KERRY WOODS. 



35 



under which the crop has been grown. The following table, 

 showing the limits of variation for woods 43 years old, has been 

 compiled from Schiffel's figures : 



From this it appears that the values of the different factors may 

 overlap to a considerable extent. For instance, a crop of mean 

 height 52 ft. at 43 years, though most likely to fall nearest quality 

 Class IX., might conceivably fall nearest Class X. or VIII. It is 

 therefore necessary, in making an estimate of the quality of the 

 locality in which a crop is growing, to consider all the factors 

 together. 



Schiffel indicates in his introduction to the tables a number 

 of properties of the spruce which are not very generally recognised 

 in this country. The chief of these is that spruce shows a greater 

 height-growth increment in open, than in dense, crops. 



With regard to the use of his tables, the following points should 

 be noted : 



(a) On soils of the same quality, with crops of the same age, 

 the height and diameter are greatest, but the form factor is 

 smallest, in the case of the least canopy density. 



(b) The total basal area and total volume per acre are least in 

 the case of light canopy conditions until the crops are 100 years 

 of age, when the three canopy classes merge into one. 



(c) The number of trees per acre is least^ in the case of the thin 

 canopy class, and greatest in the case of the dense canopy class. 



For each canopy class nine quality classes are prepared, of 

 which III. is the worst, and XI. the best. The number indicating 

 the quality class is arranged for convenience as regards the metric 

 system, since it is the number, in hundreds, of cubic metres 



C 2 



