The copper era., 1901-01-31
GEOLOGICAL SURVEY.
An Interesting Account of the Work
Now Being Done in This
District.

4 Inc nlted states geoiOS lchI survey
is making a topographic map OF the
! United States. This work has been in
progress since 1882, and about one-tfth
OF the area of the country, including
Alaska, has beer mapped. The mapped
areas are widely scattered, nearly
every state being represented, as shown
on the progress map accompanying
each annual report of the director.
The great map is being published in
atlas sheets of convenient size, which
are bounded by parallels and meridians.
! The four-cornered division OF land cor
responding to an atlas sheet Is called
Quadrangle" Ia word used as specific
ally as section is in the surveys OF
the public lands). The sheets are OF
approximately the same Size; the paper
dimensions are 2lfxlSi inches; the map
I occupies about Il. inches of height
and III to Is inches of width, the later
varying with latitude. Three scales,
however. are employed. The largest
scale Is very nearly one mile to one
inch; i. e., one linear mile on the
ground is Represented by one linear
inch on the Inap. This scale is used
for the thickly settled or industrially
important parts OF the country. For
the greater part of the country an in
termediate scale of two miles to one
inch, is employed. a third and sill
smaller scale OF four miles to one inch
has been used in the desert regions of
the arid west. a few special maps on
larger scales are made OF limited areas
in mining districts. The sheets on the
largest scale cover 10 minutes of lati-
tude by i minutes Of longitude; those
on the intermediate scale, 30x30; and
those on the smallest scale, one degree
of latitude by one degree of longitude.
The features shown on these maps
may, for convenience. be classed in
three groups: ID Notwithstanding
seas, lakes, ponds, rivers and other
streams, canals, swamps, etc: ~ re-
lief-includiDg mountains, hills, val
leys, cliffs, etc; (0 culture. e., the
works of man, such as towns, cities,
roads, railroads, boundaries, etc. The
conventional sign used for most OF these
features are shown and explained on
the marginal edges of the maps.
All water features are shown in blue,
the smaller streams and canals in full
blue lines, and the larger streams,
lakes and the sea by blue water-lining.
The land features OF the relief, us
ually represented on maps by shadings
of some sort, with pen or brush, are
here shown by contour lines in brown:
each contour passes through those
points which have the same altitude.
If one follows a contour on the ground
one will go neither uphill nor down
| hill, but on level.
! BY the use OF contours not only are
the shapes of the plains, hills and
mountains shown, but also the eleva-
ton. The line of the sea-coast itself
! is contour line, the datum or zero
of elevation being mean sea-level. The
contour line at, say, 20 feet above sea-
level is the line that would be the sea-
coast if the sea were to rise or the land
to sink 20 feet. Such line runs back
up the valleys and forward around the
hills and spurs. On a gentle slope this
contour line is far from the present
coast line, while on Il steep slope it is
near ii. Thus succession of these
contour lines far apart on the map
indicate gentle slope; if close to-
gether, a steep slope; and if they run
together in one line. as If each contour
were vertically under the one above il,
they indicate cliff.
The works of man are shown in black.
in which color all lettering also is
printed.
The sheets composing the topo-
graphic atlas are designated by the
name OF principal town or of some
prominent natural feature within the
district. The sheets are sold at five !
cents each. The topographic map is |
the base on which the facts OF geology |
and the mineral resources of Il quad |
rangle are represented. The topo- |
graphic and geologic maps of any quad /
rangle are finally bound together, !
accompanied by a description Of the |
district, to form geologic atlas OF the /
United States. The folios are sold at |
twenty-five cents each, except such Is
are unusually comprehensive, which |
are priced accordingly.
At the present time Il topographic
party of the geological survey is maxi
ing surveys for what Will be known as
the Morenci quadrangle. The area,
that will be mapped, extends from
latitude "a degrees on the south, to 81
degrees II minutes on the north; and
from longitude l09 degrees l. minutes
on the east to l09 degrees 30 minutes
on the west, enclosing an area of 247
square miles. Taking Clifton on a
point of reference the area extends 13 i
miles north. miles south, 3 miles east
and ii miles west OF the town. The
scale Of this class OF map, as before
stated, is one mile to one inch. In
addition to the above map two special
maps, on scale OF 1000 feet 20 one
IN EG E lE M 4a' EaE M Kg sH III III q
3 ~ d