CULTIVATION AND PRESERVATION OF FORESTS. 343 
suitable for better classes of furniture; it is doubtful, however, whether its wood 
will not deteriorate by cultivation in Europe. 
But the most important feature of the forest exhibition was the illustration of 
the planting of trees in places which require afforesting. This includes two very 
distinct categories, the afforesting of heights and the afforesting of dunes, as well 
as their turfing, for trees cannot prosper without the growth of grass. On the 
heights as well as on the sandy shores of the sea, the labors of the forest cultiva- 
tor meet with unusual obstacles. 
The bare lines of hills have, in winter, a superabundant of snow and water, 
while in summer they suffer from long-continued drought. By afforesting both 
evils are to be remedied, but the tree itself suffers most from them. The winds 
and storms to which the tops of mountains are exposed, and against which the 
“trees are to protect them, as well as the slopes and the valleys which they form, 
are also a great drawback to the growth of trees. The forester must consequent- 
ly apply especial means for attaining his object, the afforestation of lines of hills. 
There are many depressions in mountains where the evils indicated are not 
so pronounced, and some protection against wind and too great drought is found. 
But the water, or rather the masses of water which are collecting in these de- 
pressions when the snow melts, have always sought an exit, and as they are 
acting with continuous and, on that account, resistless force, have found it. Each 
depression, each sinking of the soil in mountains, has been formed, long before 
the existence of man, into channels and gorges, whence in spring enormous 
bodies of water have precipitated themselves into the plains below, carrying with 
them masses of stone, earth, and roots. The first step, therefore, is to provide 
the gorge, which very often has been expanded into a valley, with obstacles 
against the precipitation of water. Weirs are consequently constructed at suitable 
distances across it. They either consist of a row of strong piles, the intervals 
between which are filled up by hurdle-work, or a strong, well-constructed dike is 
built of blocks of rock. The weirs must be made stronger and multiplied accord- 
ing to the length of the gorge and the quantity of water to be met. They retain 
the water for some time, which forms by its own action a broad smooth course, a 
small lake; all the small stones and dissolved particles of earth settle down, and 
soon form a broad, deep layer of fertile soil, on which grow first, grasses, then 
bushes, and finally trees. Humidity is here longer preserved by the water kept 
back, and the edges of the gorge afford some protection against winds and a too 
powerful sun. 
As soon as bushes and trees have risen above the weirs, afforestation pro- 
ceeds and extends rapidly. More fertile soil and humus accumulate, the gorge © 
is gradually filled up, its slopes and edges become covered with grass, and upon 
grass follow regularly bush and tree. It becomes possible to lead the water from 
the weir by a horizontal channel over the edge upon the surface of the mountain, 
or rather the slope, where then the same series of growth is repeated. ‘The ver- 
dure and trees already existing afford protection and supply moisture to the plan- 
