CYCLOGRAM ANALYSIS 



39 



In this diagram the alignment of the maxima along the direction A-B 

 becomes very prominent, much more definite than it showed in previous 

 figure 14. We can investigate the meaning of the directional character of 

 that line by figure 19b. This diagram, as is evident, is prepared on the co- 

 ordinate system of 19a. Starting at any point, for example at A in 19b, 

 we lay off the maxima of a 10-year cycle. We find that they produce a 

 straight horizontal line as indicated. Now we lay off an 11-year cycle. 



1750 1800 1850 1900 

 i i i i i I i i i i i i i i i I i i — I 



B 

 C 



'.\\ - I 



r 



in 



m 



L 



s 



•> 



0. 



10- 



o- 



10- 

 20- 



*\ 



201 $ rtftb+l/i(fflUr 



c 



B 



l — i — i — r— i — I — i — i — i — ' — i — i — r 

 1750 1800 1850 



1900 



1 — i — I 



•20 



u 20 



Fig. 20 — Cyclogram plot of sunspot numbers, 1750-1930. 



Note: if the analyzing lines A-B are made to slope the other way, the interference 

 sequence CDEFG is inverted. 



This will be built up of 11-year intervals measured to the right on the main 

 time scale and 1-year residuals set off upward on the vertical scale. Wher- 

 ever we lay off an 11-year interval it will take a slant parallel to this slope 

 as plotted up to the right. If we lay off a cycle of that length the maxima 

 will form a straight line at that slant. A 12-year cycle produces maxima in 

 a straight line at a still steeper inclination wherever it occurs in the data. 

 Once started it becomes very easy to lay off a full set of directional values 



