THE DOUGLAS FIR IN SCOTLAND. 



237 



silver fir, and the highest form figures which can be expected may 

 perhaps be placed as follows : — ■ 



At the age of 32 years, . . . = -39 



,, 50 ,, . . . = -38 



,, 75 „ . . . = -38 



100 „ . . . = -37 



1-25 ,, . . . = -36 



140 ,, . . . = -35 



By utilising the figures thus estimated, the following table for the 

 Douglas fir has been calculated : — 



Let us now compare the volume of the Douglas fir with that of 

 the silver fir : — 



This table indicates that under a rotation of up to about ninety 

 years the Douglas fir, owing to its more rapid development in early 

 growth, yields larger returns of solid wood than the silver fir. 

 Under a rotation of 90 to 120 years the returns in volume are 

 about equal. Under a rotation of more than 120 years the 

 Douglas fir will again yield larger returns of volume than the silver 

 fir. The latter is of little consequence in this country, because no 

 landed proprietor would think of •s\'orking his plantations under a 

 rotation of more than 120 years, unless he had a particular fancy to 

 see large trees on his estate. Attention must also be drawn to the 



VOL. XII., PART II. Q 



