130 



LAND DRAINAGE 



Observe, that our last remainder, 8.74 feet, is the 

 elevation of bottom of ditch already indicated in column 



8, which indicates that the subtractions to this point are 

 correct. 



Introduce the elevations of ditch bottoms at stakes 8, 



9, and 10 in column 8 of Table XV. 



The elevation of bottom of ditch at stake 7 is 8.74 feet. 

 The elevation of bottom of ditch at stake 1 is 7.00 feet. 

 The fall from stake 7 to stake 1 is 1.74 feet. 



Find the fall to a hundred feet from stake 7 to stake 

 1 and record in column 7 in Table XV and compare 

 your result with that in Table XVI. 



Find the fall also for 50 feet and determine the eleva- 

 tions of bottom of ditch at stakes 6, 5, 4, 3, and 2. In- 

 troduce these elevations into the proper places in column 

 8. Then compare your results in column 8 with those in 

 column 8 of Table XVI. 



TABLE XVI 



