326 DETERMINATION OF THE YIELD. 



It will thus be seen that the volume of marketable growing 

 stock was ascertained, and that this was removed at such a 

 rate as at least to maintain it ; in other words, the maximum 

 yield was fixed at that quantity of marketable timber which 

 reached maturity every year, thus at least maintaining the 

 mature growing stock in the forest, and utilizing the actual 

 increment. With the view of utilizing an excess of mature 

 material, it was laid down that if the proportion of first class 

 trees appeared excessive as compared with the younger classes, 

 extra cuttings might temporarily be made, and vice versa, 

 hence the method is one based on increment and growing 

 stock. Various safe-guards were added, such as an allowance 

 for trees which it did not pay to extract ; where few second and 

 third class trees existed, some first class trees were left standing, 

 to provide seed for regeneration; immediately along the banks 

 of streams cuttings were made very sparingly, &c. 



For the rest, the method leaves a free hand to the forester, 

 who arranges the cutting with due regard to sylvicultural 

 requirements and a proper succession of the different coupes. 



The [number of trees of the several size classes were 

 originally ascertained by measuring or counting them along 

 narrow strips, generally 100 feet broad, laid through the 

 forest along the line of march (so called "valuation surveys"). 

 From the contents of these sample strips (or plots), the 

 contents of the blocks, or forest, were calculated. The rate of 

 increment was determined by counting the concentric rings on 

 a sufficient number of stumps, thus ascertaining the average 

 number of years which a teak tree takes to reach the limits of 

 the several size classes. 



The original method was subsequently further elaborated, 

 so that the sample plots are now systematically arranged over 

 the area, with the view of obtaining correct data for the 

 number of trees in the several blocks of the forest. The 

 cuttings, based on these data, were also localized : in other 

 words, an area check was added to the calculated yield, so 

 as to guard against overcutting. 



