354 CARNEGIE INSTITUTION OF WASHINGTON. 



Climatic Cycles and Tree Growth, by A. E. Douglass. 

 The study of the record of the sun-spot cycle in Sequoia has been extended 

 and two important principles brought to light. The first is that the effect 

 of the sun-spot cycle on growth depends upon topography, the basin trees 

 only occasionally showing the 11-year period or its multiples, which are con- 

 spicuous in upland trunks. The second principle involves the correspondence 

 of ring cycles in trees several hundred miles apart, showing them to be real 

 and climatic in origin. An endeavor is being made to fill out a series of tree 

 sections that will represent the region from northern Colorado to the Mexican 

 boundary and from western Kansas to the Pacific. A considerable number 

 of buried logs has been secured from the Flagstaff region, in which a perfect 

 cross-identification has been found between two widely separated trunks, 

 thus increasing the chance of determining their age by comparison with 

 sequoia. The cycles from beams in the ruins at Aztec have been minutely 

 compared with those of the sequoia, partly in the hope of disclosing the date 

 when the beams were cut and partly to furnish further evidence of the value 

 and reliability of cycles. Fine sequences of rings have been discovered in 

 the Egyptian coffins of the Metropolitan Museum, and other objects of wood 

 yielded excellent rings of various dates, such as B. C. 2600, 1950, 1400, etc. 

 The cross-identification of beams from prehistoric pueblos by means of the 

 annual rings has progressed to the point where a museum beam labeled 

 "Pueblo Bonito" was shown to have come from the ruins at Pefiasco, and it 

 has now become so certain that a new method in prehistoric chronology is 

 available. 



Rainfall and Climatic Cycles, by F. E. Clements. 



A preliminary investigation of rainfall cycles has shown a definite relation 

 between drought periods and sun-spot maxima, every maximum of more than 

 half the greatest annual sun-spot number coinciding with general and critical 

 drought in the western United States. A comprehensive analysis is being 

 made of all rainfall records of 20 years or more for the western United States 

 and Canada with reference to sun-spot minima and excess rainfall, the 2 to 

 3 year cycle, the seasonal and monthly balance, and crop production. The 

 principle of the excess-deficit balance has been applied in all of these and 

 reveals within the 11-year cycle a general if not universal grouping of plus 

 and minus years into cycles of 2 to 3 years, shown not only by the various 

 stations but also by the State averages. In many cases these short cycles 

 seem to be related to the drought periods occurring at the sun-spot maximum, 

 while in others no such connection is evident. Critical drought periods are 

 regularly preceded or followed by years of high or exceptional rainfall, and 

 this excess-deficit relation is also characteristic of the short cycles, though the 

 amplitude is naturally smaller. In seeking the causes of this balance it 

 seems probable that it is an expression of the physical law of action and 

 reaction, though this may be exerted primarily through the sun-spot cycle. 

 It is possible that the short cycles may be due to the reciprocal relation of 

 precipitation on the one hand and evaporation-transpiration on the other, 

 and that the water-loss from plants may be a decisive factor in this at a short 

 distance from the ocean. Particular consideration is being given to the 

 rainfall of the Colorado Basin, in the hope that the sun-spot cycle and the 



