CLASSIFICATION OF MINERAL LANDS. 51 



generally used by the geologist in the solution of problems of classi- 

 fication. 



The acts separating the mineral and agricultural estates of coal 

 lands were not passed until 1909 and 1910, so that the withdrawals 

 of coal land promulgated prior to that time prevented the initia- 

 tion of both homestead rights and coal entry on the same tract. In 

 order that this interference with agricultural development might be 

 reduced to a minimum, the first examinations were directed toward 

 the correction of the withdrawals by the prompt elimination from 

 .them of the noncoal land. The methods first used, therefore, were 

 planned with the idea of covering large areas quickly and did not 

 involve a marked departure from reconnaissance methods already in 

 vogue, except that it became necessary to tie the investigations as 

 closely as possible to such cadastral surveys as existed. One of the 

 first methods employed at the beginning of the work of coal-land 

 classification in 1906 and 1907 was that of retracing land lines. In 

 doing this work the field men rode along the section lines established 

 by the General Land Office, using the pocket compass to determine 

 direction and horse pacing to measure distance. Coal outcrops along 

 the section lines were mapped, the geology was studied in a general 

 way, and a sketch of the topography was made. 



In areas in which the absence of satisfactory land comers made it 

 necessary to construct a map independently of the Land Office sur- 

 veys a different method was adopted. By the use of a 15-inch plane 

 table and an open-sight alidade a main or control traverse was run, 

 completing a circuit of the field, distances being measured by inter- 

 sections from points previously located and altitudes determined with 

 an aneroid barometer. The topography and geology were mapped 

 by means of a network of secondary traverse lines tied to the primary 

 traverse. As the work progressed a more or less complete system of 

 triangulation was established which could be used in adjusting the 

 main plane-table traverse, and in turn the plane-table traverse served 

 to check meander traverse. In running these meander traverses a 

 pocket compass was used for obtaining directions, distances were 

 measured by pacing, and elevations were determined by aneroid. 

 The meander-traverse lines were plotted in the field as the work ad- 

 vanced, a small celluloid protractor being used for laying off angles 

 and a scale graduated to correspond to the scale of the township 

 plats being used for measuring horizontal distances. During the 

 field work especial care was taken to locate whatever land corners 

 existed, in the hope that these corners would serve as a basis for 

 later adjustment of the township and section lines on the map. 



These two methods probably represent fairly the general field 

 methods in use during 1906 and 1907, in connection with classifica- 

 tion of coal land, Some idea as to the speed attained in this work 



