38 GROWTH OF WOOD IN DIFFERENT YEARS. 



cedar, and red cedar, tbe group planted on level ground, when fully 

 grown, would appear highest in tbe middle, as if standing upon a mound. 

 A belt of Cottonwood around the margin would afford shelter while 

 needed, and should be cut away when fully established. 



Orchard belts of Scotch piue, white pine, Norway spruce, and larch, 

 have been recommended, and the use of screens on the north and west 

 sides has been mentioned as desirable. But from observation and in- 

 quiry it) the prairie States of the West, we are convinced that the most 

 injury to fruit-trees has resulted from hot, drying winds from the south- 

 west, and that a screen against these is quite necessary. 



For a mound of deciduous trees on level ground, a central plat of 

 European larch, surrounded by belts of the American larch, soft maple, 

 honey-locust, black oak, wild cherry, hickory, iron-wood, crab-apple, 

 and wild plum, has been suggested. But these combinations are too 

 variable for a general rule, and in each locality the planter, with a 

 knowledge of the habits of growth of the trees at his command, will be 

 able to vary them to suit his purposes. 



RELATIVE VALUE OF GROWTH AT DIFFERENT AGES. 



It is very often found that the layers of annual growth are thicker 

 when young, and that they progressively diminish in width as they in- 

 crease in size. The coniiers of the Ilocky Mountains, and elsewhere, 

 olten show this fact in a conspicuous manner. 



In other kinds, as the elm, the wood is more profitable when cut 

 young, because the timber deteriorates in quality with age. The inner 

 ■wood of a large elm tree is comparatively spongy and weak. But in 

 other woods, as the oak, the value increases in a gaining progression 

 with age, and large timbers are worth more per cubic foot than small 

 ones, because they can be applied to more important uses when of 

 larger size. The annual revenue from the growth of au oak tree, of the 

 species commonly used in ship-building, has been very carefully de- 

 termined from the mean of a great number of records in France, and is 

 stated as follows: 



Fr. c. 



Tree 50 years old 10 per annum. 



Tree 100 years old 80 per annum. 



Tree 150 years old 2 00 per annum. 



Tree 200 years old 4 00 per annum. 



The value per cubic foot, therefore, increases with the size of the tree, 

 and (for straight hewn timber) the length of clean trunk below the 

 branches. 



GROWTH OF WOOD IN DIFFERENT YEARS. 



Every one who has closely examined the layers of wood growth on a 

 transveVse section, must have noticed that considerable difierence occurs 

 between the growth of different years. We have here, in fact, a record 

 of the combined influences of climate upon wood growth. Soil, aspect, 

 and other circumstances of a permanent kind may largely influence 

 different trees of the same species, but in a given tree, one year with 

 another, they change so little that we may scarcely be able to appre- 

 ciate their effect ; and in comparing the thickness and quality of the 

 layers formed in different years, we may regard them as au indication 

 of the effects of temperature, moisture, winds, and other variable ele- 

 ments of the climate. 



Before trusting the conclusions to which a comparison might lead, it 

 would be most desirable to know the laws of growth under seasons recur- 

 ring with perfect regularity. We would doubtless find the layers in 



