ESTIMATING THE TREES IN THE WOODLOT 183 



than a half inch thick. For most trees an inch should be sub- 

 tracted from the diameter outside the bark to allow for the 

 thickness of the bark. The diameters inside the bark at the 

 tops of the logs above the butt log must be estimated by the 

 eye. The upper logs are much smaller usually than the butt 

 log. The first log or butt log in a tree is the important log 

 in estimating and will be found to contain a much larger 

 amount of board feet than any log above. If the diameter 

 of the butt log is measured accurately the diameters of the 

 upper logs can safely be estimated by the eye. A knowledge 

 of the diameters of upper logs as compared with butt logs 

 can be obained by measuring trees that have been cut or blown 

 down by the wind. 



When the length and top diameter of a log is known its 

 contents in board feet can be found from a log table or by 

 the simple rule of thumb already described: for logs that are 

 1 6 feet in length, if 4 inches are subtracted from the top diam- 

 eter and the result squared it will give the number of board 

 feet in the log according to the Doyle Rule, and for logs of 

 other than 1 6- foot lengths they are figured as though 16 feet 

 long and the part of the scale taken that the length of the 

 log is of 1 6 feet. 



In estimating the contents of each log in board feet in this 

 way it should be noted whether the logs are perfect or not. 

 Log rules and the rule of thumb mentioned give results for 

 perfect logs. Most logs have imperfections and allowance 

 must be made for them. No rules can be laid down for doing 

 this, but any one with good judgment can make a fairly accu- 

 rate deduction. 



In this way the board feet should be found for each log 

 in the trees in the woodlot. The total board feet will be the 

 estimate for the tract. In tallying the board feet for the logs 

 those that are of the same species of trees can be kept together 

 so that the final result will give an estimate for each kind of 

 wood. 



