The Gaining Bates of Tree-Growth. 



81 



under careful management, and very considerable at the end of the 

 appointed periods. 



288. To illustrate the rates of this increase, we will suppose that 

 the annual rings of growth in a tree are of equal 

 width. As a matter of fact, they are much 

 wider in some years than in others, but, for il- 

 lustration, we will consider them as uniform in 

 thickness. Counting from the center outward, 

 we would have the numbers 1, 2, 3, 4, 5, etc., 

 showing the years of growth. The areas of 

 these circles (each including those within it) are 66. concentric Eings of 

 as the squares of these numbers, viz., 1, 4, 9, ^^^ '^°^ 



16, 25, etc. By subtracting each of these from the preceding, we 

 have the series, 3, 5, 7, 9, etc., that represents the gain of each year 

 upon tlie year preceding. 



289. These relative rates may be shown by a simple diagram, in 

 which the gain in diameter is represented by the 

 lower diagonal, and the gain in area by the upper 

 one. The numbers along the bottom in this figure 

 represent the years, and those on the margin units 

 of quantity. The rates thus shown are actually 

 maintained for many years, while young, but be- 

 come less as the trees approach maturity. They 

 show the waste from cutting thrifty young timber 

 at the period of most profitable growth, and 

 should lead us to spare it, when possible, till it has ■Diame'tfrs and of 



1 'J. r n 1 Sectional Areas. 



gamed its full value. 



290. But these gaining rates are only those of sectional area ; the 

 trees are at the same time gaining in height, and the timber is gain- 

 ing in quality and value per euMc foot, as it grows older, for it can 

 then be applied to more important uses, when it has grown to large 

 size, besides being of intrinsically greater value, when fully mature. 



291. The planting of forests, and their management afterwards, 

 till grown to full maturitj-, can not be followed from fixed rules as 

 to time and manner, but the business must be conducted with an 

 intelligent understanding of the conditions that exist, and the cir- 

 cumstances that may influence their growth. Under equal circum- 

 stances, as in aU other forms of business, the man who pays the 

 closest attention to his afiairs, and neglects nothing, will, at the end 



