RELATION BETWEEN TERRESTRIAL AND SOLAR RECORDS 



127 



years is prominent and in the remainder a strong 19-year cycle appears, each 

 of which probably lasts through the entire data. This puzzling but strong 

 cycle near 20 years seems to be a composite of two taken in succession. 



A curve of Arizona tree growth plotted at 1/5 horizontal scale for 1200 years 

 shows approximately five times the sunspot cycle from A.D. 1168 to 1512. 

 (See fig. 54, page 128. Note the 11-year subdivision in the figure.) 



Certain long cycles in terrestrial records could easily result from interfer- 

 ence between short solar cycles already mentioned. In the solar records 

 we have the Hellmann cycle and also a cycle at 83 years; the interference 

 time between these two is 34 years, which gives us the Bruckner cycle, fre- 

 quently observed in tree growth. It is mentioned by Dr. Dodd as present in 



La £ in years 



Fig. 53 — Correlation periodograms (Alter) for — 



(a) Arizona trees, 1700-1920; 



(b) California and Oregon trees, 1700-1920. 



Udden's anhydrite measures from Texas. The interference between 14-year 

 cycles and 11.4 is about 57 years. The Arizona trees show a strong cycle of 

 this length. The interference between the most common values of the 10 and 

 11-year cycles (about 10.3 and 11.4) is closely 100 years. This cycle was 

 noted by Michelson in his analysis of the sunspot numbers. Many years 

 ago it was found by the writer in Huntington's measures of the big sequoias 

 as very prominent for nearly 2000 years. Later it has been confirmed, and 

 now is being studied, in accurately dated sequoia records. In the 1900-year 

 Arizona pine record, a 100-year cycle is very prominent, indeed. All these 

 scattering items sustain the idea of a relationship between variations in the 

 sun and in tree growth. 



