104 A MANUAL OF TOPOGBAPHIC METHODS. 



tude have never been determined. Another and, for mapping purposes, 

 important element which is wanting in this work is the relief. In some 

 cases aneroid observations have been taken along the lines of survey, but 

 they were never used for the purpose of drawing contours. 



The plats are prepared in duplicate, one copy being retained at the 

 local land office and the other deposited in the central office at Washing- 

 ton. They are now being photolithographed, and a limited number 

 printed of each. These plats are upon a scale of 2 inches to a mile 

 They show the subdivisions of the townships with their areas. They show, 

 also the streams, roads, swamps, lakes, timber, and prairie as they existed 

 at the time of survey. Relief is but feebly expressed. If any attention is 

 paid to it, it is indicated by crude hachures. 



This work is of service mainly, if not entirely, in furnishing secondary 

 locations. Its value for this purpose, however, differs widely. In some 

 regions it is not sufficiently trustworthy to be used, even when closely 

 controlled by triangulation. In forest-covered or broken country it is often 

 difficult to find the corners, so that it becomes necessary to supplement the 

 few discovered by traverses connecting one with another. This has been 

 the case with the surveys in Missouri. In open country, on the other hand, 

 where the surveys are of good quality, they furnish a complete and admi- 

 rable system of minor location, often obviating entirely the necessity of 

 making any horizontal locations, aside from the primary work necessary 

 to eliminate the accumulated errors of the system. In Iowa, Illinois, and 

 Wisconsin, traversing is done only to a limited extent and for the purpose 

 of locating the details of what are called "diagonal" roads — that is, roads 

 not upon section lines. The common practice of constructing roads upon 

 section lines, which, in the prairie states, has grown out of this plan of sub- 

 division, aids greatly in the work of survey. This system of roads is highly 

 developed in Kansas, where, by state law, every section line may have a 

 road upon it. This fact, coupled with the rectangular subdivision of the 

 sections into quarters, 80's, and 40's, marked by fences or hedges, and the 

 fact that all these subdivisions are indicated upon county maps, renders the 

 work in this state a simple matter, while the resulting map is admirably 

 controlled. The same is true of Nebraska and the Dakotas, as far as settle- 



