146 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 70 



not surprising in view of Hildebrandsson's theory, since Siberia has 

 a well-marked pressure maximum in winter which is the most defin- 

 ing part of the year for the temperature. The two regions are 

 therefore near two action centers of the same kind where the tem- 

 perature variations should naturally agree. It is more surprising 

 on the other hand, that the yearly curve for Siberia also shows 

 similarity to the yearly curves for the most easterly Danish fields 

 between o° and io° west longitude far north between 58° and 60° 

 north latitude. (Compare fig. 63, curves VII and lb). This lies 

 completely under the influence of the Icelandic pressure minimum 

 and according to Hildebrandsson should show an opposite march 

 in the temperature variations. However, as we shall show later, 

 there is a very natural explanation for this condition of affairs. 



In figures 62 and 63 at the bottom are given curves for the sun 

 spots (S) and for the protuberances (R, PC, and C). In figure 

 62 these curves are shown inverted, as indicated by the scale at the 

 right. One sees that great similarity exists between these curves 

 and the temperature curves of both figures, and even the small 

 variations of the prominence curves, for example, in the years 1884 

 to 1 901, are found in several curves for the surface temperature and 

 for the air temperature, although part of the variations of figure 62 

 and 63 occur in opposite senses. 



X. EARLIER INVESTIGATIONS ON THE RELATION BETWEEN 

 VARIATIONS OF SOLAR ACTIVITY AND THE METEORO- 

 LOGICAL PHENOMENA ON THE EARTH 



Recent investigations have made it more and more clear that a 

 dependence exists between the variations of dififerent phenomena on 

 the earth and the variations of the activity of the sun. Among 

 these variations are the number and extent of the sun spots, the 

 faculae and the prominences. That an intimate connection exists 

 between these and the magnetic forces and the Northern Lights 

 has been known as the result of numerous observations, but it has 

 gradually become more probable that there are short and long periods 

 in the variations of meteorological elements on the earth and the 

 corresponding periods in the activity of the sun. It is a priori prob- 

 able that variations in the solar activity, either directly or indirectly, 

 must call forth corresponding variations in the meteorological ele- 

 ments in the earth's atmosphere. 



