The Mimic Vesuvius. This experiment is a demonstration of the heat and light which are evolved during chemical combination. The substance phosphorus has a great affinity for oxygen gas, and wherever it can get it from it will, especially when aided by the application of heat. To perform this experiment, put half a drachm of solid phosphorus into a Florence oil-flask, holding the glass slantingly, that the phosphorus may not take fire and break the glass; pour upon it a gill and a half of water, and place the whole over a tea-kettle lamp, or any common lamp filled with spirits of wine; light the wick, which should be about half an inch from the flask; and as soon as the water is boiling hot, streams of fire, resembling sky-rockets, will burst at intervals from the water; some particles will also adhere to the sides of the glass, immediately displaying brilliant rays, and thus continue until the water begins to simmer, when a beautiful imitation of the aurora borealis will commence and gradually ascend until it collects into a pointed cone at the mouth of the flask; after a half a minute, blow out the flame of the lamp, and the apex of fire that was formed at the mouth of the flask will rush down, forming beautiful illumined clouds of fire, rolling over each other for some time; and when these disappear, a splendid hemisphere of stars will present itself. After waiting a minute or two, light the lamp again, and nearly the same phenomena will be displayed as at the beginning. Let a repetition of lighting and blowing out the lamp be made for three or four times, so that the number of stars may be increased; and after the third or fourth act of blowing out the lamp, the internal surface of the flask will be dry. Many of the stars will shoot with great splendor from side to side, while others will appear and burst at the mouth of the flask. What liquid remains in the flask will serve for the same experiment three or four times, without adding any water. Care should be taken, after the operation is over, to put the flask in a cool and secure place. The Real Will-o’-the-Wisp.