170 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. JO 



coincides with the maximum of sun spots, the maxima for the two 

 other periods occur at the crossing points of the two kinds of 

 spectrum hues. 



In a discussion of this prominence curve along with the curves 

 of air pressure variations in India they found an excellent agree- 

 ment at least for the period of time 1877 to 1890, in so far that the 

 air pressure curves showed the same periods of about 3.7 years. 

 This was so distinctly marked that it rather overshadowed the 

 eleven-year period, associated with the sun spot curves. 



In order to see if this remarkable agreement was confined to the 

 region of India they extended their investigations to other parts 

 of the earth and investigated the air pressure variations in Cordoba, 

 Argentina. They found also here a remarkable agreement, but with 

 the important difference that the curves were inverted. Years with 

 high air pressure in India corresponded with years of low air pres- 

 sure in Cordoba. This held particularly for the time April to Sep- 

 tember, that is, the summer of the northern hemisphere and the 

 winter of the southern hemisphere, and also for the whole year. On 

 the other hand it was less closely followed for the summer of the 

 southern hemisphere, that is, from October to March. It appears 

 natural that these coincident variations should be due to a common 

 cause which, while it tended to raise the mean barometric pressure 

 of the low pressure months in the Indian region, tended at the same 

 time to depress the mean value for the high pressure months at 

 Cordoba. Further investigations show also that a similar coinci- 

 dence of time in the air pressure variations at different stations in 

 Europe occurs with a similar period of a few years. 



The common cause for these air pressure variations must probably 

 be outside of the earth, and it is easy to conclude that it may be 

 associated with the coincident outbreak of prominences which also is 

 associated with variations in the latitude of the sun spots on the 

 sun's surface. All of these phenomena occur in the same period of 

 about three and one-half years. The Lockyers think it must be 

 assumed that the varying intensity in the solar activity in the course 

 of the eleven-year sun spot periods has a direct influence on the air 

 pressure and on the circulation of the atmosphere and in this way 

 produces meteorological effects over the whole earth. 



They found furthermore that these variations with a period of a 

 few (3 to 4) years were not the only operative ones, but that the 

 eleven-year and the thirty-five-year periods clearly influenced these 

 shorter variations. 



