hey will grow at a great speed, and
therefore the water column will break up regularly, every drop will be
like the one behind it, and like the one in front of it, and not all
different, as is the case when the breaking of the water merely depends
upon accidental tremors. If the drops then are all alike in every
respect, of course they all follow the same path, and so appear to fall
in a continuous stream. If the waists are about four and a half
diameters apart, then the jet will break up most easily; but it will, as
I have said, break up under the influence of a considerable range of
notes, which cause the waists to be formed at other distances, provided
they are more than three diameters apart. If two notes are sounded at
the same time, then very often each will produce its own effect, and the
result is the alternate formation of drops of different sizes, which
then make the jet divide into two separate streams. In this way, three,
four, or even many more distinct streams may be produced.

[Illustration: Fig. 46.]

I can now show you photographs of some of these musical fountains, taken
by the instantaneous flash of an electric spark, and you can see the
separate paths described by the drops of different sizes (Fig. 46). In
one photograph there are eight distinct fountains all breaking from the
same jet, but following quite distinct paths, each of which is clearly
marked out by a perfectly regular series of drops. You can also in these
photographs see drops actually in the act of bouncing against one
another, and flattened when they meet, as if they were india-rubber
balls. In the photograph now upon the screen the effect of this rebound,
which occurs at the place marked with a cross, is to hurry on the upper
and more forward drop, and to retard the other one, and so to make them
travel with slightly different velocities and directions. It is for this
reason that they afterwards follow distinct paths. The smaller drops had
no doubt been acted on in a similar way, but the part of the fountain
where this happened was just outside the photographic plate, and so
there is no record of what occurred. The very little drops of which I
have so often spoken are generally thrown out from the side of a
fountain of water under the influence of a musical sound, after which
they describe regular little curves of their own, quite distinct from
the main stream. They, of course, can only get out sideways after one or
two bouncings fro