Page:Climatic Cycles and Tree-Growth - 1919.djvu/45

Rh 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.

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-identification 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.

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