Nor is there any perceptible intimation of water upon the Moon. It is true that several dark grey patches have been given names, leading one directly to the inference that lakes and seas comprise part of the surface phenomena. Thus there is the _Mare Serenitatis_ (“the sea of serenity”) and many other designations of similar import, which we cannot but insist are wrongly applied and calculated to lead to misapprehension. Before the invention of the telescope furnished us with the means of accurately determining the character of the lunar features, such apellations may have been considered eligible; but now that the non-existence of water in any extensive form is admitted, the titles are rendered obsolete. Still their retention is in some respects advisable, for any sweeping change in a recognized system of nomenclature must cause confusion, and the names alluded to serve a useful end in facilitating reference; so that, under the circumstances, it would perhaps be unwise to attempt reform, or to introduce an innovation which must occasion many difficulties. _Only one Hemisphere visible._—In discussing the nature and appearances of the lunar formations, it must be distinctly understood that our remarks apply to those visible on the side invariably turned towards the Earth. For, in point of fact, there is a considerable expanse of the lunar disk never perceptible from the Earth at all. This is occasioned by the circumstance that the Moon rotates upon her axis in precisely the same time as she revolves around the Earth, and is therefore enabled to present the same side towards us on all occasions. A slight tilting (called libration) takes place, so that we are allowed a glimpse of fragments of the side normally invisible, and its analogous aspect leads us to suppose that there is no great distinction between the features of the Moon’s visible and invisible hemispheres. From exact computations it appears that we are enabled to see a proportion of 59/100 of the surface, and that the remaining 41/100 are permanently beyond our reach. _Earthshine._—A few mornings before new moon, and on a few evenings after it, the whole outline of the dark portion of the lunar globe may be distinctly perceived. A feeble illumination like twilight pervades the opaque part, and this is really earthlight thrown upon our satellite, for near the times of new moon the Earth appears at her brightest (her disk being fully illuminated) as seen from the Moon. The French term for this light is _la lumière cendrée_, or “the ashy light.” The appearance is often popularly referred to in our own country as “the old Moon in the new Moon’s arms.” Some of the old observers remarked that the waning Moon showed this earthlight more strongly than the new Moon.