railroads
include an enormous aggregate of works and structures in the form of
tunnels, cuts, banks, bridges, stations, and shops.

There are in the country (1914) about 2,228,000 miles of public
roads, of which 10 per cent are "surfaced" roads. No figures are now
available of the number of wagons, horses, automobiles, and
other vehicles in use on the roads and streets for purposes of
transportation.

Many of our economic problems are presented by these transportation
agencies, from the question of opening a new dirt road in a rural
township to that of building an inter-oceanic canal, from the question
whether to have free public roads or toll roads to that of regulating
the railroad rates on the whole railroad system of the country.

Sec. 11. #Raw materials for clothing, shelter, machinery, etc.# The farm
lands supply, besides food, a large part of the raw materials for many
other goods, such materials as cotton, flax, wool, hides, feathers,
lumber, and firewood. The farm woodlots compose about 200,000,000
acres, and the large forests, public and private, about 350,000,000
acres, a total of about one-fourth the area of the country in
forests, containing about one-half of the lumber that the country once
possessed. The economic problem of a sound forestry policy is one of
the largest we have to solve.

The most important other sources of raw materials for industry are
the mineral deposits in the earth's surface.[8] This country is stored
more bountifully, probably, than is any other country, with the metal
ores of iron, copper, lead, zinc, gold, and silver. Aluminum is the
most abundant metal, composing about 8 per cent of the crust of the
earth, but by present methods it can be extracted only at considerable
cost from certain compounds that are limited in amount. The details as
to our metal stores are too complex for fuller treatment here, and may
be found in treatises on economic geology or on industrial geography.
The determination of wise policies as to the use of these stores
involves many economic problems, private and public.

Another great class of material wealth is in the form of tools,
machinery, and other agencies for carrying on the industrial
processes of farming and of manufacturing. These are sometimes called
instrumental goods, or the industrial equipment. Still another class
consists of the great mass of completed direct goods, such as houses
to live in, libraries, museums, school buildings, the