AGE OF TREES. 



31 



each circle is one year's growth of the tree, 

 counting their number will give the term of its 

 duration." 



I thought/' said Harry, that wood was 

 wood, and all alike through the timber : 

 I do not remember to have noticed these 

 circles." 



But others have, whose eyes have been 

 no better than yours," I replied. However, 

 something besides eyes seems needful to con- 

 stitute an accurate observer of nature. It ap- 

 pears that the sap-vessels, just under the bark, 

 which are in a soft, spungy state during the 

 summer, harden in the winter, and become 

 firm wood. In the next spring, fresh sap 

 rises in another circle of vessels, pushing the 

 bark outwards ; and, in its turn, changes into 

 the close-grained proper wood of the tree. 

 Thus the whole is enlarged, and these annular 



