The idea of using the percentic relations for stating the increment, and of estimating the future growth upon the basis of past performance for single trees was known even to _Hartig_ (1795) and _Cotta_ (1804) who published increment per cent. tables. The methods of making the measurements of increment on standing trees were especially elaborated by _Koenig_, _Karl_, _Edward_ and _Gustav Heyer_, _Schneider_ (his formula, 1853), _Jaeger_, _Borggreve_, and especially by _Pressler_ (1860) who opened new points of view and increased the means of studying increment by causing the construction of the well-known increment borer, and in other ways. The most modern text-book which treats fully of all modern methods of forest mensuration giving also their history is that of _Udo Müller_ (_Lehrbuch der Holzmesskunde_, 1899), superseding such other good ones, as those of _Baur_ (1860-1882), _Kuntze_ (1873), _Schwappach_ (short handbook, last edition 1903). * * * * * The many sales of forest property which took place at the beginning of this period naturally stimulated the elaboration of methods of _forest valuation_. Even the soil rent theory finds its basis at the very beginning (1799) in a published letter by two otherwise unknown foresters (_Bein_ and _Eyber_), who proposed to determine the value of a forest by discounting the value of the net yield with a limited compound interest calculation to the 120th year. This idea was elaborated, in 1805, by _Nœrdlinger_ and _Hossfeld_ into the modern conception of expectancy values, and the now familiar discount calculations were inaugurated by them. _Cotta_ and _Hartig_ participated also in the elaboration of methods of forest valuation; Cotta writing his manual in 1804, recognizes the propriety of compound interest calculations, while Hartig, 1812, still uses only simple interest, and exhibits in his book as well as in his instructions for practice in the Prussian state forests rather mixed notions on the subject. Altogether, even in the earlier part of the period, there arose considerable difference of opinion and warm discussions, in which all the prominent foresters took part, as to the use of interest rates and methods of calculation. But this warfare broke into a red hot flame when _Faustmann_ (1849) with much mathematical apparatus developed his formula for the soil expectancy value, and when _Pressler_ and _G. Heyer_ transferred the discussion into statical fields, making the question of the financial rotation the issue. Then the advocates of the soil rent and of the forest rent theories ranged themselves in opposite camps. This war of opinions, although abated in fervor, still continues, and the issue is by no means settled.