54ft. 



49ft. 



37 a 



25 ft. 



13ft. 



-'y^^f^ r -T'?<*r f:p ■ " 



FIG. 8. THE PROGRESSIVE GROWTH OF A TREE 15 



A tree grows in diameter each year by the addition of a cone of wood which never 

 increase- in height after bsing formed. Compare with Fig. 7. The age of the trunk 

 is shown at various heights (44 years at the ground. 6 years near the top, corre- 

 sponding to the number of rings in cross section) 



