In the case of Mars and Jupiter, whose atmospheres are sufficiently recognized, red- and scarlet-tinted patches are frequently noticed. In Mars this is generally attributed to the geological character of the surface of the planet itself; but I have observed on Mars’s surface during the recent opposition a local rosy tint of a more diffused and indefinite character; and in the case of Jupiter the appearances seem almost always connected with the clouds’ belts, as distinguished from the regions lying nearer to the planet’s surface. [Sidenote: Prof. Dorna’s “Lunar Aurora.”] Professor Dorna, of Turin, ascribed a flickering light seen on the reddened disk of the moon during the Lunar eclipse of February 1877 to the action of a _Lunar Aurora_, holding that the refraction of the sun’s rays within the cone of the earth’s shadow was not an adequate explanation (‘L’Opinione Nazionale,’ March 3, 1877). [Sidenote: Spectroscopic observations bearing on the subject. Mr. Christie’s observations at Greenwich.] The spectroscope might have afforded some information on the question; but my own telescopes (8¼ and 3¼ in.) were not of sufficient aperture to give a sensible spectrum of a portion of the moon’s eclipsed surface, and my observations were chiefly made on the entire disk with hand-spectroscopes without a slit. Mr. Christie, at the Royal Observatory, Greenwich, made a set of observations during totality, and also during subsequent partial phase, with a single-prism spectroscope. During totality a strong absorption band was seen in the yellow, and the red and blue ends of the spectrum were completely cut off, while the orange was greatly reduced in intensity. The yellow and green were comparatively bright, and seemed to constitute the whole visible spectrum. The absorption band became narrowed as the end of the total phase approached, and during partial phase was reduced to a mere line. The red end of the spectrum was cut off by a dark band commencing about halfway from D to C, in which a black line was suspected. The bands observed were characteristic of the spectrum of light which has passed through a thick stratum of air. In the description of the spectrum of the Aurora in Part II., it will be seen that the conspicuous red and green lines of the Aurora are either coincident with, or very close to, some of these atmospheric lines. It does not appear that Mr. Christie examined the crimson patches specifically, nor that he saw bright lines on any part of the moon’s eclipsed disk. [Sidenote: Mr. Pratt’s notes of Lunar Eclipse, August 23, 1877.]