ed pilot, and the
latter must spend nearly half a lifetime as an apprentice before he
receives a license. The charges for pilotage are usually regulated
by the number of feet the vessel draws. The charges differ in
various ports, but the devices for marking and lighting the
channels are much the same in every part of the world. In the
United States all navigable channels are under the control of the
general Government.

=Inland Waters.=--Lakes, rivers, and canals furnish a very important means
of transportation. In Europe and Canada an enormous amount of slow
freight is transported by their use; in China they are the most
important means of internal traffic.

[Illustration: THE COMMERCE OF THE OHIO--TOWING COAL TO THE STEEL
MILLS, PITTSBURG]

In the United States the Great Lakes with the Erie Canal and Hudson
River form the most important internal water-way, and by them the
continent is penetrated as far west as Duluth, a distance of more than
one thousand three hundred miles. The traffic passing out of Lake
Superior alone is about one-third greater than that passing out of the
Mediterranean Sea at the Suez Canal. Much of this traffic goes across
the continent, and the route in question is one of the great commercial
highways of the world.

The Mississippi River and its branches afford not far from ten thousand
miles of navigable waters. Canals connect tributaries of this river with
the Great Lakes at Chicago and at several points in Ohio. The
development of the navigation of this great water-way was checked by the
Civil War, and after the close of the war the great advance in railway
building kept its improvement in the background. The general government,
nevertheless, has done much to encourage the use of the Mississippi as a
commercial highway, and many millions of dollars have been spent in
widening and deepening its channel.[8] On the upper river grain and
lumber form the chief traffic; on the lower part a large part of the
world's cotton-crop starts on its journey to the various markets.

On account of the soft-coal fields and the steel manufacture in western
Pennsylvania, the commerce of the Ohio River is very heavy, aggregating
not far from fifteen million tons yearly. Much of this traffic extends
to ports on the Mississippi.

The navigable parts of the Hudson and Delaware Rivers are estuaries of
the sea or "drowned valleys." In each case navigation extends about to
the