NO. 7 THE ATMOSPHERE AND THE SUN CLAYTON 35 



periods besides the ii-year period. Turner found evidences of a 

 period of 260-280 years from a study of tree rings, Nile floods, Chi- 

 nese earthquakes, and sun spots. (Mon. Not. Roy. Astron. Soc, 1919 

 and 1920.) According to a recent analysis of the Wolfer sun-spot 

 data made by Dinsmore Alter, published in the Monthly Weather 

 Review of October, 1928, there are solar periods of more than 200 

 years in length, and the ii-year sun-spot period is a subharmonic of 

 much longer periods. This view agrees with that put forward by 

 Ellsworth Huntington and S. S. Visher in '* Climatic Changes," 

 1922, p. 45. My own investigations are in accord with this view, ex- 

 cept tliat recently the longer periods seems somewhat greater than that 

 given by Alter. 



Beginning with a period of 90 years, instead of 84 as given by 

 Alter, I find periods of approximately the following length: Length 

 of solar periods in years: 90, 56, 45, 35, 30, 28, 22.5, 18, 15, 12.9, 

 11^, 10, 9, 8.2, 7^, etc. All of these shorter periods are subharmonics 

 of 90 years, except 56, 35, and 28, which are harmonics of a longer 

 period. 



They agree very well with meteorological cycles found by Prof. 

 A. E. Douglass ' from rings indicating the annual growth of trees in 

 the southwestern part of the United States where rainfall is the most 

 essential factor in growth. The periods found by Professor Douglass 

 are: 35, 31, 28, 22.5-24.0, 20.5, 17.2, 14.2, 11.2-11.7, 10.2, 8.6, 7.6, 6.8 

 years. 



A study of periodicities in the Nile floods by C. E. P. Brooks ' 

 leads him to pick out the following periods in years : 76.8, 64.6-67.4, 

 39.85, 33.49, 24.43, 21.81-22.43, 18.32, 16.68, 14.87, 12.50, 10.86- 

 11.36, 8.33, 7.33, 6.83, 5.52, 3.66, 2.86. It is pointed out that 11 out 

 of 16 of these periods are multiples or submultiples of a period of 

 22.12 years. This period is somewhat shorter than Hale's period of 

 22.6 years ; but the difference may be due to the fact that the period 

 actually was shorter during the intervals covered by Brook's data 

 which go back to the year 641. His data indicate a systematic varia- 

 tion in the phase of this period, so that at the end of about 200 

 years the phase is inverted as regards epochs 200 years earlier. 



The researches of D. Brunt" also indicate that there are a great 

 many meteorological cycles, or else there are none. His periods in 

 years derived from the Greenw^ich temperatures are : 23, 17.5, 15, 8.17, 



' Qimatic cycles and tree growth, Vol. 2, p. 123. Carnegie Inst, of Washington, 

 1928. 

 " Mem. Roy. Meteorol. Soc., Vol. II, No. 12, 1928. 

 * Quart. Journ. Roy. Meteorol. Soc, Vol. 53, No. 221, Jan., 1927. 



