Page:Popular Science Monthly Volume 59.djvu/40

30 the evening of September 2, however, there was an exhibit which could not be mistaken, I give it as written down at the time.

"Low down on the southern sky there stands a faint arc of light, and under it there is a distinct segment, darker than the sky above. This segment has been noticed in several previous auroras, but it was

not before so clearly defined. On board there is considerable difference of opinion about this segment. Some have previously doubted its existence, but to-night it is indisputable. I have taken the ground that it is produced by the haze of ice crystals which always rests over the ice, and I believe that its darkness depends upon the amount of humidity or the thickness of the suspended icy haze. The stars shine