a cover of wet clay with an iron tube in it, connecting with a tank, over the kettle. Then he built a fire under the kettle to roast, not burn the coal. Sure enough the same yellow, smoky, ill-smelling gas came through the tube. He caught a tank full of it and corked the tube. Over the end of the tube, when he opened it, he fitted a silver thimble. In this he bored a hole. He lit the gas that escaped through the hole in the thimble and had a good light to read by. You see he had a gas storage tank, a gas pipe and a gas jet. He had everything we have today, except a key to turn his gas on and off, and he could not control the pressure so as to get a strong, steady flame, as the supply of gas in the tank lowered.
You can make gas just as William Murdoch did. Buy a clay pipe for a penny. Fill it with coal dust. Cover the top with your modelling clay, or with stiff mud. Then set the bowl of the pipe over a gas jet or on a bed of coals to get very hot. In a few minutes a yellowish smoke will come through the stem of the pipe. Touch a match to it. It will burn, but not very clearly, for it is full of smoke and other impurities.
In gas-making today, these impurities are taken out to make a colorless, smokeless gas and a clear flame. First the coal is roasted to release the gas. As fast as it escapes from the coal, it goes through pipes into big tanks, and from them is forced through water and lime to purify it. At last it goes into a gasometer, or tank, that Hoats with an open bottom on a well of water. The gasometer presses the gas on the water, rising and sinking according to the amount of gas inside. This keeps the pressure always the same, and forces the gas into the service pipes that run to our houses under the streets. In this way our gas pipes are kept full. So all we have to do, when we want a light, or a fire in the kitchen gas-range, is to turn a key and light, the gas at the burner.
BIRDS AND BALLOONS, KITES AND AIR SHIPS
The Chinese and Japanese people have a kite-Hying day. Most of their kites are made in the shapes of birds and butterflies, with wide-spread wings. They make them 0f hollow bamboo, the lightest and strongest wood known, and cover them with thin, tough rice-paper or silk. Very likely, many of them think no other kind of kite could stay up in the air. But really they stay up because their weight is spread out so that a great deal of air can get under them to support them. A bar of iron rolled into a sheet and pressed into a boat floats.
