Carnegie Inst. Washington Pub. 289. Vol. Ill— Douglass 



PLATE 18 





a 



Months 

 8 



|y :>:;; 









f 



Cyclograms of monthly sunspot numbers, 1750 to 1931: horizontal alignment is at 

 10 months: 8, 9, 10, 11 and 12-months directions are indicated in pattern a; time moves 

 left to right: first and last dates in the patterns are as follows: 



b. 1750.1-1779.9 e. 1840.3-1884.6 



c. 1770.1-1814.9 /. 1875.4-1915.3 



d. 1805.1-1849.8 g. 1905.1-1931.2 



