224 BARNARD— SELF-LUMINOUS NIGHT HAZE. 



this luminous matter is perhaps only ordinary thin haze which, from 

 an unknown cause, is sometimes luminous at night. I believe this 

 same haze is also present in the daytime. 



In my previous paper to the Society attention was called to the 

 fact that the objects observed by me did not seem to have any con- 

 nection with the luminous night clouds of O. Jesse of twenty-five 

 or thirty years previous. His objects were at very great altitudes, 

 some fifty-two miles above the earth's surface, and were visible by 

 direct sunlight which shone on them long after it had ceased to 

 illuminate the ordinary clouds. They were therefore not self- 

 luminous. They were only seen at the times of the equinoxes. 

 The present observations refer to objects entirely self-luminous 

 which are seen in all parts of the sky where sunlight could not reach 

 them, and appear to be at no greater elevation than the higher clouds. 



It is only during short periods that the luminous condition of 

 this haze seems to be of frequent occurrence. Apparently it will 

 be absent for a year or so and then for a short time there will be a 

 great amount of it. In 191 1 there were frequent displays of it 

 during the spring, summer and autumn, but from 191 1, September 

 22, until 191 5, July 2, I have no record of it, though a lookout was 

 always kept for it. It was frequent in the summer and fall of 1910 

 and also in the spring of 191 1. Its prevalence seems to be inde- 

 pendent of any auroral conditions. There are a few records of 

 aurora when the haze was present, but only one case in which a 

 large auroral disturbance seems to have been nearly coincident with 

 it. One is impressed with the idea that it is not necessarily an au- 

 roral phenomenon and that an appearance of it during an aurora is 

 perhaps purely accidental. Whether this luminous appearance of 

 what is undoubtedly haze, is due to electric conditions or to phos- 

 phorescence of some kind does not seem clear. 



Sometimes it appears in rather narrow strips several degrees wide 

 and many degrees long; sometimes the form is that of broad sheets 

 covering a large part of the sky. Often both these forms are pres- 

 ent at the same time. On one or two occasions I have taken it for 

 the zodiacal light in the east until its motion revealed its true nature. 

 When seen at the eastern horizon it has at times produced the eft'ect 

 of dawn. It is frequently brighter than the Milky Way. From 



