84 Clayton — ^7 -Day Auroral Period and the Moon. 



smoothing is done by taking the second order of means, that 

 is, by taking the mean of each two and then the mean of 

 each two of these means, the results when plotted give a 



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smooth curve without destroying any of the features of the 

 original residuals. The results of this second smoothing are 

 given in column 10 and plotted in the accompanying diagram, 

 fig. 1. The numbering of the days of the period in the 

 table is made to begin one day before the time of greatest 



