138 



MR. J. BAXENDELL ON METEOROLOGICAL 



metric pressure, temperature, and rainfall under different 

 winds corresponding to the variations of solar-spot fre- 

 quency. Fortunately the means of at once testing the 

 soundness of this view were at hand in the valuable tables 

 numbered XVI. and XVIII. in the volumes of the ' Rad- 

 cliffe Observations/ which show for each year the relations 

 between barometric pressure, temperature, and rainfall 

 under different winds at Oxford. I therefore extracted 

 from these tables, and arranged in order, the mean annual 

 barometric pressures, mean temperatures, and amounts of 

 rainfall under different winds for the ten years 1858-67; 

 and on carefully examining the table thus formed I found 

 that changes had taken place in the three elements which 

 corresponded very closely in the times of their maxima 

 and minima with those of solar-spot frequency. 



The mean length of a solar-spot period is about 1 1 years 

 and 5 weeks; and as the volume of ' Radcliffe Observations ' 

 for 1868 has been published since I formed the ten-years'' 

 table, I have included the mean results for that year in 

 the following table, which thus represents the changes 

 which took place through a complete solar-spot period. 



According to the observations of Schwabe the numbers 

 of groups of solar spots which occurred in the years 1 858-68 

 were as follows : — 



Year. 

 1858 

 1859 

 i860 

 1861 

 1862 

 1863 



Number of 



groups. 

 .... 188 

 .... 205 



21 1 



204 

 160 

 124 



Year. 

 1864 

 1865 

 1866 

 1867 

 1868 



Number of 



groups. 

 .... 130 



•••• 93 

 .... 45 

 .... 25 

 101 



The mean number is 135 ; and therefore it appears that 

 during the five years 1858-62 the frequency of solar spots 

 was above the average, and during the six years 1863-68 

 it was below. In order, then, to ascertain the effects of 



