When coal was first mined in England, it was noticed that an ill-smelling gas often escaped from the seams of the coal and made miners ill. In several mines this gas was accidentally set afire and the flame could not be put out. Around such flames mine owners built brick flues and led the gas out of the mine through iron pipes. There it often burned like a torch, lighting up the mine shaft, for months and years. This gas was called the "spirit of the coal." But no one thought of trying to find out how it was made, or of making any use of it for many years.

It was a Scotch miner named William Murdoch, who earned only five dollars a week, who got to thinking and experimenting with coal gas. Perhaps because he smelled the same gas from the grate fire in his cottage, sometimes, he suspected that, far down in the mine, a seam of coal must be smouldering. He filled a kettle with coal, fitted

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 floats 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.