CLASSIFICATION OF MINEBAL LANDS. 61 



mediate locations are adjusted from them. If the country can not be 

 crossed in a vehicle, the geologist goes on horseback or on foot and 

 determines direction as before and distance by counting the number 

 of paces taken by horse or man. This method gives considerable 

 accuracy in location and provides an adequate basis for determining 

 the general mineral or nonmineral character of an area. 



State or county maps furnish locations for the geologist on some 

 reconnaissance trips. When working with such a map he starts 

 from a town, post office, or some point shown on the map and proceeds 

 toward some other point also shown. To obtain his location at inter- 

 mediate points he estimates distance and direction and records his 

 observations with regard to the estimated locations. This method is 

 seldom used, because of its inaccuracy, and it is never used to procure 

 final data for land classification. It was found applicable to condi- 

 tions in one of the Western States where large areas were withdrawn 

 on the basis of a report that later proved to be erroneous. In this 

 State the general reconnaissance proved the area to contain no coal 

 of value ; hence no careful examination was required. 



PUBLIC-LAND STJEVEYS. 



Public-land surveys made by the General Land Office result in the 

 official township maps which are the basis of all land titles and to 

 which, therefore, all data on land classification must finally be ad- 

 justed. The system now in use was adopted in essentially its present 

 form in 1785. Under this system a certain initial point is first se- 

 lected through which a north-south line, called a principal meridian, 

 and an east-west line, called a base line, are run. At successive inter- 

 vals, usually 24 miles, north and south of the base line standard 

 parallels or correction lines are established parallel to the base, and 

 similarly at intervals east and west of the principal meridian guide 

 meridians are established. Because of the convergence of meridians 

 toward the poles these guide meridians are not parallel to the prin- 

 cipal meridian but approach it toward the north. In order to 

 correct this narrowing the guide meridians are offset at each stand- 

 ard parallel and started anew northward at their original dis- 

 tance apart. The quadrilateral thus defined is subdivided into 

 townships, each approximately 6 miles square, and each township in 

 turn is divided into 36 sections 1 mile square. Each section is fur- 

 ther subdivided into quarters, and each of these is held to contain 

 four 40-acre tracts, or quarter-quarters, the smallest commonly recog- 

 nized legal subdivision of the public-land system. Appropriately 

 marked monuments are set at all township and section corners and at 

 the middle points of the side lines of sections, thus indicating the 

 limits of the quarter sections. Posts indicating the quarter-quarters 

 are not set, but this unit, and indeed in special cases smaller units of 



