PLANTING. 79 



and" its rate of progress will continue superior. The silver fir increases 

 comparatively at a much inferior rate to the larch and other fast-growing 

 trees, for ten or more years, but in general it passes all these trees in 

 height and in circumference by the thirtieth or fortieth years of its growth. 

 The comparative rate of increase annually of the following forest- trees is, 

 in the average of cases, nearly in the following order: 



Poplar, for the first 50 years of growth. 



Bedford willow . do. . 25 ditto., 



Birch . . do. . 20 ditto. 



Larch . do. . 60 ditto. 



Sycamore . do. . 50 ditto. 



Pine . . do. . 60 ditto. 



Silver fir, after the first 30 ditto. 



Alder . . do. . 25 ditto. 



Locust . . do. . 15 ditto. 



Trees of slower growth, but more equal in the rate of annual increase 

 throughout their progress, are 



Elm, ash, beech, sweet chestnut, oak. 



On comparing a variety of measurements made of different trees on the 

 same soil, and also of these in soils of different natures, the increase of the 

 oak to that of the larch, at sixty-five years of growth, proved to be as 

 6 to 3.6 nearly. The silver fir stood to these in the proportions of 8 to 6 

 and of 8 to 3.6 *. 



When a tree has attained to full maturity, or to as large a size as 

 the nature of the soil and situation are capable of inducing, the annual 

 production of shoots from the extremities of the top branches is scarcely 

 perceptible. When these begin to decay, and the tree gives indications 

 of soon becoming what is called stag headed, the profitable increase 

 of timber has ceased in that tree, arid it no longer occupies the ground 

 profitably. The most profitable stage of growth, however, at which a tree 

 may be taken, must be determined by the state of the market and the 

 demand for particular produce. The only certain rule is, to ascertain the 

 annual increase of timber in the tree, and determine thereby whether the 

 value of that increase be equal to the annual interest of the sum the tree 

 would bring, if felled, in addition to the charges of the land it occupies. 



The following statement of the increase of trees at seventeen years of 

 growth in the climate of Devonshire, on a porous soil, prepared by 

 trenching, and planted in the most judicious manner, according to in- 

 structions by the Duke of Bedford, will show the comparative value of 

 different species of forest-trees, as regards their property of affording early 

 produce on a soil of the nature mentioned. 



G irt or Circumference at Girt or Circumference at 



Two Feet from the Hoot. Seven Feet from the Root, 



Popla . 41 . . 37 



Larch . 37 . . 3 



Pine . . 32J . . 2 



English elm . 32 . .26 



Silver fir . 28j . .25 



Spruce . 27 . .22 



Chestnut . 27 . . 22 



* Well-authenticated facts relative to the comparative rate of increase of wood in the 

 different species of forest-trees are much wanted. Without such facts, ascertained by 

 careful and minute consideration of all circumstances influencing the growth of the trees, 

 as soil, local climate, age, and culture, unerring or scientific principles cannot be obtained 

 to guide the practical planter. 



