68 CLIMATIC CYCLES AND TREE-GROWTH. 
The first assumption in regard to conservation was that the ring- 
growth in any one year was built up by contributions from the current 
year and previous years in diminishing proportion. For example, 
it would be proportional to 
Rat3RoitiRn etc. 
in which R,, is the rainfall for the current year, R,_; that for the year 
preceding, etc. This may be called an additive correction. It did not 
Nia Pe 
GAL fe 
G Nil yA Lad 
10. iy AY 7 \t otis 
473.15. Dotted line = rainfall IM) 
Solid line = tree growth 
0 0.0 
ae 
20, 4 cs 2.0 
Nip el SIE iS | 
Lot ee to 
L. 
10 
Dotied kines rainfall amoothed by Schema 
0 Solid line =growth thed by S-yr 
: 20S 20h 
S | 4/2. axeaaetel N yi YF : 
Fees A , eS 
S Dotted line = accumulated rantall . 
S| Soh line = smoothed free growth ect BS 
$ 0 ao S 
é B ; 
5 6 
Dotted line = actual rainfall 
" Sold line = rainfall calevlated from tree growth 
1870 1880 4890 4900 1910 
Fig. 15.—Relation of tree-growth and rainfall at Prescott, Arizona. 
Tree-growth and rainfall uncorrected. 
Fig. 16.—Five-year smoothed curves of growth and rainfall. 
Fra. 17.—Accumulated rain and smoothed tree-growth. 
Fia. 18.—Actual tree-growth and growth calculated from rain. 
Fie. 19.—Actual rain and rain calculated from tree-growth. 
give satisfactory results for the Prescott trees, although a formula of 
this general type has been applied with some success to the sequoia, 
which grows in more moist soil. 
The variations in the Prescott trees were seen to be proportional 
both to the rainfall of the year and to the average growth or activity 
