l66 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



VARIATIONS IN AIR PRESSURE AND IN SOLAR ACTIVITY 



Variations of other meteorological elements have been connected 

 with the variations of sun spots by various authors with greater or 

 less evidences of agreement. 



That the variations in air pressure are associated with unknown 

 variations in the solar activity has long; ago been suggested. Charles 

 Chambers (1857) called attention to variations in the yearly barome- 

 tric pressure in Bombay which show a periodicity which corresponds 

 approximately with the sun spot period. A few years afterwards 

 Frederick Chambers (1878) showed that the observed air pressure 

 in Bombay for the winter and the summer months and for both 

 together give lower values when the sun spots are more intensely 

 developed and vice versa. But the curve for the air pressure lags 

 somewhat behind the curve of sun spots, particularly in the years of 

 the maximum of sun spots. The air pressure curve for the winter 

 was more regular than the air pressure curve for the summer. From 

 these observations Chambers drew the partly erroneous conclusion 

 that since the variations of air pressure depend upon the warming 

 of the earth's surface, the sun must be warmest and consequently 

 the temperature of the earth must be highest at the maximum of 

 sun spots, when a minimum of air pressure prevails. 



In the same year. 1878, John Allen Broun supported Chambers' 

 work by comparing the observations at Singapore, Trevandrum, 

 Madras and Bombay and showed that the years with the highest 

 and lowest mean air pressure were probably in common for all 

 India. From this he drew the conclusion that in this whole region 

 the air pressure varies oppositely ivith the sun spots in the same 

 way that it does for Bombay. At the end of the same year, 1878, 

 S. A. Hill confirmed this conclusion by similar data from Calcutta. 



Hill investigated also (1879) the yearly amplitude for the varia- 

 tions of the air pressure in Calcutta from 1840 to 1878, as well as 

 in Roorkee, from 1864 to 1878, and found that, like the yearly ampli- 

 tude of temperature in northwestern India they changed oppositely 

 with the sun spots, so that the maximum pressure amplitude was 

 approximately exactly coincident with the sun spot minimum and 

 vice versa. He was inclined to conclude from this that the " Solar 

 radiation " is in general more intense at the minimum of sun spot." 



In May, 1879. E. D. Archibald called attention to the remarkable 

 condition which had been brought to his notice by S. A. Hill that in 

 St. Petersburg the mean yearly air pressure varies in the same direc- 

 tion as the sun spots. It is highest at sun spot maximum and lowest 



