Forest Mensuration 23 



Instruments (hypsometers) for height measuring are sold in many 

 forms. The following are frequently used : Rudnicka's instrument ; Press- 

 ler's "Measuring Jack;" Faustmann's "Mirror Hypsometer;" Weise's Tel- 

 escope; Koenig's "Measuring Board;" Brandis' "Clinometer;" Klausner's 

 instrument; Christen's "Non plus ultra." 



Compare Woodman's Handbook, pages 136 to 137, for staff method; 

 page 138 for Faustmann's; page 140 for tangential clinometer; page 143 

 for mirror clinometer. 



Christen's stick is not accurate enough for the measurement of trees 

 over loo feet high. It does not require the measurement of distances. Its 

 form is improved by Pinchot 



PARAGRAPH XXXIV. 



FACTORS INFLUENCING THE EXACTNESS OF HYPSOMETRICAL OBSERVATIONS. 



The best results are obtained if the distance between tree and observer 

 equals the height to be measured. In sighting towards the spreading top 

 of a hardwood tree, the observer is apt to overrate the height, the tip 

 being buried in the spreading crown. The line of sight strikes the edge 

 of the crown instead of striking the apex of the crown. 



Timber cruisers are usually satisfied to determine the number of logs 

 obtainable from the bole instead of determining the length of the bole. 

 As a matter of fact, where the tree furnishes saw logs only, the total 

 height of the tree is a less reliable indicator of the total contents than 

 the length of the merchantable bole. 



Instruments like Faustmann's, Koenig's and Pressler's cannot be used 

 in windy and rainy weather. Dense undergrowth and dense cover over- 

 head render exact measurement impossible. 



PARAGRAPH XXXV. 



INDIRECT MENSURATION OF DIAMETERS. 



The following instruments are used to measure the diameter of the tree 

 at any point of bole: 



a. Winkler, an addition to Koenig's measuring board. 



b. Klausner. 



c. An ordinary transit. 



d. Wimmenauer's telescope. 



PARAGRAPH XXXVI. 

 PRESSLER'S TELESCOPE. 



Pressler's telescope is used to find the "guidepoint" and the "rectified 

 height," as defined in Paragraph XXVIIL, 3. The diameter chest-high 

 is taken between the nails at the end of the instrument. Then the tele- 

 scope is pulled out to a length double the original, divided by the cosin 



