A green flame may also be produced by using chloride of copper instead of boracic acid. And instead of mixing it with the alcohol, a small quantity may be imbedded in the wick of a candle. A BEAUTIFUL IMITATION OF HOAR FROST. Obtain a large bell-glass, with a short neck and cork at the top, such as may be seen in the chemists' shops. Then procure a small quantity of benzoic acid, which exists in the shape of snowy crystals. Elevate the bell-glass upon a little stage made of books or pieces of wood, so as to allow a spirit-lamp to be introduced underneath, and a little evaporating dish to be held above the flame by means of a ring of wire with suitable handle. Place the benzoic acid in the evaporating dish, over the flame, and presently the acid will ascend in vapor and fill the bell, which must not be quite closed at the top. Before setting up the apparatus, introduce into the bell a small branch of foliage, which may be hung by a thread from the neck of the bell. The stiffer and more delicate this branch, the better. In a short time, it will become covered with a soft white deposit of the acid, very closely resembling hoar-frost. This makes an extremely pretty ornament for the parlor. [Illustration: IMITATING HOAR-FROST.] TO BOIL WATER WITHOUT FIRE. Half fill a common oil-flask with water, and boil it for a few minutes over the flame of a spirit-lamp. While boiling, cork up the mouth of the flask as quickly as you can, and tie a bit of wet bladder over the cork, so as to exclude the air perfectly. The flask being now removed from the lamp, the boiling ceases. Pour some cold water upon the upper portion of the flask, and the ebullition recommences! Apply hot water, and it stops! And thus you may go on as long as you please. TO CONVERT A LIQUID INTO A SOLID. Dissolve about half a pound of sulphate of soda in a pint of boiling water, and after it has stood a few minutes to settle, pour it off into a clean glass vessel. Pour a little sweet oil upon the surface, and put it to stand where it can get cold, and where no one will touch it. When cold, put in a stick, and the fluid, previously clear, will at once become opaque, and begin to crystallize, until at length there is a solid crystalline mass. ICE ON FIRE. Make a hole in a block of ice with a hot poker. Pour out the water, and fill up the cavity with camphorated spirits of wine. Then ignite the spirit with a match, and the lump of ice will seem to be in flames. EXPERIMENTS REQUIRING CHEMICAL SOLUTIONS.