FOREWORD 



The study of cycles, like playing with empirical relations between 

 numbers, may well have intrigued men from very early times. How 

 else should we have been led in Asia and in America to our calendars? 

 In celestial mechanics the cycles are exceedingly regular, but there are 

 phenomena whether celestial, terrestrial or human in which it is obvious 

 that there are oscillations, but in which it is also obvious that the oscilla- 

 tions are not regular. Such phenomena raise serious questions for the 

 mathematician; it isn't even known whether Schuster's periodogram 

 analysis, which is the method most perfected mathematically, is really 

 suitable for exploring the series of oscillations. The phenomena also 

 offer perplexing challenges to the scientist: Are they, like Brownian 

 movements, to be regarded as fortuitous? Is there a relation between 

 them and other cyclic phenomena which will permit us to describe, at 

 least in part, the ones in terms of the others? And if this be true, what 

 is the real explanation of the correlations which have been discovered? 

 Finally, is there any possibility of prediction or of control of one phe- 

 nomenon by observation or by manipulation of another? 



Professor Douglass has for long been a worker in the field of cycle 

 analysis. More than fifteen years ago he described an optical instru- 

 ment and method for performing with considerable precision and with 

 extreme rapidity a type of cycle analysis. His method seems to have 

 been used little, if at all, by other workers. This neglect of a new tool 

 for analysis is regrettable. Science advances by its techniques as well 

 as by its findings of fact or its formulations of theory. Moreover, sci- 

 ence is not a collection of personal opinion or of individual performance, 

 it is a collaboration toward a consensus; until others have found out how 

 the cyclograph performs for them we have not the basis for a consensus 

 as to its merits — we have merely our faith in Douglass, and however 

 much he may appreciate this, he would appreciate yet more a demon- 

 stration of the justification for that faith. 



The collection of an enormous amount of material on tree-rings, the 

 development of methods of cross-dating and the establishment thereby 

 of a system of chronology represent a continued effort toward a knowl- 

 edge of our past. The correlations of tree-rings with solar and terrestrial 

 data and the intercorrelations of these not only illuminate the past, they 

 offer hope of some future and greater success in forecasting phenomena of 

 scientific importance and, perchance, of immediate significance to man. 



So much of the work on cycles which has been done in the past and 

 published with high hope has been found wanting by subsequent in- 



ix 



