—P ro oa ‘— 
' 
108 CLIMATIC CYCLES AND TREE-GROWTH. 
several maxima at about 8.5-year intervals. Pattern H gives the Ver- 
mont analysis. The solar cycle shows well for the last 150 years, but 
is preceded by a 9.2-year cycle for about 50 years, and then by the 
solar cycle again. This tree curve is shown in figure 27, page 78. 
The Arizona pines are given in pattern fF. The double-crested solar 
cycle shows in the larger part of it, but is best developed in the upper 
and lower thirds. By sighting along these vertical rows, a dark line 
in the upper third, indicating the more pronounced minimum, comes 
in straight line with the lesser dark minimum line in the lower third, 
indicating a transfer of emphasis from one-half of the 11-year cycle to 
the other half in passing the seventeenth century. This was noted 
above in connection with the analysis of the same record by a series 
of curves in figure 33, page 103. Further study of this pattern, how- 
ever, gives information as to how and when that change took place. 
Changes in the 11-year tree-cycle of Arizona—A careful examina- 
tion of an early differential pattern of the Flagstaff tree record gave the 
following probable history of the 11-year variation in Arizona: 
TABLE 7.—Changes in the 11-year tree-cycle of Arizona. 
Years. Period. Remarks. 
1395-1550 11.3 Double crests throughout, except 1476 and 
1487, where the second crest fails, 
1550-1595 14.3 Heavy double crest. 
1595-1661 11.0+0.5 | Heavy single crests with trace of double 
diminishing to small variable singles. 
1661-1677 16.0(?) Possibly 1 long interval. 
1677-1770 12.5 Double crests mostly; going to 10.8 from 
1702 to 1722. 
1770-1793 9.0 Sharp single crest continuing second crest 
of preceding double. 
A7OS—IBIT NS Sas ween Doubtful. 
1817-1910 11.6 Rather broad, heavy crests, sometimes 
double; 1864 has too little and 1875 too 
much crest. 
The interval from 1830 to the present time divides also extremely 
well on a 21.0-year period, and fairly well in one of 7.3 years. 
In obtaining this result no comparison was made with the sunspot 
record. So the following is of interest: 
Taste 8.—Changes in tree and sunspot cycles compared. 
Trees. Sunspots. 
Years. Period. Years. * Period. 
1595-1661 | 11.0+0.5 years. 1615.5 to 1660.0 | 11.1 (?) years. 
1661-1677 | 16(7) 1660.0 to 1675.0 | 15.0 
1677-1770 | 12.5 mostly and 10.8 | 1675.0 to 1769.7 | 10.5 
1770-1793 9.0 1769.7 to 1788.1 9.2 
1793-1817 | Doubtful. 1788.1 to 1816.4 | 14.15 
1817-1910 | 11.6, 21.0, or 7.3 1816.4 to 1905 11.08 
