Do you know something about tree rings(年轮)? Do you know they can tell us what the wwas like, sometimes even hundreds of years ago?

    A tree will grow well in a climate(气候) with lots of sunshine and rainfall. And little sunshine or rainfall will limit(限制) the growth of climate by sthe tree rings. For example, to find out the weather of ten years ago, cthe rings of a tree from the outside to the i. If the tenth ring is ffrom the eleventh ring, then we're sthat it was sunny and rainy mof that year. If it is near to the eleventh ring, then the climate that year was bad.

    Tree rings are important not only for studying the history of weather but also for studying the history of man. Many centuries ago there l a lot of people at a place in New Mexico. But now you can find only sand there—no trees and no people. What happened?

  A scientist studied the rings of dtrees there. He found that the people had to leave because they had cut down all the trees t make fires and buildings. As all the trees had gone, the people there had to move.