THE 



MENSURATIQ]^ OF TIMBER 



AND 



TIMBER CROPS. 



Chapter I. 



On the measurement of heights, lengths, sectional areas, girths, and 

 diameters of stems and trees. 



lustrumeuts for measuring the heights of trees are of two 

 kinds : — 



(i) those which give the height without calculation, their con- 

 struction being based on the principle of similar triangles ; 

 and 

 (ii) those which give the angles made with a horizontal line by 



the lines of sight to tlie top and foot of the tree. 

 Instruments of both classes are very numerous, but the two most 

 convenient are — Faustman's Mirror Hypsometer, and Weise's 

 Height Measurer. They both agree in having, at right angles to 

 the line of sight, a sliding graduated rule, which, before an observ- 

 ation is taken, is so adjusted as to represent proportionally the 

 distance of the observer from the tree to be measured, and f I'om the 

 top of which hangs a plummet. Moreover, on the body of the 

 instrument, runs a graduated scale similar to that on the sliding 

 rule, so that when the instrument is directed to the top or bottom of 

 the tree, the plummet line crosses the scale at the point which 

 gives the figure expressing the vertical distance of the top or bottom 

 of the tree, as the case may be, above or below the height of the 

 observer's eye. The difference between' the two instruments is, that 

 whereas, in Faustman's Hypsometer, this figure is at once read in 

 !i mirror as soon as the top or bottom of the tree is bisected by the 

 instrument; in Weise's Measurer, which is always made of metal, 

 the graduations of the scale form a succession of serratures, whii'U 



A 



