THE DIVING LIGHT.
On a good-sized cork or bung place a small lighted taper, and then set it afloat in a pail of water. Invert a large drinking-glass over the light, and push it carefully down into the water. The glass being full of air, prevents the water entering it. The candle will burn under water, and come up again to the surface still alight. The largest drinking-glass holds but half a pint, so that your diving light soon goes out for the want of air. A burning candle consumes as much air as a man, and he requires nearly a gallon of air every minute, so that, according to the size of the glass over the flame, you can calculate how many seconds it will remain alight, a large flame requiring more air than a small one. A quart bell-glass is very useful. A substitute is easily made from a green glass pickle bottle, with the bottom cut off.