ah * 
COLLECTION OF SECTIONS. 41 
which suggest injury, as in 1756 and 1769 and 1770. A very regular 
recovery from these depressions sustains this idea of their cause. The 
means of the 2 groups are given on page 116. 
A few trees are perhaps available for periods antedating 1740. The 
centers of 5 are as follows: B 12 in 1682, B 15 in 1641, N 2 in 1497, 
S$ 4 in 1510, 89 in 1660. But the first 3 are from separate localities in 
Norway and the other 2 are from central Sweden, so it seems hardly 
profitable to include them here in a group on account of the tendency 
to reversal between those localities. The section N 2, 400 years old, 
from high latitude on the Norwegian coast, presents a feature of interest 
as noted in connection with the Norwegian group, namely, a pronounced 
fluctuation very nearly 34 years in length. The measures on this tree 
have been plotted, a mean sinuous line drawn through them, and then 
this mean line transferred to a different scale, smoothed graphically, 
and photographed to form figure 38 on page 106. The more formal 
analysis of this interesting tree-record with the periodograph confirms 
this periodic fluctuation. 
WINDSOR (VERMONT) GROUP. 
On return from Europe it seemed desirable to learn how American 
trees react in similarly moist climates. But it was not easy to secure 
sections. There are very few large pines near the Eastern cities. One 
“pitch” pine from 50 miles south of Boston, with more than 100 
rings, was secured, but there were no others in that immediate vicinity. 
Five white-pine sections from near Middleboro, Massachusetts, were 
obtained, but their rings were too few in number, being only 50 to 60. 
Finally a satisfactory series of hemlock, T’suga canadensis, from 
Windsor, was collected. Six sections came from the northwest slopes 
of Mount Ascutney at the lower and very steep end of the Brownsville 
trail. Five of these I cut from the stumps myself and preserved, and 
one was measured on the stump itself with full cross-identification. 
The remaining 5 of the 11 were cut from logs in a lumber-yard in Wind- 
sor; they came from across the river on a farm about 3 miles from 
town. Thus 7 or 8 miles separated these two subgroups. But the 
whole are here retained in one group, for the cross-identification, 
though difficult, was perfectly satisfactory. In order to be quite sure 
on this point, the subgroups were left separate until their curves could 
be compared. The Ascutney subgroup, with one extrapolation, 
extends back to 1695, and from that date 2 trees were carried back to 
1650. A comparison between the 2 and the whole 6 showed har- 
monious curves in their overlapping parts. This curve shows an aver- 
age growth of considerably less than 1 mm. in all its earlier years and 
up to the year 1808, when its yearly growth doubled. This sudden 
