REACTIVE LOCOMOTION. 
4i 
thefe little creatures when flying feem like a play of 
golden balls or little gilded peas floating in the air; their 
wings vibrate with fuch fwiftnefs as to be perceptible only 
as a blurr about them, 300 beats in a fecond, 18,000 
beats a minute! The fan-blower is confldered to revolve 
rapidly at 3,000 a minute, a much eafler mode, too, of 
fanning the air. If we wait a moment we fhall fee one 
of them ftanding ftill. Ah! here he is, {landing as flill 
as pofllble. You can’t fee a movement, and yet there 
muft be fome fort of imperceptible vibrations reaching 
your eye from it, for it makes you feel as you look 
fteadily at it as though in a dream. How in the world 
does the creature ftand fo ftill ? A dead fly glued to the 
wall couldn’t be more fixed. Perhaps he has found an 
air-ftratum of exactly the fpecific gravity of his own little 
body. No, for now he fuddenly darts to a place higher 
up, and fixes himfelf there again; and again to another 
fpot, fixing himfelf juft where he likes. Does Mr. 
Pettigrew’s “ figure of 8 ” theory explain this ? or the 
theories of “ pawing the air,” or “ comprefling the air 
under the wings ? ” or “ attacking the air at an infinite 
variety of angles ? ” Or is it to be explained by “ the 
great range of motion of the wings, enabling them to 
convert large tracts of air into fupporting areas ? ” Or 
has Mr. Pettigrew explained it where he fpeaks of the 
multiplicity of the movements of natural wings, thus 
enabling the pinions “ to create and rife upon currents of 
