He does not seem at that time to have examined the matter spectroscopically; and on June 23, 1872, he writes again, pointing out the peculiarity in Respighi’s observation that the green line was seen everywhere as bright as in the Zodiacal Light, and suggesting that it was due to a concealed Aurora present at the time of Ångström’s and Respighi’s observations. He further states he had examined the Zodiacal Light with a Browning 5-prism spectroscope (I presume a compound direct-vision form is meant) since the last December, and, brilliant as the phenomenon had frequently been, failed to detect the slightest appearance of bright lines or bands. A faint diffuse spectrum about as intense as that of a bright portion of the Milky Way was all he had obtained. [Sidenote: Prof. Piazzi Smyth confirms this.] Professor Piazzi Smyth, in the clear sky of Italy, and with an instrument specially designed for showing faint spectra, found no lines or bands, but only a faint continuous spectrum extending from about midway between D and E in the solar spectrum to nearly F (see Plate V. fig. 3, in which the continuous spectrum is graphically shown, white on a black ground). [Sidenote: Colour of the Zodiacal Light.] It may here be mentioned that the Zodiacal Light is usually described as, in these latitudes, of a golden yellow or pale lemon tinge. [Sidenote: Rev. Mr. Webb’s observation, February 2, 1862. He found no green line of the Aurora.] On one occasion, however, it has been described as not having this tinge, but rather resembling the light of the Milky Way, but brighter. On another occasion I saw the whole cone of a crimson hue without any mixture of yellow. The Rev. Mr. Webb thought that a display seen at Hardwick Vicarage, February 2nd, 1862, showed a ruddy tinge not unlike the commencement of a crimson Aurora—“it was certainly redder or yellower than the galaxy.” He examined it with a pocket spectroscope which would show distinctly the green line of the Aurora (probably Browning’s miniature), but nothing of the kind was visible, nor could any thing be traced beyond a slight increase of general light, which, on closing the slit, was extinguished long before the auroral band would have become imperceptible. [Sidenote: A. W. Wright’s observations and conclusions.] A. W. Wright examined the Zodiacal Light with a Duboscq single-prism spectroscope, the telescope and collimator having a clear aperture of 2·4 centimetres, magnifying-power of telescope 9 diameters. Special precautions were taken about the observations, and the conclusions arrived at were:— (1) The spectrum of the Zodiacal Light is continuous, and is sensibly the same as that of faint sunlight or twilight. (2) No bright line or band can be recognized as belonging to this spectrum. (3) There is no evidence of any connexion between the Zodiacal Light and the Polar Aurora. [Sidenote: Polarization of Zodiacal Light. Burton’s observation confirmed by Wright and Tacchini.]