Clayton — 27 -Day Auroral Period and the Moon. 83 



decided excess of the frequency of auroras at the time of the 

 moon's greatest southern declination, and thus agree well with 

 the results of Dr. Ekholm which show the greatest difference 

 in potential between the earth and air in the northern hemi- 

 sphere at this time. However, the residuals in column 8 show 

 also an excess of auroras about the time of the moon's greatest 

 northern declination and about the time of the moon's passage 

 across the plane of the earth's equator. These excesses, unless 

 accidental, are not easily explained by the theory of differences 

 of potential produced by the induction of the moon. To see 



Table II. 





1 



2 



3 



4 



a 



6 



7 



8 



9 



10 



11 



12 



13 



14 



Day 



of 



Period. 



1870 

 to 

 1873 



1874 

 to 



1877 



1878 

 to 

 1881 



1881 

 to 



1881 



1885 

 to 

 1888 



1889 

 to 

 1892 



1870 

 to 

 1892 



Dept 

 from 

 mean. 



Mean 



of 

 five. 



Second 



order 



means. 



1885 

 to 

 1888 

 Winter 

 half- 

 year. 



1893 

 to 

 1896 

 Winter 

 half- 

 year. 



1885 

 to 

 1888 

 Summer 

 half- 

 year. 



1894 

 to 

 1896 

 Summer 

 halt- 

 year. 



1 



75 



77 



117 



188 



229 



75 



761 



+ 217 



- 10 



+ 105 



25 



28 



234, 



84 



® X 2 



105 



46 



97 



74 



105 



49 



476 



- 68 



+ 24 



+ 5 



17 



39 



78 



116 



3 



77 



60 



45 



91 



113 



98 



' 484 



- 60 



- 10 



- 53 



11 



66 



113 



107 



4 



93 



132 



77 



86 



50 



81 



519 



— 25 



- 75 



- 55 



8 



45 



54 



147 



5 



74 



65 



105 



86 



26 



76 



432 



-112 



- 73 



- 90 



31 



280 



13 



215 



6 



74 



89 



74 



54 



71 



70 



432 



-112 



-104 



- 98 



27 



407 



35 



150 



7 



50 



77 



74 



80 



111 



97 



489 



— 55 



- 77 



-110 



51 



310 



17 



168 



8 



47 



46 



56 



65 



42 



72 



328 



-218 



- 57 



- 94 



24 



171 



68 



126 



9 



139 



149 



100 



107 



93 



68 



656 



+ 112 



- 51 



— 2 



56 



665 



23 



35 



10 



121 



161 



57 



91 



64 



35 



529 



— 15 



- 41 



- 1 



62 



635 



14 



31 



11 



88 



69 



71 



112 



69 



52 



461 



— 83 



- 9 



- 46 



96 



248 



11 



51 



12 



115 



73 



101 



89 



108 



55 



541 



- 3 



- 19 



- 36 



57 



391 



34 



99 



13 



89 



76 



85 



44 



124 



69 



487 



- 57 



+ 62 



- 13 



66 



95 



21 



33 



14 



91 



210 



88 



54 



118 



48 



609 



+ 65 



+ 116 



+ 115 



15k 



257 



35 



56 



15 



168 



2H 



59 



77 



2Jfi 



93 



931 



+ 387 



+ 159 



+ 256 



146 



164 



69 



98 



<£■ S 16 



221 



115 



39 



103 



124 



128 



730 



+ 186 



+ 220 



+ 243 



110 



85 



76 



95 



17 



151 



251 



77 



74 



143 



61 



757 



+ 213 



+ 196 



+ 215 



82 



80 



49 



139 



18 



87 



266 



72 



233 



93 



43 



794 



+ 250 



+ 101 



+ 165 



57 



690 



39 



S4 



19 



71 



99 



32 



93 



132 



63 



490 



- 54 



+ 38 



+ 3 



62 



140 



21 



69 



20 



59 



69 



49 



97 



94 



86 



454 



- 90 



- 23 



— 90 



47 



173 



16 



78 



21 



44 



64 



51 



80 



65 



115 



419 



— 125 



- 73 



-109 



42 



159 



34 



87 



22 



127 



46 



56 



90 



54 



76 



449 



- 95 



- 51 



- 79 



28 



133 



106 



112 



23 



71 



53 



79 



166 



107 



68 



544 







- 69 



- 11 



38 



102 



98 



173 



24 



114 



57 



85 



70 



139 



133 



598 



+ 54 



- 83 



- 18 



8 



48 



68 



106 



25 



60 



39 



52 



88 



86 



40 



365 



— 179 



- 53 



-125 



29 



48 



37 



49 



26 



50 



43 



27 



112 



57 



60 



349 



-195 



- 9 



-128 



20 



43 



52 



80 



27 



69 



186 



107 



85 



103 



60 



600 



+ 56 



-30 



+ 33 



11 



39 



94 



95 



what effect smoothing would have on the somewhat irregular 

 numbers in column 8, the mean of each consecutive five was 

 taken and the results are given in column 9. In this column 

 the slight maxima found in column 8 at the time of the moon's 

 equatorial passage are smoothed out, but the maximum at the 

 time of the moon's greatest northern declination is still promi- 

 nent. However, if instead of taking the mean of five, the 



