m the regular drops in front and behind. You can easily
show that they are really formed below the place where they first
appear, by taking a piece of electrified sealing-wax and holding it near
the stream close to the nozzle and gradually raising it. When it comes
opposite to the place where the little drops are really formed, it will
act on them more powerfully than on the large drops, and immediately
pull them out from a place where the moment before none seemed to exist.
They will then circulate in perfect little orbits round the sealing-wax,
just as the planets do round the sun; but in this case, being met by the
resistance of the air, the orbits are spirals, and the little drops
after many revolutions ultimately fall upon the wax, just as the planets
would fall into the sun after many revolutions, if their motion through
space were interfered with by friction of any kind.

There is only one thing needed to make the demonstration of the
behaviour of a musical jet complete, and that is, that you should
yourselves see these drops in their different positions in an actual
fountain of water. Now if I were to produce a powerful electric spark,
then it is true that some of you might for an instant catch sight of the
drops, but I do not think that most would see anything at all. But if,
instead of making merely one flash, I were to make another when each
drop had just travelled to the position which the one in front of it
occupied before, and then another when each drop had moved on one place
again, and so on, then all the drops, at the moments that the flashes of
light fell upon them, would occupy the same positions, and thus all
these drops would appear fixed in the air, though of course they really
are travelling fast enough. If, however, I do not quite succeed in
keeping exact time with my flashes of light, then a curious appearance
will be produced. Suppose, for instance, that the flashes of light
follow one another rather too quickly, then each drop will not have had
quite time enough to get to its proper place at each flash, and thus at
the second flash all the drops will be seen in positions which are just
behind those which they occupied at the first flash, and in the same
way at the third flash they will be seen still further behind their
former places, and so on, and therefore they will appear to be moving
slowly backwards; whereas if my flashes do not follow quite quickly
enough, then the drops will, every time