Soap-Bubbles and the Forces Which Mould ThemBoys, C. V. (Charles Vernon)
Science
Soap-Bubbles and the Forces Which Mould Them
Boys, C. V. (Charles Vernon)
Bubbles; Capillarity; Surface tension
This one, large enough to hold about half a pint,
is made out of a small piece of the _Times_ newspaper. You may fill it
with water and carry it about and throw it with your full power, and the
strength of the paper skin is sufficient to hold it together until it
hits anything, when of course it bursts and the water comes out. On the
other hand, the large one made out of a whole sheet of the _Times_ is
barely able to withstand the weight of the water that it will hold. It
is only just strong enough to allow of its being filled and carried, and
then it may be dropped from a height, but you cannot throw it. In the
same way the weaker skin of a liquid will not make a large quantity take
the shape of a ball, but it will mould a minute drop so perfectly that
you cannot tell by looking at it that it is not perfectly round every
way. This is most easily seen with quicksilver. A large quantity rolls
about like a flat cake, but the very small drops obtained by throwing
some violently on the table and so breaking it up appear perfectly
round. You can see the same difference in the beads of gold now upon the
screen (Fig. 16). They are now solid, but they were melted and then
allowed to cool without being disturbed. Though the large bead is
flattened by its weight, the small one appears perfectly round. Finally,
you may see the same thing with water if you dust a little lycopodium on
the table. Then water falling will roll itself up into perfect little
balls. You may even see the same thing on a dusty day if you water the
road with a water-pot.
[Illustration: Fig. 15.]
[Illustration: Fig. 16.]
Public-domain text, read in full here on John Shaqi.
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