EECLAMATION OF THE SOIL. 139 



fit for the growth of trees ; a good plan is to grow one or two 

 field crops on the area, before the trees are planted. 



If the layer of peat is deep, 3 feet and more, the upper 

 portion must be removed, and only the remainder mixed with 

 the mineral soil. The cut peat may be used as fuel, but if 

 not so required, it may be cheaper to burn the upper layers 

 in situ when sufficiently dried by the draining, the ashes 

 being mixed with the soil. 



h. Accumulation of Raw Humus. 

 This may consist of an accumulation of leaves, needles, 

 weeds, moss and twigs, which, from want of moisture in the 

 soil, or of heat or lime, has remained undecomposed. The 

 case only occurs in already existing woods. To cure the evil, 

 the wood must be thinned heavily, some time before regenera- 

 tion is contemplated, so as to increase the admission of sunlight 

 and air currents and accelerate thereby decomposition. If 

 this measure proves insufficient, part of the humus must be 

 removed, and the rest mixed with the mineral soil. 



c. Dry Mould and Bituminous Humus. 



The first is formed by the decomposition of certain lichens 

 on over- dry soil ; the latter is the result of the decomposition 

 of heather and various species of Vaccinium. Both are 

 unsuited for young plants, and they should be removed. 



On the whole the cases mentioned under h and c occur 

 but sparingly. 



5. Fixation of Shifting Sand. 



Sand of a fine grain, without a sufficient quantity of 

 binding material such as clay or humus, is liable to be 

 blown about, and to become moving or shifting sand, which 

 overspreads adjoining lands. If the supply is kept up, these 

 shifting masses of sand form regular waves which proceed at 

 a certain rate in the same direction as that of the prevailing 

 wind. Shifting sands are most prevalent along sea shores, 



