There are iron mines in a great many of our states. The biggest ones that are now worked are near the shore 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 use compressed air drills that bore like gigantic woodpeckers. In the deep round holes they put dynamite candles. Far away, so it will take five minutes to burn, they light fuses, as you light the tails of fire crackers. Then they run. In a few minutes, bang! goes the dynamite, bringing down tons of rock.

An iron mine is like the Fourth of July all the time. Boom! Crash! Any minute there may be a terrific explosion that shakes the mountain, and great falls of rock like falling cities. You would be sure to scream with fright the first time you heard it. By and by, when the dust from an explosion has settled, the miners go back and find tons of broken up iron ore all ready to load into the ore cars. These are pulled up the shaft by cables, and sent down the railway track from twenty to a hundred miles to the lake. It is down hill all the way, a drop of ten to a hundred feet to the mile, so the little ore cars don't need an engine. They just roll along by themselves. The track runs out on a high bridge-like pier for half a mile, and over deep water. There men help the cars dump their loads into ore bins.

Ore ships steam right under these bins. The bottoms of the bins drop on hinges like doors, and the ore tumbles into the holds of the ships. The ships steam away over hundreds of miles of the great lakes and carry the ore to Chicago or to Cleveland, Ohio. From Cleveland most of the ore is sent by rail to Pittsburg, the greatest iron manufacturing city in the world.

To melt iron ores, coal and limestone are needed. The three things are not found together. The limestone and coal are around the lower lakes, and these are nearer the railroads and big markets for iron. The ores on the upper lake can be shipped cheaply. You see the cars run by their own weight to deep water, and vessels can carry things for less money than trains. So it costs very little to send ore from those mines to where there is coal and limestone.