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 of many mountains there is so much iron that it pays to melt it out. Such rocks are called iron ores. Iron is so useful that men have been melting it out of the ores for thousands of years. It takes such a terribly hot fire to melt iron stone that every ancient people made a wonder story out of how it was first done. The Greeks, who thought different gods did all the hard and mysterious things, had a god of fire called Vulcan. He was supposed to live in a burning mountain where he melted the useful metals, and hammered them into shapes on his forge. That is why we call burning mountains of ore volcanoes today.

If those old Greeks could see the blast furnaces, or volcano towers of fire, and the rolling mills and casting foundries of today, where thousands of tons of iron are melted, rolled, cast, drawn and hammered into shapes, they would open their eyes. The world has learned how to do everything in mining ores, carrying them, melting and working iron, so that iron is now one of the commonest things in use. There isn't any kind of work that men do, from hoeing a garden to pulling a train of cars in which iron is not used.

There are iron mines in a great many of our states. The biggest ones that are now worked are near the shores of Lake Superior. The ore is found deep in the heart of some low mountain ranges that lie from twenty to one hundred miles back, and a thousand or more feet above the water. These mines are very interesting. You have to walk, or ride in a little steel ore car down a sloping tunnel that bores a thousand feet into the mountain. The tunnel is lit by electric lights so it is as bright as the New York subway tunnel. This tunnel into a mine is called the shaft. At the end of it other tunnels run out in every direction. At their ends big rooms have been cut out of the solid rock.

The heart of the mountain is honeycombed with these halls and chambers. There sooty-faced miners work by electric light, electric fans whirl fresh air down the shaft, and steam pumps force out the water of the underground springs that would flood the workings. Miners used to tear down the rock with picks and hand drills, but that is too slow work. Today they used compressed air drills that bore like gigantic woodpeckers. In the deep round holes they put dynamite "candles" which are exploded and bring down tons of rock. These candles used to be fired by means of fuses, like the tails of giant fire crackers but much longer. Now they are discharged by electricity.

An iron mine is like the Fourth of July all the time. Boom! Crash! Any minute there may be a terrific explosion that shakes