gradual ly away and forma an inclined tabie-land that is 
The contour interval, or the vertica distance in feet be 
one.contour and the next, is stated at the bottom of eachi 
interval differs according to the topography of the 
mapped': in a flat country it may be as small as 1 iootj 
. 
exact altitudes—those o bench marlcs—as well as the ge 
T* ' 
Lettering and the works of man are shown in black. B 
arias such as those of a State, county, city, land grant, 
ship, or reservation, are shown by contiguous or broken 
--=.. . . . . j , , 
