Improved Agricultural Drainage Level. 



169 



drive short stakes into the ground at each station, even with the 

 surface, upon which to place the staff. Then put up your 

 instrument midway between the first and second stations, your 

 assistant holding the staff upon the first, which call the bach 

 station; adjust your instrument and take the reading, then direct 

 your assistant with the staff to the second or front station, 

 turn your instrument round on the joint, adjust and read off as 

 before. 



After which remove the instrument to midway between the 

 second and third stations ; the second station now becoming 

 the back station, and the third the front ; adjust the instrument 

 and read off the staff at both stations as before, and thus go on 

 from station to station until the whole set of observations necessary 

 between the two extreme stations is completed. 



The following example shows the form of Levelling Book, and 

 the method of reducing the observations : — 

















Height 



Quan- 











Distance 



Back 









of each 



tity 



Depth 



No. of 



No. of 



between 



Front 



Rise. 



Fall. 



Station 



deduct 



of Drain 



Stations. 



Stations. 



Stations. 



Stations. 



above 



for 



at each 



Station. 















datum 



Fall. 



Station. 



















line. 









Back- 



Front. 



Yds. 



Inch. 



Inch. 



Inch. 



Inch. 



Inch. 





Inch. 



















40 





40 



1 



1 



2 



90 



64 



52 



12 





52 



7 



45 



2 



2 



3 



100 



73 



45 



23 





80 



15 



65 



3 



3 



4 



80 



69 



51 



IS 





98 



2-1* 



76* 



4 



4 



5 



90 



57 



71 





" 14 



84 



28| 



55i 



5 



5 



6 



95 



52 



76 





24 



60 



36 



24 



6 







455 



315 



295 



58 



38 

















295 





38 

















Rise 



20 



: 



20 













The first column contains the numbers of the back and front 

 stations. 



The second — -The distance between the stations, in paces, vards, 

 or chains. 



The third — The readings of the back stations. 



The fourth — The readings of the front stations. 



The fifth — The rise from the back to the front station obtained 

 by subtracting the front reading from the back reading. 



Sixth — The fall from back to front station, obtained by sub- 

 tracting back reading from front reading. 



Seventh — Gives the height of ground at each station above datum, 

 or a horizontal line passing through the bottom or the lowest part 

 of the drain at outlet. 



This column begins with the number of inches the depth or 

 bottom of outlet of drain is, below surface of ground at first sta- 



