18 FAMILIAR TREES AND THEIR LEAVES. 



a rustic arbor some ten years ago. The roof was un- 

 wisely fastened close about the trunk, to exclude the 

 rain ; now the rafters are forced asunder fully six 

 inches on either side of the tree, and an opening of 

 that width shows itself in the arbor roof. What is 

 most astonishing is the way three or four six-inch 

 iron spikes have retained their original position, 

 while the wood has been forced (regardless of the 

 nail-heads) entirely beyond them. 



According to recent tests, it takes a pulling force 

 of six tons to dislodge a six-inch nail. Think, then, 

 of a tree growing with an irresistible pushing force 

 of thirty-six thousand pounds, and this merely the 

 trunk expansion ! It is remarkable, also, to see how 

 a tree apparently growing out of a bowlder holds it 

 with an iron grasp, as its vigorous roots (much in the 

 way one's fingers encircle a ball) pass over it on their 

 way down to the nourishing soil below. There are 

 several trees growing this way in the charming woods 

 opposite the Flume House, Franconia Mountains ; 

 one may see them beside the path leading to the 

 Pool. 



The life of a tree is not only interesting, but it is 

 of more value to us than we can easily estimate. The 

 loss of large areas of air-vivifying leaves is a menace 

 to our health. Forests prevent sudden changes of 

 temperature in all seasons of the year ; they decrease 



