NO. l8 TREE GROWTH AND RAINFALL— CLOCK 13 



Correlation.— Btcanse of the poor quality of the cross-dating and 

 because of the desire to compare the sequences each with the other 

 based upon precise measurements, the sequences were subjected to 

 statistical correlation. Table 2 gives the trend coefficients and the 

 ratios of opposed to parallel trends for certain trees and certain 

 groups. The bases of selection are evident from the captions in 

 the table. 



A comparison of the averages for uniform and variable sequences 

 shows that the uniform have a considerably higher trend coefficient, 



Table 2. — Holman Pass collection 

 Trend coefficients and ratios of opposed trends 



whereas the variable have a very slightly lower trend ratio. If any- 

 thing, the uniform have a slight advantage. 



Intragroup comparisons east of the Pass, on the Pass, and west of 

 the Pass indicate on the whole that correlations are distinctly higher 

 between trees within their own groups than between trees in different 

 groups. If the groups are averaged, this higher correlation is shown 

 even more clearly. Hence, trees grouped together appear to correlate 

 more closely than those rather widely separated. 



The matter of distance merits further attention. If the trend ratios 

 of the trees in table 2 are arranged in order of distance within the 



