Soap Bubbles
and the Forces which Mould Them
Forfatter: F. R. S., A. R. S. M., C. V. Boys
År: 1890
Serie: Romance of Science Series
Sted: London
Sider: 178
UDK: 532
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THE FORCES WHICH MOULD THEM. 79
Fig- 34-
and a half times as long as they are wide.
Now if you imagine one of these tubes joined
on to the end of the other, you will see that a
cylinder more than about three times as long
as it is wide cannot last more than a moment;
because if one end were to
contract ever so little the
pressure there would increase,
and the narrow end would
blow air into the wider end
(Fig. 34), until the sides of
the narrow end met one
another. The exact length
of the longest cylinder that <—
is stable, is a little more than
three diameters. The cylinder
just becomes unstable when
its length is equal to its cir-
cumference, and this is si-
diameters almost exactly.
I will gradually separate these rings, keep-
ing up a supply of air, and you will see
that when the tube gets nearly three times
as long as it is wide it is getting very diffi-
cult to manage, and then suddenly it grows
a waist nearer one end than the other, and