IN the interesting article by Mr. Rand Capron in the last number of NATURE—after collating the various results of the spectroscopic examinations of the aurora and zodiacal light Which have appeared at different times in your pages, together with those which have been collected by Dr. Schellen—he terminates his analysis of the general results by remarking that he is “not aware whether the zodiacal light and the aurora have been examined with the polariscope,” and suggests that the “light, though faint, might be tested with a Nicol's prism and Savart's bands.”