KR. BIRKELAND, M.-N. Kl. 



In this way probably the corpuscular ray disc round the sun is visible 

 to us as zodiacal light. 



Let us return for a moment to the intensity curve Fig. i. In colla- 

 boration with Mr. Know Shaw, Director of the Hehvan Observator}', we 

 have sometimes registered the intensity of light from Saturn by the aid of 

 the thirty inch reflector. This was done also to see how the transparency 

 of the atmosphere would generally influence the light intensity curves. 



The Saturn curves show an almost horizontal course and are quite 

 smooth when the weather was clear. 



Figure j. Fig. 3 represents a curve registrated on nth April 191 5 

 from 8^ 10 to 9^ 15. The evening was at first clear but later thin clouds 



8li lom 8^2511 çli IS"» 



Fig. 3. Registered intensity curve for Saturn partually obscured by thin clouds. 



appeared in the sky, so that the light from the planet was then partially 

 obscured. 



The chief purpose of these registrations of Saturn was to see if we 

 could detect short variations in the light-intensity of the ring system corre- 

 sponding to what was found for the Zodiacal light. 



We did not succeed in finding such variations. But with the greatest 

 reflector existing and with rather better arrangements with photo cell and 

 electrometer than we had, it would be easy to get deviations thirty times 

 as great as we got them. Under such circumstances, especially if it was 

 possible to screen off" in a constant manner the light from the planet 

 itself, so that only the ring was acting on the photo cell, the intensit}' 

 curve from Saturn would certainly be of very high scientific value. 



On the Cause of the Great Climatic Changes in the Tertiary Period. 



3. The variations in the registered intensity curves of Zodiacal light 

 are, as mentioned before, of the highest importance for the theory, for they 

 prove at once the electrical nature of the phenomenon. In my opinion 

 the zodiacal light is the present visible sign of a now rudimentary pheno- 



