Development of Forest Mensuration. 137 



being estimated at that time. He still made form 

 claBses for the same heights, but in 1823 simplified the 

 method by assuming an average form factor for the 

 whole stand. Even in 1830 Koenig still estimated the 

 form factor, although he introduced the measurement of 

 the cross-section area and determiued the height indi- 

 rectly as an average of measurement of several height 

 classes, but Huber (1834) knew how to measure both 

 the average height and form factor by means of an arith- 

 metic sample tree. This method found entrance into 

 the practice and held sway until about 1860 when the 

 well-known improvements by Draudt and Urich sup- 

 planted it. These last mentioned methods have become 

 generally used in the practice while other methods like 

 E. Hartig's and Pressler's have remained mainly theo- 

 retical. 



The study of the increment and the making of yield 

 tables which had been inaugurated by Oetellt, Paulsen, 

 Hartig and others toward the end of the last century, 

 was just at the end of that century placed upon a new 

 basis through Spath (1797), who constructed the first 

 growth curves by plotting the cubic contents of trees of 

 different ages, and through Seutter (1799) by intro- 

 ducing stem analysis, on which he based his -yield tables. 



On the shoulders of these did Hossfeld (1833) build, 

 when he conceived the idea of using sample plots for con- 

 tinued observation of the progress of increment and also 

 taught the method of interpolation with limited meas- 

 urements, laying the basis for quite elaborate formulae. 

 But the first normal yield tables, based on the average 

 trees of an index stand, were published by Huber (1834) 

 and in the same year by Hundeshagen. Prom that time 



