Chicago is the greatest distributing centre of this region, but the ports of Lake Erie handle many important industries whose traffic never enters Lake Michigan. The copper of the upper Michigan peninsula, the iron ore of the Wisconsin and Minnesota ranges, the coal of Ohio and Pennsylvania, and many a minor industry have had their share in building up the modern empire of the Great Lakes. The body of water about which this empire has risen is made up of five lakes: Superior, Huron, Michigan, Erie, and Ontario, which together form the greatest inland waterway of the world. These lakes have an area of more than half that of the Black Sea or the Caspian, while Lake Superior is the largest body of fresh water on the globe. The four upper lakes are so nearly level that one canal with a single lock has given them a navigable length of over fourteen hundred miles. Lake Ontario, however, is effectively separated from the others by Niagara Falls and its attendant rapids. Other great inland bodies of water are directly connected with the ocean by navigable straits. The Mediterranean Sea is entered from the Atlantic by the Strait of Gibraltar, the Black Sea is connected in its turn with the Mediterranean by the Dardanelles and the Bosphorus; but Niagara closes direct navigation between the Great Lakes and the sea. Canals have done much in the last hundred years to alleviate the natural inaccessibility of the lake system. Eighty-five years ago the Erie Canal gave a water route from the eastern end of Lake Erie to the Hudson River and thus to the Atlantic Ocean. Five years later the Welland Canal passed round Niagara Falls and connected Lake Erie with Lake Ontario, and a third canal soon connected Lake Erie with the Ohio River. To-day a second era of canal building is upon us. The Welland Canal has been widened, making it possible for boats of moderate draught to go from Lake Erie to Lake Ontario and thence by numerous small cuts around the rapids of the St. Lawrence to the Atlantic. The Erie Canal is being enlarged, and engineers dream of a time when it will be made sufficiently wide and deep for sea-going vessels to pass from the Atlantic Ocean to Lake Erie. The Hennepin Canal at Chicago will open a route from Lake Michigan by the Illinois and Mississippi rivers into the Gulf of Mexico. Each state bordering on the Great Lakes as well as every province of the Dominion of Canada is to-day planning extensions of this canal system.