Professor Tyndall at the Royal Institution showed a very pretty experiment. He took a funnel with a very fine bore, and permitted sand to flow from it as it will in the hour-glass. When he permitted the electric current to come in contact with the sand, however, it, instead of falling vertically to the table, spread out fan-like, each grain repelling and being repelled by its neighbour with an effect very beautiful to see. Luminous effects have frequently been produced by passing an electric spark through various bodies. For instance, a lump of sugar can be made quite brilliant in the dark by passing electricity through it, and there are other substances similarly affected. Even eggs and some fruits are thus made phosphorescent. The illumination of the “diamond” covered Leyden jar is familiar to all who ever attended a lecture on Electricity. The various effects of the electric discharge need not here be described. We have witnessed the results of lightning, but even in our laboratory many pretty little experiments can be made, such as the perforation of a card by the electric discharge. The chemical effects are various. Decomposition of water is effected by electricity, and the discharge can also be, and has been utilized for military purposes, such as employed by Professor Abel in his fuse, and in his apparatus for firing mines. Experiments at Chatham and elsewhere have been very successful in the application of electricity to modern warfare. We will illustrate one or two of these. A thick card should be placed, as in the illustration (fig. 216), between two insulated points, and to the lower portion of the apparatus a chain be attached, held in the hand, and wound round the Leyden jar. If then the knob of the jar and the knob above the upper point be brought together, the spark will pass through the card. [Illustration: Fig. 216.—Experiment with card.] In the same manner a glass may be perforated if the current be stronger. Of course the whole apparatus—and particularly the plate—must be quite dry, and it will be better to put a drop of oil under the upper needle point so as to prevent the electricity spreading over the glass. The glass will be found pierced by the electric spark when the Leyden jar is brought into requisition (fig. 217). It was at one time contended that the sudden expansion of the air by the electric spark caused heat to be generated, and a thermometer was invented by Kinnersley to show this. The illustration (fig. 218) will explain it. When the electric spark passed between the balls in the large tube the water rose in the smaller. But the immediate return of the water to its level showed that the disturbance was only mechanical, and not owing to heat. [Illustration: Fig. 217.—Experiment with glass.] [Illustration: Fig. 218.—Kinnersley’s thermometer.]