Worcester daily spy. [volume] (Worcester [Mass.]) 1850-1888, 1860-12-27
From Gosses Evenings at the Microscope

FROM Gosses Evenings at the Microscope.
How FLY HOLDS on have here in.
closed a small window fly in the live box of a
microscope, that you may examine the struct.
ure OF his feet as it presses them against the
glass cover; and thus not only get glimpse
otan exquisitely formed structure, but acquire
some correct ideas on the question of how fly
is able to DEFY all the laws Of physics, and to
walk Jaunuly about on the under surface of
polished bodies, such as glass, without falling
or apparently the fear of falling. And a per.
sona examination is the more desirable from
the hasty and erroneous notions that have
been promulgated on the matter, and that are
constantly disseminated by herd of popular
cOmpllers, who profess to teach science by
gathering up and retaining the opinions OF
others, often without the slightest knowledge
whether what they are reporting is true or
false.
The customary explanation has been that
given by Derham in his "Physico theology, -
that divers flies and other insects, besides
their sharp, hooked nails, have also skinny
palms to their feet, to enable them to stick to
glass and other smooth bodies by means of the
pressure of the atmosphere, after the manner
as | have seen boys carry heavy stones with
only wet piece OF leather slapped on top of a
stone" Bingey, citing this opinion, adds that
they are able easily to overcome the pressure
and alert but toward the end of the year this
resistance becomes too mighty for their dimin.
ished strength and we see flies laboriug along,
and sugging their feet on windows as if they
stuck last to the glass and it is with the ut
most difficulty they can drag one foot after an
other and disengage their hollows cups from
the slippery surface"
But long ago another solution was proposed
for Hooke, one OF the earliest microscopic Oh.
servers, describes the two palms, pattens, or
soles Gas he calls the puiUHla) as "beSei under.
meath with small brstes or tenters, like the
wire teeth of card for working wool, which,
having contrary direction to the claws, and
both pulling different ways, if their be any ir-
regularity or yielding in the surface OF body
enable the fly to suspend itself very firmly"
He supposed that the most perfectly polished
glass presented such irregularities, and that it
was moreover always covered with a Smoky
tarnish, =" into which the hairs of the foot pene,
trated.
Thes"smoky tarnish" is altogether gratui-
tous and Mr.. Blackwell has exploded the
idea OF atmospheric pressure for he found
that flies could walk up the interior of an eX-
hausted air.pump. He had explained their
ability to climb up vertical polished bodies by
their mechanical action Of the minute hairs of
the interior surface of the palms but further
experiments having shown him that flies
could not walk up glass which is made moist
by breathing on it, or which is thinly coated
with oil or flour, he was led to the conclusion
that these hairs are, in fact, tubular, and ex'
crete viscid fluid, by means of which they
adhere to dry polished surfaces and on close
inspection with an adequate magnifying pow
er, he was always able to discover traces OF this
adhesive material on the track on glass both
of flies and various other insects furnished
with puluila, and OF those spiders which pos
sess a similar faculty.