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



c 



D 

 A 



A 



B 



B 



A 



B' 



C 

 D' 



Enlargement of cyclogram Plate 22 g, showing Hellmann cycle in sequoias. 

 AA' and BB' give the Hellmann cycle with its two crests; CC' and DD' show a 14-year 

 cycle with two crests. 



