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Show Trees Prove History Repeats Tree rings, which tell the story of wet and dry seasons, do not indicate in-dicate there is any general trend toward either drier or wetter climate. cli-mate. In the Pacific Northwest, where the United States Department of Agriculture made studies of 1,240 ponderosa pines centuries old, show that the period from 1917 to 1935 was critically subnormal because of the lack of precipitation and lower water tables. The average ring growth from 190J to 1919 was identical identi-cal with the general average during the past COO years, bearing out the generally accepted theory that climatic cli-matic history repeats itself through the ages. |