130 THINNING. 



tree, as they year by year force their way through 

 the soils first through the active and then through 

 the subsoil thereby disintegrate the adhesive com- 

 pact parts, whether of earth or rock, and thus pul- 

 verise the soil and admit air and water to mix and 

 mingle with the deeply embedded substances, thereby 

 altering and changing their composition by a slow but 

 certain process. 



All trees, at one or other of their successive stages 

 of growth, are either susceptible of vast improvement 

 by thinning, or of being injured almost to complete 

 ruination by doing it. Some, certainly, are less in- 

 jured than others ; and some species, if once injured, 

 can never by any future treatment be at all restored 

 to vigour of growth. Amongst hardwoods, the ash, 

 of all deciduous trees, is the one most easily injured by 

 want of thinning and most benefited by it ; but if once 

 neglected, even for a few years, all its prospects are 

 for ever blasted. Amongst coniferse, again, the Scots 

 pine, on the one hand, either benefits most by thin- 

 ning, or, on the other, suffers most for want of it. 



The Scots fir (Pinus sylvestris), whether regarded 

 from its importance as a tree, a crop, commercial or 

 industrial product, demands special consideration in 

 regard to thinning. It is generally admitted to be the 

 most extensively planted tree in Great Britain (cer- 

 tainly in Scotland), and is justly esteemed, both on 

 account of its commercial and industrial value, and its 

 adaptability to a greater variety of soils and situa- 

 tions (especially that of the poorer description) than 

 any other forest-tree ; and from these and correlative 

 circumstances has arisen the saying, almost amount- 

 ing to a proverb, " Thriving like a Scots fir." 



Although this is substantially true, it is not abso- 



