TEXTBOOK OF LANDSCAPE GARDENING 
condition of an overhanging surface, in which case they always 
cross each other twice. 
A contour never ends, but we frequently show ends — 
1. At the margins of the map —an arbitrary limit beyond 
which no data are shown. 
2. At a building, wall, or other vertical surface — here one or 
more contours continue in the vertical surface but can- 
not well be shown. 
3. At the limits of a ledge, stone pile or other surface so rough 
that it is difficult to locate the contour correctly on it. 
4. At a stream shore, where we have no data to show its lo- 
cation correctly under the water. 
Plotting Level Notes 
Whenever a series of levels has been taken either with the transit, 
the plane-table or any kind of a leveling instrument, they should 
be recorded on the plan in such a way that the decimal point will 
occupy the exact position where the level was taken. 
When the survey has been made by the cross-section method 
the paper .on which the plan is to be plotted should be ruled with 
two series of fine sharp lines at right angles to each other, properly 
spaced at the scale of the plan to represent the cross-section lines 
of the survey. These lines should be lettered and numbered as the 
survey lines were lettered and numbered in the field. The levels 
should then be entered diagonally across the intersections of the 
lines, with the decimal point just where the lines cross. 
In working out the positions of the contours on any plan we 
must base our work on the supposition that the surface of the ground 
is practically straight —that is on an even slope — between any 
two adjacent levels. Therefore in taking the levels we must be 
sure to take them not only at the cross-section stakes, but also 
wherever there is a change in the slope of the surface, so that our 
supposition that the surface is on an even slope between the levels 
will be approximately correct. 
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