l creatures, but I must do no more than show
you that there are two kinds of web--those that point outwards, which
are hard and smooth, and those that go round and round, which are very
elastic, and which are covered with beads of a sticky liquid. Now there
are in a good web over a quarter of a million of these beads which catch
the flies for the spider's dinner. A spider makes a whole web in an
hour, and generally has to make a new one every day. She would not be
able to go round and stick all these in place, even if she knew how,
because she would not have time. Instead of this she makes use of the
way that a liquid cylinder breaks up into beads as follows. She spins a
thread, and at the same time wets it with a sticky liquid, which of
course is at first a cylinder. This cannot remain a cylinder, but breaks
up into beads, as the photograph taken with a microscope from a real web
beautifully shows (Fig. 39). You see the alternate large and small
drops, and sometimes you even see extra small drops between these again.
In order that you may see exactly how large these beads really are, I
have placed alongside a scale of thousandths of an inch, which was
photographed at the same time. To prove to you that this is what
happens, I shall now show you a web that I have made myself by stroking
a quartz fibre with a straw dipped in castor-oil. The same alternate
large and small beads are again visible just as perfect as they were in
the spider's web. In fact it is impossible to distinguish between one of
my beaded webs and a spider's by looking at them. And there is this
additional similarity--my webs are just as good as a spider's for
catching flies. You might say that a large cylinder of water in oil, or
a microscopic cylinder on a thread, is not the same as an ordinary jet
of water, and that you would like to see if it behaves as I have
described. The next photograph (Fig. 40), taken by the light of an
instantaneous electric spark, and magnified three and a quarter times,
shows a fine column of water falling from a jet. You will now see that
it is at first a cylinder, that as it goes down necks and bulges begin
to form, and at last beads separate, and you can see the little drops as
well. The beads also vibrate, becoming alternately long and wide, and
there can be no doubt that the sparkling portion of a jet, though it
appears continuous, is really made up of beads which pass so rapidly
before the eye that it is impossible to