RELATION BETWEEN TERRESTRIAL AND SOLAR RECORDS 125 



interference from longer cycles. A cyclogram study of this sequoia record 

 extended back to 1804 is shown in Plate 23, which is an enlargement 

 of Plate 22 g. 



Figure 51: 4(h), Plate 22 h, show the Hellmann cycle in the southernmost 

 sequoia grove, south of Sequoia National Park and near Springville, where 

 three 3000-year trees have been found. The curve is made from 500 meas- 

 ures covering 1805 to 1890. The topographic conditions are good but not the 

 very best obtainable for a climatic record, since the area on which the trees 

 grew is rather flat and the ground sometimes very moist. The altitude is 

 high enough for large quantities of snow in winter. After removing a 19- 

 year cycle by mathematical methods, the Hellmann cycle is evident with a 

 range of 15 per cent. 



Figure 51 :8(i) shows the Hellmann cycle in the San Bernardino pines, 

 derived from 800 ring values, about 1850 to 1900; Plate 22 i uses the larger 

 interval, 1825 to 1925. The trees grew at about 6000 feet elevation in Santa 

 Ana Valley, northeast of Redlands. Collection and measurement of this 

 group was made with the generous help of Mr. J. J. Prendergast, President 

 of Bear Valley Mutual Water Company. After the subtraction of a strong 

 14-year cycle the Hellmann cycle shows a range of 16 per cent, and probably 

 more. 



The Hellmann curve in the Arizona pines, given in figure 51:3(j), and 

 Plate 22 j is derived from 3000 measures in 58 trees, distributed across two 

 hundred miles of country, approximately including 1850 to 1905; the cyclo- 

 gram, Plate 22 j, uses the interval 1825 to 1920. A 19-year cycle lasting 

 since 1800 completely dominates the record. This and a 14-year cycle were 

 removed by mathematical methods, whereupon the Hellmann cycle was 

 well marked in the curve. It seems to show a lag of two or three years in 

 relation to sunspot phase. It should be added that some of the individual 

 groups in this large assemblage of trees, such as the one from the Grand 

 Canyon, give the Hellmann cycle in prominent form without the interfering 

 cycles. 



Plate 22 k shows Grand Canyon tree growth from seven trees, 1825 to 

 1920. The effect is here shown of using the center of gravity of the maxima, 

 which produces a Hellmann cycle of very good form. There is the same 

 probable two or three year lag, as in the general Arizona curve. A lag of 

 —3 or —4 years fits many of the curves very well (tree-growth maxima 

 preceding sunspot maxima). 



Plate 22 1, as already mentioned, gives a cyclogram of the sunspot numbers 

 in which there is an inversion of minimum values for comparison with the 

 Hellmann cycles from terrestrial sources. In general we find that the Hell- 

 mann cycle is common in trees since 1850 and that the interfering cycles, 

 14 and 19 years, are widely distributed. The shorter one is plainly a solar 

 cycle, as will appear later, and the longer is probably so. 



Dearth Cycles — The dearth of sunspots is given by Maunder as 1645 to 

 1715, during which time spots were very rare; two intervals of ten years and 



