UNIVERSITY OF CALIFORNIA PUBLICATIONS 



IN 



AGRICULTURAL SCIENCES 



Vol. 3, No. 4, pp. 55-61 November 27, 1917 



A NEW DENDROMETER 



BY 



DONALD BRUCE 



There is a growing demand for a satisfactory dendrometer, or 

 instrument which will measure the diameter of trees at points out of 

 reach from the ground. An indication both of the wide demand and 

 of the requirements which such an instrument must meet may be 

 gained from a consideration of the following instances. 



In certain regions, United States Forest Service timber estimators 

 have made use of a volume table based on a diameter measurement 

 at the top of the first sixteen-foot log instead of at the conventional 

 breast-high point. This was on account of the abnormal form of the 

 badly burned butts, which made a lower measurement both uncertain 

 and a poor index of volume. Considerable trouble resulted through 

 inability to check the ocular estimates of diameters except by uncer- 

 tain methods of measuring at breast height and subtracting the esti- 

 mated taper. For such cases there is needed a dendrometer of 

 moderate precision, large range, considerable rapidity, lightness, and 

 portability. 



Many volume tables are based on a measurement of height to a 

 certain fixed cutting limit, such as six, eight, or ten inches top 

 diameter. From the ground it is often more difficult to identify this 

 point than it is to estimate its height, and considerable errors result. 

 Instruments of only a small range of sizes are needed, and in fact for 

 a given volume table, or a consistent set of tables, an instrument that 

 can be fixed and adjusted for a single diameter would serve the 

 purpose. 



Other volume tables are based on height to the limit of merchant- 

 ableness. This limit, however, varies widely in different regions, even 

 for a single species, and to use such a volume table accurately one 

 must know the top diameter corresponding with cadi value of the 

 table and estimate heights accordingly. Exactly the same type of in- 



