HEIGHT MEASURING. 



19 



In this case L may be measured along the surface of the soil, 

 whether it be level or slanting, while I and h are read off on 

 the instrument. 



The number of hypsometers based upon the above theories 

 is very large ; some being used with stands, others without. 

 Only the latter are really useful for forest operations. Most 

 in use are those by Faustman, Weise, and Christen. Others 

 are those by Hossfeld, Winkler, Bose, and Klaussner. A 

 very simple instrument is the measuring board by Konig. 



.1* 



Fig. 11. 



Measurements made with the above mentioned hypsometers 

 are liable to yield inaccurate results, owing to the following 

 causes : 



(1) Inaccurate reading owing to the unsteadiness of the 



plumb line in windy weather, or in consequence of a 

 shaky hand. 



(2) Inaccurate measurement of the base line. 



(3) Slanting position of the tree. 



Other things being equal, the most accurate results are ob- 

 tained if the distance of the observer from the tree equals the 

 height of the tree. 



c 2 



