their relations to the life of the people. Objects of wealth may be
grouped in various ways. The following may serve our purpose of a
general survey of our present resources.

§ 8. #Sources of food supply#. The land area of the country in 1910
was about 1,900,000,000 acres, of which 879,000,000 acres were in
farms, this being 46 per cent of the total area. A very small part
of the remainder is used for residential and commercial purposes,
the rest being barren mountains, deserts, swamps, and forests. Of the
total in farms a little more than one-half was improved, 478,000,000
acres altogether, a per capita average of 5.2 acres; and a little
less than one-half was unimproved, 400,000,000 acres altogether, a
per capita average of 4.3 acres. The improved land produced not merely
food but many kinds of materials, such as cotton, wool, hides,
and lumber, while much of the unimproved land was either in farm
wood-lots, or in rough range pasture. Of course the kinds and amounts
of produce per acre vary with the climate, particularly with sunshine
and rainfall; possibly the proportion of the area of the United States
that is true desert and infertile mountain land is greater than that
of any other equal area in the temperate zones. The actual productive
capacity per acre of the lands of America cannot be expressed in a
very helpful way as a general average per acre, but each area must be
carefully studied in respect to its climate, rainfall, and possibility
of irrigation and drainage. It is evident that a very large number of
economic problems must arise in connection with the land supply
for food: such as problems of land-ownership, taxation, irrigation,
drainage, forestry, and encouragement or limitation of population. We
are just beginning to awaken to the needs in this direction.

The rivers, lakes, and ocean waters near our coasts are other great