100 LAND DRAINAGE 



tablished. The rod should be held perpendicular with 

 the face toward the level. 



2. The person in charge of the adjusted level turns the 

 telescope toward the rod, places the eye at the eye piece, 

 and moves the objective out or in until the figures upon 

 the face of the leveling rod are clearly seen or, if the rod 

 is too far away for that, till the view of the target is clear 

 cut. The eye piece may need adjusting to bring out clearly 

 the cross-hair. He should look now to see that the spirit 

 level indicates level and, if necessary, adjust. 



132. Direct reading. If the figures on the leveling 

 rod appear sufficiently clear to the one in charge of the 

 level, as he looks through the telescope, he should read 

 and record the height on the rod at which the horizontal 

 cross-hair crosses the face of the rod. 



133. Target reading. If the figures on the leveling 

 rod do not appear sufficiently clear to be read by the person 

 in charge of the level, then the rodman must raise or lower 

 the target as directed by signs from the person in charge 

 of the level, until the horizontal bisecting line of the target 

 lies exactly behind the horizontal cross-hair of the telescope 

 as seen through the telescope. The rodman should now 

 carefully tighten the set screw of the target and then read 

 to the level-man the height at which the horizontal bisect- 

 ing line of the target crosses the face of the rod. This 

 height the level man should carefully record. The 

 rodman may record the reading. 



134. Back-sight reading and its use. This reading is 

 called the back-sight, and is the name always given to 

 the reading taken at the point whose elevation is known, 

 or assumed, and is always taken to determine the height 

 of the instrument. Let us suppose the reading just 

 taken to be 4.95 feet. This means that the instrument is 



