PLATE 11 



E 



A. Periodogram of standard 5-year period. 



B. Periodogram of mixed periods. 



C. Periodogram of sunspot numbers, 1610-1910. 



D. Periodogram of Flagstaff 500-year record, to show cycles 



between 4 and 15 years of length. 



E. Periodogram of same continued to 25 years. 



