22o] Government Forestry Abroad. 39 



last year's seedling to the mature tree. These age-gradations suc- 

 ceed each other in a series so regular that in an hour's walk one 

 may pass from the area just cut over through a forest of steadily 

 increasing age to the trees which have reached the limit of the 

 rotation of ninety years. Three such units of management are 

 present in the Sihlwald, but .... it will be necessary to 

 speak of only one of them. The working plan for the Lower Sihl- 

 wald, then, prescribes for the forest which it controls the operations 

 of what Dr. Schlich has called in his Manual of Forestry ' The 

 Shelter-wood Compartment System . ' It may not be without inter- 

 est to follow the life history of a compartment in which this system 

 is carried out. 



"After the mature trees had been felled and removed from the 

 area which furnished the yield of the Lower Sihlwald last year the 

 thick crop of seedlings which had grown up under their shelter was 

 finally exposed to the full influence of the light and air. The fell- 

 ing and rough shaping of the timber, the piling of logs and cord- 

 wood and the trampling of the men had combined with the crisis 

 of exposure to destroy the new crop in places and create a few small 

 blanks. Here, as soon as the disappearance of the snow had made 

 it possible, groups of the kinds of seedlings necessary to preserve 

 the mixture or destined to increase the proportion of the more 

 valuable species were planted. The operation, necessarily an ex- 

 pensive one, is justified by the greater resistance of a mixed forest 

 to nearly all the calamities which may befall standing timber. 

 Simultaneously with the planting the willows, hazels and other 

 worthless species were destroyed, as well as the ' pre-existing seed- 

 lings,' whose larger growth, according to the disputed theory held 

 at the Sihlwald, would damage their younger neighbors more by 

 their shade than their greater volume would increase the final yield 

 of timber. The incipient forest, then, practically uniform in age 

 and size and broken by no blanks which the growth of a year or 

 two will not conceal, is fairly started on the course of healthy de- 

 velopment which it is to continue undisturbed until it reaches the 

 age of fifteen years. 



"At this point occurs the first of a ssries of thinnings (or more 

 exactly, 'clearing' at first and thinning later), which follow each 

 other at intervals of seven or eight years, until the trees have 

 entered the last third of their existence. There is, perhaps, no 

 silvicultural question more in dispute than this of the time and 

 degree of thinning which will yield the best results in quality and 

 quantity of timber. The method pursued at the Sihlwald, conse- 

 crated by habit and success, gives ample space for the healthy de- 

 velopment of the crown from a very early age without admitting 



