NO. 8 DAROMETRIC PRESSURK — DIMI.L AND DUELL 21 



esses alone the total ultraviolet radiation of the whole sun surface is 

 raised by several hundred percent. The total radiation of the sun 

 in the whole sjiectral ran^e is raised only by several percent. How- 

 ever, even these few additional percent are not included in the direct 

 measurements involved in the "solar constant," generally measured 

 on high mountains, because this part of the ultraviolet has already 

 been absorbed in the ionosphere and stratosphere. They are but im- 

 perfectly allowed for by estimates of unmeasured ultraviolet wave- 

 length response. Bright chromospheric eruptions are not observed in 

 heliographic latitudes higher than 40°. 



R. St.\tisti(ai. Rksui.ts 



.All chromospheric eruption data used for our statistics have been 

 collected by the sun-control service established by the International 

 Astronomical Union with the help of spectrohelioscopes and spectro- 

 iieliographs, and have been published, after a detailed examination 

 and compilation by L. d'Azambuja (Mcudon), in the lUilletin for 

 Character I^'igures of Solar riienomcna of the Eidgenoessische Stern- 

 warte in Zurich (Switzerland). 



As key dates, there have been selected all those days of the period 

 Januar}' i, 1936, to December 31, 1941, on which (between 0900 and 

 1500 G.M.T.) bright chromospheric eruptions of tiie intensity ''2-2," 

 and "3" had been observed, provided they were not preceded on the 

 previous 5 days by equally strong eruptions. The limitation to 6 years 

 was made necessary by the fact that there do not e.xist sufficiently 

 complete eruption observations for the time before 1936, and that for 

 the time after 1941, no such data had been iniblishcd at the beginning 

 of our investigation. 



I'igure 17 shows the average behavior of sea-level pressure (1300 

 (j.M.T.) at the stations Plamburg, Frankfurt a.M., and Vienna on 

 all 51 days with strong ultraviolet invasions as defined above, and 

 also on I preceding and 1 1 following days. The applied method, al- 

 ready described in detail, is the same as for figures i to 15. .\t all these 

 stations a very distinct maximum of sea-level pressure appears 4 to 6 

 flays after the ultraviolet invasions. Surprising is the fact that this 

 maximum, and even the other part of the curve course, has almost 

 the same form in the summer months Ajiril to September as in the 

 winter months October to March. The amplitudes of these curves are 

 at all three stations greater in the winter (3.4 mb. in Hamburg, 4.0 mb. 

 in I'Vankfurt a.M., and 3.0 mb. in \'ieima) than in the summer 

 (2.6 mb. in Hamburg, 2.6 mb. in Frankfurt, and 1.7 mb. in \'ienna). 



