THE CONSTRUCTION OF A HYPSOMETER 7 



Merritt (Biltmore Stick) and to construct an instrument which can be used 

 in later field problems. Either of the illustrations may be used. 



Illustration 1. — Construction of the Christen Hypsometer. 



Explanation. — The Christen hypsometer consists of a flat piece of brass or 

 wood with a notch near each end between which are placed graduations 

 representing heights of trees. The lengths of these graduations are secured 

 by the following formula : 



AXB 



x = 



C 



where .c = length of graduation, measured upward from the lower notch, inches; 



A = distance between notches, inches ; 



B = length of the pole, feet; 



C = height of the tree, feet. 



In using the instrument the observer holds the upper end of the instru- 

 ment suspended between his fingers, in front of his eyes and at any convenient 

 distance away. An assistant holds upright against the base of the tree a 

 pole of the certain length upon which the graduations of the instrument are 

 based. The observer obtains the height of the tree by moving towards or 

 from the tree until it is just included between the notches and then reads 

 as the height of the tree the graduation intersected by the line of sight to the 

 top of the pole. 

 Directions. 



A. Method of Procedure. 



1 . Draw a diagram illustrating the principle upon which the instrument is 



based and write out the complete algebraic proof. 



2. For finding the length of graduations of the instrument in terms of 



the distance between the notches of the instrument, the height of 

 the tree, and the length of the pole used with the instrument, proceed 

 as follows: 

 (a) Using 10 feet as the length of the pole and 12 inches as the dis- 

 tance between the notches of the instrument, work out the length 

 of the graduation measured upw^ard from the bottom notch for 

 each five feet of height for trees from 20 to 100 feet in height. 

 (6) Shape a stick 13X1 X0.25 inches with notches 12 inches apart and 

 to a thin beveled edge between the notches, and mark the com- 

 puted lengths of graduations on the beveled edge of the stick. 



Illustration 2.* — Construction of the Merritt Hypsometer. 



Explanation. — Markings may be placed upon the reverse side of the Biltmore 

 stick. It should be held upright in the hand 25 inches from the eye of an 

 observer when stationed 1^ chains from the tree. 



♦Note — A third type of hypsometer easily may be made by attaching near one corner of a 

 board ix3^x8 inches, a piece of wire which may swing as a pendulum. Graduations for tree 

 heights may then be computed and marked along the opposite long edge of the board. 



