plying the three rivers. Coal
is brought to the city by boats as well as by rail, and great fleets of
barges carry it and other heavy freight down the Ohio. A ship canal for
the establishment of water transportation between Pittsburgh and Lake
Erie (127.5 miles) has been projected. The railroads carry through
Pittsburgh over eight per cent. of all the railroad traffic of the
United States; and have a particularly heavy tonnage of coal, coke, and
iron and steel products; while a large proportion of the iron ore that
is produced in the Lake Superior region is brought here to supply
Pittsburgh manufactures. The total railway and river tonnage is greater
than that of any other city in the world, amounting in 1906 to
122,000,000 tons, of which about 12,000,000 tons were carried on boats
down the Ohio. Her tonnage is equal to one half the combined tonnage of
the Atlantic and Pacific coasts. The following table will be very
interesting as showing the extraordinary fact that the tonnage of
Pittsburgh exceeds the combined tonnage of the five other greatest
cities in the world (1902):

Pittsburgh 86,636,680 tons
London 17,564,110 tons
New York 17,398,000 "
Antwerp 16,721,000 "
Hamburg 15,853,490 "
Liverpool 13,157,720 "
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Total 80,694,320 "
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Pittsburgh's excess 5,942,360 "

Pittsburgh has freight yards with a total capacity for more than 60,000
cars. Its harbor has a total length on the three rivers of twenty-eight
miles, with an average width of about one thousand feet, and has been
deepened by the Davis Island Dam (1885) and by dredging. Slack water
navigation has been secured on the Allegheny River by locks and dams at
an expense of more than a million and a quarter dollars. The
Monongahela River from Pittsburgh to the West Virginia State line (91.5
miles) was improved by a private company in 1836, which built seven
locks and dams. This property was condemned and bought by the United
States Government, in 1897 for $3,761,615, and the Government is
planning to rebuild and enlarge these works.

Pittsburgh is surrounded by the most productive coal-fields in the
country. The region is also rich in petroleum and natural gas, and
although the petroleum in the immediate vicinity has been nearly
exhausted, it is still obtained through pipes from t