50 FOREST EESFRVE MANUAL. 



one log 12 feet long by 12i inches at the small end and one 10 

 feet by Hi inches. By deducting the probable thickness of 

 bark and scaling these logs by the rule, he obtains the board- 

 foot contents of the average 14-inch tree, and, multiplying 

 this by 25, has the total contents of all trees on the acre in the 

 14-inch class. By using the same process for the other diame- 

 ters and adding the results, he has the total stand per acre. 



The forest oiEcer should know the probable yield of cord 

 wood from the tops of trees of given diameter; also the 

 amount from the tops and lops of 1,000 feet of saw logs or 

 mining timber. In many cases where an estimate of both 

 cord wood and logs is required, it will be sufficient to find the 

 amount of logs and reckon the wood at the rate of so many 

 cords to the 1,000 feet. 



Given ability to judge of the contents of single trees, the 

 estimator has choice of several methods for ascertaining the 

 number of trees on his tract and therefore the total stand. 

 The simplest of these, known as the quarter-acre circle method, 

 which may be used when time does not permit more accurate 

 work, is as follows: 



The estimate is made on circles of 20 yards radius, each of 

 which contains quarter of an acre. These are taken at regu- 

 lar intervals throughout the tract and should actually cover 

 as large a portion of it as possible. Less than 5 per cent, of 

 the area is not worth doing at all. 



An experienced man can determine at a glance the area in- 

 cluded within a 20 -yard radius. An officer unfamiliar with 

 the method will insure accurac}"^ by placing a stick in the 

 ground and pacing 20 yards in several directions until the 

 size of the circle is learned. He then counts all trees within 

 the circle which are of merchantable size, estimates the con- 

 tents of the average tree or the number of trees to the thou- 

 sand feet board measure, and notes the condition of the 

 timber, per cent, clear and defective, etc. If he is familiar 

 with breast-high measurements this system should be used, in 

 which case he tallies separately the trees of different diame- 

 ters, entering them in 2-inch classes, as 12-inch, 14-inch, etc. 

 He can then compute the stand later according to the system 

 previously described. 



The figures for each circle should be kept separate, and,with 

 a diagram showing the location of the circles in the tract, be 

 forwarded with the total estimate upon the regular blank. 



