| 18 0·197 sec. |
| 19 0·217 sec. |
If Fig. 19 is reached without the top of the column having separated, then the splash follows the course shown in Figs. 20a to 23a, in which it will be observed that the disappearance of the first column is very quickly followed by the rise of a secondary column very different in shape, which itself subsides again, but has not yet (in 23a) formed, as it ultimately will, a second "cake" on the top of the first. Thus the second ripple follows late after the first.
SERIES I—(continued)
Alternative (a).
| 20a 0·240 sec. |
| 21a 0·242 sec. |
| 22a 0·248 sec. |
| 23a 0·253 sec. |