point chosen to command a view toward both ends of the cut. The 

 telescopes being parallel and in the same vertical plane, set the 

 vertical limb to the angular value of the slope, as suggested in the 

 lower cut of Fig. 107. Move the instrument forward or backward 

 until the horizontal wire of the auxiliary cuts the ground at the 

 central guide peg, D. Revolve the auxiliary on its own axis, all 

 other clamps being set, and test the sight against the extreme guide 

 pegs. A little maneuvering, perhaps by turning the whole instru- 

 ment on the vertical axis, will presently get the auxiliary revolving 

 in the direction and inclination of the slope, and in this position the 

 intersection of the sight line and the ground will mark the surface 

 horizon of the cut. 



t an 



. 107 



The pegs set, elevations for earthwork can be taken at leisure. 

 These rules apply only to tangents on which the grade is uniform. 

 At each change of grade a fresh setting must be made. The 

 appliance may be used with equal facility for embankments. 

 Following the above suggestions the modus operandi will suggest 

 itself to the surveyor. If the ground is not visible at any point, a 

 rod should be held inclined until the upper portion coincides with 

 the "horizontal" wire of the auxiliary. The origin of this idea 

 can be definitely located in England in 1864 when James Lister, 

 C. E., had the cradle theodolite remodeled for this purpose.* He 

 arranged a method also of setting slope stakes around a curve with 

 this device, but the process is rather involved and probably would 

 not be adopted if demonstrated in this text. 



nstruments. W. /'. Sfutt/ry, l^ndoit, 1895, p. 357. 

 184 



