256 FERNOW 



heights of 45 to 55 feet; trees 70 to 90 years old exhibited 

 diameters of 18 to 27 inches; trees 100 to 150 years old 

 varied between 20 and 36 inches and showed heights up 

 to 1 20 feet. The largest trees found, without chance of 

 ascertaining their age, were 45 inches in diameter and 120 

 feet in height. 



From natural dangers these forests do not appear to suf- 

 fer much. Of insect damage little was noticed. The hu- 

 midity of the atmosphere and soil furnishes, no doubt, con- 

 siderable protection against fire, the greatest enemy of the 

 American forests ; nevertheless, there are evidences that it 

 cannot be kept out entirely. Avalanches, here and there, 

 have ploughed through the forest slopes to the water's 

 edge, and the hot ashes of Iliamna Volcano, near Cook 

 Inlet, are credited with the destruction of a considerable 

 area of spruce forest. 



