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 A ; (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. 



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