36 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 82 



7.34; and in months, 64, 60, 42, ^^-j, 26, 25, 2\\, 19.3-19.5, 14.5- 

 14.7, 13, \2\. The researches of Dinsmore Aher ' pubHshed in the 

 Monthly Weather Review also bear testimony to the multiplicity of 

 meteorological cycles. 



My own researches have dealt largely with shorter periods of days 

 and months rather than years, principally because there was a much 

 larger mass of data available for discussion. In my earlier studies 

 of pressure and temperature data in the United States.' I found the 

 following periods in days: 3, 3.6, 4.6, 5.45, 6.14, 7.24, 9.1, 11, t8, 22, 

 29, 44, 58, etc. My recent studies indicate that there are many more 

 cycles and that all are probably harmonics of the sun-spot cycle. 



A. Defant ^ in a world-wide study in 1912 found the following 

 periods in days: 4.4, 7.9-8.7, 12. 0-13.0, 16.8, 24.5, 31. 2-31. 5. Arc- 

 towski. Turner, Simpson, Wallen, Myrback, Wasserfall, Schosta- 

 kowitsch, and Kidson have all found short meteorological cycles of 

 various lengths Even the short period cycles of a few days are 

 probably submultiples of much longer solar cycles, the most promi- 

 nent of which is the ii-year sun-spot cycle, or its double value, the 

 22.5-year cycle. 



In most cycles the subharmonics of small length are not important, 

 but it has been shown in table 9 that in high latitudes the subhar- 

 monics of the 1 1 -year period in meteorological cycles are of greater 

 amplitude than the primary period of 1 1 years and that the ampli- 

 tude increases with decreasing length of the harmonic. The sequence 

 has not been followed through for the entire Northern Hemisphere 

 beyond the period of about four months, but the amplitudes of 

 meteorological cycles at stations in the northern United States and 

 Canada apparently increase down to a length of about three days. 

 These shorter periods determine the origin and movement of the 

 ordinary cyclones and anticyclones seen on the weather map. 



Most investigators of meteorological cycles assume at the begin- 

 ning of their work that any cycle which may exist is constant in 

 amplitude and phase and may by repetition be separated from other 

 changes by which it is masked. This belief is the basic assumption 

 underlying the analysis by the Fourier series or the Schuster peri- 

 odogram. Prolonged investigation usually convinces the research 

 worker that this assumption cannot be maintained. I early became 



' Monthly Weather Review, Vol. 54, p. 44, and Vol. 55, pp. 60 and 263. 

 ' Amer. Meteorol. Journ., Feb., 1895, p. 376; also Amer. Journ. Sci., March, 

 1894. 

 ^ Sitzungberichte d. Wiener Akad., Bd. 121, Heft 3. 



