[Sidenote: Polarization of the Aurora light. Mr. Ranyard found none.] In ‘Nature,’ vol. vii. p. 201, is contained an account of observations of the polarization of the zodiacal light and of the Aurora, by Mr. A. Cowper Ranyard, who, using both a double-image prism and a Savart on the great Aurora of February 4th, 1872, detected no trace of polarization. He also examined a smaller one of 10th November, 1871, with a like result. [Sidenote: Prof. Alexander found strong polarization in latitude 60°.] Mr. Fleming (who refers to these observations) remarks that the only other account he had met with was contained in Prof. Stephen Alexander’s Report on his Expedition to Labrador, given in Appendix 21 of the U.S. Coast Survey Report for 1860, p. 30. Professor Alexander found strong polarization with a Savart’s polariscope, and thought that the dark parts of the Aurora gave the strongest polarization. This was in latitude about 60°, at the beginning of July, and near midnight. It is not stated whether there was twilight or air-polarization at the time, nor is the plane of polarization given. [Sidenote: Mr. Shroeder found no polarization.] The question naturally arises, especially as the darkest parts of the Aurora are usually situated low down near the horizon, whether the polarization in the latter case did not proceed from the atmosphere and not from the Aurora itself. Mr. Shroeder found no traces of polarization in the Aurora of February 4th, 1872. Further examinations of the Aurora with some delicate form of polariscope would seem very desirable. [Sidenote: Polarization not found in the zodiacal light; except faint traces by Mr. Burton.] The evidence of polarization in the case of the zodiacal light seems also almost entirely negative—Mr. Ranyard pointing out observations of his own, of Captain Tupman, and of Mr. Lockyer with this result. Mr. Burton, using a Savart set so as to give a black centre when the bands were parallel to the plane of polarization, believed he detected faint traces of polarization in the brightest parts of the zodiacal light (as seen in Sicily), the bands being black-centred when their direction coincided with the axis of the cone of light. Mr. Burton saw no trace of bands when examining the slight remaining twilight apart from the zodiacal light. Mr. Ranyard was not able to confirm Mr. Burton’s observations on the same evening and with the same instrument. _Number of Auroræ._ [Sidenote: Number of Auroræ. Sir John Franklin’s observations.] Sir John Franklin saw in the Arctic Regions, in the years 1819, 1820, 1821, 1822:—In the month of September two Auroræ, in October three, in November three, in December two, in January five, in February seven, in March sixteen, in April fifteen, and in May eleven. [Sidenote: Periodicity as to days not established.]