27 



find in the area table to be equal to 27.22 square feet. Dividing 2,534.16 

 by 27.22 we obtain a quotient equal to 93.1. Multiplying 93.1 by 832, 

 the volume of the sample trees in cubic feet, we determine the volume 

 of the oak to be 77.459 cubic feet; or, multiplying the quotient, 93.1, by 

 3,360, the number of superficial feet furnished by the sample trees after 

 they ijassed through the mill, we obtain 312,816 feet B. M., which is the 

 total amount of merchantable lumber contained in the oak of our hard- 

 wood grove. 



The volume of the other species may be determined in the same man- 

 ner, and then the growing stock of the grove is obtained by adding 

 together the volume of the trees of all its species. 



DETERMINATION OF THE GROWING STOCK BY MEANS OF SAMPLE 



AREAS. 



It is always possible to find in a forest a small area the contents of 

 which represent an average proportion of either the whole forest or of 

 at least a considerable portion of it. The volume of this small area may 

 be easily and rapidly determined by one of the methods above described. 

 Such an area may be called a sample area, and the contents found on it 

 per acre may be called an acre yield. If the small area represents an 

 average condition of the whole forest, then, in order to obtain the grow- 

 ing stock of the whole forest, the acre yield of the sample area need 

 only be multiplied by the number of acres in the forest; when the sam- 

 ple area represents only the conditions of a portion of the forest, then 

 the acre yield multiplied by the number of acres involved in that por- 

 tion gives only the growing stock of that portion, and for other portions 

 of different conditions corresponding acre yields must be found. 



Example : Let a forest containing 100 acres have three distinct forest 

 conditions represented, each by 40, 35, or 25 acres, respectively. Let 

 the 40 acres be represented by a sample area of one-half an acre; the 

 35 acres by a sample area of 1^ acres, and the 25 acres by a sample 

 area of one-fourth an acre. Let the volumes of the sample areas 

 determined by one of the methods given above be — 



(1) The volume of the one-half acre equals 3,000 cubic feet and 12,000 B. M. 



(2) The volume of the U acre equals 12,000 cubic feet and 48,000 B. M. 



(3) The volume of the one-fourth acre equals 2,500 cubic feet and 10,000 B. M. 



The acre yields of the corresponding portion of the forest equal then — 



(1) 3,000 cubic feet and 12,000 feet B. M. multiplied each by 2 equals 6,000 cubic 

 feet and 24,000 feet B. M. 



(2) 12,000 cubic feet and 48,000 feet B. M. divided each by 1^ equals 8,000 cubic 

 feet and 32,000 feet B. M. 



(3) 2,500 cubic feet and 10,000 feet B. M. multiplied each by 4 equals 10,000 cubic 

 feet and 40,000 feet B. M. 



The volume of an acre of the forest condition represented by the 40 

 acres equals 6,000 cubic feet and 24,000 feet B. M.; multiplied each by 

 40 equals 240,000 cubic feet and 960,000 feet B. M. 



