CORRELATION WITH SUNSPOTS. 



79 



crosses were placed upon the central ring, which was usually the largest 

 of the group. These crosses are well shown in plate 4, B. Their dates 

 were noted during the measuring. In figure 26 the ordinates give the 

 number of maximum marks found in each date throughout the whole 



I&30 



1850 



I860 



1870 



1870 



1880 



/890 



1900 



1310 



FIG. 28. Smoothed quarterly rainfall (upper curve), sunspot numbers (center), and 

 tree growth (lower) at Windsor, Vermont, 1835 to 1912. 



80 sections. The more recent dates show higher crests because there 

 are more trees. In the second line is the sunspot curve. The matching 

 of the crests of the two curves is unmistakable. The secondary tree- 

 crest at sunspot minimum is very regular, as would be expected from 

 the inclusion of the three groups of figure 24, some of which are evident 

 reversals. This test is only qualitative, but seems to the writer to offer 

 substantial support to the quantitative relation shown in figure 25. 



Windsor (Vermont) correlation. An interesting sidelight is thrown on 

 this type of correlation by the American curves from Windsor, Vermont. 



