EXPERIMENT STATION BULLETINS. 



495 



11.70 feet, = elevation of bottom ditch at 11. 



,74 



10.96 feet, 

 .74 



10.22 feet, 

 .74 



elevation of bottom of ditch at 10. 



elevation of bottom of ditch at 9. 



9.48 feet, = elevation of bottom of ditch at 8. 

 .74 



8.74 feet, = elevation of bottom of ditch at 7. 



Showing that our subtractions are correct; for 8.74 is the elevation 

 of bottom of ditch already in your table. 



Introduce the elevations of ditch bottoms at stakes 8, 9 and 10 in 

 column 8 of Table V. 



(b) The elevation of bottom of ditch at stake 7 = 8.74 feet. 

 The elevation of bottom of ditch at stake 1 = 7 . 00 feet. 



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



Find the fall per hundred feet from stake 7 to stake 1 and record in 

 column 7 in Table V and compare your result with that in Table VI. 



Find the fall also for 50 ft. and detei-mine the elevations of bottom of 

 ditch at stakes 6, 5, 4, 3 and 2. Introduce these elevations into the 

 proper places in column 8. Then compare your results in column 8 with 

 those in column 8 of Table VI. 



12. We are now ready to determine the depth of the ditch at the 

 stakes where the depths have not yet been determined. 



In column 6 of your table we have the elevations of all the stakes, 

 while in column 8 we have the elevations of the bottom of the ditch 

 at all the stakes. If now the elevation of the bottom of the ditch at 

 any point be subtracted from the elevation of the stake at that point, 

 the result will be the depth of the ditch at that point. Make the proper 

 subtractions and enter results in column 9. Compare your results 

 with the values recorded in column 9 of Table VI. 



