84: National Geograj)hic Magazine. 



designed by Mr. W. D. Johnson, of the U. S. G. S. and was im- 

 mediately adopted. This is substantially a modification of the 

 ball and socket movement. It consists of two cups of large size 

 fitting closely to one another and working within one another in 

 such a way as to allow of the adjustment in level, and the clamp- 

 ing of the level adjustment independently of the azimuth move- 

 ment, clamps for both level and azimuth adjustments being under- 

 neath the instrument. This form is extremely stable, admits of 

 quick adjustment and leveling, and it has been from the time of 

 its invention in general use in this state and elsewhere in the 

 Survey. 



In the undulating, forest-covered, region in the southeastern 

 part of the state it was found impracticable to use economically 

 the method of intersections, and resort was had to the traverse 

 method for making locations. In this method, as is well known, 

 one station is located from another by the measurement of a 

 distance and direction, the line of stations being connected at 

 each end either upon stations in the triangulation or upon other 

 lines, while from the stations in these traverse lines, points off the 

 lines are located by intersections, if practicable, or by distance 

 and direction measurement. For this kind of work the plane 

 table, at least such a plane table as is generally in use is an incon- 

 venient instrument. The plane table with the telescopic alidade 

 is too cumbersome an instrument to be carried about and set up 

 as frequently as is necessary in this work. Therefore for this 

 purpose theodolites, fitted with stadia wires and stadia rods, have 

 been used. Distances are measured by the angles subtended by 

 the stadia wires upon the rod, whose divisions are of known 

 length, while the directions are measured by the compass attached 

 to the theodolite, and differences of elevation by spirit level and 

 vertical angles. With this instrument lines were run along all 

 the roads and along the principal streams in this part of the state 

 and from these lines the country lying between them was located 

 and sketched. 



In the northeastern and in much of the middle portion of the 

 state a mixed method of work was employed, the plane table 

 being used for carrying on the intersection work wherever it 

 could be done, while by traversing the roads, their details, which 

 could not be obtained by the plane table in this region, were 

 reached. These traverses were platted in the office and the maps 

 drawn from notes and sketches made in the field. 



