COLLECTION OF SECTIONS. 35 
usual way by a straight sloping line reading 1.90 mm. in 1820 and 1.15 
mm. in 1910. The corrected means smoothed by Hann’s formula will 
be found plotted in figure 24. 
TABLE 3. 
Date of maxima |Differences|Suggested maxima ‘ 
as marked. in years. jon 34-year period. Residuals. 
WBSO POORER 1831 -1 
1797 33 1797 0 
1754 43 1763 9 
29 1729 
1696 { mr on \ 1 
1657 39 1661 —4 
1528 29 1627 1 
33 1593 
vite { 34 . 1559 } a 
1535 26? 1525 10? 
CHRISTIANIA GROUP. 
This group of 5 Pinus silvestris sections was secured from logs at a 
little sawmill in the outskirts of Christiania. The logs cut in the 
neighborhood were in a large pile at the mill, and after the snow was 
brushed from them suitable ones were selected. Usually in such cases 
the largest and oldest were taken, but in this group the growth was 
exceptionally complacent. Accordingly, preference was given to those 
which showed variability in size of rings. 
These sections were measured a month or two later. Cross-identi- 
fication proved very unsatisfactory. Large variations were found in 
the 5 specimens. On this account it was felt that there might be 
several errors in this group which could perhaps have been removed 
by a larger number of trees for intercomparison. The centers of the 
5 were respectively at 1848, 1824, 1797, 1807, and 1790. The average 
diameter was about 1 foot. On page 114 will be found the mean growth 
of these sections and the plot of the same will be found in figure 8. 
There seems no special change in growth with age, and the whole series 
was merely reduced to percentages by dividing each yearly value by 
1.50 mm. These values, smoothed by Hann’s formula, will be found 
plotted in figure 23. 
CENTRAL SWEDEN GROUP. 
These 12 sections, showing an average diameter of about 11 inches 
and an average age of 190 years, were obtained from the sawmill near 
Gefle, on the coast, 60 miles north of Stockholm. The mill, one of the 
largest in Sweden, was some 4 miles from the town, on the river coming 
