GAS BALLOONS.
Small Gas Balloons are made of thin sheet india-rubber or gutta-percha, or tissue paper; larger ones are made of oiled silk. Cut gores of the material to be used sufficient in number when fastened together, the sides of each gore overlapping the gore fastened to it, to form a globe of the desired size with pear-shaped ends. Join the gores together, so as to make them completely air-tight; when the heavier materials are used they should be sewn together, and then covered with glue or thin varnish. At the lower end of the balloon insert a tube, and tie all the narrow tips of the gores firmly round it. Cover all with a solution made of india-rubber dissolved in naphtha and turpentine, and over the balloon place a net bag that has been previously made of the proper size and shape.
The gas with which the balloon is to be filled is made in the following manner:—Put a pound of granulated zinc or iron filings into two quarts of water in a stone jar, and add gradually a pint of sulphuric acid. Have a tube of glass or metal run through the bung with which the jar is corked, and after taking the materials out of doors, fill the balloon by connecting this tube with the tube already placed at its mouth. When the balloon is filled, tie its neck very tightly, and it will rise into the air. Common coal-gas may be used when it can be obtained. A small car made of some light material may be attached to the netting which goes over the balloon.
Soap-bubbles inflated with gas may be made in the following manner:—Fill a bladder with hydrogen gas, adapt a tobacco-pipe to the mouth of the bladder, and dip the bowl of the pipe into soap and water; then press the bladder, and bubbles will be duly formed, which floating away will at once rise in the air.
Toy balloons ready to be filled with hydrogen gas may be now purchased at many toy-shops, or of philosophical instrument-makers.