III. DISCONTINUOUS PERIOD IN CYCLOGRAM 



ANALYSIS 



THE CLIMATIC DILEMMA 



Cycles in natural sequences and especially in climate have a very con- 

 fusing tendency to stop. Heretofore, if a cycle stopped, its consideration was 

 dropped, for on averaging further data its mean amplitude naturally grew 

 less and less and became negligible as more and more terms were included. 

 This was taken as a sign of its non-importance. 



A few students have examined these cycles that stop ; others say that they 

 do not really stop — they merely interfere with one another and appear to 

 stop. At this moment, that point does not need to be settled. Many 

 interested persons have taken an easy course and become conservative and 

 say that probabilities derived from harmonic analysis settle the matter, and 

 all these temporary cycles are imaginary. The word imaginary in this case 

 is used in its technical sense and amounts merely to a denial of permanent 

 reality. This in turn in the minds of many people has led to the thoughtless 

 denial of any reality. 



We can understand why the year and the day and other astronomical 

 cycles, including a family depending on the moon, must last indefinitely, but 

 there are vast numbers of oscillations in nature that do not last: a bell's 

 vibration is dampened ; waves on water fade out ; a cyclone movement is short- 

 lived, and so is a sunspot. Rotations in fluids may show different rates ; the 

 rotation of a tornado varies in velocity and stops eventually. 



These cycles in climate are very real, indeed, while they last, but localities 

 differ in their display. Our Atlantic seaboard, for example, seems less affected 

 by slow climatic oscillations than Arizona. People living in semi-arid regions 

 are more likely to become conscious of them. So it came about that after 

 living years in the Southwestern climate the writer felt the intensity of its ebb 

 and flow in units longer than the year, and after finding age-long records in 

 trees, worked up the cyclogram method of analysis in order to learn something 

 about these cycles in trees and climate, that have not been properly examined 

 heretofore because they do not last. This has opened a realm of cyclical 

 facts in climatic phenomena of which some of the most interesting are simi- 

 larities over large terrestrial areas and even between terrestrial changes and 

 changes in solar activity. And it is in these cycles that the resemblances 

 between sun and earth are found. 



PROBABILITIES AND CYCLES 



Cycle study by harmonic analysis in the last 30 years has provided a suc- 

 cessful display of new and long-lasting astronomical periods, chiefly those 



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