Methods of Mensuration. 71 



the original number of pegs that had been taken out, 

 the difference gave the number of trees in each diameter 

 class, and by multiplying the average cubic contents of 

 a measured sample tree in each class by the number in 

 the class its volume was found. 



The method, often employed at present, of ascertain- 

 ing by tally the diameter classes on strips forty to 

 fifty paces wide, the so-called strip method, was described 

 by Zanthier in 1763. 



These measurements were usually confined to sample 

 areas, the use of such being already known in 1739. The 

 contents of the sample area, if a special degree of ac- 

 curacy was desired, was ascertained by felling the whole 

 and measuring. 



Oettelt, of mathematical fame, was the first to publish 

 something about the determination of the age of trees 

 by counting rings, although the practice probably ante- 

 dates this account. He knew of the dependence of the 

 ring width on the site and on the density of the stand. 



It seems that long before this time the French had 

 made the determination of yield in a more scientific 

 manner, Eeaumur reporting in 1721 to the French 

 Academy comparative studies of the yield of coppice and 

 of volumes of wood. 



Oettelt, too, laid the foundation of forest financial 

 calculations when he ascertained the value of a forest 

 by determining the value of an acre of mature wood 

 the oldest age class and multiplying it by half the 

 acreage of the whole forest, suggesting the well known 



expression for the normal stock ( ^o ) ^^^^ after to be 

 developed by an obscure Austrian tax collector. 



