nr 
1C71 
gradually away and forms an inclined table-land that is j 
versed by a few shallow gullies. On the map each of 1 
features is represented, directly beneath its position in { 
sketch, by contour lines. ' ; jr.s ' j 
The contour interval, or the vertical distance in feet betw 
7 
one contour and the next, is stated at the bottom of each n 
This interval differs according to the topography of the 
mapped; in a fiat country ifcynay be as small as 1 foot; 
mountainous region it may be as great as 250 feet. Cer 
contour lines, every fourth or fifth one, are made heavier t. 
* 
the others and are accompanied by figures showing altiti 
The heights of many points—such as road corners,, sumn 
surfaces of lakes, and bench marks—are also given on the i 1 
in figures, which show altitudes to the nearest foot only. M 
exact altitudes—those of bench marks—as well as the geod 
coordinates of triangnlation stations, ate published in bulle 
that are issued free by the Geological Survey 
The lettering and works of man are shown In black. Bo 
such as those of a State, county, city, land gri 
3 -1 b V I H fi I PH I I fcj n| BjE _ I pHsj . j|i * 
township, or reservation, are shown by continuous or bro j 
lines of different kinds and weights. Metaled roads arc she 
.by double lines, one of which is accentuated. Other pul 
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roads are shown by fine double lines, private and poor ro 
by dashed double lines, tails by dashed single lines. 
Each quadrangle is designated by the name of the princ 
