Soap Bubbles
and the Forces which Mould Them

THE FORCES WHICH MOULD THEM. 175 ebonite should not be perfectly warm and dry, for it is then sure to be electrified, and this will give trouble. It must not be wet, because then it will conduct, and the sealing-wax will produce no result. If it has been used as the support for the rings for some of the pre- vious experiments, it will have been sufficiently splashed by the bursting of bubbles to be in the best condition. It must, however, be well wiped occasionally. A stick of sealing-wax should be held in readiness under the arm, in a fold or two of dry flannel or fur. If the wax is very strongly electrified, it is apt to be far too powerful, and to cause the bubbles, when it is presented to them, to destroy each other. A feeble electri- fication is sufficient; then the instant it is exposed the bubbles coalesce. The wax may be brought so near one bubble in which another one is resting, that it pulls them to one side, but the inner one is screened from electrical action by the outer one. It is im- portant not to bring the wax very near, as in that case the bubble will be pulled so far as to touch it, and so be broken. The wetting