486 STATE BOARD OF AGRICULTURE. 



(1) because of the danger of disturbing the grade stakes (and these 

 stakes must not be disturbed from the time the leveling is done till after 

 the digging of the ditch is begim) and (2) because it is not so convenient 

 to haul and distribute the tile after the digging of the ditches has begun. 



LEVELING. 



The work of leveling begins with the main, if there be a system of 

 drains to install. If there be onlv one drain the work of leveling will 

 proceed in the same manner. 



The object of the leveling is to determine the elevation above datum 

 of the surface of the field at each stake along the proposed drain. The 

 reasons for this will appear later. 



The manner of leveling will be the same as that described under the 

 use of the level, page 15. 



The work of leveling will begin at the stake driven at or nearest to the 

 proposed outlet. This stake is numbered 1. 



(a) If the level to be used is a high-class instrument and the drain 

 is not over 50 rods long, the instniment may be set up at about the 

 middle of the length of the drain. The elevation of stake 1 will be as- 

 sumed to be 10 feet above datum, and recorded as such in the proper 

 column after stake 1 in your notes. 



The first reading will be a back-sight taken at stake one. This reading 

 will be recorded in the proper column, after stake 2 in your notes. 



This back-sight reading added to the recorded height of stake 1 gives 

 the height of the instrument. 



Now take a reading on every other stake along the proposed drain. 

 These readings will all be fore-sight readings and each will be recorded 

 in your notes after the number of the stake at which it was taken. 



Each of these fore-sight readings subtracted from the height of the 

 instrument gives the elevation of the stake at which the reading was 

 taken. 



Note : Observe the cautions suggested on page 17. 



(b) If the level used is not a high class instrument, then it should 

 be set a little to one side of the proposed drain and about equidistant 

 from stakes 1 and 2. As above, the elevation of stake one is assumed 

 to be 10 ft. above datum and is recorded in the proper column after 

 stake one in your notes. 



Take a back-sight reading with the rod on stake 1, and record the 

 reading in the proper column after stake 2 in your notes. This reading 

 added to the height of stake 1 will give height of instrument. 



Take a fore-sight reading with the rod on stake 2 and record the 

 reading in the proper column after stake 2 in your notes. This reading 

 subtracted from the height of instrument will give elevation of stake 2. 



In like manner set the instrument in a similar position between stakes 

 2 and 3. Take a back-sight reading at stake 2 and a fore-sight reading 

 at 3. The back-sight reading added to the elevation of stake 2 will 

 give the height of instrument in the new position and subtracting the 

 new foresight from this new height of instrument will give the elevation 

 of stake 3. 



Proceed in this way, taking a ba£k-sight and a fore-sight reading be- 



