Page:Climatic Cycles and Tree-Growth - 1919.djvu/46

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36
CLIMATIC CYCLES AND TREE-GROWTH.

from the interior. The logs came from the vicinity of Dalarne in central Sweden, a large district. The bark is taken off as required by law and the logs are floated down to the mill. I visited the mill on Saturday, December 28, 1912. Twelve sections had been cut, but they were too thick and the whole 12 were cut a second time. These logs had been in the water a year and the last ring would therefore be of 1911 or possibly 1910. Of the 12, I think that all but 2 or 3 show the 1911 ring. Though these sections must have come from a considerable area (unless in the water and mid-afternoon darkness they accidentally secured original neighbors from thousands of logs), they identify among themselves extremely well. Cycles or pulsations were noticed and marked on all the sections of this group before identification. No. S 8 seems the most regular; a photograph of it is reproduced in plate 4, b. The cross-identification for the last 100 years hardly needs review, as it is entirely reliable and practically nowhere are there doubtful rings.

The means of the years 1820 to 1910 are given in the appendix and a plot of the same will be found in figure 8. The tree-growth in this group and others before 1820 will be taken up separately. There seems to be here no real change of growth with age, and the values were changed to standard by dividing by 0.8 mm. These results were then smoothed by Hann's formula and plotted in figure 23.


SOUTH SWEDEN GROUP.


This group of 6 sections was measured at Stockholm on December 27, 1912, in the office of Professor Gunnar Schotte, chief of the Swedish Forest Service. In my lists they are numbered from S 13 upward. They are all Pinus silvestris save S 14 and S 17, which are spruce, Picea excelsa. No. S 14 is noted particularly because it showed as perfect a sun-spot rhythm as G 8 from Eberswalde, whose photograph is given in plate 8, a. An entirely satisfactory cross-identification was made at the time of measurement.

The individual trees came from different localities and are therefore mentioned separately. No. S 13 was marked "4105-6" and was cut in May 1909. It grew about 100 miles southwest of Stockholm, in latitude 58° 40'. About 1833 it has a doubtful ring which was settled by comparison with other measures. Its center was in 1763. No. S 14, a Picea excelsa, marked "4105-14," was cut in July 1910 on the east side of Vetter Lake, less than 100 miles southwest of the preceding. Its center was in 1816. No. S 15, marked "4105-2," was cut in August 1909, about latitude 64° 30', near Lycksele, Lapland. It showed clear and well-sized rings to its center in 1701. No. S 16, marked "4131-a1," was cut in August 1910, in Elfdals, in latitude 61° 24'. Its center was about 1838, but its inner 10 rings were uncertain and therefore not