168 FIRST BOOK OF FORESTRY 



we need not remember anything more about it. Then we 

 go to station No. 2, which is twenty rods from No. 1, and 

 so on, until the "forty" is done. To have our note- 

 books orderly we should have them lined and arranged 

 somewhat like the sample on the opposite page. 



Whether the diameters are estimated or measured, it is 

 better to go by even inches, as is shown in the scheme, 

 but it is not necessary to measure by one inch, unless 

 the number of trees is very small. 



When the "forty " is finished we add up and put on the 

 same kind of sheet all the totals. Then we can calculate 

 the amount of wood very much closer than is ordinarily 

 done. First we find the amount of saw timber in the logs 

 in the way explained before. Then we calculate the real 

 volume of the wood in the following way : 



Suppose the twenty-four-inch trees are generally about 

 ninety feet high (estimated or measured) and that they 

 cut three logs each, so that they cut about five hundred 

 feet B.M., as in our example. Then we look up the area 

 of cross section of the tree in the table (Appendix II) 

 and find that a tree twenty-four inches in diameter has 

 an area of 3.14 square feet. If the tree were simply a 

 cylinder of wood, we would need only to multiply this 

 number of 3.14 with the height of the tree to find the 

 volume in cubic feet. But the trunk of the tree tapers, 

 and tapers irregularly, so that not even the contents of the 

 trunk can thus be calculated. In working up many trees 



