20 Economic Cycles: Their Law and Cause 



that our data afford. A greater confidence in the exist- 

 ence of a real period of 33 years is given by the fact that 

 Bruckner * claims to have found a true period of about 

 35 years in an examination of a vast mass of rainfall 

 material all over the world. Accordingly, the existence 

 in the Ohio Valley of a real 33 years period of rainfall we 

 shall assume to be very probable. 



The other two periods of 29 years and 36 years are 

 not easily disposed of. But in the first place, the ratios 

 of the squares of the respective amplitudes to the mean 

 square amplitude of the periodogram are not such as to 

 justify the acceptance, with any degree of confidence, of 

 the existence of true cycles of 29 years and 36 years. 

 In the second place, they are both so close to the period 

 of 33 years as to cause a doubt as to whether they may 

 not be spurious periods that are likely to appear in the 

 neighborhood of a real period. 2 



Considering the short range of our data it would not 

 be properly cautious to press the point of the existence 

 of any definite real cycle. But this much is certain: 

 If there are true cycles in the data of the 72 years of 

 rainfall in the Ohio Valley, there is far greater prob- 

 ability that two cycles are those of 8 years and 33 

 years than of any other round numbers between 3 and 



or, being done, would it be done once for all? / cannot say whether 

 anything with reference to Terrestrial Meteorology is done once for all. 

 I think probably the work will never be done." 



1 Edward Bruckner: Klimaschwankungen seit 1700. Bruckner's 

 period fluctuates greatly in length and has an average value of 35 

 years. 



2 Schuster: "The Periodogram of Magnetic Declination," p. 130. 



