Page:Popular Science Monthly Volume 11.djvu/566

548 For the next drop the spark is made to appear a shade later, either by slackening the spring or increasing the depth to which the terminal wire is immersed in the mercury.

The accompanying figures have been drawn in the way described, and show the behavior of a drop of mercury about $1/undefined$ inch in diameter, falling from a height of about three inches on to a glass plate. Each figure represents a rather later stage of the splash than the preceding.



Fig. 9 was drawn from the final stages of a milk-drop $1/undefined$ inch in diameter, falling four inches on to smoked glass; but the forms are almost identical with those of mercury. Of these d and h are vertical central sections of the middle part of the drop, while e and f are alternative forms of h and c.

From the ends of the rays of Fig. 4, usually twenty-four in number, small drops often split off. These are not shown in the figure. One of the most curious features of the phenomenon is the transition from twenty-four rays to twelve arms, shown in Fig. 5, The beauty of many of the forms, especially of the ridged, shell-like form shown in Fig. 4, when composed of shining quicksilver apparently rigidly fixed, is very striking. Very similar forms are obtained with milk, but, whether with milk or mercury, are liable to occasional variations. For a more detailed account the reader is referred to the "Proceedings of the Royal Society," Nos. 174 and 177, 1876-'77.—Nature.