. Carnegie Institution of Washington publication. INTERPRETATION OF THE CURVE OF THE SEQUOIA. 167 of this has been noticed, even in years where the precipitation amounts to two or three times the average. In the past, it seems safe to say, the relation of precipitation and growth must have been essentially the same as at present. Therefore we seem warranted in concluding that in our long curve of growth, extending back 3,000 years, and given in figures 38 and 50, high places indicate abundant moisture and low places indicate drought. How greatly the rainfall of the past exceeded that of the pr
. Carnegie Institution of Washington publication. INTERPRETATION OF THE CURVE OF THE SEQUOIA. 167 of this has been noticed, even in years where the precipitation amounts to two or three times the average. In the past, it seems safe to say, the relation of precipitation and growth must have been essentially the same as at present. Therefore we seem warranted in concluding that in our long curve of growth, extending back 3,000 years, and given in figures 38 and 50, high places indicate abundant moisture and low places indicate drought. How greatly the rainfall of the past exceeded that of the present we can not yet ascertain 1890 1900 1910 1850 1860 1870 1880 iMms. Measured growth of bequoias Growth of Sequoias calculated from rainfall as described in text Rainfall at Fresno 10 San Francisco. Fig. 48.—Tree Growth in California Calculated from Rainfall, by A. E. Douglass. (See Table I, pp. 328-329.) positively. In the modern sequoias the growth during the group of 15 favorable years exceeded that during the 14 unfavorable years by mm., or per cent of the mean. The rainfall during the periods of 5 years preceding the favorable years exceeded that during the similar periods preceding the unfavorable years by inch, or 6 per cent of the mean, while if a 4-year period is taken instead of 5 the excess is inches, or per cent. From this it would appear that the thickness of the rings of growth is closely proportional to the rainfall. By this I do not mean to be understood as making any exact or positive statement, but merely as indicating the order of magnitude of the relative changes of rainfall and growth. Increasing the rainfall by 10 per cent might increase the thickness of the rings by 5 per cent or 20 per cent, but it is quite certain that it would not increase the thickness by 50 per cent, nor would its effect be so small as 1 per cent. Before attempting an analysis of the changes of climate indicated by the long curve of the se
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