HEIGHT MEASUREMENT 165 



black and white, which target is fixed horizontally at any 

 point desirable at the base of the tree. 



" The instrument itself consists of a piece of metal about 

 18 inches long and ij inches wide, containing a longi- 

 tudinal slot about | inch wide and 17 inches long. The 

 edges of this slot must be strictly parallel. Its actual 

 width is entirely irrelevant from the mathematical stand- 

 point. 



" It might be stated that any stick or pole, even a walking- 

 cane, having parallel edges, will answer the purpose of 

 establishing and measuring upper diameters. The Bilt- 

 more pachymeter is merely a device convenient to handle. 



" The observer holds the pachymeter pendulum fashion 

 by the hand of the outstretched arm in a position parallel 

 to the tree trunk, and moves the instrument backward 

 or forward until the edges of the slot cut off even with the 

 desired diameter shown on the target. Then, the eye 

 following upward along the trunk and sighting through 

 the slot, that point on the tree bole is readily obtained 

 where the bole cuts off with the edges of the slot. The 

 position of this point above ground can be ascertained 

 easily with the help of any hypsometer." 



SECTION III 

 HEIGHT MEASUREMENT 



There are many methods of measuring the height of 

 trees. As serviceable as any are the following: 



1. Windfalls are often of great assistance in ascertain- 

 ing the height of timber. 



2. A pole 15 or 20 feet in length may be set up along- 

 side the tree to be estimated and then, standing some dis- 

 tance away, the cruiser may run his eye up the tree and 

 judge how many times the length of the pole will be con- 

 tained in it. A pencil held erect at arm's length in range 

 of the pole and then run up the tree will help the eye in 

 making the judgment. 



3. A cane or staff may be used on the principle of similar 

 triangles. Hold the staff firmly in the hand with the arm 

 straight and horizontal. Swing the end of the staff down 



