CORRELATION WITH RAINFALL. 



71 





pond, but of the moving type, as if a belated supply from the snows 

 came to hand and then passed on. The tree was assumed to receive 

 moisture from the current year and from the first and second preceding 

 years; and whichever of the three was greater, that one had the more 

 effect. The application of this formula is shown in figure 20. 



1850 



1860 



1870 



1880 



1890 



1900 



1910 



(Mms. 



Measured 4 - 

 growth of 

 Sequoias 



3.50 



3.00 



Growth of 

 Sequoias 

 calculated 

 from rainfall as 

 described in text 





Rainfall at 



Fresno 10 

 San Francisco 







FIG. 20. Huntiugton's early curves of sequoia-growth and rainfall compared with growth calcu- 

 lated by a conservation formula. 



But on identifying the rings in the trees collected from that locality 

 in 1915, and especially on finding the soft, delicate parts of the 1915 

 ring on D-5, it seemed fairly certain that the curve of growth given 

 in figure 20 is one year in error through the omission of a final ring. The 

 growth, then, which appeared to be 1902, for example, and for which a 

 pronounced conservation was necessary, really came the year before, 







Rainfall 



J?7V 



Tree Growth ' 



1850 60 70 60 30 1900 



Years 



FIG. 21. Comparison of Fresno rainfall (after Huntington) and sequoias D-l to 5. 



h* 



10 



and less conservation or none was needed. The comparison of the 

 same rainfall curve with the old sequoias of the present series is given 

 in figure 21. In this the agreement is not as good as at Prescott, but 

 there is marked similarity in many details. My curve from very old 



