NO. 7 



MONTEZUMA SOLAR-CONSTANT VALUES — ABBOT 



A period of 15^ months is 1/18 of 273 months. It was now 

 practicable to divide the data into three groups, and tabulate them 

 in 6-line tables of 15 columns.* In this way it could be decided if 

 the supposed 15^-month period continued in all three sections of the 

 interval of 273 months. Figure 3, a, gives the mean curves for the 

 three tabulations and the general mean. The three group means 



Fig. 3. — Examples of solar periodic fluctuations, a, 15^ months. Observations 

 1924-31 ; 1932-39; 1940-47; and 1924-47; h, 68 months. 1924-47; c, 39^ months. 

 1924-47. 



show no certain secular displacement of maxima and minima, have 

 nearly similar forms, and nearly equal amplitudes. Hence their mean 

 was taken as shown in figure 3, a, and is regarded as a very well- 

 determined periodicity of solar variation with an amplitude of 0.0030 

 calorie. This mean curve, being well supported in detail by the 

 group means, is used unsmoothed, and the departures of it from 



* Whenever a periodicity not of exact months is determined, values or 

 columns are omitted occasionally in tabulations, so that the mean values of 

 columns fit the exact length of the periodicity. 



