SUNLIGHT FACTORIES 
53 
any of our American history was written, or 
indeed, even thought of. But experts can tell 
something about the weather five hundred or 
a thousand years ago by examining the logs. A 
ring that is very thin means a dry season. A 
wide one means a rainy year. Several narrow 
ones close together mean there was a period of 
dry weather lasting for some years. Many of 
these huge trees have over a thousand rings, 
showing that they are over a thousand years old. 
Most of the logs cut down for lumber from the 
pine and oak forests have from thirty to one 
hundred rings. Some of these trees, however, 
are even younger. 
As the outer rings of the tree continue to 
grow, the inner ones die. They do not carry 
sap or water any more, but they do not decay 
unless they are diseased. Oftentimes only the 
outer three or four rings are alive. The outer 
living part is called the sapwood, and the inner 
dead part is the heartwood. The heartwood 
changes color and is usually darker and more 
beautiful. It still serves to support the heavy 
T he rings 
of the tree 
tell its age 
