120 



LAND DRAINAGE 



With these data properly recorded in the table we are 

 able later, by a series of computations, to obtain all the 

 facts called for in the other columns of the table, and thus 

 to obtain all the figures necessary to the proper construc- 

 tion of the drain. 



TABLE XIII 

 SAME AS TABLE XII WITH BACK-SIGHT AND FORE-SIGHT READING 



AND DISTANCES INTRODUCED 



164. Leveling with a high-grade level. Figure 47 shows 

 a high-grade instrument in position to take levels for the 

 same drain. It is located near the center of the drain. 

 The leveling rod is shown in position to take the single 

 back-sight and also the first fore-sight reading, and the last 

 fore-sight reading, with their values. The data obtained, 

 including the remaining fore-sights, appear in their proper 

 places in the following table, which is identical with 

 Table XIII above: 



