6 PRELIMINARY MEASUREMENTS 



5. In order to develop proficiency in securing heights by eye now estimate 

 the heights of a large number of trees by eye. Check each estimate 

 with the hypsometer found to be the best. 



D. References. — Numbers 4, 8, 10, 11 and 12. 



PROBLEM 4. (Office) The Construction of a Dendrometer. 



Explanation. — The object of this problem is to illustrate the principles under- 

 lying the construction of dendrometers such as the Biltmore stick or other 

 similar diameter measures, and to construct an instrument which can V)e used 

 in later field problems. 

 The formula for securing the length of graduatioo of the Biltmore stick is: 



25D 



V252+25D 

 where a: = the length of graduation; 

 D = the diameter of the tree ; 



25 = distance in inches from the eye of the observer to the circumference 

 of the tree. 



Directions. 



A. Method of Procedure. 



1. Draw a diagram illustrating the principle of the Biltmore stick de- 



scribed in Problem 2. 



2. Work out the complete algebraic proof of the formula given above for 



securing the length of graduation of the stick in terms of the 25-inch 

 distance and the diameter of the tree. 



3. Compute the exact length of graduation for each two-inch diameter 



class for trees from ten to sixty inches. 



4. Select a hardwood stick approximately | inch scjuare and of a suitable 



length, and bevel off one side. Upon this side mark the graduations 

 just computed, 



B. References. — Numbers 1, 2 and 3. 



C. Discussion. 



1. In what respects would the proof of the principle of the tree cross 



mentioned in Problem 2 be different from that for the Biltmore 

 stick? 



2. Give a list of the advantages and disadvantages of the tree cross as 



compared with the Biltmore stick. 



PROBLEM 5. (Office) The Construction of a Hypsometer. 



Explanation. — The object of this problem is to illustrate the principles 

 underlying the construction of a hypsometer such as the Christen or the 



