IC MAP OF THE UNITED STATES 
ill lines, but by lines ot 
which are dry during a 
wn by oblique parallel 
are shown by horizontal 
lifts of blue, and fresh- 
rps by blue tufts with 
ontour lines in brown. 
points which have the 
follows a contour on 
>r uphill nor downhill, 
use of contours not only 
ns, hills, and mountains 
tions. The line of the 
line, the datum or zero 
sea level. The contour 
ea level is the line that 
le sea were to rise or the 
ch a line runs back up 
round the points of hills 
lope this contour line is 
t line, while on a steep 
i succession of these con- 
e map indicates a gentle 
steep slope; and if the 
ne line, as if each were 
ibove it, they indicate a 
e country are depressions 
The contours of course 
y surround hills. Those 
nks are usually indicated 
les, on the inside of the 
val, or the vertical dis- 
‘ontour and the next, is 
h map. This interval 
character of the area 
■it mav be as small as 10 
their descriptions, as well as the descriptions and 
geodetic coordinates of triangulation stations, are 
published in the annual reports and bulletins of 
the Survey. The publications pertaining to speci- 
fied localities may be had on application. 
The works of man are shown in black, in which 
color all lettering also is printed. Boundaries, 
such as State, county, city, land-grant, reservation, 
etc., are shown by broken lines of different kinds 
and weights. Cities are indicated by black blocks, 
representing the built-up portions, and country 
houses by small black squares. Roads are shown 
by fine double lines (full for the better roads, dot- 
ted for the inferior ones), trails by single dotted 
lines, and railroads by full blackjines with cross 
lines. Other cultural features are represented by 
con ventions which are easily understood. 
The sheets composing the topographic atlas are 
designated by the name of a principal town or of 
some prominent natural feature within the district, 
and the names of adjoining published sheets are 
printed on the margins. The sheets are sold at 
five cents each when fewer than 100 copies are pur- 
chased, but when they are ordered in lots of 100 
or more copies, whether of the same sheet or of 
different sheets, the price is three cents each. 
The topographic map is the base on which the 
facts of geology and the mineral resources of a 
quadrangle are represented. The topographic and 
geologic maps of a quadrangle are finally bound 
together, accompanied by a description of the dis- 
trict, to form a folio of the Geologic Atlas of the 
United States. The folios are sold at twenty-five- 
cents each, except such as are unusually compre- 
hensive, which are priced accordingly. 
Applications for the separate topographic maps 
or for folios o f the Geo logic ^ Atlas should be 
