CEMENTING GLASS ] There are many excellent glass cements on the market. Some of these are solid and are used only on hot glass; others are liquid and are used on cold or hot glass. Cement two strips of glass together (Fig. 92) with sealing wax or solid shellac or some other solid cement as follows: Clean the glass thoroughly, place in the oven or on the stove, heat gradually until the glass just melts the cement, rub the cement over both surfaces, bring them together when the cement is fluid, press them together to squeeze out as much cement as possible, and keep them pressed together until the cement is hard. Cement a strip of wood to a strip of glass in the same way. Cement a strip of wood to a strip of glass with liquid glue, both wood and glass being cold. Keep them pressed together until the glue is dry, perhaps a day or two. MAGICAL EXPERIMENTS Boys, you can perform many magic experiments with apparatus made out of the glass tubes, rubber stoppers, and rubber unions supplied with “Experimental Glass Blowing.” We outline a number in the following pages. You can invent many more for yourselves. MAGIC WITH FLAMES Experiment 70. Magic lighting. Light your alcohol lamp, blow it out, and bring a lighted match down toward the wick from above (Fig. 93). Does the lamp light in a most magical manner =before the match touches the wick=? [Illustration: FIG. 93 MAGIC ] Repeat this with a kerosene lamp and with a candle. Do they light in the same magical manner? The “why” of it When the lamp is lighted, the alcohol or kerosene turns to a gas, and it is the gas which burns; when the candle is lighted, the wax turns to an oil, the oil turns to a gas, and it is the gas which burns. The gas rises from the wick for a short time after the flame is blown out, and it is this gas which lights when you bring the match down toward the wick. Experiment 71. Air used by flames. [Illustration: FIG. 94 THE CANDLES GO OUT AND THE WATER RISES ] Drop melted candle wax on a tin can cover and attach the bottoms of two candles to the cover (Fig. 94); use one candle about 4 inches long and another about 3 inches, stand them upright in a pan of water, light them, and invert a wide-mouthed bottle over them. Does some air escape at first due to expansion, do both candles go out, the taller one first, and does the water rise until the bottle is about one-fifth full? [Illustration: FIG. 95 THE CORK RISES ] Cut a piece of candle ½ inch long, float it on a flat cork or can cover in the pan of water, light it, and invert a fresh empty bottle over it (Fig. 95). Is the result similar? The “why” of it