Time after contact = ·0262 sec.
Fig. 8.
This hole, at a certain stage, begins to fill up. The water rushes in on all sides, and the impetus carries up the inrushing water so that it builds up a tall pillar of water in the place where an instant ago there was a hole ([see Fig. 10]). No one could anticipate such an extraordinary effect; but the instantaneous photographs, taken by the light of an electric spark, which reveal it, cannot but be truthful.
The next stage is that this pillar of water breaks up, and falls back again on the surface. Hence the water, at the place where the drop plunges into it, is subjected to two violent impulses—a downward, succeeded by an up-lifting, force. The effect of this is exactly analogous to that of giving a blow to the interconnected string of balls in the model shown in [Fig. 7]—it propagates a wave. In [Fig. 10] is illustrated the next stage, in which this outward-moving initial wave-crest is shown.
Time after contact = ·0391 sec.
Fig. 9.
Time after contact = ·101 sec.