58 Our Field and Forest Trees 



as valuable to its owner as a house would be, and 

 far more valuable to the public. A house is soon 

 built, but it takes many, many years to grow a 

 forest. 



Over one of the loveliest valleys in New Eng- 

 land towers a height which is still known in the 

 neighborhood as " Green Hill." Visitors and 

 strangers wonder whether this name was given 

 in joke, for the hilltop now is a sun-baked dome 

 of rock. But the older people in the valley re- 

 member it as a green hill indeed, covered with 

 luxuriant woods. Then came a fire so fierce that 

 it burned not only the trees but their roots, and 

 it also consumed the soft black mold of humus 

 upon the hilltop. 



It is calculated that nature takes ten thousand 

 years to make one foot in depth of this forest 

 humus. But it can burn up like the peat under an 

 Irishman's potato pot, leaving only sand and 

 gravel. With no roots left to bind it together, 

 this sand or gravel washes down steep slopes, 

 leaving only bare rock where not a sapling or a 

 bush can grow. See how lasting may be the effects 

 of a few hours' blaze! (Fig. i8). 



In the woods, especially in late summer when 

 the earth and fallen leaves are dry, any spark 

 may start an awful conflagration, destroying prop- 

 erty and life. Fires are often kindled by sparks 

 from trains. A railroad engine is by nature a fire 

 fiend. It spits live coals along the edges of for- 



