this undulating motion difappoints them in their aim-: 

 hence they often may be feen to purfue a butterfly in vain for a* 

 eonfiderable time. 



Dr. Hooke * endeavoured to inveftigate the nature of the men- 

 tions of the wings of infecls ; and although he was not able, from 

 the experiments he made, to give a fatisfaclory account of them, 

 yet as they may be ufefufto Tome future inquirer, and* lead him: 

 more readily into the path of truth, I hope an extract therefrom 

 will not prove unacceptable to the reader. To invert igate the 

 mode or manner of moving their wings, he confidered with at- 

 tention thofe fpinning infecls that fufpend, or as it were poife 

 thernfelves, in one place in. the air, without rifing or. falling, or 

 even moving backwards or forwards ; by looking down on thefe 

 he could, by a kind of faint fhadowj perceive the utmoft extremes 

 of the vibratory motion of their wings ; the fhadow, while they 

 were thus fufpended, was not very long, but was lengthened when 

 they endeavoured to fly forwards. He next tried, by fixing the 

 legs of a fly upon the top of the ff alk of a feather, 'With glue, 

 wax, Sec. and then making it endeavour to fly away ; he was- 



thereby. 



* Hooke's Micrographia, p. 172, 



