emember
that we were able to make a large drop of one liquid in another, because
in this way the effect of the weight was neutralized, and as large drops
oscillate or change their shape much more slowly than small, it is more
easy to see what is happening. I have in this glass box water coloured
blue on which is floating paraffin, made heavier by mixing with it a
bad-smelling and dangerous liquid called bisulphide of carbon.

[Sidenote: _See Diagram at the end of the Book._

Fig. 35.]

The water is only a very little heavier than the mixture. If I now dip a
pipe into the water and let it fill, I can then raise it and allow drops
to slowly form. Drops as large as a shilling are now forming, and when
each one has reached its full size, a neck forms above it, which is
drawn out by the falling drop into a little cylinder. You will notice
that the liquid of the neck has gathered itself into a little drop which
falls away just after the large drop. The action is now going on so
slowly that you can follow it. Fig. 35 contains forty-three consecutive
views of the growth and fall of the drop taken photographically at
intervals of one-twentieth of a second. For the use to which this figure
is to be put, see page 149. If I again fill the pipe with water, and
this time draw it rapidly out of the liquid, I shall leave behind a
cylinder which will break up into balls, as you can easily see (Fig.
36). I should like now to show you, as I have this apparatus in its
place, that you can blow bubbles of water containing paraffin in the
paraffin mixture, and you will see some which have other bubbles and
drops of one or other liquid inside again. One of these compound bubble
drops is now resting stationary on a heavier layer of liquid, so that
you can see it all the better (Fig. 37). If I rapidly draw the pipe out
of the box I shall leave a long cylindrical bubble of water containing
paraffin, and this, as was the case with the water-cylinder, slowly
breaks up into spherical bubbles.

[Illustration: Fig. 36.]

[Illustration: Fig. 37.]

[Illustration: Fig. 38.]

Having now shown that a very large liquid cylinder breaks up regularly
into drops, I shall next go the other extreme, and take as an example an
excessively fine cylinder. You see a photograph of a spider on her
geometrical web (Fig. 38). If I had time I should like to tell you how
the spider goes to work to make this beautiful structure, and a great
deal about these wonderfu