SOLAR VARIATION AND WEATHER—-ABBOT 
1875-1897 
Ne 
23-YEAR PERIOD IN TREE RINGS 
FROM 5 GROUPS, SO. CALIFORNIA 
15 
YEARS 5 10 20 
Fiaure 18.—The 23-year period as found in the thickness of tree rings from five 
southern California groups, 1829 to 1920. 
