HISTORIC SKETCH 11 



passed, however, and with the return of normal financial 

 conditions, more intensive working became possible. The 

 formation of woods by planting and direct sowing was given 

 much attention, and many methods were evolved, the most 

 important of which will here receive consideration. 



In the history of the tending of woods, thinnings are first 

 mentioned as having taken place at the beginning of the 

 sixteenth century. The writings of the time contain many 

 observations worthy of remark regarding the aim and im- 

 portance of this operation. But their effect upon practical 

 management seems to have been that the smaller timber was 

 removed from the older woods, and that it consisted of the 

 suppressed and superfluous material, while the actively growing 

 younger woods received no attention. 



G. L. Hartig was the first to give systematic instruction 

 on the care of woods by means of thinning. In the early 

 years of the nineteenth century this important branch of 

 forestry developed further through the work of Spath, Cotta, 

 Pfeil, and Konig ; but it still made slow progress in practical 

 application. 



This period was also marked by an advance in systems of 

 forest management. Annual and periodic increment, previ- 

 ously overlooked, was now included in calculations connected 

 with working plans. Experiments conducted in Thuringia 

 about 1750 had most important results. They consisted of 

 a comparative study of the volume accretion of woods of 

 similar character at different ages. From these investigations 

 it was seen that there was a very considerable diversity* in 

 the amount of timber produced per acre at the various periods 

 throughout the lifetime of a wood this being connected 

 with corresponding alterations in the activity of growth. It 

 was shown that to postpone the act of felling beyond a 

 certain age dependent on species and situation led to 

 serious loss of timber increment. 



As has been explained, woods may be allotted to the 

 periods of a rotation by the taking of a like volume each 

 felling time, or by cutting over the trees upon an equal area. 



