POOR, THE FIGURE OF THE SUN 



421 



observations were made on thirty-nine weeks with but three or four breaks 

 of single weeks; in the other set, observations were made on nineteen weeks 

 with but three breaks. 



To illustrate the method by which the periodicity was investigated, the 

 tabulation for the longest series of consecutive observations is given in full. 

 The first column gives the date of beginning of each of the seven-day 

 periods into which the observations were divided. The second column gives 

 the mean residual for the period as taken from Appendix IV of Ambronn's 

 work. In the first period there wxre two observations by Schur and one 

 by Ambronn; and the mean of the three, after subtracting + 0".02 from 

 each of Schur's, is — O'Ml. The remaining columns in the table give 

 the successive products formed by multiplying ao into the successive resid- 

 uals. The products of the first a^ ( — 0.11) by itself and the following five 

 residuals are found in the first horizontal line. 



Table XIV. 



Sums 



+ 0.3463 +0.0511 +0.0095 +0.0208 +0.076S —0.0189 

 +0.1476 +0.0274 +0.0601 +0.2218 —0.0546 



Each column of the table is summed up and the bottom line gives the 

 coeflScients of correlation x^, found by dividing the footings of the last five 

 columns by the sum of the a^ ag's. 



The values of x thus found are distinctly periodic. There is a marked 

 increase in the third and fourth values, and this indicates a tendency towards 

 a period of approximately twenty-eight days. The series, however, is too 

 short for any definite conclusion, and considered by itself this series would 

 have but little weight in testing the actuality of this apparent periodicity. 



