the: quality op coniferous timber. 



Ill 



25 feet higher up. If, during the next forty years, such a tree 

 forms rings of an average breadth of -| inch at the height of 



29 feet, and of i^^^h at the height of 4 feet, it follows that, 

 when seventy years old, the diameter at the upper point of 

 measurement will be 13 inches, while at the lower it will be 

 17 inches. Suppose, further, that during the succeeding forty 

 years the breadth of ring at 29 feet from the ground averages 

 Jg inch, while 4 feet from the ground it is ^.j inch, it is evident 

 that when the tree has reached the age of 110 years its diameter 

 at the upper point of measurement will be 18 inches, while 

 4 feet from the ground it will be 19J inches. Eegarded from the 

 point of view of form, the ratio of 3 : 12 is not nearly so favourable 

 as 13 : 17, nor is 13 : 17 so favourable as 18 : 19^. All through the 

 life of this tree the shape has been undergoing steady improve- 

 ment, so that, in " squaring " the bole in a saw-mill, the 

 proportion of wood wasted in slabs will be much less at the age 

 of 110 years than it would have been at the age of seventy. For 



30 feet lengths of planks or battens the wood sacrificed in slabs 

 for each 100 cubic feet of manufactured timber, at the age of 

 seventy years, would be about 108 cubic feet, whereas at the age 

 of 110 years it would only be about 71 cubic feet. 



Although in crowded woods the individual trees are smaller 

 in size than in woods that have been kept opener, still the 

 amount of useful timber in the former case will always be greater 

 than in the latter, provided the crowding has not been overdone. 

 By interposing an uninterrupted stratum of foliage between the 

 sun and the earth, the maximum amount of light is made use of 

 for the decomposition of carbonic acid gas and the formation of 

 wood ; whereas, if the stratum be broken, some of the sun's rays 

 escape, and are lost so far as the production of timber is con- 

 cerned. Suppose the case of any given area of land that can 

 just afford space for the unrestricted growth of 100 trees fifty 

 years old. If, instead of 100 trees, such an area had been stocked 

 with any greater number, say 101, then the amount of material 

 yielded by the stem and branches of each individual tree would 

 be somewhat less, although the gross yield might have suffered 

 no diminution. Suppose, further, that instead of having 100 

 trees on the area one had had 150, it is apparent that the op- 

 portunities for individual development in this case will be 

 very much curtailed. But when the space for development is 



