Scientific American Supplement, No. 717, September 28, 1889Various
Science
Scientific American Supplement, No. 717, September 28, 1889
Various
Science -- Periodicals
I shall now for a moment draw your attention to that peculiar property
of melted quartz that makes threads such as I have been describing a
possibility. A liquid cylinder, as Plateau has so beautifully shown,
is an unstable form. It can no more exist than can a pencil stand on
its point. It immediately breaks up into a series of spheres. This is
well illustrated in that very ancient experiment of shooting threads
of resin electrically. When the resin is hot, the liquid cylinders,
which are projected in all directions, break up into spheres, as you
see now upon the screen. As the resin cools, they begin to develop
tails; and when it is cool enough, i.e., sufficiently viscous, the
tails thicken and the beads become less, and at last uniform threads
are the result. The series of photographs show this well.
[Illustration: FIG. 8.]
[Illustration: FIG. 9.]
There is a far more perfect illustration which we have only to go into
the garden to find. There we may see in abundance what is now upon the
screen--the webs of those beautiful geometrical spiders. The radial
threads are smooth like the one you saw a few minutes ago, but the
threads that go round and round are beaded. The spider draws these
webs slowly, and at the same time pours upon them a liquid, and still
further to obtain the effect of launching a liquid cylinder in space
he, or rather she, pulls it out like the string of a bow, and lets it
go with a jerk. The liquid cylinder cannot exist, and the result is
what you now see upon the screen (Fig. 8). A more perfect illustration
of the regular breaking up of a liquid cylinder it would be impossible
to find. The beads are, as Plateau showed they ought to be,
alternately large and small, and their regularity is marvelous.
Sometimes two still smaller beads are developed, as may be seen in the
second photograph, thus completely agreeing with the results of
Plateau's investigations.
I have heard it maintained that the spider goes round her web and
places these beads there afterward. But since a web with about 360,000
beads is completed in an hour--that is at the rate of about 100 a
second--this does not seem likely. That what I have said is true, is
made more probable by the photograph of a beaded web that I have made
myself by simply stroking a quartz fiber with a straw wetted with
castor oil (Fig. 9); it is rather larger than a spider line; but I
have made beaded threads, using a fine fiber, quite indistinguishable
from a real spider web, and they have the further similarity that they
are just as good for catching flies.
Public-domain text, read in full here on John Shaqi.
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