100 CLIMATIC CYCLES AND TREE-GROWTH. 
England show slight relation to the solar cycle. They show more 
prominently other variations, which, taken between 1870 and 1900, may 
have given rise to Lockyer’s 3.8-year period (1905, 1906). The full 
tree record becomes more accordant on a 3.5-year period. In this 
group there appears to be a slight relation to London rainfall of a 
direct character, that is, the growth is larger with increased rain. 
Naturally in such a well-cultivated region there may have been large 
differences due to treatment of the soil, drainage, and so forth. The 
other two European groups, one from Pilsen in Bohemia and one from 
the north slopes of the Alps in southern Bavaria, do not show consistent 
agreement with the solar variation. Yet the former shows a double 
sunspot period which is illustrated below. 
Coming to the American continent, the Vermont group may also 
be considered as growing in a wet climate. It shows a very strong 
single-creasted solar period, but the maxima come 3 years early during 
the last century. During the preceding century, when the trees were 
younger, the tree maximum is only 1 year early. The rainfall in this 
region shows the solar period also, but it is roughly inverted with 
respect to the tree curve. The Oregon group must be considered as in 
the wet climate of the temperate zone. It is near the Pacific coast and 
has abundant rain or snow. The solar cycle is probably in it, but it is 
not so conspicuous as other short cycles. When these trees are summed 
up on the 11-year period, they show about 10 per cent total variation 
with maximum and minimum coinciding with the Vermont group and 
therefore anticipating the sunspot maximum by 3 years. 
The sequoias grow farther south and experience the heavy pre- 
cipitation of the temperate-zone winter combined with dry-climate 
summer conditions—that is, the summers are mostly clear, but have 
occasional sharp local showers, often with lightning The tree-growth 
shows a relation to the rainfall in the great valley below and therefore 
we could expect some similarity to the Arizona pines. This does exist, 
but the exact 11.4-year cycle shown in the pines is less evident in the 
sequoias, though unmistakably there. The analysis of the long 
sequoia record will be shown below. In it several cycles between 7 and 
15 years predominate in places. The 11-year period is plainly evident 
through most of the record and for some centuries is the predominant 
cycle, but for long periods other slightly differing cycles, such as 10 
years, 12.6 years, or 13 years, are more evident. It is as yet impossible 
to say whether at these times there was a real change in the sunspot 
period, whether some subordinate period is operating in the sun, or 
whether only local conditions of some kind are the controlling factor. 
The yellow pines of northern Arizona are dry-climate trees. They 
have a modified winter precipitation of the temperate zone. Spring 
and autumn have the complete dryness of the “horse latitudes,”’ and 
the summers have the characteristic subtropical torrential thunder- 
