MEASUREMENT 



151 



a level with the top of the smaller pole. Note 

 where these imaginary lines cross the longer 

 pole and measure the distance between them. 



J5^ is the height of the tree, D the top of 

 the smaller pole 5 feet from the ground, 6 the 



B 



longer pole 3 feet in front of D, then BC : he:: 

 DC :Dc. Assume that DC, the distance of the 

 observer's eye from the tree, is 30 feet and be 



is 3 feet, then BC = -A^ = 30, and C^ is 



o 



equal to the height of D ; therefore BA = 

 30 + 5 = 35 ; ov B A may be found by taking an 

 imaginary line from D to the base of the tree, then 



