ADDENDUM. 
In the summer of 1919 a trip was made to the sequoia groves with 
three objects in view: (1) settling an uncertainty regarding the ring 
provisionally called 1580 ; (2) gathering material bearing on the relation 
of short-period cycles to topography; (3) investigating the causes of 
enlarged or gross rings. It is only the first of these topics which has 
an important bearing on the foregoing chapters. 
The region near the General Grant National Park was visited and 
12 new trees were very carefully selected as to their water-supply, 
drainage, and distance from other trees, and short radial samples 
were cut from them. It did not seem necessary to have these include 
more than the last 500 years of growth. The radial piece, therefore, 
was made very small, but especial attention was given to procuring a 
continuous and reliable record. Critical examination showed at once 
that occurrence of the ring 1580 a was dependent on locality. The 
trees from the uplands, where identification was easy, largely failed 
to show the ring, but in specimens from swampy basins, where cross- 
identification was difficult and sometimes uncertain, the ring was 
nearly always present. A complete decision, therefore, in favor of 
its real existence was satisfactorily obtained and the necessary correc- 
tions were made in the foregoing text and in the tabular matter which 
follows. It seems likely that the year 1580, which this ring repre- 
sents, was phenomenally deficient in moisture in the locality of these 
giant trees. 
In addition to the 12 new trees added to the sequoia group, a 
cutting was made from the stump D-12, which had hitherto defied all 
attempts at satisfactory dating. A small piece going back about 800 
years was cut from a part of the circumference, entirely free from 
compressed rings, about 4 feet away from the full sample cut in 1915. 
At the time of cutting, great care was taken to insure proper cross- 
identification between the inner end of the new piece and the former 
sample. But in the laboratory the new piece proved to carry a very 
excellent series of rings and the identification was everywhere very easy 
and sure, and all doubt about the dating of that particular tree to its 
earliest ring in 135 A. D., several inches away from its original cen- 
ter, was removed; therefore, it may now be included among those 
whose dating is entirely reliable. 
A new group of 5 very old trees from near Flagstaff, has settled an 
uncertainty regarding the years 1463 and 1464 in the yellow pines 
(too late, however, to rectify figure 3 on page 25). It is now possible 
to carry a very fair cross-identification between the pines of Arizona 
and the sequoias of California through the whole five centuries of the 
former. 
112 
