APPENDIX 
CONSTRUCTION AND USES OF GOVERNMENT CONTOUR 
MAPS 
A number of plates, comprising portions of government topo- 
graphic (contour) maps, have been introduced into this book for 
the purpose of illustrating the typical relief features of various 
parts of the State. Since many persons are not familiar with these 
maps and their uses, a brief explanation is here given. 
These topographic maps, which are called sheets or quadrangles, 
are rectangular in shape and bounded by latitude and longitude 
lines. The size of each map is about 17% inches high by 11% to 
16 inches wide, the latter varying with the latitude. In New York 
State the scale is nearly always I to 62,500 or nearly one mile to 
the inch, such a sheet or quadrangle covering an area of just one- 
sixteenth of a square degree. The most valuable feature of these 
maps is the fact that the surface configuration (relief) of the 
country is so accurately shown, this feature being explained by the 
accompanying figures and the following description which is gen- 
erally found printed on the back of each map: “ Relief is shown 
by contour lines in brown. Each contour passes through points 
which have the same altitude. One who follows a contour on the 
ground will go neither up hill nor down hill, but on a level. By 
the use of the contours not only are the shapes of the plains, hills, 
and mountains shown, but also the elevations. The line of the sea 
coast itself is a contour line, the datum or zero of elevation being 
the 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 a line runs back into the valleys 
and forward around the points of hills and spurs. On a gentle 
slope this contour line is far from the present coast line, while on 
a steep slope it is near it. Thus a succession of these contour lines 
far apart on the map indicates a gentle slope; if close together, a 
steep slope; and if the contours run together in one line, as if each 
were vertically under the one above it, they indicate a cliff... . 
The contour interval, or vertical distance in feet between one 
contour and the next, is stated at the bottom of each map. This 
interval varies according to the character of the area mapped; in a 
flat country it may be as small as 5 feet; in a mountainous region 
it may be 200 feet. Certain contours, usually every fifth one, are 
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