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. 



