8 R. H. Clayton — Seven Day Weather Period. 



with Jan. 6, ll'T P. M., 1896, which maybe taken as the epoch. 

 For each of the selected stations, during the entire time cov- 

 ered by available observations, the number of barometric 

 minima which occurred on each day of the seven day period 

 was counted. The first day consisted of the first 24 hours 

 following the dates of the ephemeris, the second day consisted 

 of the succeeding 24 hours, and so on for the seven days, 

 the final quarter day being omitted. The number of barometric 

 minima occurring on each day was selected because it is 

 generally recognized by meteorologists that rain, temperature 

 changes, etc., cluster around the barometric minima, and any 

 periodicity discoverable in these minima implies a periodicity 

 in all the other weather changes. The number of barometric 

 minima observed on each day of the period at each of the 

 stations selected is given in Table I, in which the days of 

 maximum frequency are shown by the heavy-faced type. 



Table I. 



Day of Period. 

 United States. Lat. Long. Years. 12 3 4 5 6 Y 



Roseburg, 43°13'N. 123° 20' W. 1885-93 91 98 82 100 98 100 98 



Cheyenne, 41 8 104 48 1885-93 113 96 108 109 103 106 120 



Chicago, 41 52 83 38 1885-93 87 127 89 96 106 123 96 



Blue Hill, 42 12 11 6 1884-93 121 97 150 128 120 109 153 



Europe. 



Perpignan, 42°42'N. 0°33'B. 1880-90 120 120 117 107 IIT 97 99 



Lesina, 43 10 16 27 1883-91 68 83 64 69 72 58 74 



Bucharest, 44 25 26 46 1885-91 78 45 60 69 62 55 48 



Christiania, 59 55 10 43 1888-92 51 41 44 59 47 51 43 



St. Petersburg, 59 56 30 16 1885-90 57 59 39 61 65 57 67 



Arctic Region. 



PointBarrow,71°27'N". 156° 15' W. 1881-83 11 12 12 11 17 10 13 



Fort Conger. 81 44 64 45 1881-83 17 11 8 18 10 11 IT 



Ekholm, 78 28 15 40 1882-83 10 8 10 4 9 7 5 



Asia. 



ZiKaWei, 31° 11' N. 121° 23' E. 1885-92 41 49 .57 39 53 52 54 



Tokio, 35 41 139 46 j }890-93 [ ^^ ^^ ^^ ^^ ^^ ^^ ^^ 



OCEANICA. 



Manilla, 14° 35' N. 120° 59' B. 1890-91 26 21 21 21 17 19 19 



Batavia, 6 11 S. 106 50 1881-92 91 110 76 107 100 106 99 



South America. 



Matanzas, 34° 48' S. 58°37'W. 1880-89 89 84 100 83 81 81 100 



Corrientes, 27 28 58 45 1881-89 66 70 77 75 66 68 63 



Rio Janeiro, 22 20 43 56 1883-91 54 38 50 44 48 51 45 



Africa. 



Mauritius, 20° 5' S. 57° 30' B. 1887^92 31 33 39 39 40 32 34 

 Australia. 



Flagstaff, 37°48'S. 143° 45' E. 1889-92 39 28 36 33 28 27 35 



