58 



it reached the height of the second section (34 feet) in the course of 27 

 years (age of tree minus age of second cross section), etc. Making an 

 allowance of six years which was required by the tree to attain the 

 height of the stump (2 feet), the following were the heights reached by 

 the tree at corresponding ages : 



A height of 2 feet in 6 years. 



A. height of 18 feet in 17 years. 



A height of 34 feet in 27 years. 



A height of 50 feet in 39 years. 



A height of Q6 feet in 52 years. 



A height of 82 feet in 70 years. 



A height of 99 feet in 94 years. 



A height of 114 feet in 133 years. 



A height of 129 feet in 164 years. 



A height of 147 (total height) in 255 years (total age). 



These figures are used for constructing a curve of height growth as 

 follows: Take cross-section paper (see fig. 14) and let the horizontal 

 line AB reju'esent the age of the tree and the vertical line AO its cor- 

 responding height. Locate each of the above 10 points on the cross- 

 section paper with reference to age and height lines and connect them. 

 The curve thus obtained will represent graphically the height growth 

 of the average tree of the group. 



DIAMETER GROWTH. 



The progressive development of the diameter on each of the cross 

 sections can be determined in the same graphical way by plotting the 

 age of the section on the horizontal line and the corresponding distance 

 from the center on the vertical line. Connecting all the points thus 

 located, a curve is obtained representing graphically the diameter growth 

 on the particular cross section of the tree. For the tree under analysis 

 nine curves should be constructed in order to stud}- the diameter growth 

 of the tree. 



VOLUME GROWTH. 



The detail measurements of the cross sections of the average tree 

 of the group enables one to determine the volume the tree had when — 



17 years old (age of tree minus age of first section). 



27 years old (age of tree minus age of second section). 



39 years old (age of tree minus age of third section). 



52 years old (age of tree minus age of fourth section). 



70 years old (age of tree minus age of iifth section). 



94 years old (age of tree minus age of sixth section). 

 133 years old (age of tree minus age of seventh section). 

 164 years old (age of tree minus age of eighth section). 



The volume the tree had when 17 years old is determiiied as follows 

 (see fig. 15; cone rai) : Calculate the diameter of the central 11 rings on 

 the stump section and find in the tables (page 37) the area of its corre- 

 sponding circle. Multiply this area by the height of the stump (2 feet) ; 

 multipl}" also this area by one-half the length of the first section. 



