60 



The following is an example of tlie sort of calculation that vonld be made to 

 ascertain the most profiiable size for felling for fuel :— 



DesGription of 

 mnterial 

 and its thickness. 



Fuel in billets 

 of over 10" . 



Fuel in billets 

 of 10" to 6" . 



Fuel in billets 

 below 6' . 



Sellin? price 

 per 100 cubic 

 feet stacked. 



Cost of cutting 



and extracting 



per 100 cubic 



feet stacked. 



5-89 

 5-32 

 3-50 



1-6 



10 



1-51 



Net price per 



100 cubic feet 



stacked. 



4-32 



1-99 



BedQcing 

 factor per 



100 cabic 

 feet 



stacked. 



63 



0-57 



0-37 



Net price 



per 100 



cubic feet 



solid. 



681 



7-58 



5-38 



Bevises. 



It is evident from this that, assuming the average annual increment to remain 

 fairly constant, there is every financial advantage in growing trees that will faruish 

 billets of from 10" to 6" in diameter. 



The size having been decided it only remains to deter- 

 mine the age at -which the trees attain that size. This is 

 often exceedingly difficult in India, owing to the ring mark- 

 ing being indistinct, and also to the fact that several species 

 form more tiian one concentric ring of wood each year. In 

 such cases the rate of growth can only be determined when 

 trees of known age are to be found. The following remarks 

 ap})ly, therefore, only to those species which form a single 

 distinct concentric ring of wood each year. 



In the case of felled trees, the required age is found by 

 counting the number of concentric I'ings on the section of 

 the stool or base of the trunk. To ascertain the diametral 

 increase of growth the countings should be made along 

 several radii and the mean should be taken. Where necessary 

 the rings in the sap wood and barK should be separately count- 

 ed and recorded, and all great extremes should be rejected. 

 Usually, with a view to determine, as is often necessary in 

 order to calculate the possibility in selection-worked forests, 

 the number of years required by trees to pass from one size- 

 class to another, the average number of rings included in the 

 diameter of each size-class is separately recorded. 



For a good many species the age may be very roughly 

 determined without felling the trees by the use of the little 

 instrument known as Presxler's borer, a hollow gimlet 

 which, on being screwed into the trunk and then withdrawn, 

 extracts a small cylinder of wood on which the ring- markings 



