56 



ever, the financial rotation is finding more favour in the eyes of foresters. Large timber, 

 on account of the more extended use of iron for shipbuilding and in engineering struc- 

 tures, it is not now so indispensable as it was formerly, and unless it is much more 

 useful than small timber, there is no advantage in growing it. In South Africa large 

 timber is still less necessary than in Europe, certainly not sufficiently so to warrant its 

 production at a comparative loss. The larger trees found in our native forests are 

 invariably cut up into small lumber, and the interests of the country would be served 

 best by providing cheap rather than large timber. Where timber does not increase 

 sensibly in value or utility, per unit of volume, from the time it becomes large enough to 

 be cut into lumber, the maximum return is given by reaping it at that time ; for the rate of 

 profit would otherwise steadily diminish for ever afterwards, since the yearly acre incre- 

 ment cannot vary widely. For instance, assuming that the yearly acre increments remain 

 constant, and that the wood does not increase in value per unit of volume, as it becomes 

 larger, and using a 34 per cent, rate of interest in calculating the cost, to the Govern- 

 ment, of deferred returns, it is found that the present value of the prospective returns 

 increases rapidly with the length of the rotation up to a maximum at 29 years, after 

 which it steadily decreases, being reduced to half in the 78th year. Now, the normal 

 value of the timber is only reached when it has become convertible into lumber, and as 

 this usually happens after 29 years, any further lengthening of the rotation would 

 decrease the rate of profit. 



The experience of sawyers shows that, to be convertible into lumber, trees should 

 have reached a diameter of 18 inches near the base ; and taking into account the greater 

 waste in small logs, the most useful and convenient size would be a diameter of 24 inches. 

 There are other reasons which make it desirable to aim at producing timber of the latter 

 size : (a) the trees in the best managed forest cannot be made to grow quite regularly, 

 but by adopting a mean diameter of 24 inches, even the smaller trees will probably be 

 large enough to be utilized ; (6) the greatest mean acre increment per year will be 

 approached, if not reached ; (c) trees of medium growth, like those of our native 

 forests, would have an age of from 80 to 120 years when reaching the larger dimension,, 

 and would be fertile enough to ensure natural reproduction by seed. European trees do 

 not begin to seed abundantly before 50 to 80 years, according to the species, and it is 

 under old trees that the best young growth is found. 



The length of the rotation to be adopted will vary according to the rate of growth 

 of the trees and the mode of treatment. The rate of growth is not well known, but a few 

 measurements of the growth of native trees taken at Knysna since 1882, which I publish 

 in Appendix V., go to show that the rate of growth of Yellowwood and Stinkwood may 

 be averaged at 0'21 inches in diameter per annum. At this rate, trees from 18 to 24 

 inches would require for their growth 86 to 115 years. But it is quite likely that in Natal the- 



