118 FORESTRY IN EASTERN RUSSIA. 



of two contiguous ridges were contiguous, whereby they 

 might be conjointly one-sixth of the breadth of one cleared 

 strip, but one-twelfth of two if the felling did not follow 

 each other in due succession. 



Advantages likely to follow such a method of managing 

 forests suggest themselves at once, and, as described, it 

 seems to be one which must be of easy application any- 

 where. But the practical forester who has given atten- 

 tion to my statement may have remarked that I have 

 used the expression equal or equivalent portions. Good 

 will result from the adoption of division into equal 

 portions much good, but with a large admixture of evil. 

 Equal portions are not necessarily equivalent portions, 

 and such is the variation in the productiveness of different 

 portions of a forest, from variation in soil, in exposure, 

 and in adaptation to the growth of the kind of tree which 

 happens to be upon it, that it is very improbable that 

 many portions equal in extent will be equal in produc- 

 tiveness, if any at all happen to be so ; and therefore the 

 division of a forest into equal portions will not yield 

 advantages equal to what would be obtained by the divi- 

 sion of the forest into what I have called equivalent 

 portions. 



With the attempt to do this commences the difficulties 

 of the undertaking. Equivalent partitions cannot be 

 obtained by divisions founded on equality of superficial 

 areas, neither can they be obtained by divisions 

 founded on the number of trees growing in each, or even 

 on the cubic contents of these. The soil, the exposure, 

 the kind of tree growing in different localities, the adap- 

 tation of the soil and of the exposure to the growth of the 

 kind of tree, or of trees, growing in each, the age or ages 

 of these trees, the rate of their annual increase at different 

 ages, the age or ages at which they respectively attain 

 their maximum growth, and at which they attain their 

 maximum of value, these, and twenty other points, must 

 be determined to furnish the data necessary to determine 

 equivalent partitions; and such partitions are necessary 



