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.
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.