H. H. Clayton — Seven Day Weather Period, 9 



The results show that in general there are two maxima and two 

 mimima of frequency during the seven days, and at some sta- 

 tions there appear to be three. If the positions of maximum 

 frequency at each station are determined by constantly acting 

 causes, it is to be expected that when the time covered by 

 observations is divided into shorter intervals the maxima 

 would tend to occur on the same days of the period provided 

 the intervals are not too short. At all stations where the 

 observations were available for a time long enough to permit 

 it, they were separated into groups of three years, and the 

 frequency of barometric minima was determined for each day of 

 the seven day period in each group. Groups of ten years 

 would have been better had the observations been for a long 

 enough time to permit them. The results are given in Table 

 II for a few stations scattered as widely as possible, the maxima 

 being indicated as before by heavy-faced type. 











Table II 

























Day of Period. 







Station. 



Tears. 



1 



2 



3 



4 



5 



6 



7 



Chicago, 



1885 



-87 



24 



35 



24 



25 



36 



37 



34 





1888- 



-90 



25 



46 



29 



38 



28 



43 



28 





1891- 



-93 



38 



46 



36 



33 



42 



43 



34 



Perpignan, 



1880- 



-83 



47 



46 



45 



49 



46 



29 



40 





1884- 



-86 



36 



27 



32 



35 



31 



29 



20 





1887- 



-90 



37 



47 



40 



23 



40 



39 



39 



Zi Ka Wei, 



'85, '88 



'89, 



21 



31 



37 



23 



38 



27 



28 





1890, 



'92 



20 



18 



20 



16 



15 



25 



26 



Batavia, 



1881- 



-83 



16 



25 



22 



21 



23 



30 



23 





1884- 



-86 



23 



30 



18 



24 



19 



26 



26 





1881- 



-89 



27 



27 



14 



29 



30 



20 



23 





1890- 



-92 



25 



28 



22 



33 



28 



30 



26 



Matanzas, 



1880- 



-83 



34 



34 



38 



34 



30 



34 



49 





1884- 



-86 



28 



31 



28 



22 



30 



18 



21 





1887- 



-89 



27 



19 



34 



27 



21 



29 



30 



These stations are those which have the longest series of 

 available observations, and the results show that all over the 

 world the days of the period on which the maximum frequency 

 of barometric minima occurs at any station tend to remain the 

 same at that station during succeeding years. 



The results in Table I were plotted in curves and studied 

 from two different standpoints ;-^ 



(1) Stations near the same latitude but differing in longitude 

 were plotted under one another to see what relation existed 

 between adjacent stations. 



(2) Stations near the same longitude but differing in latitude 

 were plotted under one another for the same purpose. The 

 results for adjacent stations showed that the days of maximum 



