MARYLAND GEOLOGICAL SURVEY 97

A small area, however, had already been mapped prior to this date
by Mr. H. F. Walling, under the United States Coast and Geodetic
Survey. This area included the Blue Ridge and the country lying
to the eastward and southward as far as Sugar Loaf mountain, com-
prising several hundred square miles. This map, which was on the
scale of one mile to an inch, was controlled by triangulation and was in
all respects adequate for the scale. The streams were as fully repre-
sented as the scale would admit, and relief was shown by contours 100
feet apart This work was immediately discontinued when the United
States Geological Survey commenced operations in the state.

The United States Geological Survey commenced topographic work
in July, 1883. The original plans contemplated the preparation of
a map on a scale of 1: 250, 000, or about four miles to an inch, with
contours at intervals of 100 feet. Under this plan work was continued
during 1883 and 1884, and most of the western or mountainous part
of the state was thus surveyed in a preliminary way. In 1885 it was
decided to make the maps on a scale of 1: 125, 000, or about two miles
to an inch, and for several years the work was continued upon that
plan. Much of the work which had been surveyed during the first
two years upon the smaller scale was revised to adapt it to the larger
scale. Still later, in 1890, when work was commenced in the low
country near the western shore of Chesapeake Bay, it was decided to
map this region on the scale of 1: 62, 500, or about one mile to an
inch. After mapping this region on this scale it was found that all
necessary details could be represented quite as well on the scale of
1: 125, 000, and the sheets were therefore reduced to that scale,
although meantime many of them had been published on the one-
mile scale.

This successive shifting of scales has finally resulted in the adop-
tion of the two-mile scale for the entire state, with the exception of the
East Washington, West Washington and Baltimore quadrangles,
which, being centers of large population and valuable industries, seem
to require the larger or one-mile scale. At the same time the area
north of 39° 30' will be mapped on the larger scale.

The work in Maryland rests mainly upon the triangulation exe-