RELATION BETWEEN TERRESTRIAL AND SOLAR RECORDS 



129 



The frequency periodogram is a summary of certain qualities in a group of 

 data; hence comparisons between periodograms from two sets of data tell us 

 something about the nature of the material in hand. Thus there is no correla- 

 tion between the periodograms from two sets of random data but the fre- 

 quency periodograms from two different groups of our tree-ring records give 

 excellent correlation (see page 153). This shows that definite similarity exists 

 over wide areas in those bio-climatic changes that come in time units of five 

 years and longer. Five years in this statement is simply a lower limit result- 

 ing from the use of an annual unit in tree growth and its adaptation to our 

 analyzing instrument. 



Fig. 65 — A group of periodograms to show resemblance of terrestrial to solar cycles. 



Certain cycles in this complex were recognized in terrestrial records years 

 ago, such as the 11-year cycle, the Hellmann, a 19 to 21-year cycle, a 35-year 

 cycle, and something near 150 years, all noted by 1909. In 1913, cycles at 

 8£ years, 14 or so, 22 or 23 were seen. A 100-year cycle came out strongly in 

 the sequoias (Huntington's measures, not exactly dated but compensated for 

 estimated lost rings) in 1915 (vol. I, p. 109). Something between 250 and 300 

 years has been long recognized in Arizona, especially with the development of 

 the long Arizona chronology. 



The complex was named in 1926 when the three western zones were com- 

 pared in frequency periodograms and their similarity realized. These zones 



