166 THINNING. 



doubt, and the following observations strongly con- 

 firm it. One small portion of a few acres was not 

 thinned in consequence of being somewhat detached, 

 and this portion was in no way affected, the trees 

 always remaining of their natural dark -green colour, 

 and the foliage rich and good. The manner in which 

 I consider thinning to be injurious in this case, is by 

 allowing the rays of the sun to heat and dry up the 

 ground. By a wise providence the branches of a 

 tree are so spread out on every side as to shade and 

 keep the roots cool and at an equal temperature ; and 

 when, as in the act of cutting down a tree, the shade 

 is removed, the rays of the sun penetrate the soil, 

 and unduly heat it to a serious and often fatal extent. 

 The extremities of the roots, probably in every case, 

 extend beyond the spread of the branches, and are 

 thus unshaded ; but in the case of pine and fir — and 

 indeed all true plantations — it may be said that 

 each tree also shades the roots of its neighbour as 

 well as its own, and therefore, when cut down, they 

 are equally exposed and injured as if each only 

 shaded itself. 



Thinning is not equally injurious to all species of 

 trees, nor is it equally hurtful on all descriptions of 

 soils. Where I have always witnessed the worst 

 results, iS' upon Scots pine growing upon 'a dry 

 gravelly soil, bare of herbage. This also accounts for 

 the different results produced upon the growth of 

 plantations by depasturing them. When the soil is 

 inclined to wetness, and the herbage luxuriant, graz- 

 ing with sheep or light cattle is advantageous for 

 the trees ; while, on the other hand, if the ground is 

 dry, inclining to gravel, and the herbage bare, eating 

 the grass or heather is less or more injurious. I have 



