Forest Mensuration 195 



from the right angle. Drive a similar nail at the opposite 

 end of the six-inch strip. Mark the quarter and half 

 inch divisions on the short strip with small notches. Now 

 drive a nail through the center of the six-inch strip and 

 nail the triangle to the end of a pole five feet three inches 

 long, the opposite end of which has been sharpened. 

 The instrument is now complete. To measure the clear 

 length of a standing tree, pace off a distance of fifty feet 

 from the base of the tree, taking care to keep on the same 

 level. Stick up the staff in the ground so that the graduated 

 arm is parallel to the trunk of the tree, which must be in 

 sight along the line AB. Since the staff is five feet long, 

 the line AB will strike the tree five feet from the ground. 

 The observer, with his eyes at A, looks at the point to 

 which he wishes to measure and notes, by means of the 

 nails and notches, where his line of sight crosses the 

 graduated arm. The reading on the graduated arm in 

 inches gives the height of the observed point above the 

 ground in feet, each inch representing ten feet. By using 

 the sight at D instead of A, the distance from the tree 

 to the instrument may be reduced to twenty-five feet. 

 This is convenient in the case of thick brush preventing 

 a longer sight, but is more liable to error and harder on 

 the neck of the observer. Should it be desirable to meas- 

 ure something over fifty feet high, place the instrument 

 one hundred feet from the tree and double the readings. 

 Such an instrument should be used by the estimator to 

 measure the number of logs in a tree, till he trains his 

 eye to make an accurate estimate without it. Usually an 

 accurate enough estimate can be made by standing a 

 ten- or sixteen-foot pole up against the tree. 



