42 FOREST PLANTING. 



stony or steep) prevents the application of this useful im- 

 plement. As a rule the double plow is used to break up 

 larger tracts of denuded wood-lands, because it is only 

 with such a plow that the heavy swath formed by a 

 thick cover of lichens can be thoroughly peeled off, while at 

 the same time the main plow enters deep into the soil, 

 turning it over in furrows. Heaths which have remained 

 for a long time uncultivated, are liable to formations 

 of hard pan within the extent of the fertile soil. Such lay- 

 ers cannot be broken except by steam plows. These 

 should also be employed where the cultivation of extended 

 tracts justify a larger expenditure. It is a well-known 

 fact that steam plows perform this work not only cheaper 

 than horse-power, but also more thoroughly and benefici- 

 ally for the growth of trees. Owing to the greater 

 celerity of the movements of the plow, and its long screw- 

 shaped boards, the particles of the soil and subsoil are 

 infinitely pulverized and mixed together. A common 

 plow never could do the work so nicely. 



After the soil thus having been prepared, it is neces- 

 sary to give it a rest of a year or at least of an entire 

 winter, in order that the air, moisture, warmth and 

 frost may act upon the infertile subsoil, newly brought to 

 the surface, and impart upon it the ingredients which 

 are missing in the subsoil, and yet necessary for a 

 healthy growth of forest vegetation. At all events 

 plantations cannot be begun on places treated in the 

 aforesaid manner, unless the old turned under surface- 

 soil has completed its fermentation and settling. After 

 being exposed for some time to the air, the turned up 

 subsoil will have lost most of its humic acid, and the in- 

 soluble mineral ic parts of the same will have been partly 

 made soluble, and for the roots of trees available; while the 

 gases of the air, which have entered the soil, directly 

 furnish to the plants vegetable food. Only after the soil 

 has rested so long as to receive the said beneficial influ* 



