The small chart which accompanies this chapter, and which, with its key-map, I owe to the courtesy of Mr. John Murray, the publisher of Messrs. Nasmyth and Carpenter's volume on the moon, is not in any sense meant as a substitute for those already mentioned, but merely as an introduction to some of the more prominent features of lunar scenery. The list of 229 named and numbered formations will be sufficient to occupy the student for some time; and the essential particulars with regard to a few of the more important formations are added in as brief a form as possible (Appendix I.). Before we leave our satellite, something must be said as to the conditions prevailing on her surface. The early astronomers who devoted attention to lunar study were drawn on in their labours largely by the hope of detecting resemblances to our own earth, or even traces of human habitation. Schröter and Gruithuisen imagined that they had discovered not only indications of a lunar atmosphere, but also evidence of change upon the surface, and traces of the handiwork of lunarian inhabitants. Gruithuisen, in particular, was confident that in due time it would become possible to trace the cities and the works of the Lunarians. Gradually these hopes have receded into the distance. The existence of a lunar atmosphere is, indeed, no longer positively denied now, as it was a few years ago; but it is certain that such atmosphere as may exist is of extreme rarity, quite inadequate to support animal life as we understand such a thing. Certain delicate changes of colour which take place within some of the craters--Plato for instance--have been referred to vegetation; and Professor Pickering has intimated his observation of something which he considers to be the forming and melting of hoar-frost within certain areas, Messier and a small crater near Herodotus among others. But the observations at best are very delicate and the inferences uncertain. It cannot be denied that the moon may have an atmosphere; but positive traces of its existence are so faint that, even if their reality be admitted, very little can be built upon them.