114 



It appears therefore that in the years of maximum solar 

 spot frequency the maximum barometric pressure took place 

 under north-east winds, and the minimum under south- 

 west; but in years of minimum frequency the maximum 

 and minimum pressures occurred respectively under north 

 and south-east winds. The difference of pressure under 

 north-west winds is almost inappreciable; and the differ- 

 ences under north and south winds are small ; but those 

 under north-east, east, south-east, south-west, and west 

 winds are too considerable to be fairly attributable to acci- 

 dental causes. In order then to determine whether they 

 are due to the operation of a change in the intensity of solar 

 activity I have made the following comparison of the mean 

 pressures under north-east, east, and south-east winds with 

 those under south-west and west winds : — 



Mean Pressure 



iinclei> winds from 



N.E., E., & S.E. 



In. 



Mean Pressure 

 under winds from 

 S.W. & W. 

 In. 



Difference. 



1858 

 1859 

 1860 

 1861 



29-848 29-649 + 



29-813 29-672 + 



29-728 29-502 + 



29-775 29-714 + 



1862 29-756 



29-683 



+ 



Inch. 



•199 

 •141 

 '226 

 -061 

 -073 

 •012 

 •044 

 •007 

 •053 

 •150 

 -009 



1863 28-794 29-782 + 



1864 29-673 29-717 - 



1865 29-715 29-722 - 



1866 29-664 29-717 - 



1867 29-685 29-835 - 



1868 29-757 29*748 + 



The maximum difference occurred in 18C0, when solar 

 spot frequency was at a maximum, and the minimum differ- 

 ence in 1867, when solar spot frequency was also at a 

 minimum, and the general course of the differences has a 

 remarkable similarity to that of the numbers representing 

 the variations of solar spot frequency. 



As the rate of variation in the pressures during the 

 maximum years 1858-G2 was greatest in the quadrant 

 between north-west and south-west, and as winds from 

 the westward coming over the Atlantic are probably less 



