NO. 8 RAROMETRIC PRESSURE — DLEI.L AND DUELL 25 



the zero line is must duininatiii},'. The greatest differences between 

 tlie maximum lifting and the maximum sinking are accordingly 

 relatively small and amount to 2."/ dkm. in summer, 3.1 dkm. in 

 winter, and to only 1.3 dkm. for all seasons together. One day after 

 the ultraviolet invasions the picture has changed fundamentally, as 

 can be seen from the right-hand side of figure 19. Here is shown 

 the average change of the absolute topography of the 500-mb. surface 

 in dkm. which has taken place i day after all very intense ultraviolet 

 invasions since the day which preceded these invasions. The dis- 

 tribution of the isallohypses is by no means more irregular. There 

 has developed a strongly marked area of sinking over western Europe 

 and a rather distinct area of lifting over northern Europe. The 

 location of the lifting area is the same in the winter and summer, 

 whereas the sinking area is situated somewhat more southward in 

 winter and somewhat more northward in summer, compared with 

 the average over all seasons. The difTerences between maximimi 

 lifting and maximum sinking are relatively great, and amount to 6.9 

 dkm. in summer, 8.2 dkm. in winter, and 6.9 dkm. for all seasons. 

 That means that there occurs in the course of 24 hours, and in the 

 average of 6 years, an increase of the differences by 4.2 dkm. in 

 summer, 5.1 dkm. in winter, and 5.6 dkm. in the average for all 

 seasons. However, more comparative study is necessary before any 

 definite conclusions can be drawn from these results. 



Reliable data about bright chromospheric eruptions arc available for 

 only a few years. However, for future work, to be done on a very 

 broad basis, it might be desirable to extend such investigations to 

 years which lie farther in the past. For that reason we investigated 

 the possibility of using, instead of bright chromospheric eruptions, 

 other observational data from the sun, e.g., data which could likewise, 

 even if in a more or less simi)lified manner, represent such increased 

 sun activity as is connected with ultraviolet eruptions. On the basis of 

 investigations which have been made by W. M. Goodall (29) in this 

 connection, and by T. Duell and B. Duell (30), the calcium flocculi 

 of the whole sun disk were finally taken on approval as a substitute 

 for direct observations of eruptions. In these statistics we pro- 

 ceeded not from the controlling element, i.e., sun activity, but from 

 the hypothetically subordinated meteorological element. The reason 

 for this was, that in the case of the calcium flocculi it is occasionally 

 very difficult to select a certain number of distinct and well-defined 

 extreme values, e.g., the five highest figures in every month, because 

 of the occurrence of many character numbers of equal value. As 

 key days all loi days of the years 1936-1941 were selected on 



