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THE PLANET VENUS.

distance from the Earth . In this place, therefore, we need onlyremark with regard to them, that we hope, that in the comingtransit of 1882 very careful attention will he paid to anyindications which may be seen of the planet’s physical condi-tion, or of the nature and extent of any atmospheric appendagebelonging to it.

Our readers must certainly by this time (if not before) havebegun to think how little that is certain, or important, has afterall been discovered about this planet, so beauteous to the nakedeye, so baffling in the telescope. Nor is it much less tanta-lizing, that we are unable to give satisfactory explanations ofsome appearances, which are in themselves more sure. As aninstance we may refer to one, which is generally described asa greyish light occasionally noticed upon the dark part ofthe planet’s disc. It is most often seen in observations madeduring daylight or bright twilight, and is termed by French observers la lumiere cendrce. It faintly enlightens the re-mainder of the disc, when the planet is so situated that itsilluminated phase is slight (as in No. 5 of the drawings inFig . XLVI.) How it is caused it is hard to say, unless ithe by some optical delusion. No reflected light from theEarth , such as illuminates the dark part of the disc of theyoung Moon , could possibly suffice to produce it. It hasbeen suggested that it may arise from phenomena of anauroral character, or even from some kind of phosphor-escence in the planet’s surface; but it must, we think, beconfessed, that the enigma is one which is still unsolved. Itis certainly sufficiently interesting to deserve further andcareful study.

Another curious fact in the history of. the planet is, thatfor about a hundred years, viz., from 1672-1764, observationswere made from time to time of a supposed satellite belongingto it. It is generally considered that such appearances werecaused by minute images of the planet formed by successivereflections between the glasses of the eye-piece of the telescopeused, or between it and the observer’s eye,* which would the

* See also in R. A. S. Monthly Notices for January 1882, p. Ill, how asmall bright crescent was seen near to Venus by Mr. Denning, which was