NO. 10 SOLAR RADIATION AND WEATHER STUDIES ABBOT 75 



two fairly well differentiated layers, one rich in organic material, the 

 Other in mineral substance. The measurements give the thickness 

 of each part, and I have also added them to give the total thickness. 



Dr. Bradley remarks that " the organic-rich portion of each varve 

 represents the material derived from the plankton produced in the 

 lake each summer, and as the volume of the plankton varies directly 

 with the amount of sunlight and the temperature (assuming an ade- 

 quate food supply) it seems reasonable to expect a correlation with 



variations in solar energy The mineral-rich layers consist 



largely of carbonate, and therefore may also be expected to vary in 

 thickness with the temperature of the lake water." 



Figure 32 gives a 23-year analysis of these data. Five successive 

 cycles of the march of the total thickness of the varves are given, 

 and the general mean of them all, covering 115 years. In addition, 

 I give the general mean for the 115 years of the thicknesses of the 

 organic and inorganic parts separately. All three mean curves show 

 a similar march, including certain details. All appear to show not 

 only the 23-year cycle, but the approximately 11^ year cycle as well, 

 though with alternately slightly longer and shorter intervals. The 

 ranges of the mean curves are about 100 percent. 



Dr. Bradley also furnished measurements of the widths of the 

 annual rings extending from the center to the bark in a fossil conifer- 

 ous tree of late Green River Eocene age. There were 107 successive 

 rings measured. On arranging the data in 23-year cycles, they proved 

 inharmonious to this arrangement. On rearranging them in five cycles 

 of 21^ years, the result shown in figure 32 was found. In this ar- 

 rangement the first two cycles are discordant, but the last three, cover- 

 ing over 60 years show a beautiful accord. May it not be that during 

 some part of the Eocene, lasting millions of years, the unknown forces 

 which govern the periodicities in solar variation acted more vigorously 

 than in other parts of the Eocene, the Pleistocene, or the Recent ? 



25. A Weather Test of the 23-YEAR Hypothesis 



As stated under caption 9 departures from normal monthly tempera- 

 ture and rainfall and 5-month traveling means therefrom have been 

 computed from " World Weather Records." These relate to more 

 than 100 stations in many parts of the world. The departures were 

 smoothed by 5-month traveling means in order to eliminate such rapid 

 and abrupt fluctuations as would obscure principal trends. Lack of 

 funds prevents the publication of these valuable data. 



It follows that should the working hypothesis outlined in caption 17 

 be a true one, then such a series of departures from normal tempera- 



