is very fugitive and uncertain, while their number is small. 
In Mackenzie’s ‘‘ Diseases of the Eye,” the phenomenon, as 
witnessed by the unaided vision directed toward the sky, is men- 
tioned as having been noticed at different times by different ob- 
servers. [I am not aware that before the observations I have 
now detailed, any one had noted the special applicability of col- 
ored media, or the superior vividness afforded by use of th 
cobalt-glass, ) 
offering an account of the subject for the pages of this Jour- 
nal, I furnished a brief statement to Mr. Seely, and it appeared 
in the Journal of Photography published by him, July 15th, 
1859. Professor Rood’s observations, in this Journal, Septem- 
ber, 1860, recalled the consideration of the subject, especially 
Am. Jour. Sor—Seconp Series, Vou. XXXI, No. 93.—May, 1861. 
43 
