88 GARDEN DESIGN 



From A to C will give -~"" + 8 + 5) 4-4-1 

 sq. ft. =(8 + 8 + 5) 4- 3 = 21 4- 3 = 7- From 

 D to F will give (-~4 + 4 + 2) 4- 4~* = (5 + 4 



+ 2) -T- 3 = ii 4- 3 = 3t 



Set up these two levels at either end and con- 

 nect. It will be noticed that the centre coincides 

 with the horizontal line at 5^. 



But whole areas and not strips are more usually 

 the problem. The system is exactly the same and 

 if one is understood the principle can be readily 

 applied. 



Obtain levels at even distances all over the 

 ground. Treat A B as a strip, also C D, E F G H 

 and I J. Add the result of A B to I J ; halve it ; 

 and add the sum of the other results. Divide the 

 total by the number of strips minus one, and the 

 mean level of the whole is the result. 



AB 

 CD 

 EF 

 GH 



U 



