122 



LAND DRAINAGE 



TABLE XIV 



It will be observed, however, that there is but one back- 

 sight reading in this case to be introduced into the back- 

 sight column, and that after the number of the stake at 

 which the back-sight reading was taken. 



165. Making the computations. With the fore-sight 

 and back-sight readings recorded in the table, the first 

 step is to determine the elevations of the several stakes. 

 Since the cheaper instrument is the one most likely 

 to be used except by professional engineers, let us 

 use the data in Table XIII for the determination of 

 the elevations of the stakes. If the reader is sure 

 that he understands the processes of determining the 

 elevations, he may disregard what follows in paragraph 

 166. If he is not sure, it is suggested that he refer to 

 Table XIII, in which there is entered all the data de- 

 veloped to this point in the work, and that, following 

 directions below, he determine the proper values and 



