the country on an excessively elaborate plan. Over much of this area the
sheets of the map will also be constructed on a scale of 1-250,000, but in
special districts that scale will be increased to 1-125,000, and in the
case of important mining districts charts will be constructed on a much
larger scale. In the eastern portion of the United States two scales are
adopted. In the less densely populated country a scale of 1-125,000 is
used; in the more densely populated regions a scale of 1-62,500 is
adopted, or about one mile to the inch. But throughout the country a few
special districts of great importance, because of complex geologic
structure, dense population, or other condition, will require charts on
still larger scales. The area of the United States, exclusive of Alaska,
is about three million square miles, and a map of the United States,
constructed on the plan set forth above, will require not less than 2,600
sheets. It may ultimately prove to require more than that, from the fact
that the areas to be surveyed on the larger scale have not been fully
determined. Besides the number of sheets in the general map of the United
States, there will be several hundred special maps on large scales, as
above described.

Such is a brief outline of the plan so far as it has been developed at the
present time. In this connection it should be stated that the map of the
United States can be completed, with the present organization of the
Geological Survey, in about 24 years; but it is greatly to be desired that
the time for its completion may be materially diminished by increasing the
topographic force of the Geological Survey. We ought to have a good
topographic map of the United States by the year 1900. About one-fifth of
the whole area of the United States, exclusive of Alaska, has been
completed on the above plan. This includes all geographic work done in the
United States under the auspices of the General Government and under the
auspices of State Governments. The map herewith shows those areas that