226 BARNARD— SELF-LUMINOUS NIGHT HAZE. 



more frequently at night. If there is no error in my identification 

 of this form of cloud with the luminous haze, it would seem that the 

 material must be frequently present, but that the cause of its lumi- 

 nosity is much less frequent. 



Fig. I. Photograph (x^ugust 19, 1917) believed to show the day appearance 

 of the luminous night haze. 



The accompanying photograph shows the streaky haze (form- 

 ing the background for the cumulus clouds) to which Dr. Hum- 

 phreys refers in his letter and which the present writer believes to 

 be of a similar nature to the haze that sometimes is luminous at 

 night. That shown in the photograph would doubtless be so dense 

 as to blot out the stars at night. Unless, therefore, the haze were 

 much thinner at night it could not be the same. I have seen in the 

 day time a thin gauzy streaky haze, sometimes in large sheets, at the 

 time that the regular denser cirro-stratus clouds were present. 

 These would more readily represent what I refer to as luminous 

 night haze. This I infer is still some form of the cirrus cloud. It 



