86 CLIMATIC CYCLES AND TREE GROWTH 



Then the periodogram, after a trial on variable star solutions (Appendix), was 

 allowed to lapse. In the next reconstruction of the instrument in 1920 under 

 the name of the White Cyclograph, the periodogram part was not included. 



The manner of reporting cycles has progressed, but each stage had fol- 

 lowed some time after the changes in the observing process. Until 1912 or 

 even later, summated or integrated curves were used. In 1914 the Eber- 

 swalde results were given in extended curves with a parallel comparison curve 

 of sunspot numbers (Huntington, The Climatic Factor). In 1919 consider- 

 able use was made of parallel comparison cycles, which were usually plotted 

 in the original diagram by a "templet" made out of cardboard. In 1921 and 

 1922 a large piece of analytical work was done on the sequoia records of the 

 last 500 years, as a study of the relation of cycles to topography. No way 

 was apparent for stating these results in detail, and they never have been 

 so reported, although the effect of that investigation appeared in studies of 

 environment (vol. II, Chapter VIII, p. 103) in 1928. 



The cyclogram itself as a method of reporting appeared in a single plate 

 or two in 1919 (vol. I, Plate 12, called differential pattern) and in 1928 (vol. 

 II, Plate 9). It was presented in the hope that some would study it and 

 realize its efficiency. 



It is difficult to reproduce by photography the details and precision that 

 are apparent in the action of the instrument itself. So in Volume II (1928) 

 the very considerable analyses of the 42 western groups were reported in 

 descriptive paragraphs that told something of the background of the results, 

 such as the location and its topography, the aid obtained in preparing the 

 curves, and the cycle lengths and weights observed. The beginnings and 

 endings of these discontinuous periods were often observed, but as all the 

 analyses were done by the writer, it was impossible to observe and place on 

 record such additional detail in any complete form and it was generally 

 omitted. 



But in this reluctance to use cyclogram demonstrations, there was prob- 

 ably a different factor present in the writer, as well as in others. The fact 

 that these cycles are short-lived was seen from the start of cyclogram analysis 

 in 1914, but the greatness of the break from the conception of permanent 

 cycles, or periods, was not really appreciated until 1932, nor the tight hold 

 which the idea of permanence had upon the most enlightened students. 

 Hence the present need of more detailed reports of these cycles, including 

 especially their time of duration. It is hoped that later reports will contain 

 a generous use of cyclograms, but some of the problems of their publication 

 are not solved yet. Hence at present this analytical work is reported below 

 in a tabular form. 



The analyses here presented were made extensively by Mr. Edmund Schul- 

 man and compared minutely with those of the writer as performed at other 

 times and for other purposes. Some cyclograms will be given to show how 

 that form of presentation can be worked out for more extended use another 

 time. 



