methods, there is here a potential
substitute for coal equal to two to four times our present annual use
of coal (about 500,000,000 tons in 1912).

But this does not mean that it would be economical, at present costs
of mining coal and of building reservoirs, to make this substitution
now. To determine when, how far, and by what methods to develop this
water power from lakes and rivers for the use of the people and to
make this substitution, is another of our great economic problems.

Petroleum and natural gas, of which our original reservoirs were
perhaps the richest in the world, are being rapidly exhausted. These
may be merely mentioned as being related to coal in the source
of their supply, in the nature of their uses, and in the economic
problems to which they give rise.

Sec. 10. #Transportation agencies#. First to mention among the means of
transportation are the navigable waters--oceans, lakes, rivers, and
canals, with the necessary equipment of dredged inlets, harbors,
docks, locks, and lighthouses. Few of these appear in the total of
"capitals," for they are not in private possession. Yet a good system
of natural waterways may be greater wealth to one nation than costly
additional railroads are to another. Good natural harbors on the
waterways leading out to the oceans are a most important kind
of national wealth, as are the navigable great lakes within the
boundaries or on the borders of a country. Just in proportion as these
natural means of transportation are lacking, is the need to build
costly artificial means of transportation.

Both in natural and in artificial means of transportation, America
is well provided. The straight coast line is 5700 miles long, and the
line following indentations of the coast is about 64,000 miles. The
Great Lakes with a straight shore line of 2760 miles are the most
important inland waterways in the world. The 295 navigable rivers in
the country have a length of 26,400 miles of navigable water. About
2000 miles of canals are still in operation. On the waterways some
27,000 American vessels are in use, with a capacity of 8,000,000 gross
tons.[7]

There are about 250,000 route miles of steam railroads, or with
additional tracks, yard tracks, and sidings, a total of about 370,000
miles. On these are over 63,000 locomotives, 52,000 passenger cars,
and 2,400,000 freight and company cars. Besides these are 45,000 track
miles of electric railways and nearly 100,000 cars. These