116 CLIMATIC CYCLES AND TREE-GROWTH 



Antevs's big-tree tests — Dr. Antevs (1925 3 ) has made certain trials 

 of the sequoias with reference to their use in studying past climates 

 and reached an indecisive conclusion. But this result was anticipated 

 from his selection of material and method of procedure. He divided 

 Huntington's trees into basin and ridge trees, standardized them, and 

 averaged these two classes separately without correcting the dating, 

 and then compared the two curves obtained. These curves agreed 

 for something like the last thousand years and before that disagreed. 

 The difficulty lies in Huntington's incorrect dates (and possibly 

 climatic change affecting the two groups differently). Basin trees 

 grow rapidly and can be counted easily and so contain few errors, 

 while the ridge trees are slow-growing and contain most of the errors. 

 Hence, in them the average error would be of the order of twice the 

 average error found in his dating, which was ±35 years in the last 1900. 

 In view of these details, given in previous publications (Douglass, 

 1919, 1922), it should hardly have been expected that undated basin 

 and ridge curves would show satisfactory agreement. On the other 

 hand, it should be remembered that carefully dated basin and ridge 

 sequoias show perfect cross-identification and only differ in the larger 

 and more complacent growth of the former due to moist soil, as 

 described in publications referred to. 



Ocean rotation effects — One indirect effect of solar causes has been 

 studied by Dr. C. F. Brooks (1926), namely, the rotation of the 

 Atlantic Ocean under the pushing effect of the normal winds in different 

 latitudes. The ocean is a vast storehouse of heat, whose variations 

 are thus borne to different shores. The circuit takes some 2 years, 

 and thus could originate short cycles of that order of length. Similar 

 motion exists in the Pacific Ocean with probably an increased time of 

 circuit. 



Closely associated with the study of this ocean movement is the 

 work of McEwen (1918, etc.) and Helland-Hanson and Nanson (1920) 

 and others. 



Solar cycle and terrestrial seasons — If a solar cycle of 10.5 months 

 should exert a precipitation effect on the earth, it would alter the dis- 

 tribution of rainfall in different seasons, say in the temperate zone, and 

 produce a 7-year cycle. We shall see that a cycle of this length plays a 

 part in Arizona tree-growth, but it seems more likely produced by 

 corresponding changes in solar activity and not as suggested above. 

 If this short solar cycle were double the length given, or 21 months, 

 and if its effect did not interfere with the seasons but increased tree- 

 growth in each year of its occurrence, then we would find rings alter- 

 nately large and small, as has been extensively observed. This is 

 referred to in Volume I, page 106. Extended search has been made 

 for a 2-year period by taking successive annual differences in growth 



