98 FIRST BOOK OF FORESTRY 



Besides this the fanner with his thirty acres of woods 

 is not satisfied with the philosophic view tliat, in the wild 

 state, forests gradually right themselves ; he must know 

 what he had better do to protect his woods against fire 

 and insects, and how to treat them to make them more 

 resistant against wind, snow, and frost. 



TiiixxiN(; AM) Cleamxi; 



Going over a newly planted piece of young pine wdiere 

 the little plants are five feet apart, we see that each of 

 these has more than twenty times as much space as it 

 needs. If we come back five years later, we iind the little 

 bushy-topped trees beginning to touch each other. Ten 

 years later we find here a thicket of saplings, twenty feet 

 and more in height, the lower limbs mostly dead, and the 

 short crowns firmly locked. The struggle has begun, and 

 if no trees are taken out, the stronger choke the weaker ; 

 Init. and this is the serious part, the weaker also hurt the 

 stronger by using up some of tlie much-needed water and 

 mineral food from the soil and hinderinyr the srrowth of 

 both limb and root. 



If we return again ten years later, we hnd a large 

 number of trees dead. Others are dying, and the living 

 trees have grown taller and their stems have fewer dead 

 limbs. The trees have '• cleaned " more perfectly, but 

 they have grown but little in thickness ; they are a 



