I916. No, I. ARE THE SOLAR CORPUSCLE RAYS NEGATIVE OR POSITIVE? II 



nosity is due to a uniform electrical luminiscence. The spectroscope shows 

 the North h'ght Une /. 5571 all over the sky. 



In my opinion this almost permanent luminiscence is produced b}- 

 rays magnetically drawn in towards the auroral zone from the permanent 

 ray-disc round the sun which under other circumstances manifests itself as 

 zodiacal light. This phenomenon may therefore be closely allied to a 

 sort of zodiacal light seen directly in the north about the summer solstice, 

 whicl> light was studied by Cambell, Fath ^, Barnard and Newcomb. 



At the Lick Observatory it was observed in June 1908 that this liglit 

 reached at midnight 18° above the horizon in the north. The obser- 

 vations showed that before midnight the maximum of intensity was some 

 degrees to the west and after midnight the maximum was displaced gradu- 

 ally to the east. Newcomb studied this form of zodiacal light from a 

 mountain of 7700 feet in height in Switzerland. He arrived at the con- 

 clusion that this zodiacal light was sufficiently brilliant to be distinguished 

 at a distance of 35° to the north of the sun. He adds the following sig- 

 nificant words - : 



»The limit of 35°, which I have set, nevertheless seems to me much 

 more precise than any limit that has been, or can be set in the plane 01 

 the ecliptic«. 



There seems to be good reason to believe that this zodiacal light in 

 the north is due to the well defined cône of solar electric rays drawn in 

 towards the auroral zone by the earth's magnetism. In summer time this 

 cône is considerably stronger than in winter time and will be seen from 

 much lower latitudes on the earth all on account of the position of the 

 earth's axis. This hypothesis explains all observed facts. Let us first 

 remember the form of such a cône from my terella experiments. 



In my book »A. P.« p. 299 there are already some very clear photo- 

 graphs, but fig. 200 and fig. 219 give the best information, as on the 

 former we see the two cônes drawn in towards the North Pole and the 

 South Pole from the side, and on the latter we see from above the cône 

 of rays being precipitated towards the North Pole a little on the afternoon 

 side of the earth. The last photograph shows at once that if we are 

 observing at midnight at a place of suitable latitude, we shall see the 

 maximum of light to the west, but after midnight the maximum will go 

 towards the east. Compare Fath's observation cited above and Newcomb's 

 observation that the upper limit of the light was sharper than the limits 



Ï Fath, The Northern Limit of the Zodiacal Light (P. A. S. P. 1908, Vol. XX, p. 280). 

 2 Newcomb, An Observation of the Zodiacal Light to the North of the Sun (Alph. J. 22, 

 pag. 209). 



