108 



CLIMATIC CYCLES AND TREE GROWTH 



Years 



37.5 



58 



66 



95-98 



117 



(1000-1914); fainter in sequoias 

 very good in both 



(first 1000 years) ; fair but not as important as the others, 

 excellent agreement throughout. 



the half-cycle, 57 ± years is frequently seen ; emphasis sometimes 



changes from fundamental to intermediate crests, not always 



similarly in the two regions. 



"In every cycle almost all corresponding maxima may be recognized, 



although there is much variation in maxima strength. There are indications 



of a long cycle of somewhat less than three hundred years which seems to 



form, with the last two above, a controlling group." 



5 6 7 8 9 10 II IE 13 14 15 16 17 18 19 20 21 22 23 24 

 YEARS 



Fig. 46 — Frequency periodograms of Central Pueblo Chronology (CPC) 

 and Sequoia Chronology (SVI). 



GEOLOGICAL MATERIAL FOR CYCLE ANALYSIS 



Its Character — Many collections of fossil wood have been examined but 

 nearly always the specimens are massive pieces, and the long, unbroken se- 

 quences of rings for which we are searching are quite absent. That is not 

 surprising, for the breakage of such wood is not normally radial, as we would 

 wish, nor have long sequences been specially sought. In fact the deliberate 

 collection of long sequences in the field is very difficult. Unaltered wood 

 such as the "buried trees" near Flagstaff or the large logs in the German peat 

 beds is far more likely to show desired records. 



