While it may be done, it has not been found desirable to make up the entire “burden” or furnace charge of soft ores alone as long as lump or hard ores are obtainable to mix with them, but often more than half is soft ore.
Starting an Open Pit Mine. The Earth Covering is Being Removed
While ores from the shaft mines, called “Old Range” ores, are won by going down into the earth sometimes as far as 3,000 feet, drilling holes in the rock, blasting down the ore, and loading it into buggies which are hoisted to the surface, “Mesaba Range” ores are made available by simply “stripping” off the thin earth covering, then caving or loading with steam shovels the soft ore into railway cars. Some of the illustrations presented show the ore trains and shovels, and the manner in which the open pits are worked in terraces.
One naturally wonders how it is possible to mine and carry these ores to the shipping ports of Duluth, Superior, Two Harbors, Marquette, Ashland, Escanaba, etc., put them aboard ore carrying boats, transport them by steam power to Milwaukee, Chicago, Gary, Detroit, Cleveland, Pittsburg, Buffalo, and the many other iron centers and convert them into iron and steel at a profit. This, of course, is only possible because of the inventive genius of man. For every operation ingenious machinery has been constructed which has brought the cost of such operations to its lowest terms.
Unloading Cars of Coal or Ore is a Simple Matter with the Modern Car Dumper
Ore Cars are Unloaded by Gravity at Docks. The Chutes Then Convey the Ore from the Ore Pockets into the Boat’s Hold
By modern methods the cars carrying the ore from the mines are run up trestle-work into positions above the ore bins high over the docks. The mammoth ore carrying boats are merely steel shells with quarters for crew and machinery at bow and stern, and hatches built with exact twelve foot centers between. They are tied alongside the dock, long steel chutes, also spaced twelve feet apart, are lowered along most of the length of the boat and the ore slides into the vessel’s hold evenly all along as it has to do, else the buoyancy of lighter parts of the boat might break the frail shell. The entire load of 10,000 tons of ore is ordinarily taken aboard in less than one hour. Pulling out immediately the vessel traverses Lake Superior, the Sault Sainte Marie canal, Lake Michigan or Lakes Huron and Erie as the case may be, and ties up at the dock at destination. Years ago it would have been unloaded by men with buckets or wheel-barrows, requiring some days at best. Now, however, the hatches are uncovered and several ore unloaders with huge clam shell buckets taking as high as fifteen tons of ore at a “bite” descend like vultures upon it. Within four or five hours the boat is again empty with no manual labor having been done upon the ore from the mine to the furnace pile with the exception of a little heaping up of the ore in the corners of the boat’s hold, which the ore unloaders could not reach.