CYCLES. 



109 



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. 



5O 



6O 



I2O 



130 



lOO 



90 



9O 



tOO 



3O 4-Q 5O 6O 7O QO 



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 



