LAYING OUT A DRAIN OR SYSTEM 



117 



any case, the instrument should be set so that it shall 

 stand approximately mid-way between the stake at which 

 the back-sight reading is taken, and that at which the 

 last fore-sight reading is to be taken. 



NOTE : Observe carefully the cautions suggested in 

 paragraph 137. 



161. Keeping notes. A more extensive form must 

 now be employed for keeping records of readings, and the 

 like, than was shown in paragraph 138. A table like the 

 following is suggested : 



TABLE XII 



In column ( 1 are recorded the stake numbers in order. 

 In column 2 is recorded the distance of each stake from 

 stake 1. With these distances the distance between any 

 two stakes may be found. 



As the work of leveling progresses, the back-sight 

 readings should be properly recorded in column 3, and the 

 fore-sight readings in column 5. 



Usually, though not necessarily, all readings are taken 

 before computations to determine the elevations of the 

 several stakes are begun. This, of course, includes the 

 determination of the height of instrument after each 

 back-sight reading. 



