Show History From Tree For a quarter of a century Dr. Douglass of the University of Arizona Ari-zona has studied the rings which mark the annual growth of trees. He demonstrated that the rings formed each year vary in width in direct proportion to the amount of rainfall a wet year produces a thick ring and vice versa. Tree growths in the giant sequoias of California were traced back three thousand years. Doctor Douglass made an unbroken annual calendar back to 700 A. D. By the study of timbers taken from pueblos he gave exact dates of events In the history of those Indian peoples back as far as the Eighth century. |