PKEPARING THE PLANTING AREA 



85 



Therefore the height of the drain above the datum-line 

 at B 50 yards from A will be 10.00+-60=10.60. The 

 level of the ground at B is 12'60. The difference between 

 l'2-60 and 10-60=2 feet=the depth of the drain. 



C is 50 yards from B, so -60 must be added to 10'60, 

 making 11 '20. 



Ground level at C'=::=13.70. Difference between 13-70 

 and 11-20=2-50=2 feet 6 inches=depth of drain at G. 



A section of the drain is made thus : 



The datum-line is drawn corresponding with the length 

 of the drain on a scale of, say, 1 inch per 50 yards. 



The distances of each point must be marked off on this 



line and perpendiculars set up at each point (the scale of 



depths may be 1 inch per 10 feet), the figures for each 



point marked off on them, and the points of each line 



joined. 



A Al \ B D 



Level of the ground 



above datum-line .. 10-00 12-85 12-60 13-70 15-07 

 Level of the drain above 



datum-Une .. .. 10-00 10-00 10-60 11-20 11-80 



Depth of drain .. — 2-85 ' 2-00 2-50 3-27 



Rn-ia 



V 

 ISOydS 





ftsfow Li**? 



Scale I f^ 



U. 2S'0 



