52 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I46 



1837 39 «l 43 45 47 49 Sr S3 55 57 59 61 63 65 67 69 71 73 75 77 79 01 



Fig. 43. — Periods in level of Lake Huron. 



fig. 6). The two great droughts will probably begin about 1975 and 

 2020, respectively. 



11. SHORT ACCIDENTAL TRENDS IN SOLAR VARIATION 



Measurements of the solar constant of radiation reveal trends of 

 rising and of falling radiation several times each month lasting from 

 3 to 10 days each (see fig. 45). We noticed as early as 1925 that 

 the temperature at Washington seemed to respond to these acci- 

 dental solar changes. This led us to make a very extensive investi- 

 gation of this matter, in which we found (P. 3771, P. 3893, P. 4462) 

 that not only the measures of the solar constant of radiation but 

 also measures of the areas of solar flocculi and measures of Fe in the 

 ionosphere precede up-and-down temperature trends. These trends, 

 observed either in solar constant, calcium flocculi, or Fe changes, 

 produce opposite effects, like the right and left hands, on tempera- 

 tures the world over. (See figs. 45, 46, and 47.) The temperature 

 changes are not small. I cannot better bring out this phenomenon 

 than by quoting from pages 219-221 of my paper of 1939 (Quarterly 

 Journal Royal Meteorological Society, vol. 65, No. 280, April 1939). 



