The discussion of what should be considered the proper felling age or rotation naturally occupied the minds of foresters from early times; a maximum volume production being originally the main aim. As early as 1799, _Seutter_ had recognized the fact that the culmination of volume production had been obtained when the average accretion had culminated. _Hartig_, in 1808, made the distinction of a physical, an economic and a mercantilistic, i.e., financial felling age, and _Pfeil_, considerably ahead of his time, is the first to call (1820) for a rotation based on maximum soil rent. As, however, he had so often done, he changed his mind, and while he first advocated even for the state a management for the highest interest on the soil capital involved, he later rejected such money management. About the same time _Hundeshagen_ clearly pointed out the propriety and proper method of basing the rotation on profit calculations, but it was reserved for a man not a forester to stir up the modern strife for the proper financial basis, namely _Pressler_, a professor of mathematics at Tharandt, who became a sharp critic of existing forest management, and developed to the extreme the net yield theories. It was then that the danger of a shortening of the existing rotations, due to the apparent truth that long rotations were unprofitable, called for a division into the two camps alluded to; _G. Heyer_, _Judeich_ and _Lehr_, elaborated especially the mathematical methods of the soil rent theory, _Krafft_ and _Wagener_ came to the assistance of Pressler, while _Burkhardt_, _Bose_, _Baur_, _Borggreve_, _Dankelmann_, _Fischbach_ and others, pleaded for a different policy for the state at least, namely, the forest rent with the established rotations. * * * * * As in the previous period, the mathematical subjects, namely, forest measurement and forest valuation, were more systematically developed than the _natural history_ basis of forestry practice; the slower progress of the latter being caused by the greater difficulties of studying natural history and of utilizing direct observation. In _botanical_ direction, descriptive forest botany was first developed, and several good books were published by _Walther_, _Borkhausen_, _Bechstein_, _Reum_, the latter (1814), of high value, and also by _Behlen_, _Gwinner_ and _Hartig_.