Page:Climatic Cycles and Tree-Growth - 1919.djvu/137

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109
CYCLES.

The agreement seems to the writer to justify the conclusion that the tree record may indicate a possible sunspot period of 11.3 years from 1400 to 1550 and of 14.3 from the latter date to 1600.

Sequoia pattern. — Pattern B in plate 10, opposite page 94, is naturally the most interesting in respect to age, as it gives the sequoia analysis for 3,200 years. The solar cycle subject to slight variations may be dimly seen in large parts of it. It shows with some prominence during the first 500 years of our era, then for a few hundred years near the year 1000 A. D., and for a long interval in the first 500 years of the record. There is opportunity for extensive study of these short periods, interpreting them by the aid of more widely scattered groups and other kinds of trees, and when possible by weather records.

Climatic Cycles and Tree-Growth Fig 40.jpg

Fig. 40.—Two differential patterns of Huntington's preliminary 2000-year sequoia record. The most prominent cycle is about 105 years in length, shown in the upper diagram.

Other solar cycles. — Plate 12, g to p, shows the multiples of the solar cycle. Pattern G gives the Arizona tree record analyzed at 23.5 years. It shows a slightly irregular vertical row of crests. This is best seen by tipping the pattern so that the eye views it from a low angle instead of perpendicularly as in ordinary reading. A line slanting down to the left giving a period at nearly 22.2 years would answer quite as well. The lower third is somewhat broken by the triple sunspot period showing in it. The same record is analyzed at 33.0 years in pattern N. In this pattern the lower third shows the triple cycle in vertical rows and the double cycle shows in rows slanting strongly down to the left. Patterns H and I in plate 12 show the excellent double sunspot