48 



SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



Fic. 39. — Periods in ionospheric h' F2, harmonics of 273 months. 



sine curve of 7.0 months, shown in figure 42, was found after clear- 

 ing the original 7 months observations of harmonics of 1/2, 1/3, 1/6, 

 1/7, 1/11 of 212 days. Its amplitude is 2 pulses on 67. All the 

 periods named are of course exact submultiples of 273 months (p. 51). 



3. Droughts at long periods. 



By invitation I published in the year 1938 an article on solar varia- 

 tion and weather in Zvlastni Otisk, the organ of the physicists at 

 Prague in Czechoslovakia. In that article, so far as I can discover 

 now, appeared my first prediction of very long-range solar periods. 

 I quote: "Records have been kept of the levels of the Great Lakes 

 of North America regularly since 1860. In addition, partial records 

 exist which fairly indicate the levels of some of the lakes since 

 1837. From these sources 1 have prepared figure 6 |hcre fig. 43, p. 52] 

 which indicates the water-gauge values for Lake Huron for a cen- 



