VALUATION SURVEYS 73 
In Tables 19-22 the average diameters and heights are given 
for trees six, ten, twelve, and fourteen inches and over in diameter. 
As was the case in computing the yield in Tables 15 and 16, it was 
necessary to know the average diameters and heights of trees six 
to nine, ten and eleven, twelve and thirteen, and fourteen inches 
and over in diameter in order to obtain the totals by addition. 
The diameters were computed directly from Table 18, and the 
heights were determined in the following way: Having already the 
heights for alli trees six, ten, twelve, and fourteen. inches and overt 
in diameter, these values were entered on cross-section paper, 
laying off the diameters on the horizontal and the heights on the 
vertical lines. A curve was drawn through the points and the 
heights corresponding to the diameters in the following table were 
obtained by interpolation. 
