122 CLIMATIC CYCLES AND TREE GROWTH 



largely on this trip, using 52,000 measures upon 305 trees, were plotted and 

 analyzed in the summer of 1926, and then the next cycle step was made by 

 finding what we have called the "cycle complex" or "family" of preferred or 

 dominating cycle values. Late in 1926, after prolonged study of these 

 analyses, it was recognized that the dominating values in the cycle complex 

 matched the various cycle lengths found in the sunspot numbers and usually 

 bore a simple ratio to the 11-year cycle. 



Expressions of this same sort of relation have come from Clayton, Abbot, 

 C. E. P. Brooks, and others. Clayton in Our Atmosphere and the Sun finds 

 certain climatic waves that pass across the country and gets evidence of 

 dependence of these on simple ratios of the 11 -year cycle. Abbot has found 

 in radiation simple integral parts of 23 years, which is twice the sunspot cycle 

 length, and Brooks has expressed the same sort of thing in connection with 

 studies of the Nile gauge readings during the last thousand years. 



EVIDENCE OF SOLAR RELATION IN 11-YEAR CYCLE 



General Resemblance in Cycle Types — There is a general resemblance be- 

 tween tree growth and solar cycles in their discontinuous or fragmentary 

 character. When examined in cyclograms they look alike, save that the 

 former are more apt to have several cycles at a time. This may be persist- 

 ence of cycles after the cause has changed, possibly a biological character. 

 The persistence may occur in the sun in some form less conspicuous than 

 the usual smoothed annual sunspot numbers; and a part may be considered 

 as related to turbulence in the terrestrial atmosphere. 



Evidence by Cyclograms — Difficulty is anticipated here in communicating 

 the evidence we obtain in actual tests with the cyclograph. In spite of 

 general unfamiliarity with cyclogram patterns we feel sure that this method 

 should be used in the present topic because it is by far the most efficient 

 method available. At the start we illustrate the method of reading and inter- 

 preting the cyclograms in Plate 22 by reference to an enlargement in Plate 23. 

 Here, as in all cyclograms, each dot or spot represents a full crest in the orig- 

 inal curve whose analysis produced the cyclogram. The cyclograph is so 

 constructed that, when set to analyze at a certain cycle length, any series of 

 maxima giving that cycle will take the horizontal position (Plate 23, A-A'). 

 To bring out neighboring cycles the primary row of dots is repeated two or 

 more times in each pattern (Plate 23, A-A' and A-A'). If a fainter row of 

 dots (B-B') appears between the main horizontal rows, it means that two 

 crests in the curve rather than one exist in the particular period at which the 

 analyzer is set. The entire series of diagrams in Plate 22 was photographed 

 with the cyclograph set at 11.4 years. Hence one may readily see not only 

 that the 11.4-year cycle is present and dominant but also that in the majority of 

 cases it possesses two crests which, by definition, represent the Hellmann cycle. 



If the curve under analysis possesses a period different in length from the 

 one at which the instrument was set, its presence will be revealed by an oblique 

 or secondary alignment (Plate 23, C-C). The parallel row of dots, D-D', 



