REPORT OF THE SECRETARY 59 



Having so satisfactorily analyzed the variation of the sun, Dr. 

 Abbot has sought toi detect the influence of the newly discovered 

 solar variations on weather. For this purpose he analyzed the pro- 

 longed records of departures from normal for temperature and 

 precipitation for the stations Helsingfors, Berlin, Copenhagen, 

 Greenwich, Cape Town, and Adelaide. Monthly mean departures 

 were computed from "World Weather Kecords" (recently pub- 

 lished by the Smithsonian Institution under grants from Mr. Roeb- 

 ling). For greater simplicity the departures were smoothed by 

 5-month traveling means. They were then analyzed to detect the solar 

 periodicities above listed, and any others which might be disclosed. 



As a result Dr. Abbot was convinced that all the 12 solar period- 

 icities named above except that of 39^ months, and in addition sev- 

 eral others, viz, 13.6, 55, and 138 months, occur in both temperature 

 and precipitation at all stations investigated. But changes of phase 

 in the periodicities were found to occur occasionally. An important 

 regularity in these changes of phase was discovered. They are ax)t 

 to occur abruptly at times which are integral multiples of 11^/^ 

 years, or still more frequently of 23 years after January 1819. 



Having discovered the importance of the cycle of 23 years, both 

 as least common multiple of all periodicities disclosed in the varia- 

 tion of the sun and the weather, and also as a master key to changes 

 of phase in weather periodicities, the next step was to inquire if this 

 cycle appears in the levels of lakes and streams, the life cycles of 

 animals and plants, and in other terrestrial phenomena related to 

 weather. On investigation, the 23-year cycle was disclosed in the 

 level of tlie Nile for 600 years, the levels of the Great Lakes since 

 1837, the catch of cod and mackerel since 1812, the rainfall of south- 

 ern New England since 1750, the thickness of tree-rings in many 

 localities and over many centuries, and in varves of Pleistocene and 

 Eocene geologic time. 



Finally, on plotting the temperature and precipitation of more 

 than 30 stations distributed over the United States, numerous detailed 

 features which appeared in a cycle of 23 years seemed to repeat 

 themselves, though with some modifications of phase and amplitude, 

 in successive cycles of 23 years. Assuming that this phenomena 

 will continue, forecasts for the 30 or more stations for 1934, 1935, and 

 1936 were prepared, based on the weather of the preceding half 

 century or more. The year 1934 has now elapsed, and the forecast 

 for that year has been compared with the event. The predictions for 

 1934 have been grouped in four grades of success in the forecasts 

 both of temperature and precipitation. They are : A, excellent, show- 

 ing a close accord throughout the year; B, good, nearly as satis- 

 factory; C, accordant half the time; D, bad, showing complete dis- 



