CYCLES 



127 



closely than do the weather elements in which they live, and it is 

 perhaps safe to repeat the suggestion made by the writer in 1922 that 

 there may be some more direct line of cause and effect from the sun 

 to these trees than we have taken into account, such, for example, as 

 radiation (possibly of short wave-length), that is especially favorable 

 to trees growing generally under cloudy skies. In tree-groups along 

 the Atlantic coast of this continent, the 11-year cycle is also prominent, 

 but it has a phase displacement of 2 or 3 years. 



SOLAR CYCLES 

 Eleven-year cycle in long Flagstaff record — Combining the long 

 Flagstaff century curve beginning in 1285 with the Flagstaff mean 



usr 



1500 10 20 30 40 1550 60 70 80 \ ,' ' 90 1600 



*600 10 20 30 40 1650 60 70 80 90 1700 



YEARS 



Fig. 17 — Flagstaff century curve, FLC, a.d. 1285-1700; standardized 

 and smoothed 



area curve from 1700 on, one has full 625 years of sensitive tree-growth 

 (see Figs. 17 and 18). To this a superficial graphic analysis has been 

 applied with a number of interesting provisional results. The first 

 test deals with the extended half-sunspot cycle in the early Flagstaff 

 curve, found in 1908 and shown on page 102 of the previous volume. 

 The first hundred years of our present curve is made up of several 

 radials of one tree which had suffered a considerable injury in 1295. 

 It begins to show the cycle with certainty about 1320. The cycle 

 continues without interruption till 9 other trees join it between 1385 

 and 1419, during which time it is discordant, probably in part from 

 poor merging process in adding the new trees. Then it continues 

 without discord till 1541, 1550, and 1566-67. After that it is in 



