156 



CLIMATIC CYCLES AND TREE GROWTH 



The ordinates in the summation curves are related to the data given in 

 Vol. II, Appendix, in the following way: 



R 



M = 



2 AV 



where M = mean value of data in II used in amplitudes'. 



R = total range in summation curve, taken at 10 per cent change 



per division. 

 A = per cent amplitude in tables. 



V = vertical scale value in tables; a value of unity being taken where 

 no entry is made in that column. 

 For SVI cycles, M will give the actual mean ring size. Data for the 42 

 groups and CPC were largely standardized and some groups were measured 

 in different units. For comparison purposes it might be added that the 

 approximate mean ring size in the 42 groups as a whole is 1.35 mm. It is 

 proposed to publish the mean ring sizes in a forthcoming article. 



42 Western Groups 



10 12 14 



