184 TIMBERS AND THEIR USES 



quality of soil, with its capacity for tlie growth, 

 taking the land by ranges and even compart- 

 ments, if there is much variation. The dominant 

 timber, or if it is an evenly mixed forest, that 

 kind on which the working is to be based, is 

 noted, and the average rate of growth ascer- 

 tained, for the purpose of grouping the belt or 

 parcel into " age classes," which usually com- 

 prise twenty years, so that the growth of 1 to 

 20, 20 to 40, 40 to 60 years, etc., forms- a dis- 

 tinct class for utilization. The valuator also 

 carefully records the density of growth and all 

 thin or open spaces. He is further required 

 to form an opinion on the spot as to the best 

 mode of treatment for each parcel, as regards 

 its promise and fitness for early or late fellings, 

 and to estimate the thinnings which should 

 come out ■ during a period of twenty years. 

 From this information a table is prepared show- 

 ing the area of each parcel, according to its 

 age or " age class," and this again forms the 

 basis for a complete timber map, showing the 

 existing conditions of the forest, the dominant 

 timber in each parcel being marked by different 

 colours, mixed trees by signs " and the age of 

 trees by shades of colour." 



On the completion of this work plans for the 

 future arrangement of the age classes is taken 

 in hand, so that when the forest is brought into 



