104 Germany. 
although at first agreeing with Hartig, later in his sec- 
ond edition (1817) changes his mind and improves both 
upon the biological explanation of Spith and the prac- 
tice of Hartig, pointing out that the latter came too late 
with his assistance, that the struggle between the individ- 
uals should be anticipated, and the thinning repeated as 
soon as the branches begin to die, but he also recognizes 
the practical difficulty of the application of this cultural 
measure on account of the expense. Curiously enough 
he recommends severer thinnings for fuel-wood produc- 
tion than for timber forests. 
Pfeil accentuates the necessity of treating different 
sites and species differently in the practice of thinnings. 
Hundeshagen accentuates the financial result and the 
fact that the culmination of the average yield is se- 
cured earlier by frequent thinnings. Heyer formulates 
the “ golden rule :” “Early, often, moderate,” but insists 
that first thinning should not be made until the cost of 
the operation can be covered by the sale of the material. 
Propositions to base the philosophy and the results of 
thinning on experimental grounds rather than on mere 
opinion were made as early as 1825 to 1828, and again 
from 1839 to 1846, at various meetings of forestry as- 
sociations, until in 1860 Brunswick and Saxony in- 
augurated the first more extensive experiments in thin- 
nings. The two representatives of forest finance, 
Koenig and Pressler, pointed out in 1842 to 1859, the 
great significance of thinnings in a finance management 
as one of the most important silvicultural operations for 
securing the highest yield. 
In spite of the advanced development of the theory of 
thinning, the practice has largely lagged behind, be- 
