METHODS OF MAP MAKING 
115 
feet elevation, the second run 100 feet above that, and so 
on, one for each 100 feet. A little consideration will show 
that the lines indicate not only direction of the slope of the 
land, but also the rapidity of slope, for when contours are 
close together the ground is steep, while on flat land they 
are wide apart. Hill tops are circled by a succession of 
contour lines. On lower land they often run in a very 
sinuous course. 
When one examines such a map and thinks of its con¬ 
struction, the first idea is that a tremendous amount of 
labor is involved. To follow out a succession of contour 
lines with ordinary surveying methods would indeed be 
an endless task. That is not the method of construction, 
however. It is rather sketching, guided by the location, 
in horizontal position and height, of a sufficient number of 
points. If one knows how high the top of a hill is above its 
base, that tells one at once how many contours, 100 feet 
apart, come between the two, and a glance at the hill 
perhaps will tell if it is of even slope. Similarly the location 
of divides and ridge tops, and, on the other hand, of low 
points, whether occupied by water or not, gives control 
points which aid in representing the slope of the land. 
The main problem of the topographer is how best to make 
these locations — most accurately and at least cost. 
General Considerations. The instruments and methods 
available for the production of topographic maps have 
been described on previous pages. In employing them, to 
secure practical results, very much depends, of course, on 
their effective use and proper combination. In this rela¬ 
tion, some general principles of surveying work and the 
conditions of woods work, as distinct from those of ordinary 
surveying, require first to be stated. 
1. A hunger for accuracy is part of the make-up of every 
good surveyor and map-maker. At the same time, he has 
to remember that if such work costs more than it is 
worth to the man who pays for it, it will not be done. 
Accuracy to a certain degree is necessary; on the other 
hand, there are limits of cost. A proper balance between 
the two is required. The result may be called an efficient 
map. 
