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



PLATE 15 



A. Analyzing plate and mounting; the analyzing lines, 50 to the inch and inclined 

 some 17 degrees from the vertical, cover the rectangular area in the center. 



Cycle length 

 in years 



Cycle length 

 in years 



— > 



8-5 





II 4 



10.3 





14.0 



<- 



22. 8 



B. Cyclograms of sunspot numbers, using centers of mass. Notice change of align- 

 ment for different cycle lengths. Horizontal alignments at these settings show the basis 

 for the periodogram of annual sunspot numbers (figure 55). To see cyclograms best 

 hold paper nearly edgewise to the eye so as to look along pattern horizontally. 



