MENSURATION AND SURVEYING 23 



B D 



Lay off AB and CD equal to each o'her and at right angles 

 to the line, then AC = BD. 



2. Not seen over but chained round. 



F B D H 



i-: 



Lay off the lines EF, AB, equal to each other, and at 

 right angles to the line ; range the points D, H, in line with 

 FB, and set off the lines DC, HG, equal to AB and EF, and 

 at right angles to the line FH, then C and Gr are points for 

 ranging the continuation of the line EA, and AC = BD. 



3. Seen over but neither chained across nor round. 

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