It may be noticed that for observation of the waning moon there is no occasion to wait for those hours in which only the waning moon is visible _during the night_. Of course for the observation of a particular region under a particular illumination, the observer has no choice as to hour. But for generally interesting observations of the waning moon he can wait till morning and observe by daylight. The moon is, of course, very easily found by the unaided eye (in the day time) when not very near to the sun; and the methods described in Chapter V. will enable the observer to find the moon when she is so near to the sun as to present the narrowest possible sickle of light. One of the most interesting features of the moon, when she is observed with a good telescope, is the variety of colour presented by different parts of her surface. We see regions of the purest white--regions which one would be apt to speak of as _snow-covered_, if one could conceive the possibility that snow should have fallen where (now, at least) there is neither air nor water. Then there are the so-called seas, large grey or neutral-tinted regions, differing from the former not merely in colour and in tone, but in the photographic quality of the light they reflect towards the earth. Some of the seas exhibit a greenish tint, as the Sea of Serenity and the Sea of Humours. Where there is a central mountain within a circular depression, the surrounding plain is generally of a bluish steel-grey colour. There is a region called the Marsh of Sleep, which exhibits a pale red tint, a colour seen also near the Hyrcinian mountains, within a circumvallation called Lichtenburg. The brightest portion of the whole lunar disc is Aristarchus, the peaks of which shine often like stars, when the mountain is within the unillumined portion of the moon. The darkest regions are Grimaldi and Endymion and the great plain called Plato by modern astronomers--but, by Hevelius, the Greater Black Lake.