many as three or four layers are formed in those regions in the same period of time. Relying, however, on the
FIG. 6.
generally recognised rule, of one circle or layer for each year's growth, we have a measure and guide for computing the age of a tree at the time of felling it. Of course, this can only be done with trees having clearly defined concentric circles; in the instances exceptional to this, we, of necessity, have to fall back upon historical or traditional records to satisfy our inquiries.
It may be interesting here to note the size and age which some species of trees attain. It is said that specimens of the "Baobab" of Senegal are more than 5,000 years old, and that some of them have a girth of 90 feet. Again, some cedars that were seen in Lebanon in the sixteenth century were considered to be the remains of the forest from which the timber was drawn to build the temple of Solomon. By tradition, and other reasoning, the age of these Cedars was set down at about 3,000 years. Maundrell men-
