). Now I shall let
a little gas into the outer one, until the surrounding gas is about as
heavy as the inner bubble. It now no longer rests against the top, but
floats about in the centre of the large bubble (Fig. 61), just as the
drop of oil did in the mixture of alcohol and water. You can see that
the inner bubble is really lighter than air, because if I break the
outer one, the inner one rises rapidly to the ceiling.

[Illustration: Fig. 60.]

Instead of blowing the first bubble on a heavy fixed ring, I shall now
blow one on a light ring, made of very thin wire. This bubble contains
only air. If I blow inside this a bubble with coal-gas, then the
gas-bubble will try and rise, and will press against the top of the
outer one with such force as to make it carry up the wire ring and a
yard of cotton, and some paper to which the cotton is tied (Fig. 62);
and all this time, though it is the inner one only which tends to rise,
the two bubbles are not really touching one another at all.

[Illustration: Fig. 61.]

[Illustration: Fig. 62.]

I have now blown an air-bubble on the fixed ring, and pushed up inside
it a wire with a ring on the end. I shall now blow another air-bubble
on this inner ring. The next bubble that I shall blow is one containing
gas, and this is inside the other two, and when let go it rests against
the top of the second bubble. I next make the second bubble a little
lighter by blowing a little gas into it, and then make the outer one
larger with air. I can now peel off the inner ring and take it away,
leaving the two inner bubbles free, inside the outer one (Fig. 63). And
now the multiple reflections of the brilliant colours of the different
bubbles from one to the other, set off by the beautiful forms which the
bubbles themselves assume, give to the whole a degree of symmetry and
splendour which you may go far to see equalled in any other way. I have
only to blow a fourth bubble in _real_ contact with the outer bubble and
the ring, to enable it to peel off and float away with the other two
inside.

[Illustration: Fig. 63.]

We have seen that bubbles and drops behave in very much the same way.
Let us see if electricity will produce the same effect that it did on
drops. You remember that a piece of electrified sealing-wax prevented a
fountain of water from scattering, because where two drops met, instead
of bouncing, they joined together. Now there are on these two rings
bubbles which are just res