This may perhaps hint some usefull way of making other bodies,
besides Silk, be susceptible of bright tinctures, but of this onely by the
by.
The changeable colour'd Feathers also of Ducks, and several other Birds, I
have found by examination with my _Microscope_, to proceed from much the
same causes and textures.
* * * * *
Observ. XXXVII. _Of the Feet of _Flies_, and several other _Insects_._
The foot of a Fly (delineated in the first _Figure_ of the 23. _Scheme_,
which represents three joints, the two Tallons, and the two Pattens in a
flat posture; and in the second _Figure_ of the same _Scheme_, which
represents onely one joint, the Tallons and Pattens in another posture) is
of a most admirable and curious contrivance, for by this the Flies are
inabled to walk against the sides of Glass, perpendicularly upwards, and to
contain themselves in that posture as long as they please; nay, to walk and
suspend themselves against the under surface of many bodies, as the ceiling
of a room, or the like, and this with as great a seeming facility and
firmness, as if they were a kind of _Antipodes_, and had a _tendency_
upwards, as we are sure they have the contrary, which they also evidently
discover, in that they cannot make themselves so light, as to stick or
suspend themselves on the under surface of a Glass well polish'd and
cleans'd; their suspension therefore is wholly to be ascrib'd to some
Mechanical contrivance in their feet; which, what it is, we shall in brief
explain, by shewing, that its Mechanism consists principally in two parts,
that is, first its two Claws, or Tallons, and secondly, two Palms, Pattens,
or Soles.
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